Biology
Abstract
This is a practical report on human physiology EMG. The experiment recruited 85 subjects to examine the level of the signal emanating from muscle contraction in the lab. Some of the participants were left-handed while some were right handed. Males and females with varying levels of activity were recruited. The results indicated that more males exhibited maximal compression force than females as attested by the higher numbers that returned quickly to half the clench force. The level of activity of the participants positively correlated to slow return to half of the maximal compression force and reduced signs of fatigue among the subjects who engaged in physical activities.
Introduction
Muscles are critical building blocks of the human body. While many people characteristically perceive muscles as something that can be made better via exercise only, there are various other intricate processes and structures involved (Squire, 2012). The human body has three types of muscles, that is, the skeletal, smooth and cardiac muscles (Dean, 2005). All these types of muscles have a succinctly varying composition and are situated in distinct parts of our bodies. For instance, cardiac muscle is located in the heart, while the smooth muscle and the skeletal muscles are found in hollow organs and skeletal structure respectively. People often think of skeletal muscles during training and workouts (Dean, 2005).
The comprehensive process of muscle contraction is relatively intricate and encompasses a variety of physical and chemical interactions (Cifrek and Mario, et al., 2009). In general, a contraction is initiated after an electrical signal is circulated along a nerve. When an impulse originating from the nerve reaches its target, that is, the muscle, a chain reaction is set into motion resulting in the contraction of the index muscle (Squire 2012; Cifrek and Mario, et al., 2009). The contraction of muscle group translates to literal contraction of thousands of single muscle fibers. While the electrical activity associated to each one fiber contracting is minute, the overall effect of the action yields large enough a signal to be detected by electrodes placed on the skin surface.
The overall goal of this experiment is to determine the level of the signal emanating from muscle contraction in an experiment on human physiology carried out in the lab. The specific objectives are as follows:
Materials Used and Procedures
The materials used to conduct the experiment are outlined below:
BIOPAC electric lead set (SS2L)
BIOPAC disposable vinyl electrodes (EL503), six electrodes per unit
BIOPAC electrode gel (GEL 1) and abrasive bad (EL PAD) or skin cleanser
BIOPAC SS25 hand dynamometer
BIOPAC OUT1 earphones
The procedure used is outlined below:
After the setup had been completed, selection of the subjects for electromyography was done followed by cleansing of their skin on the anterior forearm on the point of attachment to the electrodes.
Subjects were categorized into two depending on whether right or left handed; followed by forearm designation with the Forearm 1 taking precedence over Forearm 2. In this step, the electrodes were placed in the designated area to make a good electrical contact. This was followed by the attachment of the electrode lead to the snap connector.
The electrode assembly (SS2L) was plugged into channel two; then followed by the attachment of the color-coded electrode.
With the subject seated and the chosen arm resting on the tabletop with the palm facing upwards, the hand dynamometer was plugged into channel 1. All the data was registered in the BIOPAC Student Lab Program after calibration.
Recording began after the clench and release motion was commenced; that is clenching for two seconds and releasing for two seconds.
Every time the highest clench force was flashed on the screen followed by its decrease by half, the “suspend” control was keyed to determine the time taken for muscle fatigue to register among different individuals.
Results
There were more women than men in the current experiment. After observing recordings from about 85 participating subjects, I observed numerous interesting trends in relation to motor unit regulation and EMG activity. First, participants with a history of regular training proved to be more facile with regards to isolation and control of single motor unit spiking as opposed to those with little or no training at all. Second, being left or right handed did not show any distinguishable patterns of motor unit spiking and a stretch of reflex responses. Third, being male or female affected the rate return to half of the maximal compression force; more males than females returned quickly to half the clench force agreeing with Cifrek and Mario, et al. (347) and Cifrek and Mario, et al. (345). Interestingly, the level of activity of the participants positively correlated to slow return to half of the maximal compression force and reduced signs of fatigue among the subjects. Such observations are of great importance and have higher meaning in classes and workplaces because they can be used in handling learners and employee whose EMG responses, for whatever reason, happen to be attenuated (Andreassi, 2013).
Discussions
Muscles start to fatigue after persistent periods of exercise. During intense use of muscles, energy supplied is lower than the energy needed by the muscle. In this instance, the force output of the muscle will decline until the muscle is rested. Biochemical determinations have revealed that the ATP in muscle may not be extensively depleted during fatigue. As such, the actual reason for the fatigue may lie somewhere in the combination of the membrane depolarization and myofilament activation. When a muscle gets weak, the quantitative signals of the EMG start to change (Jerritta et al. 2011; Cifrek and Mario, et al., 2009). As such, it may be possible to identify when a muscle is fatiguing by examining the muscle electrical activity. Classically, as a muscle starts to tire, more motor units will stop firing thereby undermining the frequency of the EMG signal. Muscle force may also be distressed by other parameters. The sum of force yielded by a muscle is influenced by the speed with which the muscle can contract as well as the length of the muscle (Cifrek and Mario, et al., 2009).
Besides the brain's voluntary control of motor unit functionality, there are various critical mechanisms via which this involuntary occurrence is controlled. One of the many ways is via reflex pathways that task distinct sensory neurons in our bodies. This involuntary activity is easily demonstrable, through the reflex control of motor entities in the muscles of the arm in several ways. As noted earlier, during intense activity, energy supplied is lesser than the energy needed by the muscle which is likely to reduce the force output of the muscle until the muscle is rested even for the short period. However, as indicated, chemical inquiries indicate that the ATP in muscle may not be ostensibly depleted during fatigue; meaning that the actual reason for the fatigue is the combination of the membrane depolarization and myofilament activation.
Bibliography
Andreassi, J.L., 2013. Psychophysiology: Human behavior & physiological response. Psychology Press.
Cifrek, M., Medved, V., Tonković, S. and Ostojić, S., 2009. Surface EMG-based muscle fatigue evaluation in biomechanics. Clinical Biomechanics,24(4), pp.327-340.
Dean, David A. 2005, "Nonviral gene transfer to skeletal, smooth, and cardiac muscle in living animals." American Journal of Physiology-Cell Physiology289.2. C233-C245.
Jerritta, S., Murugappan, M., Nagarajan, R. and Wan, K., 2011. March. Physiological signals based human emotion recognition: a review. In Signal Processing and its Applications (CSPA), 2011 IEEE 7th International Colloquium on (pp. 410-415). IEEE.
Squire, J., 2012. The structural basis of muscular contraction. Springer Science & Business Media.
