Demographic and hand-forearm anthropometric data
Demographic information including age, gender, hand dominance, and hand-forearm anthropometric characteristics of the study participants are shown in Tables 2 and 3. The sample consisted of 2637 healthy children and adolescents students-aged 7–18 years including 1391 (52.7%) boys and 1246 (47.3%) girls. Right-hand dominance was reported by 2506 (95%) students comprising 1319 (50%) boys and 1187 (45%) girls. None of the students reported ambidexterity.
Results of test-retest reliability were analyzed from 80 participants out of whole sample. Participants showed high to very high test-retest reliability for Jamar dynamometer (0.84 ≤ ICC ≤ 0.96; P ≤ 0.001) and pinch gauge (0.86 ≤ ICC ≤ 0.92; P ≤ 0.001).
Table 2
Characteristics of study participants: age, gender, and hand dominance.
Age (years)
|
N
|
Boys
|
Girls
|
n
|
Dominant Hand
|
n
|
Dominant Hand
|
|
|
|
Right
|
Left
|
|
Right
|
Left
|
7
|
230
|
126
|
121
|
5
|
104
|
100
|
4
|
8
|
213
|
110
|
103
|
7
|
103
|
98
|
5
|
9
|
235
|
125
|
121
|
4
|
110
|
105
|
5
|
10
|
223
|
116
|
111
|
5
|
107
|
100
|
7
|
11
|
208
|
108
|
105
|
3
|
100
|
96
|
4
|
12
|
212
|
116
|
110
|
6
|
96
|
92
|
4
|
13
|
218
|
114
|
107
|
7
|
104
|
103
|
1
|
14
|
218
|
107
|
103
|
4
|
111
|
105
|
6
|
15
|
208
|
109
|
102
|
7
|
99
|
95
|
4
|
16
|
226
|
118
|
110
|
8
|
108
|
104
|
4
|
17
|
224
|
120
|
111
|
9
|
104
|
96
|
8
|
18
|
222
|
122
|
115
|
7
|
100
|
93
|
7
|
Total
|
2637
|
1391
|
1319
|
72
|
1246
|
1187
|
59
|
N: number of participants per age group.
n: number of participants per gender.
|
Table 3
Descriptive statistics of demographic and hand-forearm anthropometric variables.
Variable
|
Boys (n = 1391)
|
|
Girls (n = 1246)
|
Mean ± SD
|
Min-Max
|
|
Mean ± SD
|
Min-Max
|
Age (years)
|
13.2 ± 3.7
|
7–18
|
|
12.6 ± 2.9
|
7–18
|
Stature (cm)
|
158.1 ± 9.1
|
108–193
|
|
148.8 ± 8.6
|
106–176
|
Weight (kg)
|
54.4 ± 8.5
|
24.1–84.3
|
|
44.8 ± 7.1
|
23.4–77.2
|
BMI
|
23.5 ± 9.0
|
18.8–34.8
|
|
22.1 ± 8.6
|
17.5–30.2
|
Hand length (cm)
|
17.6 ± 1.1
|
11.8–21.6
|
|
15.8 ± 0.9
|
10.0-20.5
|
Palm length (cm)
|
9.5 ± 0.8
|
7.1–12.0
|
|
8.9 ± 0.7
|
6.4–11.5
|
Hand breadth across thumb (cm)
|
8.6 ± 0.66
|
6.7–10.3
|
|
8.1 ± 0.60
|
6.3–9.3
|
Hand breath metacarpal (cm)
|
7.1 ± 0.51
|
5.4–8.1
|
|
6.5 ± 0.46
|
5.1–7.4
|
Hand circumference (cm)
|
19.5 ± 1.9
|
14.7–23.4
|
|
17.6 ± 1.6
|
14.1–21.3
|
Fist length (cm)
|
8.3 ± 0.68
|
6.4–10.2
|
|
7.9 ± 0.56
|
5.9–9.5
|
Fist circumference (cm)
|
22.4 ± 1.5
|
13.5–27.2
|
|
20.3 ± 1.3
|
13.2–25.6
|
Maximum Internal grip diameter (cm)
|
3.3 ± 0.55
|
1.8–4.6
|
|
3.0 ± 0.49
|
1.7-4.0
|
Thumb length (digit 1) (cm)
|
5.2 ± 0.49
|
4.1–6.3
|
|
4.8 ± 0.53
|
4.0-5.8
|
Index finger length (digit 2) (cm)
|
6.4 ± 0.43
|
5.3–7.8
|
|
5.9 ± 0.46
|
5.1–7.2
|
Middle finger length (digit 3) (cm)
|
7.0 ± 0.46
|
5.8–8.4
|
|
6.5 ± 0.47
|
5.6-8.0
|
Ring finger length (digit 4) (cm)
|
6.6 ± 0.51
|
4.8–7.5
|
|
6.0 ± 0.42
|
4.6–6.9
|
Pinky finger length (digit 5) (cm)
|
5.4 ± 0.48
|
4.2–6.5
|
|
4.9 ± 0.46
|
4.1-6.0
|
Hand depth (cm)
|
4.2 ± 0.40
|
2.8–5.3
|
|
3.9 ± 0.30
|
2.5–4.8
|
Wrist circumference (cm)
|
15.2 ± 1.3
|
10.9–19.8
|
|
14.4 ± 1.50
|
10.4–18.7
|
Forearm Length (cm)
|
22.1 ± 1.6
|
17.8–26.9
|
|
20.2 ± 0.48
|
17.0-24.8
|
Forearm Circumference (cm)
|
23.2 ± 1.4
|
14.5–29.6
|
|
21.0 ± 1.60
|
14.0-27.4
|
Table 4 shows the mean values for HGS, tip to tip, key, and three-jaw chuck pinches of the study population by gender, age group, and hand dominance. The ANOVA results showed significantly different levels of HGS and PSs outcomes in terms of the age group of participants in both genders (p < 0.05). According to the Tukey's post hoc tests, boys and girls students in any age group exerted significantly higher levels of HGS as well as tip to tip, key, and three-jaw chuck pinches compared to their predecessor age group (p < 0.01). Boys of 11–14 and 15–18 years were stronger and had greater handgrip and pinch strengths than their girls peer groups (p < 0.001). Grip and pinch outcomes were marginally higher in 7–10 years boys compared to the girls of the same age range, but the differences were not statistically significant. More precisely, the average of girls’ HGS in 7–10, 11–14, and 15–18 years age groups were approximately 84%, 79%, and 60% of boys. Also, the average of girls’ tip to tip, key, and three-jaw chuck pinches were approximately 84.4%, 82.2%, and 88.5% of boys, respectively. Among different types of pinch, the key pinch produced the greatest strength followed by the tip to tip and three-jaw chuck pinches, whatever the gender and hand dominance.
Hand dominance had a significant effect on HGS and PSs outcomes (p < 0.001). The dominant HGS was greater than that of the non-dominant HGS by about 8% for both genders. Further, tip to tip, key, and three-jaw chuck pinches were significantly higher for the dominant, vs. non-dominant hand (about 9.3%, 10.5%, and 11.1% within boys and about 11.1%, 10.9%, and 10.4% within girls, respectively). The dominant hand tip to tip, key, and three-jaw chuck pinches exerted by boys’ students were 17.5%, 21.3%, and 13.2% higher than those exerted by girls, respectively. These values for the non-dominant hand tip to tip, key, and three-jaw chuck pinches exerted by boys’ students were 19.4%, 21.8%, 12.5% higher than of those exerted by girls, respectively.
Table 4
Differences in HGS and PSs measurements (kg) in terms of the hand dominance among genders, and age groups, where by Mean ± SD (Min-Max).
Age group (years)
|
Number
|
Hand
|
HGS
|
Tip to tip
|
Key
|
three-jaw chuck
|
Boys
|
|
7–10
|
451
|
D
|
12.8 ± 2.6 (7.1–19.3)
|
3.3 ± 0.8 (1.6–4.8)
|
5.1 ± 1.0 (3.2–6.7)
|
4.1 ± 0.8 (1.8–6.4)
|
ND
|
11.7 ± 2.4 (6.6–18.7)
|
3.1 ± 0.8 (1.5–4.2)
|
4.7 ± 0.9 (3.3–6.5)
|
3.7 ± 0.9 (1.9–5.7)
|
|
11–14
|
435
|
D
|
24.1 ± 4.2 (13.4–37.0)
|
4.5 ± 1.0 (2.8–6.1)
|
7.3 ± 1.0 (5.0–9.2)
|
6.1 ± 1.1 (3.2–8.4)
|
ND
|
22.4 ± 4.2 (13.0–33.7)
|
4.1 ± 1.2 (2.7–5.8)
|
6.6 ± 1.2 (4.3–9.0)
|
5.4 ± 1.2 (3.0–7.8)
|
|
15–18
|
505
|
D
|
39.5 ± 4.0 (29.3–48.7)
|
6.2 ± 1.5 (3.9–8.1)
|
9.8 ± 1.5 (7.1–11.3)
|
8.0 ± 1.4 (4.8–10.1)
|
ND
|
36.8 ± 4.2 (27.3–45.1)
|
5.6 ± 1.4 (3.1–7.6)
|
8.7 ± 1.4 (7.3–10.2)
|
7.1 ± 1.4 (5.0–9.7)
|
|
Total
|
1391
|
D
|
25.5 ± 3.6 (7.1–48.7)
|
4.7 ± 1.0 (1.6–8.1)
|
7.4 ± 1.1 (3.2–11.3)
|
6.0 ± 1.1 (1.8–10.1)
|
ND
|
23.6 ± 3.3 (6.6–45.1)
|
4.3 ± 1.1 (1.5–7.6)
|
6.7 ± 1.2 (3.3–10.2)
|
5.4 ± 1.0 (1.9–9.7)
|
Girls
|
|
7–10
|
357
|
D
|
11.3 ± 2.7 (6.1–18.4)
|
3.1 ± 0.8 (1.4–4.1)
|
4.6 ± 1.0 (3.0–6.2)
|
3.9 ± 1.0 (1.8–5.6)
|
ND
|
10.2 ± 2.9 (5.3–17.8)
|
2.8 ± 0.9 (1.3–3.7)
|
4.1 ± 0.9 (2.9–5.8)
|
3.5 ± 0.9 (1.9–5.3)
|
|
11–14
|
421
|
D
|
18.9 ± 3.7 (12.7–27.5)
|
4.1 ± 1.0 (2.5–5.6)
|
6.3 ± 1.2 (4.3–8.8)
|
5.5 ± 1.1 (3.8–7.7)
|
ND
|
17.8 ± 3.4 (13.0–29.2)
|
3.7 ± 1.1 (2.6–5.2)
|
5.7 ± 1.1 (4.5–8.0)
|
4.9 ± 1.0 (3.2–8.0)
|
|
15–18
|
468
|
D
|
23.7 ± 3.3 (17.7–30.4)
|
4.8 ± 0.9 (2.9–6.3)
|
7.6 ± 1.2 (4.6–9.4)
|
6.5 ± 1.0 (4.3–9.1)
|
ND
|
22.1 ± 3.4 (16.5–29.8)
|
4.3 ± 0.8 (2.6–6.0)
|
6.8 ± 1.3 (4.9–9.0)
|
5.8 ± 1.1 (3.9–8.6)
|
|
Total
|
1246
|
D
|
17.8 ± 3.0 (6.1–30.4)
|
4.0 ± 0.9 (1.4–6.3)
|
6.1 ± 1.1 (3.0-9.4)
|
5.3 ± 1.0 (1.8–9.1)
|
ND
|
16.5 ± 3.1 (5.3–29.8)
|
3.6 ± 0.9 (1.3-6.0)
|
5.5 ± 1.1 (2.9-9.0)
|
4.8 ± 1.0 (1.9–8.6)
|
Data are Means ± SD (Minimum–Maximum).
|
Correlation analysis
Table 5 shows the Pearson’s correlation coefficients of the study variables. It was found that the correlations between 17 hand-forearm anthropometric dimensions and demographic factors with HGS are statistically significantly different from zero except fist circumference (r = 0.032; judged at p < 0.05, 2-tailed) and hand depth (r = 0.108; judged at p < 0.05, 2-tailed). The strongest correlations were found between the hand length and all types of hand strengths (0.845, 0.876, 0.892, and 0.835 for handgrip, tip to tip, key, and three-jaw chuck pinches, respectively; p < 0.01, 2-tailed). This was followed by the correlations of the stature and forearm length with HGS and PSs measurements (with the correlation coefficients being generally above 0.7). Moreover, there were significant correlations between different pinch types with demographic variables and some hand-forearm dimensions (age, stature, weight, BMI, hand length, hand circumference, thumb length, index finger length, middle finger length, wrist circumference, forearm length, and forearm circumference).
Table 5
Pearson’s correlation coefficients among hand-forearm anthropometric and demographic variables with HGS
variables
|
HGS
|
|
Tip to tip
|
|
Key (lateral)
|
|
palmar
|
r
|
p
|
|
r
|
p
|
|
r
|
p
|
|
r
|
p
|
Age
|
0.697**
|
0.000
|
|
0.623**
|
0.000
|
|
0.630**
|
0.000
|
|
0.662**
|
0.000
|
Stature
|
0.787**
|
0.000
|
|
0.783**
|
0.000
|
|
0.765**
|
0.000
|
|
0.755**
|
0.000
|
Weight
|
0.351**
|
0.000
|
|
0.411**
|
0.000
|
|
0.428**
|
0.000
|
|
0.383**
|
0.000
|
BMI
|
0.335**
|
0.001
|
|
0.331**
|
0.001
|
|
0.316**
|
0.001
|
|
0.307**
|
0.001
|
Hand length
|
0.845**
|
0.000
|
|
0.876**
|
0.000
|
|
0.892**
|
0.000
|
|
0.835**
|
0.000
|
Palm length
|
0.363**
|
0.000
|
|
0.161
|
0.165
|
|
0.137
|
0.229
|
|
0.171
|
0.153
|
Hand breadth across thumb
|
0.552**
|
0.000
|
|
0.081
|
0.248
|
|
0.131
|
0.245
|
|
0.140
|
0.227
|
Hand breath metacarpal
|
0.443**
|
0.000
|
|
0.154
|
0.176
|
|
0.117
|
0.277
|
|
0.139
|
0.230
|
Hand circumference
|
0.361**
|
0.000
|
|
0.317**
|
0.001
|
|
0.376**
|
0.000
|
|
0.351**
|
0.000
|
Fist length
|
0.301**
|
0.001
|
|
0.188
|
0.155
|
|
0.171
|
0.231
|
|
0.109
|
0.334
|
Fist circumference
|
0.032
|
0.361
|
|
0.047
|
0.310
|
|
0.127
|
0.246
|
|
0.097
|
0.360
|
Maximum Internal grip diameter
|
0.563**
|
0.000
|
|
0.117
|
0.293
|
|
0.145
|
0.209
|
|
0.107
|
0.333
|
Thumb length (digit 1)
|
0.582**
|
0.000
|
|
0.521**
|
0.000
|
|
0.672**
|
0.000
|
|
0.664**
|
0.000
|
Index finger length (digit 2)
|
0.475**
|
0.000
|
|
0.265*
|
0.010
|
|
0.247*
|
0.018
|
|
0.272*
|
0.009
|
Middle finger length (digit 3)
|
0.478**
|
0.000
|
|
0.320**
|
0.001
|
|
0.318**
|
0.001
|
|
0.302**
|
0.001
|
Ring finger length (digit 4)
|
0.245*
|
0.015
|
|
0.133
|
0.209
|
|
0.145
|
0.194
|
|
0.127
|
0.231
|
Pinky finger length (digit 5)
|
0.210*
|
0.025
|
|
0.143
|
0.220
|
|
0.165
|
0.151
|
|
0.176
|
0.142
|
Hand depth
|
0.108
|
0.331
|
|
0.122
|
0.282
|
|
0.100
|
0.353
|
|
0.087
|
0.378
|
Wrist circumference
|
0.393**
|
0.000
|
|
0.251*
|
0.012
|
|
0.237*
|
0.020
|
|
0.206*
|
0.030
|
Forearm Length
|
0.745**
|
0.000
|
|
0.771**
|
0.000
|
|
0.727**
|
0.000
|
|
0.707**
|
0.000
|
Forearm Circumference
|
0.433**
|
0.000
|
|
0.203*
|
0.030
|
|
0.241*
|
0.006
|
|
0.210*
|
0.023
|
*Correlation is significant at the 0.05 levels (2-tailed).
**Correlation is significant at the 0.01 levels (2-tailed).
Bold numbers are significant at the 0.01 or 0.05 levels (2-tailed).
|
Prediction of HGS and PSs strengths
Based on the PLS analysis, only one factor was extracted which explained 46.14% and 58.81% of the total variance for the independent (hand-forearm dimensions) and dependent (handgrip and pinches) variables, respectively. The extracted dependent factor was correlated to the HGS, tip-to-tip pinch, and key pinch, three-jaw chuck pinch strengths, with the coefficients of 0.63, 0.51, 0.47 and 0.54, respectively. PLS factor loadings for the independent variables were compared in Fig. 2. Accordingly, hand length, hand circumference, thumb length, index finger length, middle finger length, forearm length had considerable factor loadings of > 0.25 in the extracted factor.
To estimate of internal consistency in the PLS approach, Cronbach’s and item-delete Cronbach’s are used for the extracted factor and each item, respectively (Table 6). The extracted factor had good internal consistency in the present study (The internal consistency is excellent if , and good if 0.7 (48). According to the results of the analysis, if items (M2), (M7), and (M14) are deleted, Cronbach’s of the corresponding factor increases slightly.
Table 6
Internal consistency of factors
Cronbach’s
|
Item
|
Cronbach’s if item is deleted
|
0.885
|
(M1) Hand length
|
0.877
|
* (M2) Palm length
|
0.894
|
(M5) Hand circumference
|
0.861
|
*(M7) Fist circumference
|
0.888
|
(M9) Thumb length (digit 1)
|
0.875
|
(M10) Index finger length (digit 2)
|
0.869
|
(M11) Middle finger length (digit 3)
|
0.866
|
* (M14) Hand depth
|
0.891
|
(M15) Wrist circumference
|
0.875
|
(M16) Forearm Length
|
0.862
|
(M17) Forearm Circumference
|
0.879
|
* Cronbach’s 𝛼 increases if item is deleted.
Bold values indicate 0.7 ≤ Cronbach’s 𝛼 < 0.9.
|