Holding a weight at increasing length from the elbow

The actions of many muscles are antagonistic in nature, especially in the muscles of the limbs. A small portion of the effort in countering loads is exerted by one muscle, will a bigger portion of the effort exerted to counter a load is exerted by the antagonistic muscle. This concept can demonstratively be determined using a setup that uses a load whose displacement is increased gradually to produce a higher moment for each step increase of displacement. Since muscles experience depolarization during the active period, a voltage reading may be obtained when the muscles are active. This can thus be used as a determinant of the degree of activity of the muscle. the higher the voltage developed across a muscle in its active period, the higher the degree of activity of the muscle is for that period. Therefore, curves for the voltages of antagonistic muscles against the moment of exerted loads can be used to show the relationship between the two muscles. If the voltage readings at the electrodes for the biceps and triceps show a correlation, then the behavioral pattern of the two muscles can be illustrated experimentally.

Introduction

The action of muscles drives many biological processes that require motion such as the pumping of blood and lymph, the motion of food through the gut, the processes of inhalation and exhalation, as well as in the production of body reactions to external stimuli such as heat and pain. Muscles of the drivers of all by physical activities that require any form of motion. There are a number of muscles which enable this motion, including the biceps, triceps, masseter, extensor and flexor muscles. This experiment focuses on the response of the biceps and triceps muscles in holding a weight whose displacement is gradually increased from the elbow. A number of experiments have been carried out to determine the actions of muscles and the underlying phenomena between the actions (Hill, 1938; Lindstedt et al., 2001; Schaeffer, Mineo and Lindstedt, 2013). These experiments reveal that despite the fact that muscles are historically considered to be made up of fibers that are predetermined genetically in an organism, they exhibit plasticity, when considering the phenotypes of skeletal muscles response to both the nature and the extent of the demands by external loads (Hill, 1938 p. 139). The relationships between muscle tissues have been determined quantitatively using Concepts such as force and velocity curves (Hill, 1938 p. 195) In this experiment will be focusing on the relationship between the biceps and triceps muscle activity for increasing load moments and hypotheses that when the distance of weight increase the RMS value for both bicep and triceps will increase and the weight which have been holding is unrelated to the RMS value

Method

All method for these experiments were carried out as previously described in MEDS 2001 Skeletal Muscle Physiology practical on Kuracloud (Kuracloud.com)

Result

Table 1.The electrical activity of bicep and triceps

Figure 1 The RMS value for bicep and triceps muscles when increasing distance of weight from bicep insertion point

The traces for the electromyogram are made when the test object places the 1 Kg mass at the end of the stick. According from the result obtained in the experiment the highest RMS value for biceps is 0.17mV and the highest RMS value for triceps is 0.24 mV. In bicep the RMS value is showing an increasing trend from 0.03 mV increased to 0.17. mV whereas the triceps is increasing from 0.01 to 0.24 mV. RMS value for the bicep has increased for 0.14 mV and for triceps had increased 0.23 mV. However, among all the distance the RMS value is showing a similar result but when the distance reached 100 the RMS value was showing a great difference.

Discussion and Conclusions

From the results obtained it is clear that as the displacement of a 1 kg load from the biceps of the point of insertion increased in steps of 10 cm, the reading for the voltage that develops along the biceps muscle increases gradually from 0.03 mV RMS to 0.17 mV RMS. The values for the voltage across the triceps muscles also increases from 0.01-0.24 mV RMS. Both the recordings of the biceps and triceps muscles show a positive relationship between the displacement and the voltage that develops across the muscles. This leads to the conclusion that as the distance between the load and the muscle increases, the Moments produced by the load increases, which causes the exertion of a higher effort by the muscles, hence the increase in the RMS voltage recorded in the electromyogram. Therefore it supports the hypothesis when the distance is far away from the bicep insertion point the RMS value for both bicep and triceps will increase.

Relationship between the voltage developed by the biceps and triceps muscles also shows the relation between the two. Initially the values for the voltage Reading for the biceps muscles are higher the voltage readings from the triceps muscles, showing a high exertion of effort by the biceps muscles than the triceps muscles initially. Gradually, the voltage readings for the triceps muscles increase until they exceed the corresponding values of voltage for the biceps muscles. This leads to the conclusion that with the exertion of a smaller moments by the load, the biceps muscle is more active in contributing towards the effort to counter the load. However, as the moment exerted by the load continues increasing, the compensation of effort exerted by the triceps muscles increases until the triceps muscles exert a bigger percentage of the overall efforts than the biceps muscles. Therefore, the action of antagonistic muscles is in such a way that at any one instance, a bigger effort is exerted by one muscle than the other.

References

• Hill, A. (1938). The heat of shortening and the dynamic constants of muscle. Proceedings of the Royal Society of London. Series B – Biological Sciences, 126(843), pp.136-195.
• Lindstedt, S., LaStayo, P. and Reich, T. (2001). When Active Muscles Lengthen: Properties and Consequences of Eccentric Contractions. Physiology, 16(6), pp.256-261.
• Lindstedt, S., Mineo, P. and Schaeffer, P. (2013). Animal galloping and human hopping: an energetics and biomechanics laboratory exercise. Advances in Physiology Education, 37(4), pp.377-383.