- Email: [email protected]
Effects of baby walker use on the development of gait by typically developing toddlers
Journal Pre-proof Effects of baby walker use on the development of gait by typically developing toddlers Paula S.C. Chagas, Sergio T. Fonseca, Thiago R.T. Santos, Thales R. Souza, Luiz Megale, Paula L. Silva, Marisa C. Mancini
PII:
S0966-6362(19)31782-5
DOI:
https://doi.org/10.1016/j.gaitpost.2019.12.013
Reference:
GAIPOS 7408
To appear in:
Gait & Posture
Received Date:
16 February 2019
Revised Date:
22 November 2019
Accepted Date:
6 December 2019
Please cite this article as: Chagas PSC, Fonseca ST, Santos TRT, Souza TR, Megale L, Silva PL, Mancini MC, Effects of baby walker use on the development of gait by typically developing toddlers, Gait and amp; Posture (2019), doi: https://doi.org/10.1016/j.gaitpost.2019.12.013
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Effects of baby walker use on the development of gait by typically developing toddlers Paula SC Chagasa, Sergio T Fonsecab, Thiago RT Santosb Thales R Souzab, Luiz Megalec, Paula L Silvad, Marisa C Mancinie,* a
Department of Physical Therapy of the Adult, Elderly and Maternal-infant, Faculty of
Physical Therapy, Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, MG, Brazil b
Department of Physical Therapy, Universidade Federal de Minas Gerais State (UFMG),
Belo Horizonte, MG, Brazil Department of Pediatrics, Universidade Federal de Minas Gerais State (UFMG), Belo
f
c
d
oo
Horizonte, MG, Brazil
Center for Cognition, Action, and Perception, Department of Psychology, University of
Cincinnati (UC), Cincinnati, OH, United States. e
pr
Department of Occupational Therapy, Universidade Federal de Minas Gerais State
e-
(UFMG), Belo Horizonte, MG, Brazil *
Corresponding Author: Marisa Cotta Mancini, Graduate Program in Rehabilitation
Pr
Sciences, Escola de Educação Física, Fisioterapia e Terapia Ocupacional, Universidade Federal de Minas Gerais, CEP: 31270-901, Belo Horizonte – MG, BRASIL, Fone: 55 31
al
3409-4781. e-mail: [email protected]
ur n
Number of words: 2985
Highlights:
There is no delay in the age of gait acquisition in toddlers who used baby walker.
Toddlers who used baby walker had slower gait than those who did not use it.
Toddlers who used baby walker had smaller knee amplitude in the sagittal plane.
Differences tended to disappear after a few months of practice.
Jo
ABSTRACT
Background: Decisions about the use of baby walker are in part predicated on caregivers´ beliefs about its effect on gait development. The actual effects of baby walkers, however, have not been established. Research question: What are the effects of the use of baby
walker prior to gait onset on age of acquisition of this milestone and on early walking kinematics? Methods: Thirty-two toddlers, 16 in the baby walker group (BWG) and 16 in the non-users group (BWNG), were evaluated in the week of gait acquisition and monthly up to six months after this event. Spatial and temporal gait parameters and lower limb kinematics during walking were assessed using a tridimensional motion analysis system. An independent t-test compared age of gait acquisition between groups. A mixed ANOVA examined the effects of group, moment of assessment and the group x moment of assessment interaction effect on the amplitude of joint motions during walking and on spatial and temporal gait parameters. Results: The age of gait acquisition was not different
f
between groups. BWG had lower gait speed (specifically in the first, third, fourth, and
oo
fifth months after gait acquisition) and longer duration of stance and swing phases than
BWNG. Additionally, BWG had smaller knee amplitude and greater hip amplitude in sagittal plane than BWNG in the week of gait acquisition. Significance: The results
pr
demonstrated that there is no delay in the age of gait acquisition, but there are differences in kinematics. These results can contribute to evidence-based recommendations by health
e-
care professionals about the use of baby walker by toddlers during emergence and early
Pr
development of gait.
Keywords: gait, kinematics, toddlers, infants, baby walker, infant walker.
al
1. Introduction
Baby walkers are popular among parents despite frequent warnings against its use
ur n
during the period between independent sitting and gait acquisition [1–6]. Studies that investigated parental decisions on the use of a baby walker revealed that they believe it accelerates gait acquisition [7–10] and helps strengthen their infants’ legs [7,9]. In addition, parents believe that the baby walker entertains the infant [7–10]. Although the
Jo
use of a baby walker is associated with risks such as infant falls [1,3–6], the majority of parents choose to provide this experience to their children [7,9–11]. Studies that evaluated the effects of the baby walker use on the age of gait
acquisition and on children’s motor development do not provide conclusive evidence about its benefit or harm [7,9,10,12,13]. While some studies reported delays on gait acquisition [13] and late onset of other motor developmental milestones in baby walker users compared to nonusers [12,14,15], others did not reveal differences between these groups [7,9,10,16,17]. To date, the effect of this device on the kinematics of infant’s gait
have not been investigated. Therefore, lack of sound empirical evidence about the effects of the baby walker on toddlers’ patterns of locomotion leads health professionals to base clinical recommendations on their own beliefs and/or on untested clinical assumptions. A typical argument against the baby walker is that it delays independent walking onset and changes toddlers’ movement pattern [2,12–16,18]. Generally, the expected negative effects are attributed to the practicing of specific postures and movements in the baby walker that are not seen in normal independent walking. Specifically, in order to move around while sitting in a baby walker, infants often shift their trunk forward, place their feet in a plantar flexed position (i.e., tip toes) [15,16], and modify leg alignment.
f
The assumption is that walking practice with such altered patterns will not create the
oo
necessary conditions for the emergence of a typical pattern once the child starts walking independently.
The many assumptions about the immediate and longitudinal effects of the baby
pr
walker are not properly supported by the available literature. The effects of the baby walker on infant’s gait performance should be, thus, empirically evaluated. Revealing
e-
such effects will shed light on the impact of the baby walker use on the child’s motor development and will help the decision-making process regarding its use. Therefore, this
Pr
study aimed to investigate whether the use of the baby walker prior to gait onset modifies the age of acquisition of this milestone and affects early walking kinematics.
2.1. Study Design
al
2. Method
ur n
This observational longitudinal study consisted of seven repeated measurements conducted from the onset of independent walking followed by successive monthly measurements up to six months after gait acquisition. The University’s Ethics Review
Jo
Committee approved this study (ETIC 609/07).
2.2. Recruitment At routine 6-9 months well-child visit in private and public outpatient clinics,
parents were asked about their opinion regarding the baby walker. Pediatricians provided information about this study to the parents and details of a contact person in case they demonstrated interest in participating. Upon contact, parents received detailed information about this study and were invited to participate. Parents who accepted the invitation signed written informed consent agreeing to their child’s participation. Parents
decided whether or not their children would use the baby walker with no influence from the researchers.
2.3. Participants Thirty-two typically developing infants participated in this study: 16 in the baby walker user group (BWG) and 16 in the baby walker non-user group (BWNG). Participants in the BWG and BWNG groups were matched as closely as possible by sex and family socioeconomic status. Sample size was determined based on a study that documented moderate effect size (f=0.5-0.6) on age of gait acquisition and motor
f
development scores [14]. The estimated sample size (=0.05; 80% power) for an effect
oo
of 0.5 (the smallest expected effect) was 13 per group [19]. We recruited a sample 20%
greater than the estimated in order to deal with potential loss during the follow-up. Inclusion criteria were: at-term birth with no complications, normal birth weight
pr
(>2500g), and gross motor development above the 10th percentile on the Alberta Infant Motor Scale– AIMS [20,21], administered between 8-10 months post-term. Participants
e-
could neither be making use of systematic medication nor have visual/auditory problems. Groups did not differ on age of inclusion in the study (BWNG=29945.6 days;
Pr
BWG=284.829.9 days; p=0.29), total AIMS raw score (BWNG=43.806.61; BWG=42.736.81; p=0.70), body weight (BWNG=10.041.00 kg; BWG=10.071.45 kg; p=0.96) and height (BWNG=75.502.58 cm; BWG=75.553.01 cm; p=0.96). Groups
al
also had similar sex distribution (BWG=7 females and 9 males; BWNG=8 females and 8
ur n
males).
2.4. Procedures
At enrollment, all participants received one home visit from the first author, who administered the AIMS and identified their motor development percentile. We provided
Jo
parents of infants in the BWG a daily log booklet and asked them to register the time their infant spent using the baby walker. After the first visit, we called parents weekly to determine whether their infant had begun to walk independently, which was defined as the moment the child was able to walk five steps unsupported [20,22]. First measurement of the outcomes was performed on the week of gait acquisition followed by monthly measurements until six months after gait acquisition.
2.5. Measurement of the Study Outcomes The motion analysis system Qualisys ProReflex MCU (QUALISYS MEDICAL AB®, Gothenburg, Switzerland) was used to evaluate gait kinematics. Kinematic data was collected from toddlers’ right lower limb at a sample rate of 120 Hz and analyzed using the Visual 3D software (C-Motion, Inc., Rockville, USA). A standard kinematic model of the pelvis and right lower limb was created, assuming pelvis, thigh, shank and foot as rigid bodies with individual three-dimensional coordinate systems embedded. To create this model, reflective markers were fixed on the following anatomical landmarks: the apex of the iliac crests, great trochanters, femoral epicondyles (medial and lateral), ankle
f
malleoli (medial and lateral), and the 1st and 5th metatarsal joints (Figure 1). Clustered
oo
tracking markers were fixed on the pelvis, thigh and shank. The tracking markers used
for the foot were placed on the metatarsal joints and on the posterior aspect of the calcaneus.
pr
Toddlers walked on a four-meter walkway three to 12 times, with no help or support, accompanied by an assistant to guarantee safety. The mother was positioned at
e-
the end of the walkway to stimulate the toddler’s independent walking. Data collection lasted up to 20 minutes. For data analysis, a minimum of three regular and stable gait
Pr
cycles (i.e., cycles during which the toddler walked on a straight-line path with no change in speed) were selected from each assessment session. Gait cycle definition procedure is
al
described elsewhere [23].
ur n
Insert_Figure_1
Raw data were filtered using a lowpass, fourth order Butterworth filter with a cutoff frequency of 6Hz [24]. Pelvis, hip, knee and ankle angles were calculated using the following Cardan rotation sequence: flexion/extension, adduction/abduction, longitudinal
Jo
rotation. Angles of hip, knee, and ankle were computed by taking the orientation of thigh, leg, and foot with respect to their proximal segments [25]. Pelvis angles were calculated with respect to the laboratory coordinate system. The amplitude of joint angular displacements in the sagittal plane and the amplitude of hip and pelvis in the frontal plane were extracted. Furthermore, the following spatial and temporal gait parameters were extracted: cycle length, duration of stance, and duration of swing phases. These parameters were calculated based on the initial contact and toe-off events determined by a single trained examiner based on displacement plots of the foot markers in the anterior-
posterior direction. The initial contact was defined as the time when any foot marker stopped moving in the anterior-posterior direction (i.e. the marker touches the ground) and toe-off, as the time when the markers on the anterior part of the foot (i.e. 1st and 5th metatarsal head markers) started to have a continuous forward motion. The examiner had excellent intra-rater reliability (intraclass correlation coefficient–ICC3,10.996) on the definition of gait events demonstrated by the results of a pilot study in which ten gait cycles were analyzed on two occasions separated by one week. In addition, gait velocity was calculated as the pelvis velocity relative to the laboratory, in the anterior-posterior
f
direction.
oo
2.6. Statistical analysis
The assumptions of normality and homogeneity of variance were checked and confirmed prior to the inferential tests. An independent t-test compared the age of gait
pr
acquisition between groups. A mixed analysis of variance (ANOVA) with one independent factor (BWG and BWNG groups) and one repeated measure factor (seven
e-
longitudinal assessments) tested the effects of group, moment of assessment, and the group moment of assessment interaction effect on the amplitude of joints and spatial
Pr
and temporal parameters. A type I error probability of 0.05 was considered for all the analyses.
al
3. Results
The BWG spent 44.0029.40 min/day on the baby walker. Age of gait acquisition
ur n
was not different between the BWG (373.125.0 days) and the BWNG (384.326.7 days, p=0.23). Table 1 shows descriptive statistics of the spatial and temporal gait parameters and the p values of the inferential statistics. The BWG had lower gait velocity [F(1,29)=8.77,p2=0.23], and longer duration of stance [F(1,29)=8.67,p2=0.23] and
Jo
swing phases [F(1,29)=5.89,p2=0.17] compared to BWNG. Groups did not differ with respect to cycle length. Overall, both groups had an increase in cycle length [F(4.24,122.90)=38.21, p2=0.57] and gait velocity [F(4.02,116.46)=20.67, p2=0.42] throughout measurements. Both groups showed an increase in the duration of stance phase in each measurement session compared to the one at gait acquisition [F(2.43,70.54)=9.20, p2=0.24]. The groups did not change the duration of swing phase throughout
the
study.
There
was
an
interaction
effect
for
gait
velocity
[F(4.02,116.46)=2.71, p2=0.09] (Figure 2A). The BWG had lower gait velocity than BWNG only at the first [t(30)=2.56, d=0.91], third [t(30)=2.12, d=0.75], fourth [t(30)=2.06, d=0.73] and fifth [t(30)=2.15, d=0.76] months after gait acquisition. There was no interaction between factors for cycle length and duration of the stance and swing phases.
Insert_Table_1
Descriptive statistics of joint amplitudes in the sagittal and frontal planes and p
f
values from inferential statistics are presented in Table 2 and 3. The BWG showed smaller
oo
knee amplitude in the sagittal plane than the BWNG [F(1,29)=4.38,p2=0.13]. No other differences in the amplitude of joint motion were observed. Despite the within subjects factor
difference
for
ankle
[F(4.64,134.45)=2.68,p2=0.09]
and
hip
pr
[F(3.62,105.02)=3.13,p2=0.10] amplitudes in sagittal plane, there was no difference in the pairwise comparison between measurements at the post-hoc analysis. Hip amplitude
e-
in the frontal plane changed across measurements [F(3.98,115.35)=5.20,p2=0.15]. Post hoc analysis showed that it reduced in the fourth and sixth months after gait acquisition
Pr
compared to the measurement at gait acquisition. There was no difference among measurements for the amplitude of other joints in sagittal and frontal planes. An interaction effect was found for hip amplitude in the sagittal plane [F(228.66,70.55)=2.24,
al
p2=0.10] (Figure 2B). The BWG presented greater hip amplitude in the sagittal plane than BWNG at gait acquisition [t(26.76)=-2.26, d=0.80]. There was no interaction
Insert_Tables_2_and_3
Jo
ur n
between factors for other joints in sagittal and frontal planes.
4. Discussion
This study tested if the use of the baby walker prior to gait acquisition affected
the age at which infants begin to walk independently and their pattern of walking from gait onset up to six months thereafter. Despite the absence of difference on the age of gait acquisition, there were differences of walking kinematics between toddlers who used the baby walker from those who did not. The group who used the baby walker had lower gait velocity, greater duration of both stance and swing phases, and reduced knee amplitude
in sagittal plane. Furthermore, this group showed greater hip amplitude in the sagittal plane at gait acquisition. To date, this is the first systematic longitudinal study to assess these effects in infants with typical development. The use of the baby walker did not change the age of gait acquisition. Both groups developed gait around 12 months, as expected for typically developing children [20,23]. The absence of difference between groups corroborates the findings reported by the majority of studies investigating this outcome [10,12,16–18,26,27], but it is contrary to others [13–15]. In addition, our results do not confirm the clinical assumption that the use of the baby walker delays the acquisition of independent gait, nor does it support the
f
belief of parents who expected that the use of this device could accelerate the emergence
oo
and development of gait [8,10].
The lack of between-group differences could be attributed to the duration of walker use by our sample (less than one hour per day), registered according to parents'
pr
reports. Compared to what has been reported in the literature our participants had a relative short period of daily use [10,12,17,26]. This duration was similar to another study
e-
conducted in Brazil [26], possibly informing about the frequency of use of this device in this country. The short period of daily use may be related to recent guidelines from
Pr
professional organizations against baby walker [1,3-6]. Consistent warnings about the risk of baby walkers have been ingrained in the culture and, thus, may have changed infants’ current experiences from that of previous cohorts whose parents did not receive these warnings. That is, even parents who did not explicitly follow such guidelines might
al
be affected by the warnings of risk (albeit unconsciously) and restrict their child’s daily
ur n
use of walkers. Given that past studies reported that the use of the baby walker for more than two hours a day may delay the age of gait acquisition [12–15], our findings might be cohort specific. Thus, our results should not be generalized to infants who use baby walker for longer periods. Future studies should, however, investigate the dose-response
Jo
relationship of baby walker use with the risk of gait acquisition delay. Toddlers who used the baby walker had lower gait velocity (especially at the first,
third and fourth months after gait acquisition) and greater duration of both stance and swing phases than toddlers who did not use this device. Notably, the two groups did not differ in cycle length, indicating that the reduced gait velocity of toddlers who used the baby walker was a product of reduced stride frequency. This result could be interpreted in light of biomechanical models of walking dynamics. Fonseca et al. [28] for instance modeled gait using an inverted pendulum with springs system, whose oscillation is
maintained by a periodically applied force. According to this model, stride frequency is (a) directly proportional to the stiffness of the spring (equivalent to composite stiffness of leg soft tissues); and (b) inversely proportional to the length of the pendulum (equivalent to the effective length of the stance leg). The observed reduction of knee amplitude in toddlers who used baby walker implicates an overall longer dynamic length of the leg during the stance phase. Thus, the inverted pendulum model would predict the reduction in gait frequency observed in these children. Interestingly, the knee amplitude in the sagittal plane of the BWG (67.7º9.3º, 95%CI 63.1º-72.3º) is closer to the amplitude observed in adults (60º to 65º) [29,30] than that observed for the BWNG (71.7º6.8º,
f
95%CI 68.4º-75.0º). The implication is that the reduced gait frequency (and thus velocity)
oo
is grounded in kinematic change that signals a more mature gait and, thus, do not likely
represent an adverse effect of baby walker use. However, further studies should examine the long-term effect of the baby walker on gait speed to substantiate this claim.
pr
Higher hip amplitude in the sagittal plane at gait acquisition was observed in toddlers who used a baby walker. In fact, children that used a baby walker showed a hip
e-
range of motion in the sagittal plane that would only be expected one month later in the development of gait (Figure 2). To walk with this device, the toddler leans his/her trunk
Pr
forward aiming to propel his body. This would require greater hip amplitude in the sagittal plane to exploit these dynamics. Also, the typical design of the baby walker allows more hip motion in the sagittal plane than in the other planes. Thus, toddlers who used a baby
al
walker ended up learning a gait pattern typical of an inverted pendulum. This interpretation is reinforced by the findings of smaller knee amplitude previously
ur n
discussed. It seems that toddlers who used the baby walker transferred the typical baby walker dynamics to their freely chosen gait pattern after gait acquisition. Meanwhile, this effect was not observed in toddlers who did not use a baby walker. It must be noted that the observed group difference in hip amplitude in the sagittal plane disappeared in the
Jo
first months following gait acquisition. This fact highlights the high adaptability of the musculoskeletal system and suggests that the initially observed groups' differences tended to disappear after a few months of practice and that the baby walker may not have longterm effects. Both groups demonstrated changes in kinematics throughout longitudinal measurements. The results showed that both groups increased cycle length, gait velocity, and duration of stance and swing phases as expected in the development of gait [22,31]. In addition, both groups showed smaller hip amplitude in the frontal plane at the fourth
and sixth months compared with the evaluation at gait acquisition. This may demonstrate a more stable gait due to less side-to-side oscillation, which may also be related to a decrease in the base of support [31]. As expected, both groups demonstrated modifications in their gait pattern due to the development of gait. The present study tested the common clinical assumption that the use of a baby walker can harm gait development. The results demonstrated that there is no delay in the age of gait acquisition, but there are differences in children’s kinematics. These differences are not suggestive of a pathologic pattern. Instead, our findings suggest that toddlers developed gait patterns that are appropriate for the experiences they were
oo
f
exposed to during the period prior to its acquisition.
Funding sources: This work was supported by the following Brazilian agencies: National Council for Scientific and Technological Development (CNPq; Process:
pr
306948/2014-1), Research Support Foundation from the State of Minas Gerais (FAPEMIG; CDS-APQ-00704-15), Coordination of Higher Education Improvement
e-
(CAPES; Finance code 001, PROEX).
Pr
Conflict of interest: None declared.
al
Acknowledgements:
The authors are grateful to all families that agreed to the participation of their child and
ur n
the following research assistants: Brena Pinho, Emmanuelle Rodrigues, Isabella Nascimento, Karolina Albuquerque, Paula Simões and Priscilla Figueiredo. This study
Jo
was funded by the Brazilian agencies CNPq, FAPEMIG and CAPES.
References
[1]
L. Al-Nouri, S. Al-Isami, Baby walker injuries, Ann. Trop. Paediatr. 26 (2006) 67–71. doi:10.1179/146532806X90637.
[2]
P. Burrows, P. Griffiths, Do baby walkers delay onset of walking in young children?, Br. J. Community Nurs. 7 (2002) 581–586. doi:10.12968/bjcn.2002.7.11.10889.
[3]
D. Kendrick, R. Illingworth, A. Woods, K. Watts, J. Collier, M. Dewey, R. Hapgood, C.-M. Chen, Promoting child safety in primary care: a cluster
f
randomised controlled trial to reduce baby walker use., Br. J. Gen. Pract. 55
oo
(2005) 582–8.
http://www.ncbi.nlm.nih.gov/pubmed/16105365%5Cnhttp://www.pubmedcentral .nih.gov/articlerender.fcgi?artid=PMC1463224.
R. Rehmani, Baby walkers - friend or foe, J. Pak. Med. Assoc. 60 (2010) 891–
pr
[4]
892.
O.C. Cassell, M. Hubble, M.A. Milling, W.A. Dickson, Baby walkers--still a
e-
[5]
major cause of infant burns., Burns. 23 (1997) 451–3. doi:10.1007/BF01957011. L.E. Fazen, P.I. Felizberto, Baby walker injuries., Pediatrics. 70 (1982) 106–9.
Pr
[6]
http://www.ncbi.nlm.nih.gov/pubmed/7088607. [7]
D.G. Dogan, M. Bilici, A.E. Yilmaz, F. Catal, N. Keles, Baby walkers: A
al
perspective from Turkey, Acta Paediatr. Int. J. Paediatr. 98 (2009) 1656–1660. doi:10.1111/j.1651-2227.2009.01397.x. M.E. Bar-on, R.M. Boyle, E.K. Endriss, Parental decisions to use infant walkers,
ur n
[8]
Inj. Prev. 4 (1998) 299–300. doi:10.1136/ip.4.4.299. [9]
P.S. Chagas, M.C. Mancini, M.G. Tirado, L. Megale, R.F. Sampaio, Beliefs about the use of baby walkers, Rev Bras Fisioter. 15 (2011) 303–309.
Jo
doi:10.1590/S1413-35552011005000015.
[10] F. Shiva, F. Ghotbi, S.F. Yavari, The use of baby walkers in Iranian infants., Singapore Med. J. 51 (2010) 645–9. http://www.ncbi.nlm.nih.gov/pubmed/20848062. [11] D. DiLillo, A. Damashek, L. Peterson, Maternal use of baby walkers with young children: Recent trends and possible alternatives, Inj. Prev. 7 (2001) 223–227. doi:10.1136/ip.7.3.223. [12] M. Crouchman, The effects of babywalkers on early locomotor development.,
Dev. Med. Child Neurol. 28 (1986) 757–61. http://www.ncbi.nlm.nih.gov/pubmed/3817314. [13] M. Garrett, A.M. McElroy, A. Staines, Locomotor milestones and babywalkers: cross sectional study., BMJ. 324 (2002) 1494. doi:10.1136/bmj.325.7365.657/a. [14] A.C. Siegel, R. V Burton, Effects of baby walkers on motor and mental development in human infants., J. Dev. Behav. Pediatr. 20 (1999) 355–61. doi:10.1097/00004703-199910000-00010. [15] R.H.H. Engelbert, R. Van Empelen, N.D. Scheurer, P.J.M. Helders, O. Van Nieuwenhuizen, Influence of infant-walkers on motor development: Mimicking
f
spastic diplegia?, Eur. J. Paediatr. Neurol. 3 (1999) 273–275. doi:10.1016/S1090-
oo
3798(99)90982-0.
[16] I.B. Kauffman, M. Ridenour, Influence of an infant walker on onset and quality of walking pattern of locomotion:an electromyographic investigation, Percept.
pr
Mot. Skills. 45 (1977) 1323–1329. doi:10.2466/pms.1977.45.3f.1323.
[17] M. V Ridenour, Infant walkers: developmental tool or inherent danger, Percept.
e-
Mot. Skills. 55 (1982) 1201–1202.
[18] S. Badihian, N. Adihian, O. Yaghini, The Effect of Baby Walker on Child
Pr
Development: A Systematic Review., Iran. J. Child Neurol. 11 (2017) 1–6. doi:10.1056/NEJMra1313875.
[19] J. Cohen, Statistical power analysis for the behavioral sciences, 2nd ed.,
al
Lawrence Erbaum Associates, Hillsdale, N.J., 1988. [20] M.C. Piper, J. Darrah, Motor assessment of the developing infant, Saunders,
ur n
Philadelphia, 1994.
[21] J. Darrah, M. Piper, M.J. Watt, Assessment of gross motor skills of at-risk infants: predictive validity of the Alberta Infant Motor Scale., Dev. Med. Child Neurol. 40 (1998) 485–91. doi:10.1111/j.1469-8749.1998.tb15399.x.
Jo
[22] B. Bril, Y. Breniere, Posture and independent locomotion in early childhood: learning to walk or learning dynamic postural control?, in: G.J.P. Savelsbergh (Ed.), Dev. Coord. Infancy, North Holland, Amsterdam, 1993: pp. 337–358.
[23] P.S.C. Chagas, M.C. Mancini, S.T. Fonseca, T.B.C. Soares, V.P.D. Gomes, R.F. Sampaio, Neuromuscular mechanisms and anthropometric modifications in the initial stages of independent gait, Gait Posture. 24 (2006) 375–381. doi:10.1016/j.gaitpost.2005.11.005. [24] D.A. Winter, Kinematics, in: D.A. Winter (Ed.), Biomech. Mot. Control Hum.
Mov., 4th ed., John Wiley & Sons, Inc., Hoboken, NJ, USA, 2009: pp. 45–81. doi:10.1002/9780470549148.ch3. [25] G. Wu, P.R. Cavanagh, ISB recommendations for standardization in the reporting of kinematic data., J. Biomech. 28 (1995) 1257–61. http://www.ncbi.nlm.nih.gov/pubmed/8550644. [26] C. Iwabe, S.C. Olmos, B.M. Granço, Influência do andador infantil no desenvolvimento motor de crianças a partir dos 10 meses de idade, Temas Sobre Desenvolv. 97 (2009) 28–31. http://pepsic.bvsalud.org/pdf/rbcdh/v25n2/pt_04.pdf.
f
[27] M. Mete, G. Keskindemirci, G. Gokçay. Baby walker use and child development.
oo
Int J Pediatr Res (2019) 5(1):051-6. doi: 10.23937/2469-5769/1510051
pr
[28] S.T. Fonseca, K.G. Holt, E. Saltzman, L. Fetters, A dynamical model of
locomotion in spastic hemiplegic cerebral palsy: influence of walking speed.,
e-
Clin. Biomech. (Bristol, Avon). 16 (2001) 793–805. http://www.ncbi.nlm.nih.gov/pubmed/11714557.
[29] P. A. Houglum, D.B. Bertoti. Stance and Gait. In: P. A. Houglum, D.B. Bertoti.
Pr
(Org.). Brunnstrom´s Clinical Kinesiology. 6th. Ed. Philadelphia, PA: F. A. Davis Company, 2012. pp. 535–592.
[30] G. G. Simoneau. Kinesiology of Walking. In: D. A. Neumann (Org.).
al
Kinesiology of the Musculoskeletal System - Foundations for Physical Rehabilitation. New York: Mosby, 2002. pp. 523–569.
ur n
[31] A. Hallemans, D. De Clercq, P. Aerts, Changes in 3D joint dynamics during the first 5 months after the onset of independent walking: A longitudinal follow-up
Jo
study, Gait Posture. 24 (2006) 270–279. doi:10.1016/j.gaitpost.2005.10.003.
B
f
A
Jo
ur n
al
Pr
e-
pr
oo
Figure 1: A) Toddler with reflective markers on anatomical landmarks; B) Toddler walking independently during data collection
A
Gait velocity
Velocity (m/s)
1.05 0.04*
0.049*
0.90 0.11
0.75
0.08
0.04*
0.02*
0.60 0.45
0.90
0.30 2nd
BWG
5th
6th
pr
BWNG
3rd 4th Months
f
1st
oo
Acq
B
e-
Hip Amplitude in Sagittal Plane 50.0
0.26
0.14
0.35
0.22
3rd 4th Months
5th
6th
0.63
Pr
45.0 0.03*
40.0 35.0
al
Amplitude (º)
0.77
30.0
Jo
ur n
Acq
1st
2nd
BWNG
BWG
Figure 2: A) Plot showing the gait velocity through measurements for each group; B) Plot showing the hip amplitude in sagittal plane through measurements for each group. Both plots: The value just superior to the circle marker represents the p value of the pairwise comparison in each measurement. *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition.
of
Jo u
rn a
lP
re
-p
ro
Table 1 – Spatial and temporal gait parameters: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups 0.33 0.15 Acq 0.31 (0.11) 0.32 (0.10) <0.01* 0.12 (0.09) 0.39 <0.01 1st 0.42 (0.08) 0.40 (0.07) * (0.06) 0.46 <0.01 2nd 0.43 (0.07) 0.44 (0.07) 0.08 * (0.07) 0.44 <0.01 <0.01 3rd 0.49 (0.07) 0.46 (0.07) 1.00 * * Cycle (0.07) length (m) 0.47 <0.01 <0.01 4th 0.52 (0.09) 0.49 (0.08) 0.18 1.00 * * (0.07) 0.50 <0.01 <0.01 0.001 5th 0.54 (0.07) 0.52 (0.07) 0.03* 1.00 * * * (0.08) 0.52 <0.01 <0.01 <0.01 <0.01 6th 0.57 (0.08) 0.54 (0.08) 0.06 1.00 * * * * (0.08) Mean 0.44 0.47 (0.11) 0.45 (0.10) (SD) (0.09) 0.42 0.006* Acq 0.41 (0.15) 0.42 (0.14) <0.01* 0.03* (0.14) Gait 0.52 <0.01 1st 0.63 (0.14) 0.58 (0.14) * velocity (0.12) (m/s) 0.70 <0.01 2nd 0.62 (0.13) 0.66 (0.16) 0.06 * (0.17) 3rd 0.62 0.78 (0.21) 0.69 (0.20) <0.01 0.005 1.00
Acq 1st 2nd Duration of stance phase (s)
3rd 4th 5th
Jo u
6th
Mean (SD)
Duration of swing phase (s)
Acq 1st
2nd
0.73 (0.26) 0.61 (0.26) 0.42 (0.05)
0.87 (0.28) 0.68 (0.25) 0.59 (0.21)
0.45 (0.08) 0.41 (0.09) 0.40 (0.09) 0.37 (0.08) 0.38 (0.10) 0.44 (0.14) 0.25 (0.03) 0.25 (0.02)
of
1.00
1.00
<0.01
<0.01
*
*
0.03*
0.53
<0.01
<0.01 *
0.01*
0.046
*
ro
0.96 (0.26)
0.81 (0.23)
-p
Mean (SD)
0.91 (0.21)
0.006*
*
0.04*
*
re
6th
<0.01
0.84 (0.28) 0.74 (0.27)
*
1.00 0.83
1.00
<0.01*
0.11 0.03*
0.47 (0.08)
lP
5th
*
rn a
4th
(0.16) 0.65 (0.23) 0.72 (0.21) 0.77 (0.28) 0.63 (0.22) 0.57 (0.16) 0.51 (0.08) 0.42 (0.06) 0.48 (0.07) 0.48 (0.10) 0.47 (0.09) 0.46 (0.12) 0.48 (0.11) 0.26 (0.04) 0.27 (0.02) 0.26
0.44 (0.07)
0.01*
0.29
0.44 (0.08)
0.02*
1.00
1.00
0.44 (0.11)
0.04*
1.00
1.00
1.00
0.42 (0.10)
0.01*
0.31
1.00
1.00
1.00
0.42 (0.11)
0.02*
1.00
1.00
1.00
1.00
1.00
0.46 (0.13) 0.26 (0.03)
0.02*
0.36
0.37
0.26 (0.02)
1.00
0.27 (0.02) 0.27 (0.02)
1.00
1.00
of
Jo u
rn a
lP
re
-p
ro
(0.02) 0.28 0.25 (0.02) 1.00 1.00 1.00 3rd 0.27 (0.03) (0.03) 0.28 0.26 (0.03) 1.00 1.00 1.00 1.00 4th 0.27 (0.03) (0.04) 0.27 0.25 (0.01) 1.00 1.00 1.00 1.00 1.00 5th 0.26 (0.03) (0.03) 0.28 0.26 (0.03) 1.00 1.00 1.00 1.00 1.00 1.00 6th 0.27 (0.03) (0.04) Mean 0.27 0.26 (0.02) 0.26 (0.03) (SD) (0.03) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation
of
Jo u
rn a
lP
re
-p
ro
Table 2 – Joint range of motion in the sagittal plane: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups Acq 22.0 (4.6) 21.2 (4.6) 21.6 (4.5) 0.56 0.02* 0.08 1st 21.1 (3.8) 20.4 (5.1) 20.7 (4.4) 1.00 2nd 22.0 (4.4) 21.6 (3.5) 21.8 (4.0) 1.00 1.00 3rd 21.7 (3.0) 22.2 (3.3) 22.0 (3.1) 1.00 1.00 1.00 Ankle (º) 4th 21.4 (2.9) 23.7 (4.5) 22.5 (3.9) 1.00 0.49 1.00 1.00 5th 24.1 (4.8) 23.7 (4.7) 23.9 (4.7) 0.33 0.12 0.72 0.90 1.00 6th 20.6 (3.2) 24.1 (4.5) 22.3 (4.2) 1.00 1.00 1.00 1.00 1.00 0.84 Mean 21.8 (3.9) 22.3 (4.3) 22.1 (4.1) (SD) 65.9 0.045* Acq 68.1 (11.6) 66.9 (11.7) 0.17 0.54 (12.0) 1st 68.2 (8.7) 70.6 (6.9) 69.4 (7.9) 1.00 2nd 68.3 (6.9) 70.6 (5.5) 69.4 (6.3) 1.00 1.00 66.7 1.00 1.00 1.00 3rd 73.2 (5.7) 69.9 (9.3) Knee (º) (10.9) 4th 66.6 (9.8) 73.4 (4.0) 69.4 (8.0) 1.00 1.00 1.00 1.00 5th 70.5 (8.4) 73.6 (5.9) 72.0 (7.4) 0.88 1.00 0.76 1.00 0.47 6th 67.8 (8.7) 74.4 (4.8) 71.0 (7.8) 1.00 1.00 1.00 1.00 1.00 1.00 Mean 67.7 (9.3) 71.7 (6.8) 69.7 (8.4) (SD) Acq 43.2 (9.6) 34.9 (13.5) 39.2 (12.2) 0.99 0.02* 0.02* Hip (º) 1st 44.4 (5.6) 44.8 (8.4) 44.6 (7.0) 0.21 2nd 45.7 (7.5) 42.8 (6.0) 44.3 (6.8) 0.56 1.00
of
Jo u
rn a
lP
re
-p
ro
3rd 43.4 (7.2) 45.3 (5.5) 44.3 (6.4) 0.42 1.00 1.00 4th 41.5 (5.8) 44.7 (6.0) 43.0 (6.0) 1.00 1.00 1.00 1.00 5th 43.1 (8.3) 45.9 (4.7) 44.5 (6.8) 0.34 1.00 1.00 1.00 1.00 6th 43.7 (4.9) 46.4 (5.8) 45.0 (5.4) 0.48 1.00 1.00 1.00 1.00 1.00 Mean 43.6 (7.0) 43.2 (8.5) 43.4 (7.8) (SD) Acq 7.9 (1.7) 8.1 (1.5) 8.0 (1.6) 0.28 0.09 0.32 1st 7.0 (1.6) 7.5 (1.2) 7.2 (1.4) 0.69 2nd 8.3 (1.7) 7.6 (1.5) 8.0 (1.6) 1.00 0.63 3rd 7.8 (1.6) 7.7 (2.0) 7.8 (1.8) 1.00 1.00 1.00 Pelvis (º) 4th 7.7 (1.4) 8.1 (2.0) 7.9 (1.7) 1.00 1.00 1.00 1.00 5th 7.7 (2.4) 8.7 (1.4) 8.2 (2.0) 1.00 0.51 1.00 1.00 1.00 6th 7.9 (1.0) 9.0 (1.8) 8.5 (1.5) 1.00 0.04 1.00 1.00 1.00 1.00 Mean 7.8 (1.7) 8.1 (1.7) 7.9 (1.7) (SD) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation
of
Jo u
rn a
lP
re
-p
ro
Table 3 – Joint range of motion in the frontal plane: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups Acq 21.5 (5.3) 20.6 (4.4) 21.1 (4.8) 0.68 <0.01* 0.23 1st 19.9 (3.7) 21.0 (5.9) 20.5 (4.8) 1.00 2nd 21.1 (2.9 17.1 (4.5) 19.2 (4.2) 1.00 1.00 3rd 18.5 (4.5) 19.1 (6.4) 18.8 (5.4) 1.00 1.00 1.00 Hip (º) 4th 16.6 (3.6|) 17.1 (4.0) 16.9 (3.7) 0.02* 0.10 0.35 1.00 5th 17.2 (4.8) 17.1 (4.8) 17.2 (4.7) 0.18 0.22 1.00 1.00 1.00 6th 17.3 (3.1) 17.6 (3.6) 17.4 (3.3) 0.02* 0.08 0.40 1.00 1.00 1.00 Mean 18.9 (4.4) 18.5 (4.9) 18.7 (4.6) (SD) Acq 0.06 (0.01) 0.07 (0.02) 0.06 (0.02) 0.80 0.96 0.06 1st 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 0.64 2nd 0.06 (0.02) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 3rd 0.07 (0.02) 0.05 (0.01) 0.06 (0.02) 1.00 1.00 1.00 Pelvis (º) 4th 0.06 (0.01) 0.06 (0.02) 0.06 (0.02) 1.00 1.00 1.00 1.00 5th 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 1.00 1.00 1.00 6th 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 1.00 1.00 1.00 1.00 Mean 0.06 (0.02) 0.06 (0.01) 0.06 (0.01) (SD) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation
PII:
S0966-6362(19)31782-5
DOI:
https://doi.org/10.1016/j.gaitpost.2019.12.013
Reference:
GAIPOS 7408
To appear in:
Gait & Posture
Received Date:
16 February 2019
Revised Date:
22 November 2019
Accepted Date:
6 December 2019
Please cite this article as: Chagas PSC, Fonseca ST, Santos TRT, Souza TR, Megale L, Silva PL, Mancini MC, Effects of baby walker use on the development of gait by typically developing toddlers, Gait and amp; Posture (2019), doi: https://doi.org/10.1016/j.gaitpost.2019.12.013
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier.
Effects of baby walker use on the development of gait by typically developing toddlers Paula SC Chagasa, Sergio T Fonsecab, Thiago RT Santosb Thales R Souzab, Luiz Megalec, Paula L Silvad, Marisa C Mancinie,* a
Department of Physical Therapy of the Adult, Elderly and Maternal-infant, Faculty of
Physical Therapy, Universidade Federal de Juiz de Fora (UFJF), Juiz de Fora, MG, Brazil b
Department of Physical Therapy, Universidade Federal de Minas Gerais State (UFMG),
Belo Horizonte, MG, Brazil Department of Pediatrics, Universidade Federal de Minas Gerais State (UFMG), Belo
f
c
d
oo
Horizonte, MG, Brazil
Center for Cognition, Action, and Perception, Department of Psychology, University of
Cincinnati (UC), Cincinnati, OH, United States. e
pr
Department of Occupational Therapy, Universidade Federal de Minas Gerais State
e-
(UFMG), Belo Horizonte, MG, Brazil *
Corresponding Author: Marisa Cotta Mancini, Graduate Program in Rehabilitation
Pr
Sciences, Escola de Educação Física, Fisioterapia e Terapia Ocupacional, Universidade Federal de Minas Gerais, CEP: 31270-901, Belo Horizonte – MG, BRASIL, Fone: 55 31
al
3409-4781. e-mail: [email protected]
ur n
Number of words: 2985
Highlights:
There is no delay in the age of gait acquisition in toddlers who used baby walker.
Toddlers who used baby walker had slower gait than those who did not use it.
Toddlers who used baby walker had smaller knee amplitude in the sagittal plane.
Differences tended to disappear after a few months of practice.
Jo
ABSTRACT
Background: Decisions about the use of baby walker are in part predicated on caregivers´ beliefs about its effect on gait development. The actual effects of baby walkers, however, have not been established. Research question: What are the effects of the use of baby
walker prior to gait onset on age of acquisition of this milestone and on early walking kinematics? Methods: Thirty-two toddlers, 16 in the baby walker group (BWG) and 16 in the non-users group (BWNG), were evaluated in the week of gait acquisition and monthly up to six months after this event. Spatial and temporal gait parameters and lower limb kinematics during walking were assessed using a tridimensional motion analysis system. An independent t-test compared age of gait acquisition between groups. A mixed ANOVA examined the effects of group, moment of assessment and the group x moment of assessment interaction effect on the amplitude of joint motions during walking and on spatial and temporal gait parameters. Results: The age of gait acquisition was not different
f
between groups. BWG had lower gait speed (specifically in the first, third, fourth, and
oo
fifth months after gait acquisition) and longer duration of stance and swing phases than
BWNG. Additionally, BWG had smaller knee amplitude and greater hip amplitude in sagittal plane than BWNG in the week of gait acquisition. Significance: The results
pr
demonstrated that there is no delay in the age of gait acquisition, but there are differences in kinematics. These results can contribute to evidence-based recommendations by health
e-
care professionals about the use of baby walker by toddlers during emergence and early
Pr
development of gait.
Keywords: gait, kinematics, toddlers, infants, baby walker, infant walker.
al
1. Introduction
Baby walkers are popular among parents despite frequent warnings against its use
ur n
during the period between independent sitting and gait acquisition [1–6]. Studies that investigated parental decisions on the use of a baby walker revealed that they believe it accelerates gait acquisition [7–10] and helps strengthen their infants’ legs [7,9]. In addition, parents believe that the baby walker entertains the infant [7–10]. Although the
Jo
use of a baby walker is associated with risks such as infant falls [1,3–6], the majority of parents choose to provide this experience to their children [7,9–11]. Studies that evaluated the effects of the baby walker use on the age of gait
acquisition and on children’s motor development do not provide conclusive evidence about its benefit or harm [7,9,10,12,13]. While some studies reported delays on gait acquisition [13] and late onset of other motor developmental milestones in baby walker users compared to nonusers [12,14,15], others did not reveal differences between these groups [7,9,10,16,17]. To date, the effect of this device on the kinematics of infant’s gait
have not been investigated. Therefore, lack of sound empirical evidence about the effects of the baby walker on toddlers’ patterns of locomotion leads health professionals to base clinical recommendations on their own beliefs and/or on untested clinical assumptions. A typical argument against the baby walker is that it delays independent walking onset and changes toddlers’ movement pattern [2,12–16,18]. Generally, the expected negative effects are attributed to the practicing of specific postures and movements in the baby walker that are not seen in normal independent walking. Specifically, in order to move around while sitting in a baby walker, infants often shift their trunk forward, place their feet in a plantar flexed position (i.e., tip toes) [15,16], and modify leg alignment.
f
The assumption is that walking practice with such altered patterns will not create the
oo
necessary conditions for the emergence of a typical pattern once the child starts walking independently.
The many assumptions about the immediate and longitudinal effects of the baby
pr
walker are not properly supported by the available literature. The effects of the baby walker on infant’s gait performance should be, thus, empirically evaluated. Revealing
e-
such effects will shed light on the impact of the baby walker use on the child’s motor development and will help the decision-making process regarding its use. Therefore, this
Pr
study aimed to investigate whether the use of the baby walker prior to gait onset modifies the age of acquisition of this milestone and affects early walking kinematics.
2.1. Study Design
al
2. Method
ur n
This observational longitudinal study consisted of seven repeated measurements conducted from the onset of independent walking followed by successive monthly measurements up to six months after gait acquisition. The University’s Ethics Review
Jo
Committee approved this study (ETIC 609/07).
2.2. Recruitment At routine 6-9 months well-child visit in private and public outpatient clinics,
parents were asked about their opinion regarding the baby walker. Pediatricians provided information about this study to the parents and details of a contact person in case they demonstrated interest in participating. Upon contact, parents received detailed information about this study and were invited to participate. Parents who accepted the invitation signed written informed consent agreeing to their child’s participation. Parents
decided whether or not their children would use the baby walker with no influence from the researchers.
2.3. Participants Thirty-two typically developing infants participated in this study: 16 in the baby walker user group (BWG) and 16 in the baby walker non-user group (BWNG). Participants in the BWG and BWNG groups were matched as closely as possible by sex and family socioeconomic status. Sample size was determined based on a study that documented moderate effect size (f=0.5-0.6) on age of gait acquisition and motor
f
development scores [14]. The estimated sample size (=0.05; 80% power) for an effect
oo
of 0.5 (the smallest expected effect) was 13 per group [19]. We recruited a sample 20%
greater than the estimated in order to deal with potential loss during the follow-up. Inclusion criteria were: at-term birth with no complications, normal birth weight
pr
(>2500g), and gross motor development above the 10th percentile on the Alberta Infant Motor Scale– AIMS [20,21], administered between 8-10 months post-term. Participants
e-
could neither be making use of systematic medication nor have visual/auditory problems. Groups did not differ on age of inclusion in the study (BWNG=29945.6 days;
Pr
BWG=284.829.9 days; p=0.29), total AIMS raw score (BWNG=43.806.61; BWG=42.736.81; p=0.70), body weight (BWNG=10.041.00 kg; BWG=10.071.45 kg; p=0.96) and height (BWNG=75.502.58 cm; BWG=75.553.01 cm; p=0.96). Groups
al
also had similar sex distribution (BWG=7 females and 9 males; BWNG=8 females and 8
ur n
males).
2.4. Procedures
At enrollment, all participants received one home visit from the first author, who administered the AIMS and identified their motor development percentile. We provided
Jo
parents of infants in the BWG a daily log booklet and asked them to register the time their infant spent using the baby walker. After the first visit, we called parents weekly to determine whether their infant had begun to walk independently, which was defined as the moment the child was able to walk five steps unsupported [20,22]. First measurement of the outcomes was performed on the week of gait acquisition followed by monthly measurements until six months after gait acquisition.
2.5. Measurement of the Study Outcomes The motion analysis system Qualisys ProReflex MCU (QUALISYS MEDICAL AB®, Gothenburg, Switzerland) was used to evaluate gait kinematics. Kinematic data was collected from toddlers’ right lower limb at a sample rate of 120 Hz and analyzed using the Visual 3D software (C-Motion, Inc., Rockville, USA). A standard kinematic model of the pelvis and right lower limb was created, assuming pelvis, thigh, shank and foot as rigid bodies with individual three-dimensional coordinate systems embedded. To create this model, reflective markers were fixed on the following anatomical landmarks: the apex of the iliac crests, great trochanters, femoral epicondyles (medial and lateral), ankle
f
malleoli (medial and lateral), and the 1st and 5th metatarsal joints (Figure 1). Clustered
oo
tracking markers were fixed on the pelvis, thigh and shank. The tracking markers used
for the foot were placed on the metatarsal joints and on the posterior aspect of the calcaneus.
pr
Toddlers walked on a four-meter walkway three to 12 times, with no help or support, accompanied by an assistant to guarantee safety. The mother was positioned at
e-
the end of the walkway to stimulate the toddler’s independent walking. Data collection lasted up to 20 minutes. For data analysis, a minimum of three regular and stable gait
Pr
cycles (i.e., cycles during which the toddler walked on a straight-line path with no change in speed) were selected from each assessment session. Gait cycle definition procedure is
al
described elsewhere [23].
ur n
Insert_Figure_1
Raw data were filtered using a lowpass, fourth order Butterworth filter with a cutoff frequency of 6Hz [24]. Pelvis, hip, knee and ankle angles were calculated using the following Cardan rotation sequence: flexion/extension, adduction/abduction, longitudinal
Jo
rotation. Angles of hip, knee, and ankle were computed by taking the orientation of thigh, leg, and foot with respect to their proximal segments [25]. Pelvis angles were calculated with respect to the laboratory coordinate system. The amplitude of joint angular displacements in the sagittal plane and the amplitude of hip and pelvis in the frontal plane were extracted. Furthermore, the following spatial and temporal gait parameters were extracted: cycle length, duration of stance, and duration of swing phases. These parameters were calculated based on the initial contact and toe-off events determined by a single trained examiner based on displacement plots of the foot markers in the anterior-
posterior direction. The initial contact was defined as the time when any foot marker stopped moving in the anterior-posterior direction (i.e. the marker touches the ground) and toe-off, as the time when the markers on the anterior part of the foot (i.e. 1st and 5th metatarsal head markers) started to have a continuous forward motion. The examiner had excellent intra-rater reliability (intraclass correlation coefficient–ICC3,10.996) on the definition of gait events demonstrated by the results of a pilot study in which ten gait cycles were analyzed on two occasions separated by one week. In addition, gait velocity was calculated as the pelvis velocity relative to the laboratory, in the anterior-posterior
f
direction.
oo
2.6. Statistical analysis
The assumptions of normality and homogeneity of variance were checked and confirmed prior to the inferential tests. An independent t-test compared the age of gait
pr
acquisition between groups. A mixed analysis of variance (ANOVA) with one independent factor (BWG and BWNG groups) and one repeated measure factor (seven
e-
longitudinal assessments) tested the effects of group, moment of assessment, and the group moment of assessment interaction effect on the amplitude of joints and spatial
Pr
and temporal parameters. A type I error probability of 0.05 was considered for all the analyses.
al
3. Results
The BWG spent 44.0029.40 min/day on the baby walker. Age of gait acquisition
ur n
was not different between the BWG (373.125.0 days) and the BWNG (384.326.7 days, p=0.23). Table 1 shows descriptive statistics of the spatial and temporal gait parameters and the p values of the inferential statistics. The BWG had lower gait velocity [F(1,29)=8.77,p2=0.23], and longer duration of stance [F(1,29)=8.67,p2=0.23] and
Jo
swing phases [F(1,29)=5.89,p2=0.17] compared to BWNG. Groups did not differ with respect to cycle length. Overall, both groups had an increase in cycle length [F(4.24,122.90)=38.21, p2=0.57] and gait velocity [F(4.02,116.46)=20.67, p2=0.42] throughout measurements. Both groups showed an increase in the duration of stance phase in each measurement session compared to the one at gait acquisition [F(2.43,70.54)=9.20, p2=0.24]. The groups did not change the duration of swing phase throughout
the
study.
There
was
an
interaction
effect
for
gait
velocity
[F(4.02,116.46)=2.71, p2=0.09] (Figure 2A). The BWG had lower gait velocity than BWNG only at the first [t(30)=2.56, d=0.91], third [t(30)=2.12, d=0.75], fourth [t(30)=2.06, d=0.73] and fifth [t(30)=2.15, d=0.76] months after gait acquisition. There was no interaction between factors for cycle length and duration of the stance and swing phases.
Insert_Table_1
Descriptive statistics of joint amplitudes in the sagittal and frontal planes and p
f
values from inferential statistics are presented in Table 2 and 3. The BWG showed smaller
oo
knee amplitude in the sagittal plane than the BWNG [F(1,29)=4.38,p2=0.13]. No other differences in the amplitude of joint motion were observed. Despite the within subjects factor
difference
for
ankle
[F(4.64,134.45)=2.68,p2=0.09]
and
hip
pr
[F(3.62,105.02)=3.13,p2=0.10] amplitudes in sagittal plane, there was no difference in the pairwise comparison between measurements at the post-hoc analysis. Hip amplitude
e-
in the frontal plane changed across measurements [F(3.98,115.35)=5.20,p2=0.15]. Post hoc analysis showed that it reduced in the fourth and sixth months after gait acquisition
Pr
compared to the measurement at gait acquisition. There was no difference among measurements for the amplitude of other joints in sagittal and frontal planes. An interaction effect was found for hip amplitude in the sagittal plane [F(228.66,70.55)=2.24,
al
p2=0.10] (Figure 2B). The BWG presented greater hip amplitude in the sagittal plane than BWNG at gait acquisition [t(26.76)=-2.26, d=0.80]. There was no interaction
Insert_Tables_2_and_3
Jo
ur n
between factors for other joints in sagittal and frontal planes.
4. Discussion
This study tested if the use of the baby walker prior to gait acquisition affected
the age at which infants begin to walk independently and their pattern of walking from gait onset up to six months thereafter. Despite the absence of difference on the age of gait acquisition, there were differences of walking kinematics between toddlers who used the baby walker from those who did not. The group who used the baby walker had lower gait velocity, greater duration of both stance and swing phases, and reduced knee amplitude
in sagittal plane. Furthermore, this group showed greater hip amplitude in the sagittal plane at gait acquisition. To date, this is the first systematic longitudinal study to assess these effects in infants with typical development. The use of the baby walker did not change the age of gait acquisition. Both groups developed gait around 12 months, as expected for typically developing children [20,23]. The absence of difference between groups corroborates the findings reported by the majority of studies investigating this outcome [10,12,16–18,26,27], but it is contrary to others [13–15]. In addition, our results do not confirm the clinical assumption that the use of the baby walker delays the acquisition of independent gait, nor does it support the
f
belief of parents who expected that the use of this device could accelerate the emergence
oo
and development of gait [8,10].
The lack of between-group differences could be attributed to the duration of walker use by our sample (less than one hour per day), registered according to parents'
pr
reports. Compared to what has been reported in the literature our participants had a relative short period of daily use [10,12,17,26]. This duration was similar to another study
e-
conducted in Brazil [26], possibly informing about the frequency of use of this device in this country. The short period of daily use may be related to recent guidelines from
Pr
professional organizations against baby walker [1,3-6]. Consistent warnings about the risk of baby walkers have been ingrained in the culture and, thus, may have changed infants’ current experiences from that of previous cohorts whose parents did not receive these warnings. That is, even parents who did not explicitly follow such guidelines might
al
be affected by the warnings of risk (albeit unconsciously) and restrict their child’s daily
ur n
use of walkers. Given that past studies reported that the use of the baby walker for more than two hours a day may delay the age of gait acquisition [12–15], our findings might be cohort specific. Thus, our results should not be generalized to infants who use baby walker for longer periods. Future studies should, however, investigate the dose-response
Jo
relationship of baby walker use with the risk of gait acquisition delay. Toddlers who used the baby walker had lower gait velocity (especially at the first,
third and fourth months after gait acquisition) and greater duration of both stance and swing phases than toddlers who did not use this device. Notably, the two groups did not differ in cycle length, indicating that the reduced gait velocity of toddlers who used the baby walker was a product of reduced stride frequency. This result could be interpreted in light of biomechanical models of walking dynamics. Fonseca et al. [28] for instance modeled gait using an inverted pendulum with springs system, whose oscillation is
maintained by a periodically applied force. According to this model, stride frequency is (a) directly proportional to the stiffness of the spring (equivalent to composite stiffness of leg soft tissues); and (b) inversely proportional to the length of the pendulum (equivalent to the effective length of the stance leg). The observed reduction of knee amplitude in toddlers who used baby walker implicates an overall longer dynamic length of the leg during the stance phase. Thus, the inverted pendulum model would predict the reduction in gait frequency observed in these children. Interestingly, the knee amplitude in the sagittal plane of the BWG (67.7º9.3º, 95%CI 63.1º-72.3º) is closer to the amplitude observed in adults (60º to 65º) [29,30] than that observed for the BWNG (71.7º6.8º,
f
95%CI 68.4º-75.0º). The implication is that the reduced gait frequency (and thus velocity)
oo
is grounded in kinematic change that signals a more mature gait and, thus, do not likely
represent an adverse effect of baby walker use. However, further studies should examine the long-term effect of the baby walker on gait speed to substantiate this claim.
pr
Higher hip amplitude in the sagittal plane at gait acquisition was observed in toddlers who used a baby walker. In fact, children that used a baby walker showed a hip
e-
range of motion in the sagittal plane that would only be expected one month later in the development of gait (Figure 2). To walk with this device, the toddler leans his/her trunk
Pr
forward aiming to propel his body. This would require greater hip amplitude in the sagittal plane to exploit these dynamics. Also, the typical design of the baby walker allows more hip motion in the sagittal plane than in the other planes. Thus, toddlers who used a baby
al
walker ended up learning a gait pattern typical of an inverted pendulum. This interpretation is reinforced by the findings of smaller knee amplitude previously
ur n
discussed. It seems that toddlers who used the baby walker transferred the typical baby walker dynamics to their freely chosen gait pattern after gait acquisition. Meanwhile, this effect was not observed in toddlers who did not use a baby walker. It must be noted that the observed group difference in hip amplitude in the sagittal plane disappeared in the
Jo
first months following gait acquisition. This fact highlights the high adaptability of the musculoskeletal system and suggests that the initially observed groups' differences tended to disappear after a few months of practice and that the baby walker may not have longterm effects. Both groups demonstrated changes in kinematics throughout longitudinal measurements. The results showed that both groups increased cycle length, gait velocity, and duration of stance and swing phases as expected in the development of gait [22,31]. In addition, both groups showed smaller hip amplitude in the frontal plane at the fourth
and sixth months compared with the evaluation at gait acquisition. This may demonstrate a more stable gait due to less side-to-side oscillation, which may also be related to a decrease in the base of support [31]. As expected, both groups demonstrated modifications in their gait pattern due to the development of gait. The present study tested the common clinical assumption that the use of a baby walker can harm gait development. The results demonstrated that there is no delay in the age of gait acquisition, but there are differences in children’s kinematics. These differences are not suggestive of a pathologic pattern. Instead, our findings suggest that toddlers developed gait patterns that are appropriate for the experiences they were
oo
f
exposed to during the period prior to its acquisition.
Funding sources: This work was supported by the following Brazilian agencies: National Council for Scientific and Technological Development (CNPq; Process:
pr
306948/2014-1), Research Support Foundation from the State of Minas Gerais (FAPEMIG; CDS-APQ-00704-15), Coordination of Higher Education Improvement
e-
(CAPES; Finance code 001, PROEX).
Pr
Conflict of interest: None declared.
al
Acknowledgements:
The authors are grateful to all families that agreed to the participation of their child and
ur n
the following research assistants: Brena Pinho, Emmanuelle Rodrigues, Isabella Nascimento, Karolina Albuquerque, Paula Simões and Priscilla Figueiredo. This study
Jo
was funded by the Brazilian agencies CNPq, FAPEMIG and CAPES.
References
[1]
L. Al-Nouri, S. Al-Isami, Baby walker injuries, Ann. Trop. Paediatr. 26 (2006) 67–71. doi:10.1179/146532806X90637.
[2]
P. Burrows, P. Griffiths, Do baby walkers delay onset of walking in young children?, Br. J. Community Nurs. 7 (2002) 581–586. doi:10.12968/bjcn.2002.7.11.10889.
[3]
D. Kendrick, R. Illingworth, A. Woods, K. Watts, J. Collier, M. Dewey, R. Hapgood, C.-M. Chen, Promoting child safety in primary care: a cluster
f
randomised controlled trial to reduce baby walker use., Br. J. Gen. Pract. 55
oo
(2005) 582–8.
http://www.ncbi.nlm.nih.gov/pubmed/16105365%5Cnhttp://www.pubmedcentral .nih.gov/articlerender.fcgi?artid=PMC1463224.
R. Rehmani, Baby walkers - friend or foe, J. Pak. Med. Assoc. 60 (2010) 891–
pr
[4]
892.
O.C. Cassell, M. Hubble, M.A. Milling, W.A. Dickson, Baby walkers--still a
e-
[5]
major cause of infant burns., Burns. 23 (1997) 451–3. doi:10.1007/BF01957011. L.E. Fazen, P.I. Felizberto, Baby walker injuries., Pediatrics. 70 (1982) 106–9.
Pr
[6]
http://www.ncbi.nlm.nih.gov/pubmed/7088607. [7]
D.G. Dogan, M. Bilici, A.E. Yilmaz, F. Catal, N. Keles, Baby walkers: A
al
perspective from Turkey, Acta Paediatr. Int. J. Paediatr. 98 (2009) 1656–1660. doi:10.1111/j.1651-2227.2009.01397.x. M.E. Bar-on, R.M. Boyle, E.K. Endriss, Parental decisions to use infant walkers,
ur n
[8]
Inj. Prev. 4 (1998) 299–300. doi:10.1136/ip.4.4.299. [9]
P.S. Chagas, M.C. Mancini, M.G. Tirado, L. Megale, R.F. Sampaio, Beliefs about the use of baby walkers, Rev Bras Fisioter. 15 (2011) 303–309.
Jo
doi:10.1590/S1413-35552011005000015.
[10] F. Shiva, F. Ghotbi, S.F. Yavari, The use of baby walkers in Iranian infants., Singapore Med. J. 51 (2010) 645–9. http://www.ncbi.nlm.nih.gov/pubmed/20848062. [11] D. DiLillo, A. Damashek, L. Peterson, Maternal use of baby walkers with young children: Recent trends and possible alternatives, Inj. Prev. 7 (2001) 223–227. doi:10.1136/ip.7.3.223. [12] M. Crouchman, The effects of babywalkers on early locomotor development.,
Dev. Med. Child Neurol. 28 (1986) 757–61. http://www.ncbi.nlm.nih.gov/pubmed/3817314. [13] M. Garrett, A.M. McElroy, A. Staines, Locomotor milestones and babywalkers: cross sectional study., BMJ. 324 (2002) 1494. doi:10.1136/bmj.325.7365.657/a. [14] A.C. Siegel, R. V Burton, Effects of baby walkers on motor and mental development in human infants., J. Dev. Behav. Pediatr. 20 (1999) 355–61. doi:10.1097/00004703-199910000-00010. [15] R.H.H. Engelbert, R. Van Empelen, N.D. Scheurer, P.J.M. Helders, O. Van Nieuwenhuizen, Influence of infant-walkers on motor development: Mimicking
f
spastic diplegia?, Eur. J. Paediatr. Neurol. 3 (1999) 273–275. doi:10.1016/S1090-
oo
3798(99)90982-0.
[16] I.B. Kauffman, M. Ridenour, Influence of an infant walker on onset and quality of walking pattern of locomotion:an electromyographic investigation, Percept.
pr
Mot. Skills. 45 (1977) 1323–1329. doi:10.2466/pms.1977.45.3f.1323.
[17] M. V Ridenour, Infant walkers: developmental tool or inherent danger, Percept.
e-
Mot. Skills. 55 (1982) 1201–1202.
[18] S. Badihian, N. Adihian, O. Yaghini, The Effect of Baby Walker on Child
Pr
Development: A Systematic Review., Iran. J. Child Neurol. 11 (2017) 1–6. doi:10.1056/NEJMra1313875.
[19] J. Cohen, Statistical power analysis for the behavioral sciences, 2nd ed.,
al
Lawrence Erbaum Associates, Hillsdale, N.J., 1988. [20] M.C. Piper, J. Darrah, Motor assessment of the developing infant, Saunders,
ur n
Philadelphia, 1994.
[21] J. Darrah, M. Piper, M.J. Watt, Assessment of gross motor skills of at-risk infants: predictive validity of the Alberta Infant Motor Scale., Dev. Med. Child Neurol. 40 (1998) 485–91. doi:10.1111/j.1469-8749.1998.tb15399.x.
Jo
[22] B. Bril, Y. Breniere, Posture and independent locomotion in early childhood: learning to walk or learning dynamic postural control?, in: G.J.P. Savelsbergh (Ed.), Dev. Coord. Infancy, North Holland, Amsterdam, 1993: pp. 337–358.
[23] P.S.C. Chagas, M.C. Mancini, S.T. Fonseca, T.B.C. Soares, V.P.D. Gomes, R.F. Sampaio, Neuromuscular mechanisms and anthropometric modifications in the initial stages of independent gait, Gait Posture. 24 (2006) 375–381. doi:10.1016/j.gaitpost.2005.11.005. [24] D.A. Winter, Kinematics, in: D.A. Winter (Ed.), Biomech. Mot. Control Hum.
Mov., 4th ed., John Wiley & Sons, Inc., Hoboken, NJ, USA, 2009: pp. 45–81. doi:10.1002/9780470549148.ch3. [25] G. Wu, P.R. Cavanagh, ISB recommendations for standardization in the reporting of kinematic data., J. Biomech. 28 (1995) 1257–61. http://www.ncbi.nlm.nih.gov/pubmed/8550644. [26] C. Iwabe, S.C. Olmos, B.M. Granço, Influência do andador infantil no desenvolvimento motor de crianças a partir dos 10 meses de idade, Temas Sobre Desenvolv. 97 (2009) 28–31. http://pepsic.bvsalud.org/pdf/rbcdh/v25n2/pt_04.pdf.
f
[27] M. Mete, G. Keskindemirci, G. Gokçay. Baby walker use and child development.
oo
Int J Pediatr Res (2019) 5(1):051-6. doi: 10.23937/2469-5769/1510051
pr
[28] S.T. Fonseca, K.G. Holt, E. Saltzman, L. Fetters, A dynamical model of
locomotion in spastic hemiplegic cerebral palsy: influence of walking speed.,
e-
Clin. Biomech. (Bristol, Avon). 16 (2001) 793–805. http://www.ncbi.nlm.nih.gov/pubmed/11714557.
[29] P. A. Houglum, D.B. Bertoti. Stance and Gait. In: P. A. Houglum, D.B. Bertoti.
Pr
(Org.). Brunnstrom´s Clinical Kinesiology. 6th. Ed. Philadelphia, PA: F. A. Davis Company, 2012. pp. 535–592.
[30] G. G. Simoneau. Kinesiology of Walking. In: D. A. Neumann (Org.).
al
Kinesiology of the Musculoskeletal System - Foundations for Physical Rehabilitation. New York: Mosby, 2002. pp. 523–569.
ur n
[31] A. Hallemans, D. De Clercq, P. Aerts, Changes in 3D joint dynamics during the first 5 months after the onset of independent walking: A longitudinal follow-up
Jo
study, Gait Posture. 24 (2006) 270–279. doi:10.1016/j.gaitpost.2005.10.003.
B
f
A
Jo
ur n
al
Pr
e-
pr
oo
Figure 1: A) Toddler with reflective markers on anatomical landmarks; B) Toddler walking independently during data collection
A
Gait velocity
Velocity (m/s)
1.05 0.04*
0.049*
0.90 0.11
0.75
0.08
0.04*
0.02*
0.60 0.45
0.90
0.30 2nd
BWG
5th
6th
pr
BWNG
3rd 4th Months
f
1st
oo
Acq
B
e-
Hip Amplitude in Sagittal Plane 50.0
0.26
0.14
0.35
0.22
3rd 4th Months
5th
6th
0.63
Pr
45.0 0.03*
40.0 35.0
al
Amplitude (º)
0.77
30.0
Jo
ur n
Acq
1st
2nd
BWNG
BWG
Figure 2: A) Plot showing the gait velocity through measurements for each group; B) Plot showing the hip amplitude in sagittal plane through measurements for each group. Both plots: The value just superior to the circle marker represents the p value of the pairwise comparison in each measurement. *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition.
of
Jo u
rn a
lP
re
-p
ro
Table 1 – Spatial and temporal gait parameters: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups 0.33 0.15 Acq 0.31 (0.11) 0.32 (0.10) <0.01* 0.12 (0.09) 0.39 <0.01 1st 0.42 (0.08) 0.40 (0.07) * (0.06) 0.46 <0.01 2nd 0.43 (0.07) 0.44 (0.07) 0.08 * (0.07) 0.44 <0.01 <0.01 3rd 0.49 (0.07) 0.46 (0.07) 1.00 * * Cycle (0.07) length (m) 0.47 <0.01 <0.01 4th 0.52 (0.09) 0.49 (0.08) 0.18 1.00 * * (0.07) 0.50 <0.01 <0.01 0.001 5th 0.54 (0.07) 0.52 (0.07) 0.03* 1.00 * * * (0.08) 0.52 <0.01 <0.01 <0.01 <0.01 6th 0.57 (0.08) 0.54 (0.08) 0.06 1.00 * * * * (0.08) Mean 0.44 0.47 (0.11) 0.45 (0.10) (SD) (0.09) 0.42 0.006* Acq 0.41 (0.15) 0.42 (0.14) <0.01* 0.03* (0.14) Gait 0.52 <0.01 1st 0.63 (0.14) 0.58 (0.14) * velocity (0.12) (m/s) 0.70 <0.01 2nd 0.62 (0.13) 0.66 (0.16) 0.06 * (0.17) 3rd 0.62 0.78 (0.21) 0.69 (0.20) <0.01 0.005 1.00
Acq 1st 2nd Duration of stance phase (s)
3rd 4th 5th
Jo u
6th
Mean (SD)
Duration of swing phase (s)
Acq 1st
2nd
0.73 (0.26) 0.61 (0.26) 0.42 (0.05)
0.87 (0.28) 0.68 (0.25) 0.59 (0.21)
0.45 (0.08) 0.41 (0.09) 0.40 (0.09) 0.37 (0.08) 0.38 (0.10) 0.44 (0.14) 0.25 (0.03) 0.25 (0.02)
of
1.00
1.00
<0.01
<0.01
*
*
0.03*
0.53
<0.01
<0.01 *
0.01*
0.046
*
ro
0.96 (0.26)
0.81 (0.23)
-p
Mean (SD)
0.91 (0.21)
0.006*
*
0.04*
*
re
6th
<0.01
0.84 (0.28) 0.74 (0.27)
*
1.00 0.83
1.00
<0.01*
0.11 0.03*
0.47 (0.08)
lP
5th
*
rn a
4th
(0.16) 0.65 (0.23) 0.72 (0.21) 0.77 (0.28) 0.63 (0.22) 0.57 (0.16) 0.51 (0.08) 0.42 (0.06) 0.48 (0.07) 0.48 (0.10) 0.47 (0.09) 0.46 (0.12) 0.48 (0.11) 0.26 (0.04) 0.27 (0.02) 0.26
0.44 (0.07)
0.01*
0.29
0.44 (0.08)
0.02*
1.00
1.00
0.44 (0.11)
0.04*
1.00
1.00
1.00
0.42 (0.10)
0.01*
0.31
1.00
1.00
1.00
0.42 (0.11)
0.02*
1.00
1.00
1.00
1.00
1.00
0.46 (0.13) 0.26 (0.03)
0.02*
0.36
0.37
0.26 (0.02)
1.00
0.27 (0.02) 0.27 (0.02)
1.00
1.00
of
Jo u
rn a
lP
re
-p
ro
(0.02) 0.28 0.25 (0.02) 1.00 1.00 1.00 3rd 0.27 (0.03) (0.03) 0.28 0.26 (0.03) 1.00 1.00 1.00 1.00 4th 0.27 (0.03) (0.04) 0.27 0.25 (0.01) 1.00 1.00 1.00 1.00 1.00 5th 0.26 (0.03) (0.03) 0.28 0.26 (0.03) 1.00 1.00 1.00 1.00 1.00 1.00 6th 0.27 (0.03) (0.04) Mean 0.27 0.26 (0.02) 0.26 (0.03) (SD) (0.03) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation
of
Jo u
rn a
lP
re
-p
ro
Table 2 – Joint range of motion in the sagittal plane: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups Acq 22.0 (4.6) 21.2 (4.6) 21.6 (4.5) 0.56 0.02* 0.08 1st 21.1 (3.8) 20.4 (5.1) 20.7 (4.4) 1.00 2nd 22.0 (4.4) 21.6 (3.5) 21.8 (4.0) 1.00 1.00 3rd 21.7 (3.0) 22.2 (3.3) 22.0 (3.1) 1.00 1.00 1.00 Ankle (º) 4th 21.4 (2.9) 23.7 (4.5) 22.5 (3.9) 1.00 0.49 1.00 1.00 5th 24.1 (4.8) 23.7 (4.7) 23.9 (4.7) 0.33 0.12 0.72 0.90 1.00 6th 20.6 (3.2) 24.1 (4.5) 22.3 (4.2) 1.00 1.00 1.00 1.00 1.00 0.84 Mean 21.8 (3.9) 22.3 (4.3) 22.1 (4.1) (SD) 65.9 0.045* Acq 68.1 (11.6) 66.9 (11.7) 0.17 0.54 (12.0) 1st 68.2 (8.7) 70.6 (6.9) 69.4 (7.9) 1.00 2nd 68.3 (6.9) 70.6 (5.5) 69.4 (6.3) 1.00 1.00 66.7 1.00 1.00 1.00 3rd 73.2 (5.7) 69.9 (9.3) Knee (º) (10.9) 4th 66.6 (9.8) 73.4 (4.0) 69.4 (8.0) 1.00 1.00 1.00 1.00 5th 70.5 (8.4) 73.6 (5.9) 72.0 (7.4) 0.88 1.00 0.76 1.00 0.47 6th 67.8 (8.7) 74.4 (4.8) 71.0 (7.8) 1.00 1.00 1.00 1.00 1.00 1.00 Mean 67.7 (9.3) 71.7 (6.8) 69.7 (8.4) (SD) Acq 43.2 (9.6) 34.9 (13.5) 39.2 (12.2) 0.99 0.02* 0.02* Hip (º) 1st 44.4 (5.6) 44.8 (8.4) 44.6 (7.0) 0.21 2nd 45.7 (7.5) 42.8 (6.0) 44.3 (6.8) 0.56 1.00
of
Jo u
rn a
lP
re
-p
ro
3rd 43.4 (7.2) 45.3 (5.5) 44.3 (6.4) 0.42 1.00 1.00 4th 41.5 (5.8) 44.7 (6.0) 43.0 (6.0) 1.00 1.00 1.00 1.00 5th 43.1 (8.3) 45.9 (4.7) 44.5 (6.8) 0.34 1.00 1.00 1.00 1.00 6th 43.7 (4.9) 46.4 (5.8) 45.0 (5.4) 0.48 1.00 1.00 1.00 1.00 1.00 Mean 43.6 (7.0) 43.2 (8.5) 43.4 (7.8) (SD) Acq 7.9 (1.7) 8.1 (1.5) 8.0 (1.6) 0.28 0.09 0.32 1st 7.0 (1.6) 7.5 (1.2) 7.2 (1.4) 0.69 2nd 8.3 (1.7) 7.6 (1.5) 8.0 (1.6) 1.00 0.63 3rd 7.8 (1.6) 7.7 (2.0) 7.8 (1.8) 1.00 1.00 1.00 Pelvis (º) 4th 7.7 (1.4) 8.1 (2.0) 7.9 (1.7) 1.00 1.00 1.00 1.00 5th 7.7 (2.4) 8.7 (1.4) 8.2 (2.0) 1.00 0.51 1.00 1.00 1.00 6th 7.9 (1.0) 9.0 (1.8) 8.5 (1.5) 1.00 0.04 1.00 1.00 1.00 1.00 Mean 7.8 (1.7) 8.1 (1.7) 7.9 (1.7) (SD) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation
of
Jo u
rn a
lP
re
-p
ro
Table 3 – Joint range of motion in the frontal plane: Descriptive statistics and p values of the mixed repeated measures ANOVAs and pairwise comparisons p Values Mean (SD) Post hoc for Within-Subjects Factora Between WithinVariable Month Interactio -Subjects Subject BWG BWNG Both n Effect 1st 2nd 3rd 4th 5th Factor s Factor Acq (N = 16) (N = 16) groups Acq 21.5 (5.3) 20.6 (4.4) 21.1 (4.8) 0.68 <0.01* 0.23 1st 19.9 (3.7) 21.0 (5.9) 20.5 (4.8) 1.00 2nd 21.1 (2.9 17.1 (4.5) 19.2 (4.2) 1.00 1.00 3rd 18.5 (4.5) 19.1 (6.4) 18.8 (5.4) 1.00 1.00 1.00 Hip (º) 4th 16.6 (3.6|) 17.1 (4.0) 16.9 (3.7) 0.02* 0.10 0.35 1.00 5th 17.2 (4.8) 17.1 (4.8) 17.2 (4.7) 0.18 0.22 1.00 1.00 1.00 6th 17.3 (3.1) 17.6 (3.6) 17.4 (3.3) 0.02* 0.08 0.40 1.00 1.00 1.00 Mean 18.9 (4.4) 18.5 (4.9) 18.7 (4.6) (SD) Acq 0.06 (0.01) 0.07 (0.02) 0.06 (0.02) 0.80 0.96 0.06 1st 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 0.64 2nd 0.06 (0.02) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 3rd 0.07 (0.02) 0.05 (0.01) 0.06 (0.02) 1.00 1.00 1.00 Pelvis (º) 4th 0.06 (0.01) 0.06 (0.02) 0.06 (0.02) 1.00 1.00 1.00 1.00 5th 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 1.00 1.00 1.00 6th 0.06 (0.01) 0.06 (0.01) 0.06 (0.01) 1.00 1.00 1.00 1.00 1.00 1.00 Mean 0.06 (0.02) 0.06 (0.01) 0.06 (0.01) (SD) Note: a = Pairwise comparisons were performed using Bonferroni adjustments for multiple comparisons; *= significant difference (i.e. p < 0.05); BWG = Baby walker users; BWNG = Baby walker non-users; Acq = Walking acquisition; SD = Standard deviation