Analysing the changes in muscle activity between male and female as the power of clench is increased.

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.


INTRODUCTION:

Muscle is a type of excitable tissue which has the ability to generate and propagate electrical signals called action potentials. In muscles, the basic functional unit of contraction is a motor unit. A motor unit consists of one motor neuron and the respective muscle fibres it innervates. On activation of a motor unit, its respective muscle fibres generate and conduct electrical impulses which cause contraction of muscle. When considered individual voltage of the impulses it’s quite weak but when a group of muscle fibres are considered the voltage generated by the muscles is large enough to be measured by placing electrodes on the skin surface. The techniques of detection and measurement of skin voltage generated by the underlying skeletal muscles is called Electromyography. Two types of electrodes can be used while performing electromyography (1) Needle electrodes or (2) Surface electrodes.

Fatigue describes a reversible condition in which a muscle is no longer able to generate or sustain the expected power output.1 Fatigue is influenced by the intensity and duration of the contractile activity, by whether the muscle fiber is using aerobic or anaerobic metabolism, by the composition of the muscle, and by the fitness level of the individual.1

The learning objective of this experiment is to record and analyse the difference between muscle activity between the dominant and non-dominant arm and between male and female as the power of clench is increased and understand the physiology behind it.

The null hypothesis for this experiment is that muscle activity does not change with fatigue (1) between dominant arm and non-dominant arm (2) between males and females. The alternate hypothesis states that the muscle activity changes with fatigue (1) between dominant arm and non-dominant arm (2) between males and females.

MATERIALS AND METHOD:

For this experiment the materials used were as follows BIOPAC electrode lead set (SS2LA/L), BIOPAC disposable vinyl electrodes (EL503)( 6 electrodes per Subject), BIOPAC electrode gel, Tennis Ball, Biopac Student Lab System: BSL 3.7.5 software and MP30 data acquisition unit and Computer system .

The electrode lead set was connected to channel 1 of the data acquisition unit. The disposable vinyl electrodes were attached to patient’s arms as shown in the figure 1. A small amount of gel is applied on electrode for better conductivity. Then using the Biopac Student Lab Software the system was calibrated first. During calibration, the subjects were asked to squeeze a tennis ball as hard as possible for 5 seconds by dominant and non-dominant hands for both males and females. Entire calibration took about 8 seconds. For the experiment, while recording the EMG the subject was asked to perform clench-release-wait cycle, holding for 2 seconds and waiting for two seconds after releasing before beginning the next cycle. Subjects were asked to try to increase the strength in equal increments such that the fourth clench had the maximum force. This was done for both dominant and non-dominant arm for all subjects.

Figure 1: Electrode placement and Lead attachment

The experiment was performed for 10 subjects in total.5 males and 5 females. For analysis, "Clusters" i.e. EMG bursts associated with each clench were analysed by measuring the mean mV value. The portion between two clenches was also measured. This was done for dominant and non-dominant arm for all subjects. Percentage increase in EMG activity recorded between the weakest clench and the strongest clench for both the arms was also calculated.

For further analysis i.e. to check the hypothesis two t-tests was performed to calculate difference between the means for each group. First, t-test was performed to determine the difference in the muscle activity change with fatigue between dominant and non-dominant hand for all subjects. The second t-test performed to determine the difference in the muscle activity change with fatigue between male and female dominant and non-dominant hand.

RESULTS AND ANALYSIS:

First, a paired one tailed t-test was performed to determine the difference in the muscle activity change with fatigue between dominant and non-dominant hand for all subjects. A paired t-test was chosen because the dominant and non-dominant arm was from the same subject and a one tailed test was chosen because the alternate hypothesis suggests that one mean will be greater than other to indicate whether there is a change or not in the muscle fatigue between dominant and non-dominant arm. To calculate the fatigue, the difference between the strongest clench and the weakest clench was taken for every subject. On performing the test the p value was found to be 0.0623 at significance level of 0.05. So we failed to reject the null hypothesis.

Subject

Dominant arm (mV-sec)

Non-dominant arm (mV-sec)

1

0.132

0.086

2

0.208

0.137

3

0.215

0.109

4

0.165

0.089

5

0.189

0.193

6

0.190

0.258

7

0.113

0.081

8

0.103

0.099

9

0.138

0.129

10

0.056

0.050

Average

0.151

0.123

Standard Deviation

0.052

0.061

Table 1: Integrated EMG (mV) values of all subjects for dominant and non-dominant arm

Figure 2: Mean and Standard deviation of integrated EMG (mV) values of dominant and non-dominant arm for all subjects

Power is the probability (prob = 1 - β) of correctly rejecting null hypothesis when it really is false. Power analysis was done using G Power software. From the power analysis, the probability of rejecting null hypothesis was 0.4147. For 80% power the sample size should be 28.

For the second t-test the subjects were divided into two categories based on gender. Two unpaired one tailed t-tests were performed to determine the difference between male and female for dominant and non-dominant hand. A unpaired t-test was chosen because the male and female are two different independent groups and a one tailed test was chosen because the alternate hypothesis suggests that one mean will be greater than other to show a difference/change in between males and female for dominant and non-dominant arm. For this test we have 5 male subjects 5 female subjects in each group. First, the difference between the strongest clench and the weakest clench was taken for every subject to calculate fatigues. Then the t-test was performed on the group for dominant arm and the p value was found to be 0.195 at significance level of 0.05. So we failed to reject our Null hypothesis. The t-test was performed on the group for non-dominant arm and the p value was found to be 0.103 at significance level of 0.05. So we failed to reject our Null hypothesis

Subject

Dominant arm(mV-sec)

Non-Dominant arm(mV-sec)

Male

Female

Male

Female

1

0.132

0.209

0.086

0.137

2

0.215

0.165

0.109

0.089

3

0.189

0.138

0.193

0.129

4

0.190

0.056

0.258

0.050

5

0.103

0.113

0.099

0.081

Average

0.166

0.136

0.149

0.097

Standard Deviation

0.046

0.057

0.071

0.036

Table 2: Integrated EMG (mV-sec) values of dominant and non-dominant arm for males and females

Figure 3: Mean and Standard deviation of integrated EMG (mV-sec) values of dominant arm between male and female

Figure 4: Mean and Standard deviation of integrated EMG (mV-sec) values of non-dominant arm between male and female

Power is the probability (prob = 1 - β) of correctly rejecting null hypothesis when it really is false. Power analysis was done using G Power software. From the power analysis, the probability of rejecting null hypothesis for dominant arm was 0.2081 and for non-dominant arm was 0.3626. For 80% power the sample size for dominant arm should be total 78 with 39 per group and for non-dominant arm should be total 34 with 17 per group.

DISCUSSION AND CONCLUSION:

From the results and analysis, we failed to reject the null hypothesis for the first t-test. The null hypothesis in the experiment states that there is no change in muscle activity with fatigue between dominant and non-dominant arm for all subjects. The overall mean for dominant arm is 0.15105 and for the non-dominant arm is 0.123205.This indicates that there is a difference in the two means i.e. there is a change in muscle activity with fatigue between dominant arm and non-dominant arm in all subjects. Low statistical power of 0.4147 indicates that a type II error of hypothesis testing was committed. To correct this error power analysis was done. The sample size should be as specified in the results so that the null hypothesis can be rejected. A change in muscle activity with fatigue between dominant arm and non-dominant arm in all subjects for this experiment can be supported by the following literature. The degree of fatigue that develops during exercise may be affected by muscle size and, consequently, vascular constriction during contraction.2 Generally the dominant arm has well developed muscles with good blood perfusion compared to the non-dominant hand indicating that degree of fatigue is less in that hand. Thus depending on the muscle size and blood flow during contraction the muscle activity with fatigue either increases or decreases.

From the results and analysis, we failed to reject the null hypothesis for the second two t-tests as well. The null hypothesis in the experiment states that there is no difference in the fatigue level between male and female for dominant and non-dominant arm. The overall mean of dominant arm for males is 0.1660 and for female is 0.1361 and of the non-dominant arm for males is 0.1491 and for female is 0.09731.This indicates that there is a difference in the two means between male and female for both arms i.e. there is a change in muscle activity with fatigue for dominant arm and non-dominant arm between males and females. So type II error of hypothesis testing has been identified. To correct this error power analysis was done. The sample size should be as specified in the results section so that the null hypothesis can be rejected. From the results it can be seen that, male have greater values of muscle activity (mV) than female for both dominant and non-dominant arm, this can be supported by the following literature. Differences in fatigability across age or gender could occur as a result of differences in neural drive, fiber-type composition, contractile function, muscle membrane excitability, metabolic capacity, or muscle mass and blood flow.2Since the ratio of type 2 to type 1 fiber in male is relatively higher than in female, they can generate a greater clench force than female.3 Although in this experiment the results support the fact that men can generate a greater clench force than females. Further research is still required as the sample size of the experiment is small so it’s not sufficient to represent a general population. Also clench force and muscle strength can be increased by training.

REFERENCES:

  1. Silverthorn, Dee Unglaub.Human physiology: an integrated approach. San Francisco: Pearson/Benjamin Cummings,398-439(2007).
  2. Kent-Braun, J. A., Doyle, J. W. & Towse, T. F.,J. Appl. Physiol.93, 1813-1823 (2002).
  3. Hunter, S. K. & Enoka, R. M.,J. Appl. Physiol.91, 2686-2694 (2001).

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.