In order for animals to be able to perform any type of movement, its body requires the use of muscles. The human body is composed of around six hundred muscles while only around forty through fifty percent of those muscles are skeletal muscles. In order to make the body move, it uses skeletal muscles and bones as a lever. The muscle provides a force on the bone that moves the bone. The muscle is also able to contract, extend, relax and flex to cause a bone to rotate around a joint. The bones, muscles, and joints work together as a lever where the joint acts as the fulcrum, the bone as a lever, and the muscles provide the effort.
This experiment was performed in order to observe the electromyogram (EMG) activity while winning or losing an arm wrestling match. An EMG is an electrical impulse that is produced whether the muscle is active or inactive. The muscles used for arm wrestling are mainly the pronator teres, biceps brachii, pectoralis major and flexor carpi ulnaris along with the deltoid, latissimus dorsii, and triceps brachii which are also used but not as much (iWorx Labs 2019). In this lab, we put the majority of the focus on the pronator teres and biceps brachii muscles.
The pronator teres is a rectangular muscle which is located on the superficial region of the anterior compartment of the forearm. This muscle has two origins at the proximal end of the humerus and at the distal end of the ulna, and it also has an insertion near the middle of the radius (Muscles of the Upper Limb, N.D.). The pronator teres serves as a third-class lever and is responsible for the flexion of the elbow and pronate the forearm. Since the motion in relation to arm wrestling for the pronator teres is turning toward the center when the muscle is active, this muscle will most likely be associated with winning the arm wrestling match.
The biceps brachii is a two-headed muscle that is located in the anterior compartment of the upper arm. The majority of its muscle mass is located anteriorly to the humerus and on average is 9 cm in length (Tiwana and Varacallo 2019). The two heads consist of a short and long head, with the short head’s origin is the tip of the coracoid process while the long head origin is located on the supraglenoid tubercle of the scapula. The biceps brachii is located anteriorly to the humerus, but it does not attach to the bone. The function of the biceps brachii is primarily as a strong forearm supinator and a weak elbow flexor.
MATERIAL AND METHODS
In order to compare the EGM activity from each muscle, the experiment was separated into two different exercises. The first exercise consisted of taking measurements in a simulated arm wrestling match for the Pronator teres and the Biceps brachii. The measurements in the simulated match were recorded while the subject was both winning and losing. The second exercise was similar except instead of a simulated match, the subject took part in an actual arm wrestling match and recorded the same data as the previous exercise.
Before either exercise can be started, the electrodes need to be attached to the right arm and lower abdomen. The red “+1” lead was placed on the anterior forearm on the Pronator teres near the middle of the muscle. The black “-1” lead was placed on the same muscle 2-4cm away towards the subject’s elbow. The white “+2” lead was placed on the anterior upper arm on the Biceps brachii near the elbow, while the brown “-2” was on the same muscle 2-4cm further up. The green “C” lead was placed on the lower right abdomen to serve as the ground.
After all five electrodes were connected, the first exercise was able to be started. This was done by having the subject place their right arm on the rubber mat in the neutral position where their arm was perpendicular to the table. The subject’s arm was then moved from the neutral position to the winning position, which was the subject’s palm facing the table, while the opponent providing minimum resistance. This position was held for four seconds then was returned to neutral for another four seconds. The subject’s arm was then moved from the neutral position to the losing position, which was the subject’s palm facing the ceiling, while the opponent providing minimum resistance. This position was held for four seconds then was returned to neutral for at least two seconds. This cycle was repeated two more times in order to conclude exercise 1.
For the second exercise, the same experimental setup from exercise 1 was used. The difference in this exercise was the recording was started and the command “Start Wrestling” was given to the subject and their opponent. When the command was given, both opponents tried to win using their full strength. During the match, the sections where the subject was in a winning or losing position was marked. The test was recorded from when the command was given until one of the opponents’ hands was pinned to the table, which ends exercise 2 and the data can then be analyzed. The data gathered from both exercise was done by using the mathematical functions, Abs. Int and T2-T1 which was then plugged into the class’s main chart to be compared to the other groups.
When performing the first exercise, the purpose was to identify the electromyogram activity in the biceps brachii and pronator teres muscles when both winning and losing the arm wrestling matches. Since these matches were stimulated, the muscles being observed were not being used to their maximum potential. This is because the muscle was not being fully flexed or extended. Flexion and extension are responsible for the muscles to contract which creates tension. Tension is responsible for driving the EMG activity and the EMG activity and levels of tension are directly proportional to each other. Since the muscles were not being used to their full extent so they only serve as a baseline that can be used to serve as a control for the second exercise. All the EMG activity recorded was formatted together to compare each group’s results for each situation as seen in Table 1.1. When analyzing the data recorded from exercise one, the results were better split into two subsections which were winning and losing.
When analyzing the data for the stimulated winning arm wrestling matches, the pronator teres had the most EMG activity in every group except for Group 3T, 5T, and 3W. The average of all the groups winning pronator teres was 0.936 mV. The average of the groups for the winning biceps brachii was lower at 0.684 mV which means that when the subject was winning they were using more of the pronator teres muscle than the biceps brachii.
When analyzing the data for the stimulated losing arm wrestling matches, the pronator teres had the most EMG activity in five of the nine groups which were 0.804 mV. The average of the groups for the activity in the biceps brachii muscle was 0.679 mV. These results were the opposite of what was expected, but this could be from the lack of effort given by the subjects.
Exercise two was done to observe the electromyogram activity in the biceps brachii and pronator teres muscles when both winning and losing an actual arm wrestling match. This exercise was also split into the same subsections as exercise one.
The data from the actual winning arm wrestling matches showed that the pronator teres had the highest EMG activity in all nine of the groups with an average of 9.103 mV. The average of the groups for the biceps brachii muscle activity was 6.046 mV. This data concurs with the results from exercise one.
The data received for the actual losing arm wrestling match was the opposite of the results of the stimulated losing arm wrestling with the activity of the biceps brachii being higher than the pronator teres in the actual match except for Groups 1T, 2T, and 3W. The biceps brachii muscle average was 8.273 mV while the average activity for the pronator teres was 7.02 mV. The results of this exercise agreed with what was expected.
The results of the actual matches had a much higher strength in EMG activity than that of the stimulated matches, as shown in Graph 1.1. This is due to the actual match having much higher levels of tension which causes the EMG activity to be greater. During the experiment, the subjects were able to feel the strain in the forearm when they were winning and a strain in the upper arm when they were losing. These feelings correlate with the data by the pronator teres being located in the forearm and the biceps brachii being located in the upper arm. Along with the pronator teres and the biceps brachii, there are other muscles that are also used in arm wrestling such as the pectoralis major and flexor carpi ulnaris. The deltoid, latissimus dorsii, and triceps brachii are also being used, but not as much as the other four muscles. The reason that the pronator teres and the biceps brachii were chosen to be analyzed was because of the function of the pronator teres is to pronate the forearm while the function of the biceps brachii is supination of the forearm.
In conclusion, the pronator teres play a large role in winning an arm wrestling match while the biceps brachii plays a major role in losing in an arm wrestling match. Along with this information, it was discovered that there was a large difference in the strength of the EMG activity from that of the stimulated arm wrestling match and that of an actual arm wrestling match. This was due to the actual match having more tension due to flexion and extension of the muscles. The results of the experiment further strengthened the earlier hypothesis of which muscle was responsible for winning or losing the match.
- Muscles of the Upper Limb | Boundless Anatomy and Physiology. [accessed 2019 Nov 5]. https://courses.lumenlearning.com/boundless-ap/chapter/muscles-of-the-upper-limb/.
- Tiwana MS, Varacallo M. 2019. Anatomy, Shoulder and Upper Limb, Biceps Muscle. In: StatPearls. Treasure Island (FL): StatPearls Publishing. [accessed 2019 Nov 5]. http://www.ncbi.nlm.nih.gov/books/NBK519538/.
- iWorx Labs. 2019. Experiment HM-7: Electromyogram (EMG) Activity while Arm Wrestling: Abraham Baldwin Agricultural College Lab Handout 1-2p.