- Email: [email protected]
The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait
Accepted Manuscript Title: The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait Authors: Kazunori Okamura, Shusaku Kanai, Masaki Hasegawa, Akira Otsuka, Sadaaki Oki PII: DOI: Reference:
S0958-2592(17)30086-X http://dx.doi.org/10.1016/j.foot.2017.08.002 YFOOT 1492
To appear in:
The Foot
Received date: Revised date: Accepted date:
11-5-2017 28-6-2017 13-8-2017
Please cite this article as: Okamura Kazunori, Kanai Shusaku, Hasegawa Masaki, Otsuka Akira, Oki Sadaaki.The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait.The Foot http://dx.doi.org/10.1016/j.foot.2017.08.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait
Kazunori Okamura a*, Shusaku Kanai b, Masaki Hasegawa b, Akira Otsuka c, Sadaaki Oki b.
a
Graduate School of Comprehensive Scientific Research, Prefectural University of
Hiroshima: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan b
Department of Physical Therapy, Faculty of Health and Welfare, Prefectural
University of Hiroshima: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan c
Hiroshima Cosmopolitan University: 3-2-1 Otsuka Higashi Asaminami-ku,
Hiroshima-shi, Hiroshima 731-3166, Japan
Corresponding author: Kazunori Okamura Complete address: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan E-mail address: [email protected]
1
Highlight (Brief Summary) What is already known ・ The plantar intrinsic foot muscles contribute to the support of the medial longitudinal arch. ・ The activities of the plantar intrinsic foot muscles increase with increasing gait velocity and ground reaction force. ・ The relationship between the hypofunction of the plantar intrinsic foot muscles and plantar fasciitis has been suggested.
What this study adds ・ The additional activation of the plantar intrinsic foot muscles during gait caused a delay in the timing for the navicular height to reach the minimum value, and a reduction of the vertical ground reaction force (2nd peak). ・ The plantar intrinsic foot muscles most likely contribute to shock absorption and facilitate efficient foot ground force transmission during gait. ・ The failure of these functions may be related to plantar fasciitis.
2
Abstract Background: The plantar intrinsic foot muscles (PIFMs) contribute to support the medial longitudinal arch. But the functional role of the PIFMs during dynamic activities is not clear. The purpose of this study was to examine the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to determine the functional role of the PIFMs during gait. Methods: Twenty healthy male subjects were randomly assigned to the electrical stimulation group (ESG) or control group (CG). In the ESG, the electrical stimulation to the PIFMs was provided from mid-stance to pre-swing using surface electrodes to simulate reinforcement of the PIFMs. The foot dynamics during the stance phase of gait was measured using a 3D motion analysis, and the amount of change from baseline (electrical stimulation was not provided) was compared between groups using an independent sample t-test. Results: In the ESG, the timing for the navicular height to reach the minimum value was significantly later, and the vertical ground reaction force (2nd peak) significantly decreased more. There were no group differences in the amount of change from baseline
3
on gait velocity, stance phase duration, minimum navicular height and ground reaction force in other directions. Conclusion: Results from this study showed that the functions of the PIFMs most likely include shock absorption and facilitation of efficient foot ground force transmission during the stance phase of gait.
Keywords: plantar intrinsic foot muscle; gait; electrical stimulation; 3D motion analysis; plantar fasciitis.
1. Introduction The plantar intrinsic foot muscles (PIFMs) contribute to the support of the medial longitudinal arch (MLA) [1,2], and the relationship between the hypofunction of the PIFMs and plantar fasciitis associated with a collapsing of the MLA [3,4] has been suggested. Previous computational modelling studies reported that an increase in tension in the PIFMs decreased the stress on the plantar fascia [5]. Moreover, using an MRI, Chang et al. [6] and Cheung et al. [7] confirmed that patients with plantar fasciitis had less volume in the PIFMs.
4
In human locomotion, the PIFMs are active during the phase from mid-stance to pre-swing [8]. Previous studies [9] showed that the activities of the three largest PIFMs, i.e., abductor hallucis (ABH), flexor digitorum brevis and quadratus plantae muscles, increased with increasing gait velocity and the associated increase in ground reaction force. Therefore, it has been considered that the PIFMs may have the capacity to contribute to shock absorption and propulsion power generation in the foot during locomotion [9], and the failure of these functions in the PIFMs may be related to plantar fasciitis. However, these functions of the PIFMs have been speculative, because no study has confirmed the change in the foot dynamics during in vivo locomotion accompanied with the change of the PIFMs activity. Understanding the functional role of the PIFMs during locomotion is important for the explanation of the relationship between the hypofunction of the PIFMs and plantar fasciitis. Furthermore, the selections of the target and effect evaluation methods of the PIFMs training, whose effects during locomotion have also been unclear [10-12], may be helpful. Kelly et al. [2] simulated the reinforcement of the PIFMs by using electrical stimulation to confirm the role of these muscles as MLA supporters in a static condition. Similar to this, in a previous experiment from our laboratory, the authors attempted to simulate reinforcement of the PIFMs during gait by electrical stimulation from surface
5
electrodes attached to the muscle belly of the ABH. Using this method, the reinforcement of the PIFMs during stance phase of gait could be simulated without an increase in the internal ankle inversion moment associated with an avoidance response from a sensation such as pain from electrical stimulation given through the surface electrodes on the medial aspect of the foot [13]. Therefore, the purpose of this study was to examine the effect of the reinforcement of the PIFMs simulated by electrical stimulation on foot dynamics during gait and to confirm the functional role of the PIFMs during gait. Our hypotheses were that the simulated reinforcement of the PIFMs would cause the changes in foot dynamics during gait associated with the enhanced functions of shock absorption and propulsion power generation.
2. Material and methods 2.1. Subjects Twenty healthy male subjects participated in this study. The exclusion criteria included a history of a lower extremity injury up to six months prior to participation and excessive pronation determined by the measurement of the navicular drop. Excessive pronation was defined as a navicular drop of > 10 mm, which is similar to the
6
definitions used in previous studies [14,15]. Moreover, subjects who had preexisting conditions such as seizures and demand pacemakers were also excluded, following the specification of the electrical stimulation device. Subjects were randomly allocated to one of two groups: electrical stimulation group (ESG) and control group (CG). After randomization, both groups included 10 subjects, respectively (CG: age = 20.5±1.6 years, height = 172.5±6.2cm, mass = 61.5±4.4kg, ESG: age = 21.2±1.2 years, height = 170.5±4.8cm. weight = 61.9±6.9kg). This study was approved by the Ethics Committee of the 〇〇〇 ( We concealed the name of institution to blind authors details. ), and written informed consent was obtained from all subjects.
2.2. Instruments In this study, the electrical stimulation to the PIFMs was performed using the WalkAide device (Innovative Neurotronics Inc, Austin, Texas). This is a functional electrical stimulation device to improve foot drop in conditions such as stroke [16] and cerebral palsy [17]. Moreover, because this device can control the timing of stimulation by pushing the hand switch, we could apply it to stimulate the PIFMs during the stance phase of gait.
7
The foot dynamics were measured using a VICON system (Oxford Metrics, UK). The VICON system comprised of 12 MX-T20S cameras running at 100 Hz and 6 force plates running at 1000 Hz (2 Kistler and 4 AMTI). Reflective markers (diameter: 9.5 mm and 14mm) were placed on the subjects with double-sided tape. The VICON NEXUS was used to visualize and process the 3D motions.
2.3. Electrical stimulation to the PIFMs The electrical stimulation (250µs pulse width, 20Hz frequency) to the PIFMs was provided from surface electrodes attached on the muscle belly of the ABH (Fig. 1). The ABH has the largest physiological cross-sectional area of the PIFMs and has been reported to contribute to supporting the MLA in static conditions [1,2]. Therefore, we decided to use the ABH as the main target of reinforcement. However, because we used surface electrodes, the target of reinforcement was not only the ABH but also other PIFMs, such as the flexor hallucis brevis. The timing of electrical stimulation was controlled using the hand switch by the same tester (KO). In gait trials, the phase from mid-stance to pre-swing, when the PIFMs are active in the normal gait pattern [8], was watched carefully by the tester to determine when to provide electrical stimulation. Moreover, the WalkAide device and the VICON system were synchronized at 1000Hz to
8
confirm the timing of electrical stimulation. Our previous experiment [13] confirmed that the tester (KO) could provide electrical stimulation at almost a corresponding timing with the phase from mid-stance to pre-swing. The stimulation intensity was determined to be the threshold that each subject could endure without feeling pain.
2.4. Data collection protocol First, the following characteristics were collected: weight, height, leg length, and pelvic, knee and ankle width. Then, the 16 markers (14mm) were placed on the pelvis and both lower extremities in accordance to the Plug-in-Gait lower model specifications, and the 13 markers (9.5mm) were attached to the right lower extremity, following the specifications of the Oxford Foot Model [18,19]. In addition to these, a marker was attached to the right navicular tuberosity and the WalkAide device was attached to the right lower extremity (Fig. 1). Then the calibration was performed with the subjects in an anatomical neutral position. Next, the medial malleolus and posterior calcaneus proximal markers were removed, according to the protocol of the Oxford Foot Model [18,19]. The marker of the distal 1st metatarsal recorded as one of the removable markers on the protocol was not removed, because this marker was necessary to calculate the MLA height. In this study, the MLA height during gait was represented by
9
the navicular height. The navicular height during gait was defined as the perpendicular distance of the navicular tuberosity marker above the plantar plane of the foot bisecting markers on the distal 1st metatarsal, distal 5th metatarsal, and heel. In our pilot study, the measures of the minimum navicular height and timing during the stance phase of gait were taken using this method for 2 sessions on 9 individuals during which the reflective markers were not removed between each session, and the average values of 5 trials revealed strong intra-tester reliabilities (ICC1,1 = 0.99 and 0.96, respectively) and precision of measurement (SEM = 0.5mm and 1.1% stance phase, respectively). Following these preparations, the baseline gait trials were conducted with 28 markers. All subjects were asked to walk on the 8m walkway at their preferred normal speed. Five gait trials were recorded. If the subjects did not clearly strike the force plate, an additional trial was recorded as a replacement. Then, the stimulation intensity was decided for each subject. The decision for stimulation intensity was done not only for the ESG but also for the CG. Then, to compare the simulated contractile force of the PIFMs with previous studies [2,12], a static standing trial was conducted. The subjects were required to place approximately 90% of their body weight on the right lower extremity and were allowed to stabilize their balance with a rod in the opposite hand and toe-touch contact to the floor with the opposite lower extremity [12]. After the force
10
plate data recorded that weight bearing on the right lower extremity was approximately 90% of body weight, a recording for 10 seconds was conducted. Only for the ESG, electrical stimulation to the PIFMs was provided for the last 5 seconds. Upon completion of a static standing trial, gait trials were conducted again. At this time, only for the ESG, electrical stimulation to the PIFMs was provided from mid-stance to pre-swing. Regardless whether electrical stimulation was provided or not, all gait trials in both groups were performed under the condition that the tester (KO) walked diagonally behind the subject to operate the hand switch (Fig. 2).
2.5. Statistical analysis In the gait trials, gait velocity and the following parameters during the right stance phase were selected for statistical analysis; stance phase duration, minimum navicular height, timing when the navicular height reached the minimum value, forefoot angle relative to the rear foot and rear foot angle relative to the tibia at that timing, internal ankle moment (plantar flexion, eversion, abduction) at that timing, and maximum ground reaction force (anterior, medial and vertical direction) in the second half of stance phase. All parameters in all 5 trials were averaged.
11
Only in the standing trials, to compare with previous studies [2,12], the navicular height not from plantar plane of the foot but from the floor was selected for statistical analysis. The navicular height from the floor of the intervals excluding the first and last second of the first and second half of the 10-second recordings, were averaged respectively. For the baseline value of all of the parameters and the amount of change from the baseline of all parameters, independent sample t-tests were conducted to evaluate the differences between the two groups. Differences were considered significant at the p < 0.05 level. All statistical tests were conducted using the SPSS 20.0 for Windows.
3. Results There were no statistically significant differences in the baseline values of all the parameters between the two groups (Table 1). In both groups, the timing when the navicular height reached the minimum value was equivalent to the phase of terminal stance, as noted in previous studies [20]. Table 2 represents the amount of change from baseline. In the gait analysis, regardless whether electrical stimulation to the PIFMs that was provided from 19.2±2.7% to
12
54.9±2.9% of the gait cycle was provided or not, gait velocity, right stance phase duration and minimum navicular height were consistent. Despite this, the timing when the navicular height reached the minimum value was significantly later in the ESG as compared to the CG. Moreover, at that timing, the significantly increased reduction of forefoot abduction (transverse plane) angle relative to the rear foot was seen in the ESG, but there were no significant differences in the changes of forefoot dorsiflexion (sagittal plane) and eversion (frontal plane) angles. In the ankle moment and ground reaction force data, only the maximum vertical ground reaction force (2nd peak) was significantly decreased more in the ESG. Figures 3 and 4 illustrate the changes in the navicular height, forefoot angle relative to the rear foot, and ground reaction force during the stance phase in the baseline of ESG, and indicated the point selected for statistical analysis. In the standing analysis, the increase from baseline in the navicular height from the floor was significantly larger in the ESG.
4. Discussion
13
This was the first in vivo study that examined the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to verify the functional role of the PIFMs during gait. The reinforcement of the PIFMs during the stance phase of gait caused a delay in the timing for the navicular height to reach the minimum value. Furthermore, in the second half of stance phase, although the maximum ground reaction forces of anterior and medial directions did not change, the maximum vertical ground reaction force was weaker in the ESG. These results showed the function of the PIFMs to be shock absorbers during late stance. This function could contribute to the reduction of the stress on the plantar fascia, because the stress on the plantar fascia reaches the maximum value during late stance as well [21]. This suggestion does not contradict previous computational modelling studies [5] that showed the reduction of the stress on the plantar fascia accompanied the increase of PIFMs tension in static states. Patients with plantar fasciitis have less volume in the PIFMs [6,7], and patients with pes planus, which is one of the risk factors for plantar fasciitis [3,4], have smaller cross sectional areas of the PIFMs as well [22]. Therefore, the hypofunction of the PIFMs as shock absorbers may be one of the etiologic factors for plantar fasciitis, and the training of the PIFMs should be performed not only to correct static foot alignment [11,12] but also to
14
recover this function. On the other hand, from the perspective of propulsion power generation, the results of this study suggest that the reinforcement of the PIFMs contributed to facilitate efficient foot ground force transmission, because the vertical ground reaction force peak weakened without a decrease in gait velocity and progression force. Interestingly, contrary to our expectations, the minimum navicular height during stance phase did not increase with the reinforcement of the PIFMs. Kelly et al. [2] reported that individual electrical stimulation of the PIFMs caused approximately a 5% increase in the navicular height under a load of 100% of the body weight. This indicates that the simulated additional contractile force in this study which caused approximately a 3% increase in the navicular height under a load of 90% body weight was weaker than that in the previous study [2]. Moreover, because the load exceeding body weight was given to the forefoot during late stance [21], the simulated additional contractile force in this study would be insufficient to increase the navicular height at that timing. Therefore, the possibility that a more powerful contractile force of the PIFMs may increase the minimum navicular height during stance phase still remains. This study had several limitations. The first limitation was that we could not confirm how much force was added to the contractile force of the PIFMs during gait. However,
15
because the reductions of the forefoot abduction angle associated with the contraction of the ABH [1,2] were shown in the ESG, we believe that there were some additional activations of the PIFMs. Furthermore, in the standing analysis, a 1.5mm increase in the navicular height was confirmed in ESG. This was similar to the change seen in a 4-week PIFMs training program [12]. Therefore, even in gait trials, the simulated additional contractile force would not exceed the physiological level. In addition, although the electrical stimulation in this study was provided at almost a corresponding timing with the phase from mid-stance to pre-swing when the PIFMs are active [8, 23], a previous study reported that the commencement timing of activity was slightly different among PIFMs [8]. Because we used surface electrodes, it was not possible to stimulate each PIFM at the most suitable timing. Therefore, further studies should be performed using a more physiological reinforcement method, such as, strength training. The results of this study may be helpful to such a further study, because the outcome to focus on is presented in this study. Finally, this study was limited to the evaluation during gait. Because plantar fasciitis is also common in runners [3,4] and the PIFMs activity increase with increasing gait velocity [9], future studies should be performed during running.
16
In conclusion, the reinforcement of the PIFMs simulated by electrical stimulation most likely caused the changes in foot dynamics during gait associated with the enhanced shock absorption and the facilitated efficient foot ground force transmission. This suggests that the function of the PIFMs as the shock absorber and propulsion power generator during gait and the failure of these functions may be related to plantar fasciitis.
References [1] Wong YS. Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study. Foot Ankle Int 2007;28:617-20. [2] Kelly LA, Cresswell AG, Racinais S, Whiteley R, Lichtwark G. Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch. J R Soc Interface 2014;11:20131188. [3] Pohl MB, Hamill J, Davis IS. Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners. Clin J Sport Med 2009;19:372-6. [4] Schwartz EN, Su J. Plantar fasciitis: a concise review. Perm J 2014;18:105-7.
17
[5] Wu L. Nonlinear finite element analysis for musculoskeletal biomechanics of medial and lateral plantar longitudinal arch of Virtual Chinese Human after plantar ligamentous structure failures. Clin Biomech (Bristol, Avon) 2007;22:221-9. [6] Chang R, Kent-Braun JA, Hamill J. Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs. Clin Biomech (Bristol, Avon) 2012;27:500-5. [7] Cheung RT, Sze LK, Mok NW, Ng GY. Intrinsic foot muscle volume in experienced runners with and without chronic plantar fasciitis. J Sci Med Sport 2016;19:713-5. [8] Mann R, Inman VT. Phasic activity of intrinsic muscles of the foot. J Bone Joint Surg Am 1964;46:469-81. [9] Kelly LA, Lichtwark G, Cresswell AG. Active regulation of longitudinal arch compression and recoil during walking and running. J R Soc Interface 2015;12:20141076. [10] Jung DY, Koh EK, Kwon OY. Effect of foot orthoses and short-foot exercise on the cross-sectional area of the abductor hallucis muscle in subjects with pes planus: a randomized controlled trial. J Back Musculoskelet Rehabil 2011;24:225-31.
18
[11] Lynn SK, Padilla RA, Tsang KK. Differences in static- and dynamic-balance task performance after 4 weeks of intrinsic-foot-muscle training: the short-foot exercise versus the towel-curl exercise. J Sport Rehabil 2012;21:327-33. [12] Mulligan EP, Cook PG. Effect of plantar intrinsic muscle training on medial longitudinal arch morphology and dynamic function. Man Ther 2013;18:425-30. [13] 〇〇〇 ( We concealed this reference to blind authors details. ) [14] Mueller MJ, Host JV, Norton BJ. Navicular drop as a composite measure of excessive pronation. J Am Podiatr Med Assoc 1993;83:198-202. [15] O'Sullivan K, Kennedy N, O'Neill E, Ni Mhainin U. The effect of low-dye taping on rearfoot motion and plantar pressure during the stance phase of gait. BMC Musculoskelet Disord 2008;9:111. [16] Morone G, Fusco A, Di Capua P, Coiro P, Pratesi L. Walking training with foot drop stimulator controlled by a tilt sensor to improve walking outcomes: a randomized controlled pilot study in patients with stroke in subacute phase. Stroke Res Treat 2012;2012:523564. [17] Damiano DL, Prosser LA, Curatalo LA, Alter KE. Muscle plasticity and ankle control after repetitive use of a functional electrical stimulation device for foot drop in cerebral palsy. Neurorehabil Neural Repair 2013;27:200-7.
19
[18] Carson MC, Harrington ME, Thompson N, O'Connor JJ, Theologis TN. Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis. J Biomech 2001;34:1299-307. [19] van Hoeve S, de Vos J, Weijers P, Verbruggen J, Willems P, Poeze M, et al. Repeatability of the oxford foot model for kinematic gait analysis of the foot and ankle. Clin Res Foot Ankle 2015;3:171. [20] Prachgosin T, Chong DY, Leelasamran W, Smithmaitrie P, Chatpun S. Medial longitudinal arch biomechanics evaluation during gait in subjects with flexible flatfoot. Acta Bioeng Biomech 2015;17:121-30. [21] Caravaggi P, Pataky T, Günther M, Savage R, Crompton R. Dynamics of longitudinal arch support in relation to walking speed: contribution of the plantar aponeurosis. J Anat 2010;217:254-61. [22] Angin S, Crofts G, Mickle KJ, Nester CJ. Ultrasound evaluation of foot muscles and plantar fascia in pes planus. Gait Posture 2014;40:48-52. [23] Gray EG, Basmajian JV. Electromyography and cinematography of leg and foot ("normal" and flat) during walking. Anat Rec 1968;161:1-15.
20
Hand switch The main unit of WalkAide
Fig. 1. WalkAide and marker placements.
Fig. 2. The gait trial. The tester walked diagonally behind the subject to operate the hand switch.
21
Fig. 3. The mean changes of the navicular height and forefoot angle relative to the rear foot during the stance phase in baseline for ESG. The dashed line indicates the timing when the navicular height reached the minimum value and the point where the forefoot angles were selected for statistical analysis. NH = navicular height from plantar plane, AB = abduction angle (transverse plane), DF = dorsiflexion angle (sagittal plane), EV = eversion angle (frontal plane).
Fig. 4. The mean changes of the ground reaction force during the stance phase in baseline for ESG.
The dashed line circles indicate the points selected for statistical analysis. BW = body weight.
22
CG (N = 10)
Variables
ESG (N = 10)
Mean Diff
95%CI
p
0.1
0.01
-0.1 to 0.1
0.85
42.1
-6.6
-44.2 to 31.0
0.72
18.9
4
4.8
-0.7 to 10.4
0.09
73.7
6.7
0.2
-5.8 to 6.2
0.95
Mean
SD
Mean
SD
1.3
0.1
1.3
635.2
37.8
641.8
Minimum value (mm)
23.7
7.4
Timing (% stance phase)
73.9
6.2
Gait Speed (m/s) Stance phase duration (ms) NH from plantar plane
Foot kinematics FF angle relative to RF (°)
RF angle relative to TB (°)
DF
5.1
5.6
4.7
4
0.3
-4.2 to 4.9
0.88
EV
-1.8
3.9
-3.1
3.5
1.3
-2.2 to 4.8
0.44
AB
4.3
6.3
8.4
3.8
-4.1
-8.9 to -0.8
0.10
DF
12.8
2.9
13.3
5.3
-0.6
-4.5 to 3.4
0.78
EV
-4.1
3.3
-3.9
4.4
-0.2
-3.9 to 3.4
0.90
AB
-19.2
10.2
-23.2
9.4
4.1
-5.1 to 13.3
0.37
PF
1407.5
146
1316.7
209.8
90.8
-79.0 to 206.5
0.28
EV
97.9
54.5
55.2
62.2
42.7
-12.2 to 97.6
0.12
AB
57.7
72.2
27.4
92.2
30.3
-47.5 to 108.2
0.42
Internal ankle moment (N・mm/kg)
Ground reaction force (% BW) Anterior direction
17.4
6.8
15.5
6.9
1.9
-4.5 to 8.3
0.55
Medial direction
7.4
0.8
7.5
1.6
-0.1
-1.3 to 1.2
0.92
Vertical direction
112.2
6.5
112.9
5.9
-0.7
-6.5 to 5.1
0.80
53.3
9.4
49.2
6.6
4.1
-3.6 to 11.7
0.28
Standing NH from floor (mm)
Table 1. The baseline value in each group. NH = navicular height, FF = forefoot, RF = rear foot, TB = tibia, DF = dorsiflexion, EV = eversion, AB = abduction, PF = plantarflexion, BW = body weight. 23
CG (N = 10)
Variables
ESG (N = 10)
Mean Diff
95%CI
p
0.08
0.05
-0.01 to 0.1
0.12
32.5
-9
-34.6 to 16.6
0.47
Mean
SD
Mean
SD
Speed (m/s)
0.02
0.06
-0.03
Stance phase duration (ms)
-4.2
20.8
4.8
Gait
NH from plantar plane Minimum value (mm)
-0.4
0.4
-0.5
1.1
0.1
-0.7 to 0.9
0.75
Timing (% stance phase)
0.1
3.2
3
1.6
-2.9
-5.3 to -0.5
0.02
Foot kinematics FF angle relative to RF (°)
RF angle relative to TB (°)
DF
0.09
0.5
0.2
0.8
-0.1
-0.7 to 0.5
0.71
EV
-0.2
0.5
-0.8
0.8
0.6
-0.03 to 1.2
0.06
AB
0.3
0.3
-0.9
0.7
1.1
0.6 to 1.6
0.0002
DF
-0.03
0.4
0.08
1
-0.1
-0.8 to 0.6
0.75
EV
0.2
0.6
-0.6
1.4
0.8
-0.2 to 1.9
0.12
AB
-0.3
1
-0.4
1.9
0.2
-1.3 to 1.6
0.81
PF
-33.6
73.9
-2.4
91.6
-31.2
-109.4 to 47.0
0.41
EV
9.1
29.5
34.7
42.7
-25.7
-60.2 to 8.9
0.14
AB
-11.5
33
18.5
77.7
-30
-88.1 to 28.2
0.28
Internal ankle moment (N・mm/kg)
Ground reaction force (% BW) Anterior direction
-0.9
4
-0.2
2.7
-0.6
-3.9 to 2.6
0.68
Medial direction
0.3
0.6
0.02
0.6
0.2
-0.3 to 0.8
0.39
Vertical direction
0.5
2.7
-2.2
2.2
2.7
0.4 to 5.0
0.03
0.04
0.4
1.6
1.9
-1.5
-2.9 to -0.1
0.04
Standing NH from floor (mm)
Table 2. The amount of change from baseline in each group. NH = navicular height, FF = forefoot, RF = rear foot, TB = tibia, DF = dorsiflexion, EV = eversion, AB = abduction, PF = plantarflexion, BW = body weight. 24
S0958-2592(17)30086-X http://dx.doi.org/10.1016/j.foot.2017.08.002 YFOOT 1492
To appear in:
The Foot
Received date: Revised date: Accepted date:
11-5-2017 28-6-2017 13-8-2017
Please cite this article as: Okamura Kazunori, Kanai Shusaku, Hasegawa Masaki, Otsuka Akira, Oki Sadaaki.The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait.The Foot http://dx.doi.org/10.1016/j.foot.2017.08.002 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. 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.
The effect of additional activation of the plantar intrinsic foot muscles on foot dynamics during gait
Kazunori Okamura a*, Shusaku Kanai b, Masaki Hasegawa b, Akira Otsuka c, Sadaaki Oki b.
a
Graduate School of Comprehensive Scientific Research, Prefectural University of
Hiroshima: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan b
Department of Physical Therapy, Faculty of Health and Welfare, Prefectural
University of Hiroshima: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan c
Hiroshima Cosmopolitan University: 3-2-1 Otsuka Higashi Asaminami-ku,
Hiroshima-shi, Hiroshima 731-3166, Japan
Corresponding author: Kazunori Okamura Complete address: 1-1 Gakuen-cho, Mihara-shi, Hiroshima 723-0053, Japan E-mail address: [email protected]
1
Highlight (Brief Summary) What is already known ・ The plantar intrinsic foot muscles contribute to the support of the medial longitudinal arch. ・ The activities of the plantar intrinsic foot muscles increase with increasing gait velocity and ground reaction force. ・ The relationship between the hypofunction of the plantar intrinsic foot muscles and plantar fasciitis has been suggested.
What this study adds ・ The additional activation of the plantar intrinsic foot muscles during gait caused a delay in the timing for the navicular height to reach the minimum value, and a reduction of the vertical ground reaction force (2nd peak). ・ The plantar intrinsic foot muscles most likely contribute to shock absorption and facilitate efficient foot ground force transmission during gait. ・ The failure of these functions may be related to plantar fasciitis.
2
Abstract Background: The plantar intrinsic foot muscles (PIFMs) contribute to support the medial longitudinal arch. But the functional role of the PIFMs during dynamic activities is not clear. The purpose of this study was to examine the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to determine the functional role of the PIFMs during gait. Methods: Twenty healthy male subjects were randomly assigned to the electrical stimulation group (ESG) or control group (CG). In the ESG, the electrical stimulation to the PIFMs was provided from mid-stance to pre-swing using surface electrodes to simulate reinforcement of the PIFMs. The foot dynamics during the stance phase of gait was measured using a 3D motion analysis, and the amount of change from baseline (electrical stimulation was not provided) was compared between groups using an independent sample t-test. Results: In the ESG, the timing for the navicular height to reach the minimum value was significantly later, and the vertical ground reaction force (2nd peak) significantly decreased more. There were no group differences in the amount of change from baseline
3
on gait velocity, stance phase duration, minimum navicular height and ground reaction force in other directions. Conclusion: Results from this study showed that the functions of the PIFMs most likely include shock absorption and facilitation of efficient foot ground force transmission during the stance phase of gait.
Keywords: plantar intrinsic foot muscle; gait; electrical stimulation; 3D motion analysis; plantar fasciitis.
1. Introduction The plantar intrinsic foot muscles (PIFMs) contribute to the support of the medial longitudinal arch (MLA) [1,2], and the relationship between the hypofunction of the PIFMs and plantar fasciitis associated with a collapsing of the MLA [3,4] has been suggested. Previous computational modelling studies reported that an increase in tension in the PIFMs decreased the stress on the plantar fascia [5]. Moreover, using an MRI, Chang et al. [6] and Cheung et al. [7] confirmed that patients with plantar fasciitis had less volume in the PIFMs.
4
In human locomotion, the PIFMs are active during the phase from mid-stance to pre-swing [8]. Previous studies [9] showed that the activities of the three largest PIFMs, i.e., abductor hallucis (ABH), flexor digitorum brevis and quadratus plantae muscles, increased with increasing gait velocity and the associated increase in ground reaction force. Therefore, it has been considered that the PIFMs may have the capacity to contribute to shock absorption and propulsion power generation in the foot during locomotion [9], and the failure of these functions in the PIFMs may be related to plantar fasciitis. However, these functions of the PIFMs have been speculative, because no study has confirmed the change in the foot dynamics during in vivo locomotion accompanied with the change of the PIFMs activity. Understanding the functional role of the PIFMs during locomotion is important for the explanation of the relationship between the hypofunction of the PIFMs and plantar fasciitis. Furthermore, the selections of the target and effect evaluation methods of the PIFMs training, whose effects during locomotion have also been unclear [10-12], may be helpful. Kelly et al. [2] simulated the reinforcement of the PIFMs by using electrical stimulation to confirm the role of these muscles as MLA supporters in a static condition. Similar to this, in a previous experiment from our laboratory, the authors attempted to simulate reinforcement of the PIFMs during gait by electrical stimulation from surface
5
electrodes attached to the muscle belly of the ABH. Using this method, the reinforcement of the PIFMs during stance phase of gait could be simulated without an increase in the internal ankle inversion moment associated with an avoidance response from a sensation such as pain from electrical stimulation given through the surface electrodes on the medial aspect of the foot [13]. Therefore, the purpose of this study was to examine the effect of the reinforcement of the PIFMs simulated by electrical stimulation on foot dynamics during gait and to confirm the functional role of the PIFMs during gait. Our hypotheses were that the simulated reinforcement of the PIFMs would cause the changes in foot dynamics during gait associated with the enhanced functions of shock absorption and propulsion power generation.
2. Material and methods 2.1. Subjects Twenty healthy male subjects participated in this study. The exclusion criteria included a history of a lower extremity injury up to six months prior to participation and excessive pronation determined by the measurement of the navicular drop. Excessive pronation was defined as a navicular drop of > 10 mm, which is similar to the
6
definitions used in previous studies [14,15]. Moreover, subjects who had preexisting conditions such as seizures and demand pacemakers were also excluded, following the specification of the electrical stimulation device. Subjects were randomly allocated to one of two groups: electrical stimulation group (ESG) and control group (CG). After randomization, both groups included 10 subjects, respectively (CG: age = 20.5±1.6 years, height = 172.5±6.2cm, mass = 61.5±4.4kg, ESG: age = 21.2±1.2 years, height = 170.5±4.8cm. weight = 61.9±6.9kg). This study was approved by the Ethics Committee of the 〇〇〇 ( We concealed the name of institution to blind authors details. ), and written informed consent was obtained from all subjects.
2.2. Instruments In this study, the electrical stimulation to the PIFMs was performed using the WalkAide device (Innovative Neurotronics Inc, Austin, Texas). This is a functional electrical stimulation device to improve foot drop in conditions such as stroke [16] and cerebral palsy [17]. Moreover, because this device can control the timing of stimulation by pushing the hand switch, we could apply it to stimulate the PIFMs during the stance phase of gait.
7
The foot dynamics were measured using a VICON system (Oxford Metrics, UK). The VICON system comprised of 12 MX-T20S cameras running at 100 Hz and 6 force plates running at 1000 Hz (2 Kistler and 4 AMTI). Reflective markers (diameter: 9.5 mm and 14mm) were placed on the subjects with double-sided tape. The VICON NEXUS was used to visualize and process the 3D motions.
2.3. Electrical stimulation to the PIFMs The electrical stimulation (250µs pulse width, 20Hz frequency) to the PIFMs was provided from surface electrodes attached on the muscle belly of the ABH (Fig. 1). The ABH has the largest physiological cross-sectional area of the PIFMs and has been reported to contribute to supporting the MLA in static conditions [1,2]. Therefore, we decided to use the ABH as the main target of reinforcement. However, because we used surface electrodes, the target of reinforcement was not only the ABH but also other PIFMs, such as the flexor hallucis brevis. The timing of electrical stimulation was controlled using the hand switch by the same tester (KO). In gait trials, the phase from mid-stance to pre-swing, when the PIFMs are active in the normal gait pattern [8], was watched carefully by the tester to determine when to provide electrical stimulation. Moreover, the WalkAide device and the VICON system were synchronized at 1000Hz to
8
confirm the timing of electrical stimulation. Our previous experiment [13] confirmed that the tester (KO) could provide electrical stimulation at almost a corresponding timing with the phase from mid-stance to pre-swing. The stimulation intensity was determined to be the threshold that each subject could endure without feeling pain.
2.4. Data collection protocol First, the following characteristics were collected: weight, height, leg length, and pelvic, knee and ankle width. Then, the 16 markers (14mm) were placed on the pelvis and both lower extremities in accordance to the Plug-in-Gait lower model specifications, and the 13 markers (9.5mm) were attached to the right lower extremity, following the specifications of the Oxford Foot Model [18,19]. In addition to these, a marker was attached to the right navicular tuberosity and the WalkAide device was attached to the right lower extremity (Fig. 1). Then the calibration was performed with the subjects in an anatomical neutral position. Next, the medial malleolus and posterior calcaneus proximal markers were removed, according to the protocol of the Oxford Foot Model [18,19]. The marker of the distal 1st metatarsal recorded as one of the removable markers on the protocol was not removed, because this marker was necessary to calculate the MLA height. In this study, the MLA height during gait was represented by
9
the navicular height. The navicular height during gait was defined as the perpendicular distance of the navicular tuberosity marker above the plantar plane of the foot bisecting markers on the distal 1st metatarsal, distal 5th metatarsal, and heel. In our pilot study, the measures of the minimum navicular height and timing during the stance phase of gait were taken using this method for 2 sessions on 9 individuals during which the reflective markers were not removed between each session, and the average values of 5 trials revealed strong intra-tester reliabilities (ICC1,1 = 0.99 and 0.96, respectively) and precision of measurement (SEM = 0.5mm and 1.1% stance phase, respectively). Following these preparations, the baseline gait trials were conducted with 28 markers. All subjects were asked to walk on the 8m walkway at their preferred normal speed. Five gait trials were recorded. If the subjects did not clearly strike the force plate, an additional trial was recorded as a replacement. Then, the stimulation intensity was decided for each subject. The decision for stimulation intensity was done not only for the ESG but also for the CG. Then, to compare the simulated contractile force of the PIFMs with previous studies [2,12], a static standing trial was conducted. The subjects were required to place approximately 90% of their body weight on the right lower extremity and were allowed to stabilize their balance with a rod in the opposite hand and toe-touch contact to the floor with the opposite lower extremity [12]. After the force
10
plate data recorded that weight bearing on the right lower extremity was approximately 90% of body weight, a recording for 10 seconds was conducted. Only for the ESG, electrical stimulation to the PIFMs was provided for the last 5 seconds. Upon completion of a static standing trial, gait trials were conducted again. At this time, only for the ESG, electrical stimulation to the PIFMs was provided from mid-stance to pre-swing. Regardless whether electrical stimulation was provided or not, all gait trials in both groups were performed under the condition that the tester (KO) walked diagonally behind the subject to operate the hand switch (Fig. 2).
2.5. Statistical analysis In the gait trials, gait velocity and the following parameters during the right stance phase were selected for statistical analysis; stance phase duration, minimum navicular height, timing when the navicular height reached the minimum value, forefoot angle relative to the rear foot and rear foot angle relative to the tibia at that timing, internal ankle moment (plantar flexion, eversion, abduction) at that timing, and maximum ground reaction force (anterior, medial and vertical direction) in the second half of stance phase. All parameters in all 5 trials were averaged.
11
Only in the standing trials, to compare with previous studies [2,12], the navicular height not from plantar plane of the foot but from the floor was selected for statistical analysis. The navicular height from the floor of the intervals excluding the first and last second of the first and second half of the 10-second recordings, were averaged respectively. For the baseline value of all of the parameters and the amount of change from the baseline of all parameters, independent sample t-tests were conducted to evaluate the differences between the two groups. Differences were considered significant at the p < 0.05 level. All statistical tests were conducted using the SPSS 20.0 for Windows.
3. Results There were no statistically significant differences in the baseline values of all the parameters between the two groups (Table 1). In both groups, the timing when the navicular height reached the minimum value was equivalent to the phase of terminal stance, as noted in previous studies [20]. Table 2 represents the amount of change from baseline. In the gait analysis, regardless whether electrical stimulation to the PIFMs that was provided from 19.2±2.7% to
12
54.9±2.9% of the gait cycle was provided or not, gait velocity, right stance phase duration and minimum navicular height were consistent. Despite this, the timing when the navicular height reached the minimum value was significantly later in the ESG as compared to the CG. Moreover, at that timing, the significantly increased reduction of forefoot abduction (transverse plane) angle relative to the rear foot was seen in the ESG, but there were no significant differences in the changes of forefoot dorsiflexion (sagittal plane) and eversion (frontal plane) angles. In the ankle moment and ground reaction force data, only the maximum vertical ground reaction force (2nd peak) was significantly decreased more in the ESG. Figures 3 and 4 illustrate the changes in the navicular height, forefoot angle relative to the rear foot, and ground reaction force during the stance phase in the baseline of ESG, and indicated the point selected for statistical analysis. In the standing analysis, the increase from baseline in the navicular height from the floor was significantly larger in the ESG.
4. Discussion
13
This was the first in vivo study that examined the change in the foot dynamics during gait accompanied with the change in the PIFMs activity to verify the functional role of the PIFMs during gait. The reinforcement of the PIFMs during the stance phase of gait caused a delay in the timing for the navicular height to reach the minimum value. Furthermore, in the second half of stance phase, although the maximum ground reaction forces of anterior and medial directions did not change, the maximum vertical ground reaction force was weaker in the ESG. These results showed the function of the PIFMs to be shock absorbers during late stance. This function could contribute to the reduction of the stress on the plantar fascia, because the stress on the plantar fascia reaches the maximum value during late stance as well [21]. This suggestion does not contradict previous computational modelling studies [5] that showed the reduction of the stress on the plantar fascia accompanied the increase of PIFMs tension in static states. Patients with plantar fasciitis have less volume in the PIFMs [6,7], and patients with pes planus, which is one of the risk factors for plantar fasciitis [3,4], have smaller cross sectional areas of the PIFMs as well [22]. Therefore, the hypofunction of the PIFMs as shock absorbers may be one of the etiologic factors for plantar fasciitis, and the training of the PIFMs should be performed not only to correct static foot alignment [11,12] but also to
14
recover this function. On the other hand, from the perspective of propulsion power generation, the results of this study suggest that the reinforcement of the PIFMs contributed to facilitate efficient foot ground force transmission, because the vertical ground reaction force peak weakened without a decrease in gait velocity and progression force. Interestingly, contrary to our expectations, the minimum navicular height during stance phase did not increase with the reinforcement of the PIFMs. Kelly et al. [2] reported that individual electrical stimulation of the PIFMs caused approximately a 5% increase in the navicular height under a load of 100% of the body weight. This indicates that the simulated additional contractile force in this study which caused approximately a 3% increase in the navicular height under a load of 90% body weight was weaker than that in the previous study [2]. Moreover, because the load exceeding body weight was given to the forefoot during late stance [21], the simulated additional contractile force in this study would be insufficient to increase the navicular height at that timing. Therefore, the possibility that a more powerful contractile force of the PIFMs may increase the minimum navicular height during stance phase still remains. This study had several limitations. The first limitation was that we could not confirm how much force was added to the contractile force of the PIFMs during gait. However,
15
because the reductions of the forefoot abduction angle associated with the contraction of the ABH [1,2] were shown in the ESG, we believe that there were some additional activations of the PIFMs. Furthermore, in the standing analysis, a 1.5mm increase in the navicular height was confirmed in ESG. This was similar to the change seen in a 4-week PIFMs training program [12]. Therefore, even in gait trials, the simulated additional contractile force would not exceed the physiological level. In addition, although the electrical stimulation in this study was provided at almost a corresponding timing with the phase from mid-stance to pre-swing when the PIFMs are active [8, 23], a previous study reported that the commencement timing of activity was slightly different among PIFMs [8]. Because we used surface electrodes, it was not possible to stimulate each PIFM at the most suitable timing. Therefore, further studies should be performed using a more physiological reinforcement method, such as, strength training. The results of this study may be helpful to such a further study, because the outcome to focus on is presented in this study. Finally, this study was limited to the evaluation during gait. Because plantar fasciitis is also common in runners [3,4] and the PIFMs activity increase with increasing gait velocity [9], future studies should be performed during running.
16
In conclusion, the reinforcement of the PIFMs simulated by electrical stimulation most likely caused the changes in foot dynamics during gait associated with the enhanced shock absorption and the facilitated efficient foot ground force transmission. This suggests that the function of the PIFMs as the shock absorber and propulsion power generator during gait and the failure of these functions may be related to plantar fasciitis.
References [1] Wong YS. Influence of the abductor hallucis muscle on the medial arch of the foot: a kinematic and anatomical cadaver study. Foot Ankle Int 2007;28:617-20. [2] Kelly LA, Cresswell AG, Racinais S, Whiteley R, Lichtwark G. Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch. J R Soc Interface 2014;11:20131188. [3] Pohl MB, Hamill J, Davis IS. Biomechanical and anatomic factors associated with a history of plantar fasciitis in female runners. Clin J Sport Med 2009;19:372-6. [4] Schwartz EN, Su J. Plantar fasciitis: a concise review. Perm J 2014;18:105-7.
17
[5] Wu L. Nonlinear finite element analysis for musculoskeletal biomechanics of medial and lateral plantar longitudinal arch of Virtual Chinese Human after plantar ligamentous structure failures. Clin Biomech (Bristol, Avon) 2007;22:221-9. [6] Chang R, Kent-Braun JA, Hamill J. Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs. Clin Biomech (Bristol, Avon) 2012;27:500-5. [7] Cheung RT, Sze LK, Mok NW, Ng GY. Intrinsic foot muscle volume in experienced runners with and without chronic plantar fasciitis. J Sci Med Sport 2016;19:713-5. [8] Mann R, Inman VT. Phasic activity of intrinsic muscles of the foot. J Bone Joint Surg Am 1964;46:469-81. [9] Kelly LA, Lichtwark G, Cresswell AG. Active regulation of longitudinal arch compression and recoil during walking and running. J R Soc Interface 2015;12:20141076. [10] Jung DY, Koh EK, Kwon OY. Effect of foot orthoses and short-foot exercise on the cross-sectional area of the abductor hallucis muscle in subjects with pes planus: a randomized controlled trial. J Back Musculoskelet Rehabil 2011;24:225-31.
18
[11] Lynn SK, Padilla RA, Tsang KK. Differences in static- and dynamic-balance task performance after 4 weeks of intrinsic-foot-muscle training: the short-foot exercise versus the towel-curl exercise. J Sport Rehabil 2012;21:327-33. [12] Mulligan EP, Cook PG. Effect of plantar intrinsic muscle training on medial longitudinal arch morphology and dynamic function. Man Ther 2013;18:425-30. [13] 〇〇〇 ( We concealed this reference to blind authors details. ) [14] Mueller MJ, Host JV, Norton BJ. Navicular drop as a composite measure of excessive pronation. J Am Podiatr Med Assoc 1993;83:198-202. [15] O'Sullivan K, Kennedy N, O'Neill E, Ni Mhainin U. The effect of low-dye taping on rearfoot motion and plantar pressure during the stance phase of gait. BMC Musculoskelet Disord 2008;9:111. [16] Morone G, Fusco A, Di Capua P, Coiro P, Pratesi L. Walking training with foot drop stimulator controlled by a tilt sensor to improve walking outcomes: a randomized controlled pilot study in patients with stroke in subacute phase. Stroke Res Treat 2012;2012:523564. [17] Damiano DL, Prosser LA, Curatalo LA, Alter KE. Muscle plasticity and ankle control after repetitive use of a functional electrical stimulation device for foot drop in cerebral palsy. Neurorehabil Neural Repair 2013;27:200-7.
19
[18] Carson MC, Harrington ME, Thompson N, O'Connor JJ, Theologis TN. Kinematic analysis of a multi-segment foot model for research and clinical applications: a repeatability analysis. J Biomech 2001;34:1299-307. [19] van Hoeve S, de Vos J, Weijers P, Verbruggen J, Willems P, Poeze M, et al. Repeatability of the oxford foot model for kinematic gait analysis of the foot and ankle. Clin Res Foot Ankle 2015;3:171. [20] Prachgosin T, Chong DY, Leelasamran W, Smithmaitrie P, Chatpun S. Medial longitudinal arch biomechanics evaluation during gait in subjects with flexible flatfoot. Acta Bioeng Biomech 2015;17:121-30. [21] Caravaggi P, Pataky T, Günther M, Savage R, Crompton R. Dynamics of longitudinal arch support in relation to walking speed: contribution of the plantar aponeurosis. J Anat 2010;217:254-61. [22] Angin S, Crofts G, Mickle KJ, Nester CJ. Ultrasound evaluation of foot muscles and plantar fascia in pes planus. Gait Posture 2014;40:48-52. [23] Gray EG, Basmajian JV. Electromyography and cinematography of leg and foot ("normal" and flat) during walking. Anat Rec 1968;161:1-15.
20
Hand switch The main unit of WalkAide
Fig. 1. WalkAide and marker placements.
Fig. 2. The gait trial. The tester walked diagonally behind the subject to operate the hand switch.
21
Fig. 3. The mean changes of the navicular height and forefoot angle relative to the rear foot during the stance phase in baseline for ESG. The dashed line indicates the timing when the navicular height reached the minimum value and the point where the forefoot angles were selected for statistical analysis. NH = navicular height from plantar plane, AB = abduction angle (transverse plane), DF = dorsiflexion angle (sagittal plane), EV = eversion angle (frontal plane).
Fig. 4. The mean changes of the ground reaction force during the stance phase in baseline for ESG.
The dashed line circles indicate the points selected for statistical analysis. BW = body weight.
22
CG (N = 10)
Variables
ESG (N = 10)
Mean Diff
95%CI
p
0.1
0.01
-0.1 to 0.1
0.85
42.1
-6.6
-44.2 to 31.0
0.72
18.9
4
4.8
-0.7 to 10.4
0.09
73.7
6.7
0.2
-5.8 to 6.2
0.95
Mean
SD
Mean
SD
1.3
0.1
1.3
635.2
37.8
641.8
Minimum value (mm)
23.7
7.4
Timing (% stance phase)
73.9
6.2
Gait Speed (m/s) Stance phase duration (ms) NH from plantar plane
Foot kinematics FF angle relative to RF (°)
RF angle relative to TB (°)
DF
5.1
5.6
4.7
4
0.3
-4.2 to 4.9
0.88
EV
-1.8
3.9
-3.1
3.5
1.3
-2.2 to 4.8
0.44
AB
4.3
6.3
8.4
3.8
-4.1
-8.9 to -0.8
0.10
DF
12.8
2.9
13.3
5.3
-0.6
-4.5 to 3.4
0.78
EV
-4.1
3.3
-3.9
4.4
-0.2
-3.9 to 3.4
0.90
AB
-19.2
10.2
-23.2
9.4
4.1
-5.1 to 13.3
0.37
PF
1407.5
146
1316.7
209.8
90.8
-79.0 to 206.5
0.28
EV
97.9
54.5
55.2
62.2
42.7
-12.2 to 97.6
0.12
AB
57.7
72.2
27.4
92.2
30.3
-47.5 to 108.2
0.42
Internal ankle moment (N・mm/kg)
Ground reaction force (% BW) Anterior direction
17.4
6.8
15.5
6.9
1.9
-4.5 to 8.3
0.55
Medial direction
7.4
0.8
7.5
1.6
-0.1
-1.3 to 1.2
0.92
Vertical direction
112.2
6.5
112.9
5.9
-0.7
-6.5 to 5.1
0.80
53.3
9.4
49.2
6.6
4.1
-3.6 to 11.7
0.28
Standing NH from floor (mm)
Table 1. The baseline value in each group. NH = navicular height, FF = forefoot, RF = rear foot, TB = tibia, DF = dorsiflexion, EV = eversion, AB = abduction, PF = plantarflexion, BW = body weight. 23
CG (N = 10)
Variables
ESG (N = 10)
Mean Diff
95%CI
p
0.08
0.05
-0.01 to 0.1
0.12
32.5
-9
-34.6 to 16.6
0.47
Mean
SD
Mean
SD
Speed (m/s)
0.02
0.06
-0.03
Stance phase duration (ms)
-4.2
20.8
4.8
Gait
NH from plantar plane Minimum value (mm)
-0.4
0.4
-0.5
1.1
0.1
-0.7 to 0.9
0.75
Timing (% stance phase)
0.1
3.2
3
1.6
-2.9
-5.3 to -0.5
0.02
Foot kinematics FF angle relative to RF (°)
RF angle relative to TB (°)
DF
0.09
0.5
0.2
0.8
-0.1
-0.7 to 0.5
0.71
EV
-0.2
0.5
-0.8
0.8
0.6
-0.03 to 1.2
0.06
AB
0.3
0.3
-0.9
0.7
1.1
0.6 to 1.6
0.0002
DF
-0.03
0.4
0.08
1
-0.1
-0.8 to 0.6
0.75
EV
0.2
0.6
-0.6
1.4
0.8
-0.2 to 1.9
0.12
AB
-0.3
1
-0.4
1.9
0.2
-1.3 to 1.6
0.81
PF
-33.6
73.9
-2.4
91.6
-31.2
-109.4 to 47.0
0.41
EV
9.1
29.5
34.7
42.7
-25.7
-60.2 to 8.9
0.14
AB
-11.5
33
18.5
77.7
-30
-88.1 to 28.2
0.28
Internal ankle moment (N・mm/kg)
Ground reaction force (% BW) Anterior direction
-0.9
4
-0.2
2.7
-0.6
-3.9 to 2.6
0.68
Medial direction
0.3
0.6
0.02
0.6
0.2
-0.3 to 0.8
0.39
Vertical direction
0.5
2.7
-2.2
2.2
2.7
0.4 to 5.0
0.03
0.04
0.4
1.6
1.9
-1.5
-2.9 to -0.1
0.04
Standing NH from floor (mm)
Table 2. The amount of change from baseline in each group. NH = navicular height, FF = forefoot, RF = rear foot, TB = tibia, DF = dorsiflexion, EV = eversion, AB = abduction, PF = plantarflexion, BW = body weight. 24