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Hand grip strength and dexterity function in children aged 6-12 years: A cross-sectional study
Journal of Hand Therapy xxx (2017) 1e8
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Journal of Hand Therapy journal homepage: www.jhandtherapy.org
Scientific/Clinical Article
Hand grip strength and dexterity function in children aged 6-12 years: A cross-sectional study Mohammed T.A. Omar PhD, PT a, b, *, Ahmad H. Alghadir PhD, PT b, Hamayun Zafar PhD, PT b, c, Shaheerah Al Baker BSc, PT d a
Department of Physical Therapy for Surgery, Faculty of Physical Therapy, Cairo University, Giza, Egypt Department of Rehabilitation Health Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia c Department of Odontology, Clinical Oral Physiology, Faculty of Medicine, Umeå University, Umeå, Sweden d Physical Therapy Department, King Saud Medical City, Riyadh, Saudi Arabia b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 December 2015 Received in revised form 11 January 2017 Accepted 6 February 2017 Available online xxx
Study Design: Cross-sectional and clinical measurement. Introduction: Assessment of hand function considers an essential part in clinical practice. Purpose of the Study: To develop normative values of hand grip strength and dexterity function for 6-12year-old children in Saudi Arabia. Methods: Grip strength and dexterity function was measured in 525 children using Grip Track hand dynamometer (JTECH Medical, Midvale, UT, USA) and 9-hole pegboard test respectively. Results: The grip strength and dexterity function was improved as age progressed regardless of gender. Across all age groups, the hand grip strength of boys was significantly higher than girls for dominant hand (31.75 10.33 vs 28.24 9.35; P < .001) and nondominant hand (31.01 10.27 vs 27.27 9.30; P < .001). The girls performed slightly faster than boys for dominant hand (19.70 vs 20.68; P < .05) and nondominant hand (21.79 vs 23.46; P < .05). In general, girls completed a 9-HPT faster than boys in the 2 of 7 age groups: 11 years (9-HPT scores ¼ 2.10 seconds; P < .01) and 12 years (9-HPT scores ¼ 1.93 seconds; P < .01). Discussion: The overall patterns of hand grip strength and dexterity function observed in the present study are similar to the previous studies that established acceleration of grip strength with advanced age, and faster performance scores in older children than younger children in both genders. Conclusions: Norms of hand grip strength and dexterity enable therapists to identify some developmental characteristics of hand function among Saudi children, determine the presence of impairment, and compare scores from children in different clinical settings. Level of Evidence: Not applicable. Ó 2017 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved.
Keywords: Hand strength Dexterity function Children
Introduction Hands are the most effective means of communication and performing the complex tasks of daily living activities (eg, eating, grooming, and bathing). Work activities as well as play and leisure
Conflict of interest: All named authors hereby declare that they have no conflicts of interest to disclose. The authors alone are responsible for the content and writing of the article. The authors extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this research through the research group no. RGP-VPP-209. * Corresponding author. Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia. Tel.: þ966 542 115404. E-mail addresses: [email protected], [email protected], momarar@ ksu.edu.sa (M.T.A. Omar).
activities require both grip strength and manual dexterity.1-3 Moreover, 60% of school activities require fine motor and manual dexterity skills.4 Therefore, the assessment of hand function is an essential part of physical and occupational therapy evaluation for children with a range of disorders, such as trauma, congenital, and neurologic disorders. Normal data on hand grip strength and manual dexterity are important to identify the developmental level and degree of disability; determine efficacy of rehabilitation and assess the integrity of upper limb functions; and compare scores from typical and atypical children according to the age, gender, race/ethnicity, and body measures.1-3,5,6 A few studies have been published on measurement of manual dexterity of the hand in children.7-11 Smith et al7 and Yim et al8 published a normative data of hand dexterity using the 9-hole peg test (9-HPT) for children aged 5-10 and 7-12 years, respectively. Furthermore, Poole et al9 measured manual dexterity in
0894-1130/$ e see front matter Ó 2017 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jht.2017.02.004
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children aged 4-19 years using 9-HPT. The authors proposed that the 9-HPT may be an appropriate screening tool because it reflects multiple aspects of motor control, such as preshaping the hand, grasping, moving, and releasing the object.8,9 However, this manual screening test is not routinely performed for children to detect their dexterity level, and there is no report on the normative values among Saudi children. Several studies have reported norms of hand grip strength in children.8,12-27 The most recent studies provided data from children in Sweden,20 Korea,8 The Netherlands,21 the United States,22 Spain,23 England,24 and Canada.25 Earlier studies were from children in the United States13,15,17,18 and Australia.14,16 A thorough review of these studies suggests a decreased grip strength over the past 3 decades and concluded that hand functions (eg, grip strength and manual dexterity) might be changed over generations and across countries.20-25 Thus, establishing the norms of hand grip strength and manual dexterity for each geographic region is important for hand therapists to assess impairment and tracking progress among patients. Moreover, past research has suggested that Saudi children have lower values of height and weight than Western children.28,29 This variation in demographic characteristics might influence grip strength and dexterity vs existing Western demographics. Therefore, the norms of grip strength and manual dexterity from Western countries are inappropriate because they did not consider the differences in physical characteristics according to race/ethnicity and region.20 Therefore, the purpose of this study was to develop reference values for grip strength and dexterity function in Saudi children aged 6-12 years.
Methods Subjects Elementary school children (6-12 years; n ¼ 525) were recruited from the urban central area of Riyadh, Saudi Arabia. All children and their parents signed consent form describing the aims and procedures of this study. The study was approved by the Ethics Committee, Rehabilitation Research Chair, King Saud University, Saudi Arabia. To establish accurate norms, children with certain abnormalities were excluded from this study such as cognitive/ neurologic disorders, delayed milestones, pain or functional limitations of the upper limbs, or inability to understand the test procedures.
Instrumentation and procedures Researchers collected the demographic data, including age, gender, weight, and height. The body weight was measured using a portable weighing scale (Camry, model: EF921; Zhonghan, Camry Electronic, Co, Ltd, China) to the nearest 0.1 kg. The height was measured with a stadiometer to the nearest 0.1 cm. Then, body mass index was computed. Hand dominance was determined by the child’s reported preference for use in activities of daily living, such as writing, eating, throwing a ball, and opening and closing doors or window shutters.8,20 All measurements were obtained in the air-conditioned room of the health supervisor during the school day from 8 to 11 AM. The children were allowed to short practice using the dynamometer and 9-HPT to become familiar with test procedures. A sample of 40 children was randomly selected to evaluate test-retest reliability of the hand dynamometer and 9-HPT among Saudi children under the same conditions and procedures with a mean interval of 7 days.
Assessment of hand grip strength Hand grip strength was measured using a standard adjustable hand dynamometer (J-Tech 12-0259 Commander Grip Track Dynamometer, JTECH Medical, Midvale, UT, USA) based on the recommendation of the American Society of Hand Therapists.5 For standardization, the dynamometer was set at the second handle position for measurement of hand grip strength. Grip strength was measured while children were in a sitting position with shoulder adducted and neutrally rotated, elbow at 90 flexion, and the forearm and wrist in neutral position.4,30,31 Children were instructed to squeeze the handle of the dynamometer as hard as they could and to sustain the effort for 5 seconds. Verbal encouragement (ie, squeeze as hard as you can) was provided to children during testing. Children performed 3 trials for each hand, and the mean values of these trials were recorded. Children were given 1 minute to rest between trials, and trials were completed with alternating hands to minimize the effects of fatigue.32 Results were recorded in pounds. If a measurement showed a difference greater than 10% from previously obtained measurements, then we did not retain that measurement and instead conducted a fourth trial.21 These procedures have been previously well documented as reliable.33,34 The calibration of instruments was tested periodically during the study according to the manufacturer’s manual. Assessment of hand dexterity Hand dexterity was measured using the 9-HPT (Sammons Preston, PO Box 93040, Chicago, IL). The 9-hole pegboard is on a 5inch square pegboard. Each peg hole is 3 cm deep, 2.5 cm diameter, and located 2 cm from adjacent peg holes, which are arranged in 3 rows of 3. Each peg measures 4 cm in height and 2.2 cm in diameter and has a dot marked on 1 side. A stopwatch was used to time the 9-HPT. The procedures described by Mathiowetz et al35 were used in this study. Each child was tested separately while he and she sat at a desk and chair of appropriate height with their feet supported on the floor to ensure that the tabletop was at the midchest level. The pegboard was centered in front of a child with the container next to the board on the same side of the hand being tested.7-9 The dominant hand was tested first followed by the nondominant hand. The child was instructed to pick up 1 peg at a time using 1 hand only and to put them in the holes until all 9 were filled. The child then removed the pegs from the holes one by one. The order of placement was not prescribed. For the nondominant hand, the pegboard was turned so that the container was on the same side as the nondominant hand. During the test, the therapist instructed the child not to touch the peg with the free hand and chest.7-9 The score was the total time in seconds to complete the task. Timing began on contact with the first peg and ended with return of the final peg to the dish. The average time of 3 trials was used in analysis. Statistical analysis Data were described as mean and standard deviation for continuous variables and median and mode for categorical variables. Test-retest reliability was analyzed using interclass correlation coefficient (ICC). Unpaired and paired t tests were used to determine between-subjects and within-subject differences regarding hand grip differences and dexterity, respectively. A 2-way mixed-design analysis of variance was used to compare sex (between-subject factor) and hand dominance (within-subject factor). The Tukey post hoc test in separate analyses of variances was used to examine differences between specific age groups for boys and girls. Correlation between variables was assessed using Pearson correlation coefficient, and simple and multiple liner regression
M.T.A. Omar et al. / Journal of Hand Therapy xxx (2017) 1e8
3
Table 1 Physical characteristics of the children who participated in the study Age
Boys N
Girls Right dominance
Left dominance
Weight (kg)
Height (cm)
N
Right dominance
Left dominance
Mean (SD) 6 7 8 9 10 11 12 Total
29 34 30 20 37 41 31 222
27 32 23 17 34 37 26 196
2 2 7 3 3 4 5 26
21.04 23.46 27.06 28.25 33.21 36.87 41.77 30.72
(3.01) (2.06) (2.77) (2.35) (3.47) (4.38) (5.99) (7.84)
Weight (kg)
Height (cm)
Mean (SD) 116.72 119.82 125.23 132.40 135.67 139.29 146.48 131.24
(2.80) (2.92) (2.86) (2.39) (4.70) (4.96) (2.93) (10.6)
22 49 56 51 33 56 36 303
20 46 49 48 31 53 32 279
2 3 7 3 2 3 4 24
22.13 23.51 27.19 29.82 34.18 38.19 42.44 31.28
(2.88) (2.65) (4.71) (5.76) (5.87) (6.58) (4.65) (8.32)
115.04 119.12 123.80 130.96 134.06 137.07 144.89 129.68
(3.04) (3.94) (5.05) (4.21) (4.70) (7.24) (5.42) (10.31)
N ¼ number of participants; SD ¼ standard deviation.
analyses were used to determine relations and variability between variables. In addition, the percentile curves were constructed for the hand grip and dexterity for boys and girls separately. The percentiles for hand grip and dexterity for boys and girls were separately estimated. Percentile curves were plotted against the age with 5 points placed at the 10th, 25th, 50th, 75th, and 90th centiles. All statistical analyses were performed with the Statistical Package for Social Sciences (SPSS, version 21.0; SPSS Inc, Chicago, IL). Statistical significance was set at P < .05. Results Physical characteristics of the subjects Table 1 describes the physical characteristics of the participating children. Five hundred twenty-five children completed the test procedures: 222 (42%) were boys and 303 (58%) were girls. Right-hand dominance was reported in 475 children (90.5%) comprising 196 (37.3%) boys and 279 (53.2%) girls, whereas 50 children (9.5%) reported left-hand dominance comprising 26 (4.9%) boys and 24 (4.6%) girls. None of the children reported ambidexterity. There were no differences in the weight (P > .05) and height (P > .05) between boys and girls in each age group. There was a significant and steady increase in weight (P < .05) and height (P < .05) with age. However, there were no significant differences in weight for 6-7 year olds (boys, P > .36; girls, P > .98) and 8-9 year olds (boys, P > .97; girls, P > .31) and height at 6-7
year olds (boys, P > .08; girls, P > .15) and 9-10 year olds (boys, P > .11; girls, P > .32). The results of test-retest reliability from study sample (n ¼ 40) were analyzed. Children showed high to very high test-retest reliability for Jamar dynamometer (0.81 ICC 0.95; P .001) and 9HPT (0.80 ICC 0.91; P .001). Hand grip strength Table 2 represents reference value of hand grip strength according to age, hand dominance, and gender. There were significant main effects for age (F ¼ 269.47; P < .01) and gender (F ¼ 133.09; P < .01) and a significant age by sex interaction (F ¼ 84.45; P < .01). The grip strength was increased with age regardless of gender and toward the older children for both dominant (boys: F ¼ 122.5, P < .001; girls: F ¼ 132.98, P < .001) and nondominant hands (boys: F ¼ 112.4, P < .001; girls: F ¼ 100.29, P < .001). However, 6-7-year-old and 9-10-year-old children did not show significant differences in grip strength in either boys (P > .05) or girls (P > .05). Comparison of hand grip strength for the dominant vs nondominant hands indicated nonsignificant differences regardless of gender (P > .05). However, the grip strength of the dominant hands tends to be higher than that of the nondominant hands in all age groups, except for 7-year-old children in both genders. Across all age groups, the hand grip strength of boys was significantly higher than that of girls for dominant hand (31.75 10.33 vs 28.24 9.35; P < .001) and nondominant hand (31.01 10.27 vs
Table 2 Mean values of hand grip strength (pounds) using Jamar dynamometer across age range and gender Grip strength for boys Hand Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
Age (y)
Grip strength for girls N
6
29
7
34
8
30
9
20
10
37
11
41
12
31
Total
222
Mean SD 19.15 18.34 21.82 21.29 26.52 25.86 32.28 31.08 33.89 32.81 39.09 38.49 46.86 46.41 31.75 31.01
2.23 2.34 4.94a 4.14a 4.79a,b 4.51a,b 5.44a,b 6.02a,b 6.12a 5.05a 4.76a,b 5.34a,b 5.59a,b 5.28a,b 10.33a 10.27a
Minimum
Maximum
Hand
15.27 14.94 15.33 13.67 20.00 18.00 24.00 23.67 24.00 22.67 29.33 25.00 38.44 35.10 15.27 13.67
22.94 22.61 30.33 29.00 39.67 35.00 46.33 41.67 49.33 43.00 49.67 47.33 57.30 55.34 57.30 55.34
Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
N ¼ number of participants; SD ¼ standard deviation. a Significantly different between boys and girls within age group (P < .005). b Significantly different from previous age group (P < .05).
Age (y)
N
6
22
7
49
8
56
9
51
10
33
11
56
12
36
Total
303
Mean SD 17.88 17.33 18.92 18.04 23.30 22.68 27.63 26.97 29.76 28.26 36.25 34.40 41.92 41.36 28.24 27.27
3.20 3.43 4.19 3.85 5.84b 5.58b 5.82b 6.28b 6.48 7.70 3.95b 4.14b 5.81b 5.67b 9.35 9.30
Minimum
Maximum
10.56 9.96 12.68 12.98 13.80 13.80 19.00 19.00 20.60 20.60 27.60 26.10 32.20 32.20 10.56 9.96
22.76 21.66 30.58 29.18 37.00 35.80 41.20 39.80 47.00 40.40 47.60 44.60 53.70 51.40 53.70 51.40
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Table 3 Summary of sample and multiple liner regression of hand grip strength for boys and girls separately and for both genders combined Gender
Hand dominance
Boys
Dominant Dominant Nondominant Nondominant Girls Dominant Dominant Nondominant Nondominant All combined (both hands and both sex) All combined (both hands and both sex)
Model variables
R2
Age Age, Age Age, Age Age, Age Age, Age
0.79 0.80 0.77 0.78 0.69 0.71 0.70 0.72 0.72
weight, and height weight, and height weight, and height weight, and height
Age, weight, and height
0.75
27.27 9.30; P < .001). Boys were significantly stronger than girls with the dominant hand at ages 7 (P ¼ .02), 8 (P ¼ .04), 9 (P ¼ .003), 10 (P ¼ .001), 11 (P ¼ .001), and 12 (P < .001). For the nondominant hand, this was true at ages 7 (P ¼ .03), 8 (P ¼ .02), 9 (P < .001), 10 (P < .001), 11 (P ¼ .01), and 12 (P < .001). There was no difference in grip strength between boys and girls at 6 year olds for both dominant (P ¼ .10) and nondominant (P ¼ .20). The percentage difference in grip strength between boys and girls was fluctuated from 6.5% to 15% for 6-year-old and 12-year-old boys, respectively. To establish the association of gender, age, height, and weight with grip strength in more detail, we performed a multilevel analysis with the simpler and multiple level model analysis as shown in Table 3. For both the dominant and nondominant hands, the age, height, weight, and gender had a significant association with grip strength (P .001). In the boys, the R2 for the dominant and nondominant hands was 0.80 (P < .001) and 0.78 (P < .001) indicating that the combination of age, weight, and height accounted for 80% and 78% of the variability in hand grip strength. In the girls, the R2 for the dominant and nondominant hands was 0.71 (P < .001) and 0.72 (P < .001) indicating that the combination of age, weight, and height accounted for 71% and 78.2% of the variability in hand grip strength. This analysis showed that for both genders, the parameters age, weight, and height accounted for most of the variability in grip strength. The contribution of age, weight, and height was significant for both girls and boys (P < .01 in all cases).
Figure 1A-D presented the centile curves for the hand grip for boys and girls aged 6-12 years. Scores are plotted as 10%, 25%, 50%, 75%, and 90% percentiles. The upper and lower limits indicate the borders of reference values for strength at the corresponding age. Manual hand dexterity Table 4 represents reference values for 9-HPT according to age, hand dominance, and gender. The speed of dexterity improved with age regardless of gender and toward the older children for both dominant hands (boys: F ¼ 71.68, P < .001; girls: F ¼ 58.24, P < .001) and nondominant hands (boys: F ¼ 96.57, P < .001; girls: F ¼ 95.30, P < .001). However, the scores for dominant hand between 6-7-year-old, 9-10-year-old, and 11-12-year-old children were similar in boys (P > .05) and girls (P > .05). The results are similar for the nondominant hand. Regardless of gender, the dominant hand demonstrated shortest completion time than nondominant hand (P < .001) at every age group. Across all age groups, the girls performed slightly faster than boys for dominant hand (19.70 vs 20.68; P < .05) and nondominant hand (21.79 vs 23.46; P < .05). In general, girls completed a 9-HPT faster than boys in 2 of 7 age groups: 11 years (9-HPT scores ¼ 2.10 seconds; P < .01) and 12 years (9-HPT scores ¼ 1.93 seconds; P < .01). Figure 2A-D represents reference values for 9-HPT in seconds according to age, hand dominance, and gender. Scores are plotted as 10%, 25%, 50%, 75%, and 90% percentiles. The upper and lower limits indicate the borders of reference values for 9-HPT at the corresponding age. Discussion To our knowledge, this is the first published normative data of hand grip strength and manual dexterity function in 6-12-year-old Saudi children. In the present study, a hand dynamometer and 9HPT were used to measure grip strength and hand dexterity and demonstrated a high to very high test-retest reliability. This confirms the literature stating good-to-excellent test-retest (r > 0.80) reproducibility for Jamar dynamometer34,36 and 9-HPT (r ¼ 0.81),7 which supports their use as objective measures to determine hand grip strength and manual dexterity among Saudi children. Moreover, besides having a high test-retest reliability, all children were
Table 4 Mean values of time to complete the 9-HPT (seconds) for manual dexterity across age range and gender 9-HPT for boys Hand Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
9-HPT for girls Age (y)
N
6
29
7
34
8
30
9
20
10
37
11
41
12
31
Total
222
Mean SD 25.18 29.20 24.62 27.60 22.18 24.63 19.88 22.37 19.46 21.90 17.49 19.96 16.87 19.63 20.68 23.46
2.83 2.28 2.81 2.69 2.29a 2.60a 1.76a 1.79a 2.21 2.12 1.48a 1.54a 1.63 1.66 3.79 4.05
Minimum
Maximum
Hand
21.09 25.01 19.63 20.13 18.97 20.67 17.27 18.83 15.99 16.69 14.28 16.69 12.05 15.02 12.05 15.02
32.30 32.70 30.43 31.23 28.93 30.90 23.73 25.53 23.68 25.43 20.82 22.75 19.84 22.44 32.30 32.70
Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
N ¼ number of participants; SD ¼ standard deviation. a Significantly different from previous age group (P < .05). b Significantly different between boys and girls within age group (P < .005).
Age (y)
N
6
22
7
49
8
56
9
51
10
33
11
56
12
36
Total
303
Mean SD 24.71 28.33 23.61 26.80 21.31 23.86 19.46 21.02 18.50 21.00 16.07 17.19 15.88 16.75 19.70 21.79
2.59 3.28 2.88 2.97 3.34a 3.26a 2.42a 2.40a 2.99 2.82 2.64a,b 2.63a,b 2.48b 2.39b 4.10b 4.78b
Minimum
Maximum
20.70 23.92 16.10 20.10 14.50 18.50 14.50 13.20 12.50 16.40 10.10 11.80 12.80 12.50 10.10 12.50
31.30 35.60 31.10 34.50 28.50 32.80 23.90 24.20 24.80 24.70 21.50 24.50 21.50 21.50 31.30 37.30
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Fig. 1. Reference values for grip strength according to gender, dominance, and age. Scores are plotted as 10, 50, 75, and 90 percentiles. The upper and lower limits indicate the borders of reference values for strength at the corresponding age.
measured in the same manner and again to follow standardized methods according to the American Society of Hand Therapists protocol.5 Normative data for grip strength are usually presented in table format or as growth curves as a function of age.21,37 The latter approach was chosen in the present study to illustrate grip strength development at different ages. Our data confirm significant difference and progressive increases in hand grip strength with age in favor of the older children across both genders, and the differences in grip strength between boys and girls are varied across age. The described curve of grip strength showed a trend for boys to be stronger than girls in almost age groups (except for 6 year olds) and marked acceleration of grip strength around 10-12 years, specifically for boys. The overall patterns of hand grip strength observed in the present study are similar to the previous studies that established acceleration of grip strength with advanced age.8,12,20-22,36,37 Considering gender and age, the grip strengths in boys and girls at 6 years were similar, when dominant or nondominant hands were tested. This aligns with the results of Robertson and Deitz,18 De-Smet and Vereammen,19 and Häger-Ross and Rösblad20 who
found no differences in grip strength for those younger than 7 years. Differences between genders in grip strength were apparent by 10 years in the present study. This results in agreement with Häger-Ross and Rösblad20 and Moura et al38 who concluded that boys are stronger than girls particularly after 10 years. Moreover, fluctuated differences in the percentage of grip strength observed in the present study are in accordance with the results of Molenaar et al,21 who concluded that, the difference in grip strength between boys and girls does not appear to be the same for each age, and boys are always stronger. The gender differences and acceleration of hand grips around 10-12 years are partially attributed to the onset of puberty and biological maturity (eg, muscles mass, total body mass, and height), which has a strong impact on strength measures especially for boys.20,39,40 Moreover, data from a limited number of studies indicate that 60% of Saudi children and 71% of young people do not engage in physical activity of sufficient duration and frequency,40-43 and families may not encourage girls to take part in leisure time and activities either inside or outside school.41-43 These lifestyle changes and physical inactivity are believed to influence muscular
6
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Fig. 2. Reference values for 9-HPT (seconds) according to gender, dominance, and age. Scores are plotted as 10, 50, 75, and 90 percentiles. The upper and lower limits indicate the borders of reference values for 9-HPT strength at the corresponding age. 9-HPT ¼ 9-hole pegboard test.
strength among Saudi children and might be responsible for gender-specific differences in hand grip strength. In the present study, nonsignificant differences in grip strength were reported between dominant and nondominant hands for all ages regardless of genders. However, the scores of the dominant hands tend to be higher than that of the nondominant hands in all age groups. These results are similar to the previously published reports,8,13,16,19,22 which demonstrated nonsignificant differences between dominant and nondominant hands. In contrast, some studies reported significant differences according to the hand dominance.21,37,44 Furthermore, grip strength was positively correlated with height and weight, and it was consistent with the previous studies.21,22,37 Therefore, the reason for this contradictory needs to be clarified in the future, and the therapist should consider age, sex, weight, and height when comparing their children’s measurement with normative values and in clinical practice. Comparing grip strength results with former studies in more detail proved to be difficult due to differences in methods between studies. Both Ager et al13 and McQuiddy et al22 reported scores
according to the right or left hand and not according to dominance, whereas Newman et al14 contained use of a different device that is no longer commonly used, and age subgroups were not divided in the same way, and the variable dominance was not considered, using right and left hands instead. Where comparison was possible, the results of the present study were relatively lower than those of Ploegmakers et al37; however, the 2 attempts for each hand were performed, but the age subgroups were similar to the present study. Moreover, our results were lower than those of Molenaar et al21 and Ferreira et al,44 where 3 attempts were allowed; however, the age subgroups were not divided in the same way in the later study. In addition, the results of present study were relatively lower than early finding of De-Smet and Vereammen19 who allowed only 1 attempt with each hand. Our data confirm significant and faster performance scores on the 9-HPT in older children than younger children in both genders. These findings were supported by previously published research from other countries.7-9,45 In this study, the children’ scores of hand dexterity using 9-HPT were slightly slower than that of Smith et al7 and Poole et al9 and approximately similar to the scores reported in
M.T.A. Omar et al. / Journal of Hand Therapy xxx (2017) 1e8
the study by Yim et al8 but slightly faster than scores reported for the study of Wang et al.45 In addition, the youngest subjects, aged 6 years, had performance scores of 26.36 seconds, whereas 12-yearold children had the lowest mean performance scores of 18.87 seconds. This showed that fine motor dexterity was faster in older children than younger ones. This variation in scores of fine manual dexterities is supported by the work of Folio and Fewell46 and Pehoski et al47 and might be attributed to maturation of the brain and corticospinal tract. The white matter increases and the gray matter decreases in childhood and adolescence. Thus, the associated increases in myelination and axon diameter are favorable for increased motor speed of motor performance.48 In addition, Slowne says “It seems that girls are really better at motor skills than boys at the age of 6 to 13 years.”49 Moreover, grade-school girls tend to excel in speed and accuracy of handwriting compared with boys. This probably reflects their faster maturation.41-55 However, none of this association has been studied in Saudi children. Regardless of the group, our findings show that the girls typically perform faster than boys. In addition, the dominant hands were more dexterous than nondominant hands. These findings are consistent with results of Smith et al,7 Poole et al,9 Wang et al, and others.45 Discrepancy in hand grip strength and dexterity function of Saudi children in the present study might be related to certain aspects of their lifestyle and environmental factors (eg, availability of high-fat and dense-caloric foods, satellite TV, increased reliance on computer, and telecommunication technology as well as decreased leisure and recreation time) over the past few decades and sedentary lifestyles among Saudi children,41-43 as well as racial and anthropometric differences between them and Western populations.7-9,12-20,26 Recently, Jeune et al27 compared the hand grip strength across regions and found that it may provide some insight as to the historical regional differences in genetic factors, nutritional deficiencies, and sociocultural environment. Our data suggest that grip strength norms and dexterity function from the Western population may not accurately represent the local population; hence, local reference values are needed. Moreover, making direct comparison between hand function reported here and previous research is difficult because of variations in the protocol used for measurements and the methods of reporting the scores. These variations include differences in the number of trials and types of the dynamometer and pegboard, whether dominant or nondominant or both hands are assessed, and if the mean of 2 or more trials or the highest value is reported. Some limitations of this study are data collection occurred in a localized region from the urban central area of Riyadh, King Saudi Arabia limiting generalizability of the study results and only to the age range of 6-12 years. The cohort was not representative of a broad range of the sociocultural and economic aspects of Saudi Arabia. Thus, further study using the same standardized procedures in another area within the country is required. In addition, the growth diagrams do not represent the development of the grip strength and dexterity function in children with hand disorders. However, the curves allow discriminations of the development of typical children and evaluate the effects of therapeutic interventions. Conclusion Normative values of hand grip strength and dexterity identify some developmental characteristics of hand function among Saudi children aged 6-12 years old. These growth curves of grip strength and dexterity function norms will allow rehabilitation therapists to determine the presence of impairment, monitor progression overtime, and compare scores from children in different clinical settings. In addition, the results from this study show that gender, age, height, and weight are positively
7
associated with the development of grip strength and dexterity function in children. References 1. Exner CE. Development of hand skills. In: Case-Smith J, ed. Occupational Therapy for Children. 4th ed. St. Louis, MO: Mosby; 2001:289e327. 2. Bohannon RW, Peolsson A, Massy-Westropp N, Desrosiers J, Bear-Lehman J. Reference values for adult grip strength measured with a Jamar dynamometer: a descriptive meta-analysis. Physiotherapy. 2006;92:11e15. 3. Marr D, Cermak S, Cohn E, Henderson A. Fine motor activities in head start and kindergarten classrooms. Am J Occup Ther. 2003;57:550e557. 4. McHale K, Cermak S. Fine motor activities in elementary school: preliminary findings and provisional implications for children with fine motor problems. Am J Occup Ther. 1992;46:898e903. 5. Fess EE. Documentation: essential elements of an upper extremity assessment battery. In: Hunter JM, Mackin EJ, Callhan AD, eds. Rehabilitation of Hand: Surgery and Therapy. 4th ed. Vol. 1. St. Louis, MO: Mosby; 1995:185e214. 6. American Society of Hand Therapists. Clinical Assessment Recommendations. 2nd ed. Chicago, IL: American Society of Hand Therapists; 1992. 7. Smith YA, Hong E, Presson C. Normative and validation studies of the NineHole Peg Test with children. Percept Mot Skills. 2000;90:823e843. 8. Yim SY, Cho JR, Lee IY. Normative data and developmental characteristics of hand function for elementary school children in Suwon area of Korea: grip, pinch and dexterity study. J Korean Med Sci. 2003;18(4):552e558. 9. Poole JL, McMullen CK, Markham A, et al. Measuring dexterity in children using the nine-hole peg test. J Hand Ther. 2005;18:348e351. 10. Lee-Valkov P, Aaron DH, Eladoumikdachi F, Thornby J, Netscher DT. Measuring normal hand dexterity values in normal 3-, 4-, and 5-years-old children and their relationship with grip and pinch strength. J Hand Ther. 2003;16: 22e28. 11. McPhee SD. Functional hand evaluations: a review. Am J Occup Ther. 1987;41: 158e163. 12. Weiss MW, Flatt AE. A pilot study of 198 normal children pinches strength and hand size in the growing hand. Am J Occup Ther. 1971;25:10e12. 13. Ager CL, Olivett BL, Johnson CL. Grasp and pinch strength in children 5 to 12 years old. Am J Occup Ther. 1984;38:107e113. 14. Newman DG, Pearn J, Barnes A, Young CM, Kehoe M, Newman J. Norms for hand grip strength. Arch Dis Child. 1984;59:453e459. 15. Bowman OJ, Katz B. Hand strength and prone extension in right-dominant 6 to 9 year olds. Am J Occup Ther. 1984;38:367e376. 16. Fullwood D. Australian norms for hand and finger strength of boys and girls aged 5e12 years. Aust Occup Ther J. 1986;33:26e36. 17. Mathiowetz V, Wiemer DM, Federman SM. Grip and pinch: norms for 6- to 19year-olds. Am J Occup Ther. 1986;40:705e711. 18. Robertson A, Deitz CJ. A description of grip strength in preschool children. Am J Occup Ther. 1988;42:647e652. 19. De-Smet LD, Vereammen A. Grip strength in children. J Pediatr Orthop B. 2001;10(4):352e354. 20. Häger-Ross C, Rösblad B. Norms for grip strength in children aged 4e16 years. Acta Paediatr. 2002;91:617e625. 21. Molenaar HM, Selles RW, Zuidam JM, Willemsen SP, Stam HJ, Hovius SE. Growth diagrams for grip strength in children. Clin Orthop Relat Res. 2010;468: 217e223. 22. McQuiddy VA, Scheerer CR, Lavalley R, McGrath T, Lin L. Normative values for grip and pinch strength for 6- to 19-year-olds. Arch Phys Med Rehabil. 2015;96(9):1627e1633. 23. Moliner-Urdiales D, Ruiz JR, Ortega FB, et al. Secular trends in health-related physical fitness in Spanish adolescents: the AVENA and HELENA studies. J Sci Med Sport. 2010;13:584e588. 24. Cohen DD, Voss C, Taylor MJ, Delextrat A, Ogunleye AA, Sandercock GR. Tenyear secular changes in muscular fitness in English children. Acta Paediatr. 2011;100:e175ee177. 25. Tremblay MS, Shields M, Laviolette M, Craig CL, Janssen I, Connor Gorber S. Fitness of Canadian children and youth: results from the 2007-2009 Canadian Health Measures Survey. Health Rep. 2010;21:7e20. 26. Monpetit RR, Montoye HJ, Laeding L. Grip strength of school children, Saginaw Michigan: 1899 and 1964. Res Q. 1967;38:231e240. 27. Jeune B, Skytthe A, Cournil A, et al. Handgrip strength among nonagenarians and centenarians in three European regions. J Gerontol Biol Sci. 2006;61:707e 712. 28. Almuzaini KS. Muscle function in Saudi children and adolescents: relationship to anthropometric characteristics during growth. Pediatr Exerc Sci. 2007;19: 319e333. 29. Hazzaa MH. Anthropometric measurements of Saudi boys aged 6-14 years. Ann Hum Biol. 1990;17:33e40. 30. Richards LG, Olson B, Palmiter Thomas P. Grip strength measurement: a critical review of tools, methods and clinical utility. Crit Rev Phys Rehab Med. 1996;8:87e109. 31. Mathiowetz V. Grip and pinch strength measurements. In: Amundsen LR, ed. Muscle Strength Testing: Instrumented and Non-Instrumented System. New York, NY: Churchill Livingstone; 1990:163e177. 32. Trossman PB, Li PW. The effect of the duration of intertribal rest periods on isometric grip strength performance in young adults. Occup Ther J Res. 1989;9:362e378.
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33. Hamilton A, Balnave R, Adams R. Grip strength testing reliability. J Hand Ther. 1994;7:163e170. 34. Mathiowetz V, Weber K, Volland G, Kashman N. Reliability and validity of grip and pinch strength evaluation. J Hand Ther. 1984;9:222e226. 35. Mathiowetz V, Weber K, Kashman N, Volland G. Adult norms for the nine-hole peg test of finger dexterity. Occup Ther J Res. 1985;5:24e38. 36. Peolsson A, Hedlund R, Oberg B. Intra- and inter-tester reliability and reference values for hand strength. J Rehab Med. 2001;33:36e41. 37. Ploegmakers JJW, Hepping AM, Geertzen JHB, Bulstra SK. Grip strength is strongly associated with height, weight and gender in childhood: a cross sectional study of 2241 children and adolescents providing reference values. J Physiother. 2013;95:255e261. 38. Moura PMLS, Moreira D, Caixeta APL. Hand strength in healthy children and teenagers. Rev Paul Pediatr. 2008;26:290e294. 39. Al Alwan I, Felimban N, Altwaijri Y, Tamim H, Shoukri AAM, Tamimi W. Puberty onset among boys in Riyadh, Saudi Arabia. Clin Med Insights Pediatr. 2010;4:19e24. 40. Jones M, Hitchen P, Stratton G. The importance of considering biological maturity when assessing physical fitness measures in girls and boys aged 10 to 16 years. Ann Hum Biol. 2000;27:57e65. 41. Al-Hazzaa HM, Abahussain NA, Al-Sobayel HI, Qahwaji DM, Musaiger AO. Physical activity, sedentary behaviors and dietary habits among Saudi adolescents relative to age, gender and region. Int J Behav Nutr Phys Act. 2011;8:140e153. 42. Al-Hazzaa HM, Musaiger A, ATLS Group. Physical activity patterns and eating habits of adolescents living in major Arab cities. The Arab Teens Lifestyle Study. Saudi Med J. 2010;31:210e211. 43. Al-Hazzaa HM. Physical activity, fitness and fatness among Saudi children and adolescents: implications for cardiovascular health. Saudi Med J. 2002;23:144e 150.
44. Ferreira ACC, Shimano AC, Mazzer N, Barbieri CH, Elui VMC, Fonseca MCR. Grip and pinch strength in healthy children and adolescents. Acta Ortop Bras. 2011;19(2):92e97. 45. Wang YC, Bohannon RW, Kapellusch J, Garg A, Gershon RC. Dexterity as measured with 9-Hole Peg Test (9-HPT) across the age span. J Hand Ther. 2015;28:53e60. 46. Folio MR, Fewell RR. Peabody Developmental Motor Scales and Activity Cards [Manual]. Hingham, MA: Teaching Resources; 1983. 47. Pehoski C, Henderson A, Tickle-Degnen L. In hand manipulation in young children: rotation of an object in the fingers. Am J Occup Ther. 1997;51: 544e552. 48. Gogtany N, Giedd DN, Lusk L, et al. Dynamic mapping of human cortical development during childhood through early adulthood. Proc Natl Acad Sci U S A. 2004;101:817e879. 49. Slowne W. The validity and reliability of LOMDS by age and sex. Am J Occup Ther. 1999;45:317e322. 50. Dorfberger S, Adi-Japha E, Karni A. Sex differences in motor performance and motor learning in children and adolescents: an increasing male advantage in motor learning and consolidation phase gains. Behav Brain Res. 2009;198(1): 165e171. 51. Al-Hazzaa H. Prevalence of physical inactivity in Saudi Arabia: a brief review. East Mediterr Health J. 2004;10:663e670. 52. Cohen MR. Individual and sex differences in speed of handwriting among high school students. Percept Mot Skills. 1997;84(3 pt 2):1428e1430. 53. Ziviani J, Elkins J. An evaluation of handwriting performance. Educ Rev. 1984;36(3):249e261. 54. Tenwolde H. More on sex differences in handwriting. J Appl Psychol. 1934;18S: 705e710. 55. Starch D. The measurement of handwriting. J Educ Psychol. 1913;4:445e464.
Contents lists available at ScienceDirect
Journal of Hand Therapy journal homepage: www.jhandtherapy.org
Scientific/Clinical Article
Hand grip strength and dexterity function in children aged 6-12 years: A cross-sectional study Mohammed T.A. Omar PhD, PT a, b, *, Ahmad H. Alghadir PhD, PT b, Hamayun Zafar PhD, PT b, c, Shaheerah Al Baker BSc, PT d a
Department of Physical Therapy for Surgery, Faculty of Physical Therapy, Cairo University, Giza, Egypt Department of Rehabilitation Health Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia c Department of Odontology, Clinical Oral Physiology, Faculty of Medicine, Umeå University, Umeå, Sweden d Physical Therapy Department, King Saud Medical City, Riyadh, Saudi Arabia b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 December 2015 Received in revised form 11 January 2017 Accepted 6 February 2017 Available online xxx
Study Design: Cross-sectional and clinical measurement. Introduction: Assessment of hand function considers an essential part in clinical practice. Purpose of the Study: To develop normative values of hand grip strength and dexterity function for 6-12year-old children in Saudi Arabia. Methods: Grip strength and dexterity function was measured in 525 children using Grip Track hand dynamometer (JTECH Medical, Midvale, UT, USA) and 9-hole pegboard test respectively. Results: The grip strength and dexterity function was improved as age progressed regardless of gender. Across all age groups, the hand grip strength of boys was significantly higher than girls for dominant hand (31.75 10.33 vs 28.24 9.35; P < .001) and nondominant hand (31.01 10.27 vs 27.27 9.30; P < .001). The girls performed slightly faster than boys for dominant hand (19.70 vs 20.68; P < .05) and nondominant hand (21.79 vs 23.46; P < .05). In general, girls completed a 9-HPT faster than boys in the 2 of 7 age groups: 11 years (9-HPT scores ¼ 2.10 seconds; P < .01) and 12 years (9-HPT scores ¼ 1.93 seconds; P < .01). Discussion: The overall patterns of hand grip strength and dexterity function observed in the present study are similar to the previous studies that established acceleration of grip strength with advanced age, and faster performance scores in older children than younger children in both genders. Conclusions: Norms of hand grip strength and dexterity enable therapists to identify some developmental characteristics of hand function among Saudi children, determine the presence of impairment, and compare scores from children in different clinical settings. Level of Evidence: Not applicable. Ó 2017 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved.
Keywords: Hand strength Dexterity function Children
Introduction Hands are the most effective means of communication and performing the complex tasks of daily living activities (eg, eating, grooming, and bathing). Work activities as well as play and leisure
Conflict of interest: All named authors hereby declare that they have no conflicts of interest to disclose. The authors alone are responsible for the content and writing of the article. The authors extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this research through the research group no. RGP-VPP-209. * Corresponding author. Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, P.O. Box 10219, Riyadh 11433, Saudi Arabia. Tel.: þ966 542 115404. E-mail addresses: [email protected], [email protected], momarar@ ksu.edu.sa (M.T.A. Omar).
activities require both grip strength and manual dexterity.1-3 Moreover, 60% of school activities require fine motor and manual dexterity skills.4 Therefore, the assessment of hand function is an essential part of physical and occupational therapy evaluation for children with a range of disorders, such as trauma, congenital, and neurologic disorders. Normal data on hand grip strength and manual dexterity are important to identify the developmental level and degree of disability; determine efficacy of rehabilitation and assess the integrity of upper limb functions; and compare scores from typical and atypical children according to the age, gender, race/ethnicity, and body measures.1-3,5,6 A few studies have been published on measurement of manual dexterity of the hand in children.7-11 Smith et al7 and Yim et al8 published a normative data of hand dexterity using the 9-hole peg test (9-HPT) for children aged 5-10 and 7-12 years, respectively. Furthermore, Poole et al9 measured manual dexterity in
0894-1130/$ e see front matter Ó 2017 Hanley & Belfus, an imprint of Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jht.2017.02.004
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children aged 4-19 years using 9-HPT. The authors proposed that the 9-HPT may be an appropriate screening tool because it reflects multiple aspects of motor control, such as preshaping the hand, grasping, moving, and releasing the object.8,9 However, this manual screening test is not routinely performed for children to detect their dexterity level, and there is no report on the normative values among Saudi children. Several studies have reported norms of hand grip strength in children.8,12-27 The most recent studies provided data from children in Sweden,20 Korea,8 The Netherlands,21 the United States,22 Spain,23 England,24 and Canada.25 Earlier studies were from children in the United States13,15,17,18 and Australia.14,16 A thorough review of these studies suggests a decreased grip strength over the past 3 decades and concluded that hand functions (eg, grip strength and manual dexterity) might be changed over generations and across countries.20-25 Thus, establishing the norms of hand grip strength and manual dexterity for each geographic region is important for hand therapists to assess impairment and tracking progress among patients. Moreover, past research has suggested that Saudi children have lower values of height and weight than Western children.28,29 This variation in demographic characteristics might influence grip strength and dexterity vs existing Western demographics. Therefore, the norms of grip strength and manual dexterity from Western countries are inappropriate because they did not consider the differences in physical characteristics according to race/ethnicity and region.20 Therefore, the purpose of this study was to develop reference values for grip strength and dexterity function in Saudi children aged 6-12 years.
Methods Subjects Elementary school children (6-12 years; n ¼ 525) were recruited from the urban central area of Riyadh, Saudi Arabia. All children and their parents signed consent form describing the aims and procedures of this study. The study was approved by the Ethics Committee, Rehabilitation Research Chair, King Saud University, Saudi Arabia. To establish accurate norms, children with certain abnormalities were excluded from this study such as cognitive/ neurologic disorders, delayed milestones, pain or functional limitations of the upper limbs, or inability to understand the test procedures.
Instrumentation and procedures Researchers collected the demographic data, including age, gender, weight, and height. The body weight was measured using a portable weighing scale (Camry, model: EF921; Zhonghan, Camry Electronic, Co, Ltd, China) to the nearest 0.1 kg. The height was measured with a stadiometer to the nearest 0.1 cm. Then, body mass index was computed. Hand dominance was determined by the child’s reported preference for use in activities of daily living, such as writing, eating, throwing a ball, and opening and closing doors or window shutters.8,20 All measurements were obtained in the air-conditioned room of the health supervisor during the school day from 8 to 11 AM. The children were allowed to short practice using the dynamometer and 9-HPT to become familiar with test procedures. A sample of 40 children was randomly selected to evaluate test-retest reliability of the hand dynamometer and 9-HPT among Saudi children under the same conditions and procedures with a mean interval of 7 days.
Assessment of hand grip strength Hand grip strength was measured using a standard adjustable hand dynamometer (J-Tech 12-0259 Commander Grip Track Dynamometer, JTECH Medical, Midvale, UT, USA) based on the recommendation of the American Society of Hand Therapists.5 For standardization, the dynamometer was set at the second handle position for measurement of hand grip strength. Grip strength was measured while children were in a sitting position with shoulder adducted and neutrally rotated, elbow at 90 flexion, and the forearm and wrist in neutral position.4,30,31 Children were instructed to squeeze the handle of the dynamometer as hard as they could and to sustain the effort for 5 seconds. Verbal encouragement (ie, squeeze as hard as you can) was provided to children during testing. Children performed 3 trials for each hand, and the mean values of these trials were recorded. Children were given 1 minute to rest between trials, and trials were completed with alternating hands to minimize the effects of fatigue.32 Results were recorded in pounds. If a measurement showed a difference greater than 10% from previously obtained measurements, then we did not retain that measurement and instead conducted a fourth trial.21 These procedures have been previously well documented as reliable.33,34 The calibration of instruments was tested periodically during the study according to the manufacturer’s manual. Assessment of hand dexterity Hand dexterity was measured using the 9-HPT (Sammons Preston, PO Box 93040, Chicago, IL). The 9-hole pegboard is on a 5inch square pegboard. Each peg hole is 3 cm deep, 2.5 cm diameter, and located 2 cm from adjacent peg holes, which are arranged in 3 rows of 3. Each peg measures 4 cm in height and 2.2 cm in diameter and has a dot marked on 1 side. A stopwatch was used to time the 9-HPT. The procedures described by Mathiowetz et al35 were used in this study. Each child was tested separately while he and she sat at a desk and chair of appropriate height with their feet supported on the floor to ensure that the tabletop was at the midchest level. The pegboard was centered in front of a child with the container next to the board on the same side of the hand being tested.7-9 The dominant hand was tested first followed by the nondominant hand. The child was instructed to pick up 1 peg at a time using 1 hand only and to put them in the holes until all 9 were filled. The child then removed the pegs from the holes one by one. The order of placement was not prescribed. For the nondominant hand, the pegboard was turned so that the container was on the same side as the nondominant hand. During the test, the therapist instructed the child not to touch the peg with the free hand and chest.7-9 The score was the total time in seconds to complete the task. Timing began on contact with the first peg and ended with return of the final peg to the dish. The average time of 3 trials was used in analysis. Statistical analysis Data were described as mean and standard deviation for continuous variables and median and mode for categorical variables. Test-retest reliability was analyzed using interclass correlation coefficient (ICC). Unpaired and paired t tests were used to determine between-subjects and within-subject differences regarding hand grip differences and dexterity, respectively. A 2-way mixed-design analysis of variance was used to compare sex (between-subject factor) and hand dominance (within-subject factor). The Tukey post hoc test in separate analyses of variances was used to examine differences between specific age groups for boys and girls. Correlation between variables was assessed using Pearson correlation coefficient, and simple and multiple liner regression
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3
Table 1 Physical characteristics of the children who participated in the study Age
Boys N
Girls Right dominance
Left dominance
Weight (kg)
Height (cm)
N
Right dominance
Left dominance
Mean (SD) 6 7 8 9 10 11 12 Total
29 34 30 20 37 41 31 222
27 32 23 17 34 37 26 196
2 2 7 3 3 4 5 26
21.04 23.46 27.06 28.25 33.21 36.87 41.77 30.72
(3.01) (2.06) (2.77) (2.35) (3.47) (4.38) (5.99) (7.84)
Weight (kg)
Height (cm)
Mean (SD) 116.72 119.82 125.23 132.40 135.67 139.29 146.48 131.24
(2.80) (2.92) (2.86) (2.39) (4.70) (4.96) (2.93) (10.6)
22 49 56 51 33 56 36 303
20 46 49 48 31 53 32 279
2 3 7 3 2 3 4 24
22.13 23.51 27.19 29.82 34.18 38.19 42.44 31.28
(2.88) (2.65) (4.71) (5.76) (5.87) (6.58) (4.65) (8.32)
115.04 119.12 123.80 130.96 134.06 137.07 144.89 129.68
(3.04) (3.94) (5.05) (4.21) (4.70) (7.24) (5.42) (10.31)
N ¼ number of participants; SD ¼ standard deviation.
analyses were used to determine relations and variability between variables. In addition, the percentile curves were constructed for the hand grip and dexterity for boys and girls separately. The percentiles for hand grip and dexterity for boys and girls were separately estimated. Percentile curves were plotted against the age with 5 points placed at the 10th, 25th, 50th, 75th, and 90th centiles. All statistical analyses were performed with the Statistical Package for Social Sciences (SPSS, version 21.0; SPSS Inc, Chicago, IL). Statistical significance was set at P < .05. Results Physical characteristics of the subjects Table 1 describes the physical characteristics of the participating children. Five hundred twenty-five children completed the test procedures: 222 (42%) were boys and 303 (58%) were girls. Right-hand dominance was reported in 475 children (90.5%) comprising 196 (37.3%) boys and 279 (53.2%) girls, whereas 50 children (9.5%) reported left-hand dominance comprising 26 (4.9%) boys and 24 (4.6%) girls. None of the children reported ambidexterity. There were no differences in the weight (P > .05) and height (P > .05) between boys and girls in each age group. There was a significant and steady increase in weight (P < .05) and height (P < .05) with age. However, there were no significant differences in weight for 6-7 year olds (boys, P > .36; girls, P > .98) and 8-9 year olds (boys, P > .97; girls, P > .31) and height at 6-7
year olds (boys, P > .08; girls, P > .15) and 9-10 year olds (boys, P > .11; girls, P > .32). The results of test-retest reliability from study sample (n ¼ 40) were analyzed. Children showed high to very high test-retest reliability for Jamar dynamometer (0.81 ICC 0.95; P .001) and 9HPT (0.80 ICC 0.91; P .001). Hand grip strength Table 2 represents reference value of hand grip strength according to age, hand dominance, and gender. There were significant main effects for age (F ¼ 269.47; P < .01) and gender (F ¼ 133.09; P < .01) and a significant age by sex interaction (F ¼ 84.45; P < .01). The grip strength was increased with age regardless of gender and toward the older children for both dominant (boys: F ¼ 122.5, P < .001; girls: F ¼ 132.98, P < .001) and nondominant hands (boys: F ¼ 112.4, P < .001; girls: F ¼ 100.29, P < .001). However, 6-7-year-old and 9-10-year-old children did not show significant differences in grip strength in either boys (P > .05) or girls (P > .05). Comparison of hand grip strength for the dominant vs nondominant hands indicated nonsignificant differences regardless of gender (P > .05). However, the grip strength of the dominant hands tends to be higher than that of the nondominant hands in all age groups, except for 7-year-old children in both genders. Across all age groups, the hand grip strength of boys was significantly higher than that of girls for dominant hand (31.75 10.33 vs 28.24 9.35; P < .001) and nondominant hand (31.01 10.27 vs
Table 2 Mean values of hand grip strength (pounds) using Jamar dynamometer across age range and gender Grip strength for boys Hand Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
Age (y)
Grip strength for girls N
6
29
7
34
8
30
9
20
10
37
11
41
12
31
Total
222
Mean SD 19.15 18.34 21.82 21.29 26.52 25.86 32.28 31.08 33.89 32.81 39.09 38.49 46.86 46.41 31.75 31.01
2.23 2.34 4.94a 4.14a 4.79a,b 4.51a,b 5.44a,b 6.02a,b 6.12a 5.05a 4.76a,b 5.34a,b 5.59a,b 5.28a,b 10.33a 10.27a
Minimum
Maximum
Hand
15.27 14.94 15.33 13.67 20.00 18.00 24.00 23.67 24.00 22.67 29.33 25.00 38.44 35.10 15.27 13.67
22.94 22.61 30.33 29.00 39.67 35.00 46.33 41.67 49.33 43.00 49.67 47.33 57.30 55.34 57.30 55.34
Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
N ¼ number of participants; SD ¼ standard deviation. a Significantly different between boys and girls within age group (P < .005). b Significantly different from previous age group (P < .05).
Age (y)
N
6
22
7
49
8
56
9
51
10
33
11
56
12
36
Total
303
Mean SD 17.88 17.33 18.92 18.04 23.30 22.68 27.63 26.97 29.76 28.26 36.25 34.40 41.92 41.36 28.24 27.27
3.20 3.43 4.19 3.85 5.84b 5.58b 5.82b 6.28b 6.48 7.70 3.95b 4.14b 5.81b 5.67b 9.35 9.30
Minimum
Maximum
10.56 9.96 12.68 12.98 13.80 13.80 19.00 19.00 20.60 20.60 27.60 26.10 32.20 32.20 10.56 9.96
22.76 21.66 30.58 29.18 37.00 35.80 41.20 39.80 47.00 40.40 47.60 44.60 53.70 51.40 53.70 51.40
4
M.T.A. Omar et al. / Journal of Hand Therapy xxx (2017) 1e8
Table 3 Summary of sample and multiple liner regression of hand grip strength for boys and girls separately and for both genders combined Gender
Hand dominance
Boys
Dominant Dominant Nondominant Nondominant Girls Dominant Dominant Nondominant Nondominant All combined (both hands and both sex) All combined (both hands and both sex)
Model variables
R2
Age Age, Age Age, Age Age, Age Age, Age
0.79 0.80 0.77 0.78 0.69 0.71 0.70 0.72 0.72
weight, and height weight, and height weight, and height weight, and height
Age, weight, and height
0.75
27.27 9.30; P < .001). Boys were significantly stronger than girls with the dominant hand at ages 7 (P ¼ .02), 8 (P ¼ .04), 9 (P ¼ .003), 10 (P ¼ .001), 11 (P ¼ .001), and 12 (P < .001). For the nondominant hand, this was true at ages 7 (P ¼ .03), 8 (P ¼ .02), 9 (P < .001), 10 (P < .001), 11 (P ¼ .01), and 12 (P < .001). There was no difference in grip strength between boys and girls at 6 year olds for both dominant (P ¼ .10) and nondominant (P ¼ .20). The percentage difference in grip strength between boys and girls was fluctuated from 6.5% to 15% for 6-year-old and 12-year-old boys, respectively. To establish the association of gender, age, height, and weight with grip strength in more detail, we performed a multilevel analysis with the simpler and multiple level model analysis as shown in Table 3. For both the dominant and nondominant hands, the age, height, weight, and gender had a significant association with grip strength (P .001). In the boys, the R2 for the dominant and nondominant hands was 0.80 (P < .001) and 0.78 (P < .001) indicating that the combination of age, weight, and height accounted for 80% and 78% of the variability in hand grip strength. In the girls, the R2 for the dominant and nondominant hands was 0.71 (P < .001) and 0.72 (P < .001) indicating that the combination of age, weight, and height accounted for 71% and 78.2% of the variability in hand grip strength. This analysis showed that for both genders, the parameters age, weight, and height accounted for most of the variability in grip strength. The contribution of age, weight, and height was significant for both girls and boys (P < .01 in all cases).
Figure 1A-D presented the centile curves for the hand grip for boys and girls aged 6-12 years. Scores are plotted as 10%, 25%, 50%, 75%, and 90% percentiles. The upper and lower limits indicate the borders of reference values for strength at the corresponding age. Manual hand dexterity Table 4 represents reference values for 9-HPT according to age, hand dominance, and gender. The speed of dexterity improved with age regardless of gender and toward the older children for both dominant hands (boys: F ¼ 71.68, P < .001; girls: F ¼ 58.24, P < .001) and nondominant hands (boys: F ¼ 96.57, P < .001; girls: F ¼ 95.30, P < .001). However, the scores for dominant hand between 6-7-year-old, 9-10-year-old, and 11-12-year-old children were similar in boys (P > .05) and girls (P > .05). The results are similar for the nondominant hand. Regardless of gender, the dominant hand demonstrated shortest completion time than nondominant hand (P < .001) at every age group. Across all age groups, the girls performed slightly faster than boys for dominant hand (19.70 vs 20.68; P < .05) and nondominant hand (21.79 vs 23.46; P < .05). In general, girls completed a 9-HPT faster than boys in 2 of 7 age groups: 11 years (9-HPT scores ¼ 2.10 seconds; P < .01) and 12 years (9-HPT scores ¼ 1.93 seconds; P < .01). Figure 2A-D represents reference values for 9-HPT in seconds according to age, hand dominance, and gender. Scores are plotted as 10%, 25%, 50%, 75%, and 90% percentiles. The upper and lower limits indicate the borders of reference values for 9-HPT at the corresponding age. Discussion To our knowledge, this is the first published normative data of hand grip strength and manual dexterity function in 6-12-year-old Saudi children. In the present study, a hand dynamometer and 9HPT were used to measure grip strength and hand dexterity and demonstrated a high to very high test-retest reliability. This confirms the literature stating good-to-excellent test-retest (r > 0.80) reproducibility for Jamar dynamometer34,36 and 9-HPT (r ¼ 0.81),7 which supports their use as objective measures to determine hand grip strength and manual dexterity among Saudi children. Moreover, besides having a high test-retest reliability, all children were
Table 4 Mean values of time to complete the 9-HPT (seconds) for manual dexterity across age range and gender 9-HPT for boys Hand Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
9-HPT for girls Age (y)
N
6
29
7
34
8
30
9
20
10
37
11
41
12
31
Total
222
Mean SD 25.18 29.20 24.62 27.60 22.18 24.63 19.88 22.37 19.46 21.90 17.49 19.96 16.87 19.63 20.68 23.46
2.83 2.28 2.81 2.69 2.29a 2.60a 1.76a 1.79a 2.21 2.12 1.48a 1.54a 1.63 1.66 3.79 4.05
Minimum
Maximum
Hand
21.09 25.01 19.63 20.13 18.97 20.67 17.27 18.83 15.99 16.69 14.28 16.69 12.05 15.02 12.05 15.02
32.30 32.70 30.43 31.23 28.93 30.90 23.73 25.53 23.68 25.43 20.82 22.75 19.84 22.44 32.30 32.70
Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant Dominant Nondominant
N ¼ number of participants; SD ¼ standard deviation. a Significantly different from previous age group (P < .05). b Significantly different between boys and girls within age group (P < .005).
Age (y)
N
6
22
7
49
8
56
9
51
10
33
11
56
12
36
Total
303
Mean SD 24.71 28.33 23.61 26.80 21.31 23.86 19.46 21.02 18.50 21.00 16.07 17.19 15.88 16.75 19.70 21.79
2.59 3.28 2.88 2.97 3.34a 3.26a 2.42a 2.40a 2.99 2.82 2.64a,b 2.63a,b 2.48b 2.39b 4.10b 4.78b
Minimum
Maximum
20.70 23.92 16.10 20.10 14.50 18.50 14.50 13.20 12.50 16.40 10.10 11.80 12.80 12.50 10.10 12.50
31.30 35.60 31.10 34.50 28.50 32.80 23.90 24.20 24.80 24.70 21.50 24.50 21.50 21.50 31.30 37.30
M.T.A. Omar et al. / Journal of Hand Therapy xxx (2017) 1e8
5
Fig. 1. Reference values for grip strength according to gender, dominance, and age. Scores are plotted as 10, 50, 75, and 90 percentiles. The upper and lower limits indicate the borders of reference values for strength at the corresponding age.
measured in the same manner and again to follow standardized methods according to the American Society of Hand Therapists protocol.5 Normative data for grip strength are usually presented in table format or as growth curves as a function of age.21,37 The latter approach was chosen in the present study to illustrate grip strength development at different ages. Our data confirm significant difference and progressive increases in hand grip strength with age in favor of the older children across both genders, and the differences in grip strength between boys and girls are varied across age. The described curve of grip strength showed a trend for boys to be stronger than girls in almost age groups (except for 6 year olds) and marked acceleration of grip strength around 10-12 years, specifically for boys. The overall patterns of hand grip strength observed in the present study are similar to the previous studies that established acceleration of grip strength with advanced age.8,12,20-22,36,37 Considering gender and age, the grip strengths in boys and girls at 6 years were similar, when dominant or nondominant hands were tested. This aligns with the results of Robertson and Deitz,18 De-Smet and Vereammen,19 and Häger-Ross and Rösblad20 who
found no differences in grip strength for those younger than 7 years. Differences between genders in grip strength were apparent by 10 years in the present study. This results in agreement with Häger-Ross and Rösblad20 and Moura et al38 who concluded that boys are stronger than girls particularly after 10 years. Moreover, fluctuated differences in the percentage of grip strength observed in the present study are in accordance with the results of Molenaar et al,21 who concluded that, the difference in grip strength between boys and girls does not appear to be the same for each age, and boys are always stronger. The gender differences and acceleration of hand grips around 10-12 years are partially attributed to the onset of puberty and biological maturity (eg, muscles mass, total body mass, and height), which has a strong impact on strength measures especially for boys.20,39,40 Moreover, data from a limited number of studies indicate that 60% of Saudi children and 71% of young people do not engage in physical activity of sufficient duration and frequency,40-43 and families may not encourage girls to take part in leisure time and activities either inside or outside school.41-43 These lifestyle changes and physical inactivity are believed to influence muscular
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Fig. 2. Reference values for 9-HPT (seconds) according to gender, dominance, and age. Scores are plotted as 10, 50, 75, and 90 percentiles. The upper and lower limits indicate the borders of reference values for 9-HPT strength at the corresponding age. 9-HPT ¼ 9-hole pegboard test.
strength among Saudi children and might be responsible for gender-specific differences in hand grip strength. In the present study, nonsignificant differences in grip strength were reported between dominant and nondominant hands for all ages regardless of genders. However, the scores of the dominant hands tend to be higher than that of the nondominant hands in all age groups. These results are similar to the previously published reports,8,13,16,19,22 which demonstrated nonsignificant differences between dominant and nondominant hands. In contrast, some studies reported significant differences according to the hand dominance.21,37,44 Furthermore, grip strength was positively correlated with height and weight, and it was consistent with the previous studies.21,22,37 Therefore, the reason for this contradictory needs to be clarified in the future, and the therapist should consider age, sex, weight, and height when comparing their children’s measurement with normative values and in clinical practice. Comparing grip strength results with former studies in more detail proved to be difficult due to differences in methods between studies. Both Ager et al13 and McQuiddy et al22 reported scores
according to the right or left hand and not according to dominance, whereas Newman et al14 contained use of a different device that is no longer commonly used, and age subgroups were not divided in the same way, and the variable dominance was not considered, using right and left hands instead. Where comparison was possible, the results of the present study were relatively lower than those of Ploegmakers et al37; however, the 2 attempts for each hand were performed, but the age subgroups were similar to the present study. Moreover, our results were lower than those of Molenaar et al21 and Ferreira et al,44 where 3 attempts were allowed; however, the age subgroups were not divided in the same way in the later study. In addition, the results of present study were relatively lower than early finding of De-Smet and Vereammen19 who allowed only 1 attempt with each hand. Our data confirm significant and faster performance scores on the 9-HPT in older children than younger children in both genders. These findings were supported by previously published research from other countries.7-9,45 In this study, the children’ scores of hand dexterity using 9-HPT were slightly slower than that of Smith et al7 and Poole et al9 and approximately similar to the scores reported in
M.T.A. Omar et al. / Journal of Hand Therapy xxx (2017) 1e8
the study by Yim et al8 but slightly faster than scores reported for the study of Wang et al.45 In addition, the youngest subjects, aged 6 years, had performance scores of 26.36 seconds, whereas 12-yearold children had the lowest mean performance scores of 18.87 seconds. This showed that fine motor dexterity was faster in older children than younger ones. This variation in scores of fine manual dexterities is supported by the work of Folio and Fewell46 and Pehoski et al47 and might be attributed to maturation of the brain and corticospinal tract. The white matter increases and the gray matter decreases in childhood and adolescence. Thus, the associated increases in myelination and axon diameter are favorable for increased motor speed of motor performance.48 In addition, Slowne says “It seems that girls are really better at motor skills than boys at the age of 6 to 13 years.”49 Moreover, grade-school girls tend to excel in speed and accuracy of handwriting compared with boys. This probably reflects their faster maturation.41-55 However, none of this association has been studied in Saudi children. Regardless of the group, our findings show that the girls typically perform faster than boys. In addition, the dominant hands were more dexterous than nondominant hands. These findings are consistent with results of Smith et al,7 Poole et al,9 Wang et al, and others.45 Discrepancy in hand grip strength and dexterity function of Saudi children in the present study might be related to certain aspects of their lifestyle and environmental factors (eg, availability of high-fat and dense-caloric foods, satellite TV, increased reliance on computer, and telecommunication technology as well as decreased leisure and recreation time) over the past few decades and sedentary lifestyles among Saudi children,41-43 as well as racial and anthropometric differences between them and Western populations.7-9,12-20,26 Recently, Jeune et al27 compared the hand grip strength across regions and found that it may provide some insight as to the historical regional differences in genetic factors, nutritional deficiencies, and sociocultural environment. Our data suggest that grip strength norms and dexterity function from the Western population may not accurately represent the local population; hence, local reference values are needed. Moreover, making direct comparison between hand function reported here and previous research is difficult because of variations in the protocol used for measurements and the methods of reporting the scores. These variations include differences in the number of trials and types of the dynamometer and pegboard, whether dominant or nondominant or both hands are assessed, and if the mean of 2 or more trials or the highest value is reported. Some limitations of this study are data collection occurred in a localized region from the urban central area of Riyadh, King Saudi Arabia limiting generalizability of the study results and only to the age range of 6-12 years. The cohort was not representative of a broad range of the sociocultural and economic aspects of Saudi Arabia. Thus, further study using the same standardized procedures in another area within the country is required. In addition, the growth diagrams do not represent the development of the grip strength and dexterity function in children with hand disorders. However, the curves allow discriminations of the development of typical children and evaluate the effects of therapeutic interventions. Conclusion Normative values of hand grip strength and dexterity identify some developmental characteristics of hand function among Saudi children aged 6-12 years old. These growth curves of grip strength and dexterity function norms will allow rehabilitation therapists to determine the presence of impairment, monitor progression overtime, and compare scores from children in different clinical settings. In addition, the results from this study show that gender, age, height, and weight are positively
7
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