Hand Size Influences Optimal Grip
Span in Women but not in Men
Jonathan Ruiz-Ruiz, BSc, Jose L.M. Mesa, BSc,
Angel Gutiérrez, MD, PhD, Manuel J. Castillo, MD, PhD, Granada, Spain
This study investigates which position (grip span) on the standard grip dynamometer results in
maximum grip strength. Our null hypotheses included (1) no optimal grip span exists for
measuring grip strength and (2) optimal grip span is unrelated to hand size. We also intended
to derive a simple mathematical algorithm to adapt grip span to hand size. Seventy healthy
subjects (40 women/30 men; mean age, 40 years; range; 20 – 80 years) free of upper-limb
lesions were evaluated. Each hand was randomly tested on 10 occasions using 5 different grip
spans. Our findings showed that (1) optimal grip span was identified for both genders and (2)
hand size and optimal grip span correlated in women but not in men. When measuring
handgrip strength in women, hand size must be taken into consideration. We provide a
mathematical equation (y ⫽ x/5 ⫹ 1.5 cm) to adapt optimal grip span (y) to hand size (x) in
women. In adult men, optimal grip span can be set at a fixed value (5.5 cm). (J Hand Surg
2002;27A:897–901. Copyright © 2002 by the American Society for Surgery of the Hand.)
Key words: Dynamometer, handgrip strength, hand size, optimal grip span.
Measurement of handgrip strength using a hand
dynamometer is a simple and economical test that
gives practical information on muscle, nerve, bone,
or joint disorders.1–5 Similarly it represents a good
index of the rehabilitation process in lesions affecting upper extremities,6,7 and it is a predictor of
disability (or need of external aid for daily activities)
in older people.8 Differences in handgrip strength are
markedly associated with levels of physical activity
and health.9,10 Grip strength is also measured in
several sport disciplines and on the admission tests
for different types of work as police, army, or fire
brigade.11
From the Department of Physiology, School of Medicine and School
of Sport Sciences, University of Granada, Granada, Spain.
Received for publication May 18, 2001; accepted in revised form
April 11, 2002.
No benefits in any form have been received or will be received from
a commercial party related directly or indirectly to the subject of this
article.
Reprint requests: Manuel J. Castillo, MD, PhD, Department of
Physiology, School of Medicine, University of Granada, 18071
Granada, Spain.
Copyright © 2002 by the American Society for Surgery of the Hand
0363-5023/02/27A05-0020$35.00/0
doi:10.1053/jhsu.2002.34315
In addition to muscle activity the measure of handgrip strength can be influenced by several factors
including age, gender, muscle length, and insertion
angle of tendons at the time of contraction.12,13 A
factor that also can be of influence is hand size, but
no specific adaptation is used to adapt the dynamometer grip span to the hand size. Although middle grip
spans allow for greater absolute forces than extreme
sizes,14,15 the question of which position on the grip
dynamometer will result in maximum strength has
not been answered thoroughly. Accordingly the aim
of our present research was to answer the question of
which setting on the standard grip dynamometer
should be used when evaluating maximum grip
strength. Whether gender has some influence is also
of practical importance. Our null hypotheses included (1) there is not an optimal grip span for
measuring grip strength and (2) there is no association between hand size and optimal grip span. Therefore our first purpose was to determine if in men
and/or women an optimal grip span exists for measuring handgrip strength and if that grip span is
related to hand size. If so our second purpose was to
derive a simple mathematical equation relating hand
The Journal of Hand Surgery 897
898 Ruiz-Ruiz et al / Handgrip Strength
Figure 1. Measure of hand size (5-mm precision).
size and grip span in an attempt to guide the clinician
in the selection of the ideal setting on the dynamometer when measuring grip strength.
Materials and Methods
Subjects
Seventy healthy subjects (40 women, 30 men)
participated in the study after receiving information
about the aim and clinical implications of the investigation. Mean age was 39 years (range, 20 – 80 y) for
men and 41 years (range, 20 – 80 y) for women. The
sample size secures a precision ⬍0.36␴ for inferred
values, with 95% of confidence; therefore, the sample size is satisfactory to make comments about the
adult population at large. All the subjects included in
the present study were in good health and free of any
lesion or impairment in the upper limbs. As previously reported,16 the subjects were encouraged to do
their best when performing the tests and were advised not to perform strenuous physical activity in
the 24 hours preceding the test.
Methods
Measurement of hand size. Hand size was measured in both hands at maximal width and by measuring the distance separating distal extremes of the
first and fifth digits (Fig. 1). The precision of the
measure was 0.5 cm. The results of hand size were
therefore rounded to the nearest whole centimeter.
Measurement of handgrip strength. Handgrip
strength was measured using the same digital dynamometer on all occasions (TKK 5101 Grip-D;
Takey, Tokyo, Japan). The reported precision of the
device was 0.1 kg. When performing the dynamometry, subjects maintained the standard bipedal position during the entire test with the arm in complete
extension and did not touch any part of the body with
the dynamometer except the hand being measured.
Each subject performed (alternately with both hands)
the test twice using different grip spans in random
order and allowing a 1-minute rest period between
measures. For each measure the hand to be tested
first was chosen randomly. The grip spans used were
4.5, 5.0, 5.5, 6.0, 6.5, and 7.0 cm, which corresponded to 6 different positions on the TKK dynamometer. If the hand size was ⬍20 cm, the highest
grip span was rejected; if the hand size was ⬎20 cm,
the lowest grip span was rejected. For each hand the
best result at each grip span was retained. In the
JAMAR hand dynamometer (Fit Systems Inc, Calgary, Canada), the grip-span equivalence for the different positions are the following: I, 3.5 cm; II, 4.8
cm; III, 6.0 cm; IV, 7.3 cm; V, 8.6 cm.
Determination of optimal grip span. The optimal grip span is the grip span at which maximum
handgrip strength is obtained. To determine the individual optimal grip span, we first established for
each hand of each individual the kind of association
relating grip span and handgrip strength (ie, the results of handgrip strength obtained at the different
grip spans). For that purpose, we used the statistical
package SPSS 9.0 (SPSS Inc, Chicago, IL). In all
cases the association was statistically significant.
This association could be linear, logarithmic, potential, exponential, or polynomial. All distributions
were considered, and the most relevant one was
retained. The mathematical function of the relation
was individually determined through the least square
fit and graphically represented (Fig. 2). In most of the
cases (n ⫽ 64) it was quadratic and parabolic (corresponding to a second degree polynomial equation).
Once we defined the equation, the optimal grip span
was calculated as x 兩 f⬘(x) ⫽ 0, where x ⫽ optimal
grip span (cm) and f(x) ⫽ handgrip strength (kg). In
graphical terms this corresponded to the maximum of
the curves (Fig. 2). For nonpolynomial equations
(n ⫽ 6), the optimal grip span was graphically determined, and this corresponded to one of the extreme grip spans used for that particular subject.
Determination of the optimal grip span for a
given hand size. Using the SPSS package, we
studied if optimal grip spans were significantly related to hand size. In case of statistically significant
relation we used the least square fit to establish the
mathematical function relating both variables. This
The Journal of Hand Surgery / Vol. 27A No. 5 September 2002 899
Table 1. Optimal Grip Span Determined in
Women (n ⫽ 40) for Each Hand Size
Hand Size
(cm)
17 (16.5–17.4)
18 (17.5–18.4)
19 (18.5–19.4)
20 (19.5–20.4)
21 (20.5–21.4)
Figure 2. Association relating handgrip strength and grip
span in one of the cases. The maximum of the seconddegree polynomial regression equation relating handgrip
strength and grip span [f(x)] was the optimal grip span for
each hand of each individual.
equation allows establishment of the optimal grip
span for a given hand size. In case of nonsignificant
relation the conclusion is that optimal grip spans are
not related to hand size.
Usefulness and reliability of the optimal grip
span. To confirm the usefulness of using the optimal grip span when measuring handgrip strength, we
studied an additional group of 12 young healthy
subjects (5 women, 7 men) who were preparing for
the demanding physical tests requested for admission
into the local fire brigade. In these subjects handgrip
strength was measured at 3 grip spans (optimal grip
span, 1 cm below, 1 cm above).
For confirming the reliability of measurements of
handgrip strength at optimal grip span, 10 of the
previous 12 subjects (5 women, 5 men) were tested
on 2 occasions 2 days apart.
Statistical Analysis
Results are presented as mean ⫾ SD. The normality
of the distribution of the measured variables was ascertained using the Shapiro-Wilk test. Mean values were
compared using the Welch test because it is more
powerful than the Student’s t-test.17 Evidence of statistical association between variables was obtained using
the statistical package SPSS 9.0. In case of association
the mathematical function defining the association was
calculated through the least square fit.
For confirming the usefulness of measuring handgrip strength at optimal and suboptimal grip spans,
1-way analysis of variance was used. Reliability coefficient of handgrip strength measured at optimal
grip span in 2 different occasions was calculated;
Right-Hand Optimal
Grip Span (cm)
Left-Hand Optimal
Grip Span (cm)
Mean
SD
Mean
SD
4.81
5.05
5.16
5.58
5.72
0.32
0.57
0.60
0.29
0.95
5.00
5.14
5.15
5.52
5.63
0.42
0.56
0.59
0.25
0.52
No differences between the results of optimal grip span were
obtained in both hands for each hand size (p ⬎ .40).
values were compared through the Student’s t-test
for paired samples and correlated through parametric
bivariate correlation analysis.
The alpha error was fixed at ␣ ⫽ 0.05 except for
the Shapiro-Wilk test (␣ ⫽ 0.20).
Results
All subjects completed the tests satisfactorily. The
mean ⫾ SD measured hand size was 19 ⫾ 1.8 cm for
women (n ⫽ 40) and 20 ⫾ 1.7 cm for men (n ⫽ 30)
(p ⬍ .05) with no observed differences between both
hands in any of the gender groups. In both genders and
for both hands we found an optimal grip span for
measuring handgrip strength. Consequently the first
null hypothesis (there is not an optimal grip span for
measuring handgrip strength) can be rejected. At the
different hand sizes the corresponding optimal grip
spans are presented in Tables 1 and 2 for women and
men, respectively.
Table 2. Optimal Grip Span Determined in Men
(n ⫽ 30) for Each Hand Size
Hand Size
(cm)
17 (16.5–17.4)
18 (17.5–18.4)
19 (18.5–19.4)
20 (19.5–20.4)
21 (20.5–21.4)
22 (21.5–22.4)
23 (22.5–23.4)
25 (24.5–25.4)
Mean
Right-Hand Optimal
Grip Span (cm)
Left-Hand Optimal
Grip Span (cm)
Mean
SD
Mean
SD
5.20
4.90
6.10
5.91
5.80
5.45
5.83
5.00
5.52
0.54
0.55
0.32
0.45
0.58
0.65
0.45
0.41
0.62
5.34
4.81
6.05
5.90
5.96
5.84
5.60
5.00
5.56
0.52
0.36
0.39
0.75
0.43
0.68
0.36
0.55
0.55
There were no significant differences between the results of
both hands (p ⫽ .90).
900 Ruiz-Ruiz et al / Handgrip Strength
Figure 3. Evidence of association between hand size and
optimal grip span for both hands in women (n ⫽ 40).
Values are means and standard errors of the mean. A
simplified calculation algorithm is presented.
In women hand size and optimal grip span showed a
significant linear association (Fig. 3) so the second null
hypothesis can be rejected for women. The equation
relating grip span as a function of hand size in women
is formulated as y ⫽ 0.235x ⫹ 0.799 (r ⫽ 0.984, p ⫽
.002) for the right hand and y ⫽ 0.164x ⫹ 2.172 (r ⫽
0.955, p ⫽ .011) for the left hand. Because there were
no differences between the results of optimal grip span
obtained in both hands (p ⬎ .40; Table 1) for each hand
size, we can derive a single algorithm encompassing
both hands. This algorithm is y ⫽ 0.1997x ⫹ 1.4798,
where x is the hand size and y is the optimal grip span
(Fig. 3). A simplification of this algorithm allowing its
clinical use for adapting grip span to hand size in
women would be y ⫽ x/5 ⫹ 1.5, where x is the hand
size (maximal width between first and fifth finger)
measured in centimeters, and y is the optimal grip span
at which the dynamometer should be settled before the
test.
By contrast, as shown in Figure 4, the regression
analysis (either linear or nonlinear) between hand size
and optimal grip span was not statistically significant in
men. Consequently the second null hypothesis (there is
no relation between hand size and optimal grip span)
cannot be rejected for men. Because there were no
significant differences between the results of both
hands (5.52 ⫾ 0.62 cm right vs 5.56 ⫾ 0.55 cm left,
p ⫽ .90), we propose that 5.5 cm is the optimal grip
span for measuring grip strength in men for both hands
and independent of the hand size.
When handgrip strength was measured at optimal
grip span, 1 cm below, and 1 cm above, maximal
handgrip strength was obtained at optimal grip span
(Fig. 5). When handgrip strength was repeatedly measured at optimal grip span, a reliability coefficient of
Figure 4. Hand size and optimal grip span measured in
men (n ⫽ 30) show no evidence of statistically significant
association.
0.96 and 0.97 for left and right hands, respectively, was
obtained. Moreover, the Student’s t-test for paired samples did not show statistical difference between test and
retest (p ⫽ .36 and .22 for right and left hands), and a
highly significant correlation between test and retest
values was obtained for the left (r ⫽ 0.9874, p ⬍ .001)
and right hand (r ⫽ 0.9892, p ⬍ .001) at the optimal
grip spans. These results suggest the usefulness and
reliability of measuring handgrip strength at the optimal
grip span.
Discussion
The results presented here show that when measuring handgrip strength there is an optimal grip span
Figure 5. Handgrip strength measured in right and left
hands at optimal grip span, 1 cm below, and 1 cm above.
Values are mean ⫾ standard error of the mean (n ⫽ 12)
**p ⬍ .01 from 1-way analysis of variance.
The Journal of Hand Surgery / Vol. 27A No. 5 September 2002 901
at which the standard dynamometer should be set.
This occurs for both men and women. In men the
optimal grip span is a fixed value (5.5 cm) and is not
influenced by hand size. In women the optimal grip
span is influenced by hand size; this implies the need
of adapting the dynamometer grip span to the hand
size. For that a simple algorithm is proposed. This
algorithm can be applied to all female hands.
Firrell and Crain14 reported that the majority of hands
(89%) had a maximal strength at setting II (of V) of a
hand dynamometer, but no clear significant correlation
between body mass or hand size and maximal setting
was evident in 288 normal individuals ranging in age
from 4 to 78 years. This is in accordance with our own
results in men but not in women. In another report15
middle grip spans allowed for greater absolute forces
than smaller or larger ones. In that study15 the association between hand size and optimal grip span was not
analyzed. Oh and Radwin18 also reported that handle
span affected maximal and submaximal grip force. For
these investigators hand size affected grip strength, grip
force, and exertion level. In another study19 the optimal
grip span was 5.0 to 6.0 cm for women and 5.5 to 6.5
cm for men. Our results are in accordance and complement these data.
It has been reported that significant differences
may exist between rural and industrial communities
regarding handgrip strength.20 Our subjects came
from an urban setting, and specifically the women
did not perform hard manual activities. By contrast
the men in our study were mostly manual workers;
therefore, they presented higher muscle mass and
strength in their forearm than the women. In men this
may compensate for any effect of hand size and may
partially explain the lack of association between
hand size and optimal grip span.
The authors thank the subjects for participating in and committing to
this study.
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