Tsz Wing Ho
PHYS 1
Mon & Wed 2-5pm
April 9, 2012
Gender Difference on Clench Force (Dominant Forearm)
Abstract
Physiologically, the degree of skeletal muscle contraction in an individual is controlled
by activation of a desired number of motor units within the muscle. And activation of the
different types of muscle fibers will generate different strength of muscle contraction. For
instance, a reserach has been shown that since the ratio of type 2 to type 1 fibers in male is
relatively higher than in female, they can generate a greater clench force than female (Hunter,
2001). The purpose of this experiment is to test whether men can actaully generate a greater
clench force than female with their dominant arm. Their clench forces can be measured by the
Biopac Hand Dynamometer under the EMG lab. Results support the hypothesis that male can
generate a greater clench force in each increment than female by using their dominant arm.
Nevertheless, more investigations are required to be more confirmed with the hypothesis, since
the sample size is so small that it is insufficenct to represent the general population. In addition,
the grip strength may vary in person since people can increase the strength if they have more
muscle training.
Introduction
It has been suggested that men are more able to generate target forecs than women due to
a greater muscle mass in male. Recent finding showed that men has significantly more skeletal
muscle mass in comparison to women in both absolute terms (33.0 vs. 21.0kg) and relative to
body mass (38.4 vs. 30.6%) and that gender differences are greater in the upper body (Janssen,
2000). In addition, fiber type composition has been cited as a reason for gender differences, with
a higher percentage of type 1 slow fibers in a normal population of female subjects, whereas a
higher percentage of type 2 fast fibers in male subjects ( Doyle, 2002). Since the type 2 fibers are
larger in size and contain a higher level of mysoin ATPase, they can generate a faster and
greater muscle contraction (Tompson, 1994). Therefore, it is hypothsized that male can generate
a higher clench force than female. Since the dominant arm has a better control of limb dynamics
(Bagesteiro, 2002), all the subjects in this experiment were used their dominant forearm to
measure the clench force in the five target forces.
Methods and Materials
In this experiment, we compared the clench force between the six female subjects (the
experimental group) and the six male subjects (the control group). By using the
electromyography (EMG) in the Biopac system, the grip strength of the 12 subjects could be
measured. All the subjects were required to attach the electrodes on their dominant forearm
(generally if the subject is right-handed, the electrodes will be attached on the right arm). It is
suggested to using alcohol to wipe out the skin before attaching the electrodes in order to have a
better connection between the electrodes and the skin. And it is better to wait for 5 minutes to
give the electrodes time to establish contact with the surface of the skin. After that, the recorder
could plug the electrode assembly (SS2L) into channel 3 and told the subject to seat on a chair.
In order to collect a better and more accuarate result, all the subjects should be seated away from
the computer screen so that they could not see their data while they were clenching on the hand
dynamometer. Once the recorder logged into the Biopac Student Lab to start the experiment, He
or she would have to calibrate before actually recording the subject's data. After the 8 seconds
for calibration, the subjects would start to repeat a cycle of clench-release-wait. They held the
clench for 2 seconds, and waited for 2 seconds after releasing before beginning the next cycle.
The subject should try to increase clench strength in equal increments such that the fourth clench
was the maximum clench force. We would record an incraese in the numebr of active grip
muscle motor units (motor unit recruitment) as grip force increased.
Result
Student 1
Student 2
Student 3
Student 4
Student 5
Student 6
Mean
Stdev
1
9.98
9.611
7.929
8.985
9.017
8.77
9.0487
0.709925
2
19.65
17.057
17.748
18.08
19.446
19.17
18.525
1.0475
3
28.58
22.158
29.097
28.081
28.603
38.41
29.155
5.2231
4
38.17
22.936
28.34
38.33
36.235
57.011
36.837
11.634
Table 1. The mean and the standard deviation of clench force in the 6 male subjects.
Student 1
Student 2
Student 3
Student 4
Student 5
Student 6
Mean
Stdev
1
4.498
5.977
3.04
8.908
3.04
5.79
5.2088
2.2147
2
8.66
9.847
6.7
19.169
2.968
9.88
9.5388
5.3842
3
13.288
14.228
11.25
23.244
4.954
14.36
13.554
5.9049
4
19.042
18.372
12.01
21.656
8.521
19.75
16.5585
5.11697
Table 2. The mean and standard deviation of clench force in the 6 female subjects.
Figure 1. Dominant Forearm : The mean value of the clench force at equal increments in target
forces (1: 5kg, 2: 10kg, 3: 15kg, 4: 20kg). The error bar is also shown in each target force.
In Table 1 and 2. the mean and standard deviation of clench force for both male and female
sunjects were calculated at each target force. And the data for both male and female subjects
were used to plot a bar graph, which is shown in Figure 1. In Figure 1, the mean value of clench
force for both gender was combined together at each target force. The graph shows that at each
target force (5 kg, 10kg, 15kg, 20kg), the clench force of the male subjects is greater than that of
the famle subjects.
Discussion
The result in this experiment supports the hypothesis that men are more likely to generate
a greater clench force than women do. According to Figure 1, the mean value of the clench force
at each target force is greater in male than in female. For instance, at the target force in 5 kg, the
male subjects generate 9.05 kg clench force compared to 5.2kg clench force in the female
subjects, In addition, at each tartget force, the standard deviations between male and female do
not overlap each other, which indicates that the mean values of both subjects are statistically
different. Hence, it further supports the hypothesis that there is actually a difference of clench
force between male and female.
As mentioned above, due to the fact that there is a difference in fiber type composition
between male and female, men are therefore more likely to produce a greater clench force than
female do. In one study comparing biceps of male and female bodybuilders, it was found that the
relative amount of Type 1 fibers was comparable; however, the ratio of Type 1 to Type 2 in the
male group was much higher than in the female, suggesting that there is a greater preferentail
hypertrophy of Type 2 fibers in males ( Anderson, 1977). Histochemically, the type 2 fibers (also
called fast fibers) have a high level of myosin ATPase, a rapid calcium release with uptake of
scaroplasmic reticulum. Myosin ATPase is used to split the ATP to ADP with Pi to provide
instantaneous energy for muscle contraction. Furthermore, the fast fiber is rich in glucoltic
enzymes to allow instantaneous release of intramuscular glycogen. They are therefore able to
activate at a rate of 2-3 times that of slow fibers. As a result, these fibers are best suited to
generate a fast forceful muscle contraction (Thompson, 1994). Besides that, another study also
indicated that testosterone ,one of the steriod hormones, contributes to skeletal msucle growth
(Devold, 1990). Thus, men tend to have a higher muscle mass ratio to body weight than female
do.
Although this experiment supports the hypothesis that men can generate a greater clench
force than female, further investigations are still required since only a small sample size (12
people in total) was used. It is therefore insufficent to represent the general population. Besides
that, the muscle strength can be incraesed by having more training. The experimental group
(female) and the control group (male) can only represent the ordinary people, so the analysis has
to be excluded for those who are often tarined such as altheletes.
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