Relationship Between Muscle Movement and Electric Activity

Relationship Between Muscle Movement and Electric Activity



To bring out and understand better the electromyography procedure. The measurement of the muscles’ electrical activity and to identify any relevant issues related to its assessment. The test documents the electrical signals moving through muscles.

Data Analysis

Table 1:  Examining the activity of the flexor digitorum superficialis (forearm muscle


( Mv/s)

Close hand 0.65% 55.51 ×10ˆ-6
Forcible hand 87.67% 21.05 ˟10ˆ-5
50% contraction 53.18% 38.18 ˟10ˆ-5
Squeeze             73.92%             23.76 ˟10ˆ-5
Maximal hold             76.17%             21.74 ˟10ˆ-5
5,squeeze after 61.05%


32.45 ˟10ˆ-5



Figure 1

Table 2:  Examining the activity of antagonistic muscles.

Flexion           16.33×10ˆ5 11.76×10ˆ5
Extension           86.98×10ˆ6 30.85×10ˆ5
Flexion with resistance           18.94×10ˆ5 30.43×10ˆ5
Extension with resistance           62.95×10ˆ6 61.13×10ˆ5
Pronation           51.03×10ˆ6 11.99×10ˆ5
Supination 0.00003414s 0.00009212s
Pronation with resistance 0.0000518s 0.00006171s
Supination with resistance 0.00006347s 0.0000721s


Figure 2: A line graph showing the relationship between time and the activity of each antagonistic muscles.



The test was carried out to help identify the electrical activity and force generated by the muscles. Table 1 shows different muscle power in percentage against the electrical activity. As illustrated initially, when the subject gently closes their hand around the dynamometer without any force application, there is minimal muscle power; less than a percentage with slight electrical activity to show the muscles are active even without stimulation. On forcible squeeze, there is maximal muscle power, i.e., 87.67%. Squeezing stimulates the electrical activity to rise, recording the most significant electrical activity increasingly. The difference is recorded when the subject squeezes the dynamometer hard enough to want a 50% contraction that lasts about two seconds; this records a peak in electrical muscle activity with reduced muscle power, i.e., 53.18%.

When subjected to squeeze five times, with each lasting about a second, the muscle power and electrical activity rises but peaks in the double squeeze, then declines steadily and stabilizes at the fifth squeeze. There is a positive muscle power of 4.27% with a negative electrical conductivity when noting the differences, i.e., negative 0.000031s. When the subject maximally squeezes the dynamometer and held it as long as possible, peak muscle power si recorded at the beginning with higher electrical activity. But with time, the muscle power declines steadily, but the electrical activity doesn’t decline the muscle power; it declines then stabilizes towards the end of the procedure.

Then on the immediate subject squeeze of the dynamometer five times with each lasting a duration of one second, there is a record of the steady increase of muscle power to the end of the procedure while the electrical activity peaks in the second squeeze stabilize at the end of the process. Table 2 shows a significant deviation of the biceps’ electrical activity that is greater than the triceps brachii muscles on flexion of the arm. On the extension of the same component, the triceps electrical activity is greater than that of the biceps. On flexion of the arm against resistance, the triceps electrical activity was greatly stimulated than the bicep muscles.

In contrast, on extension against the opposition, the triceps still records more excellent electrical activity than the bicep muscles. On pronation of the hand, the triceps illustrates more excellent electrical activity than the biceps muscles and the supination of the hand. In both pronation and supination against resistance, the electrical activity almost equals but with a slight rise in the triceps muscles.

 Discussion points

  1. Describe the relationship between the electrical activity of a muscle and the force generated by that muscle. Use examples from your data to support your discussion.
  2. Discuss your results of the EMG recording following fatigue. Propose a mechanism that would explain the differences seen in the EMG activity prior to and after fatigue.
  3. Based upon your results, describe the role of the biceps brachii and triceps brachii in the following movements of the arm: extension, flexion, pronation and supination.  Be sure to explain why activity is seen in both muscle groups for any one movement.







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