Muscle Fatigue Lab Report
Carol Mas
BIO 201
Professor Washo-Krupps
February 16, 2017
Motor Unit Recruitment and Muscle Fatigue Lab
Introduction
Human skeletal muscles are made up of hundreds of cylindrically-shaped cells called myofibers, and they are bound together by connective tissue. These muscles are stimulated to contract by somatic motor nerves, or motor neurons, that carry signals in the form of nerve impulses from the brain or spinal cord, to the skeletal muscles. Although a motor neuron can innervate several fibers, each muscle fiber can only be innervated by one motor neuron. This combination of a single motor neuron and all of the muscle fibers is referred to as a motor unit.
Using electromyogram (EMG) technology, I am able to measure the electrical …show more content…
The first part of the lab was conducted in order to observe the recruitment of motor units during a muscle contraction in which increasing grip force was applied using the dynamometer in steps up to 40kg. The second part of the lab dealt with determining the time it took for 50% muscle fatigue to occur when maximum grip force was applied to the same muscle using the dynamometer. All results were recorded in the lab notebook for subsequent analysis.
Results
In Figure 1, we can see that as increasing grip force is applied to the muscle, the number of active motor units also increases. In Figure 2, it is clear that when grip strength is maintained at a maximum, muscle fatigue occurs at the rate of 50% after 54 …show more content…
The slow twitch fibers resist fatigue, but are the weakest of the three, while the fast twitch fibers, although they tire easily, are the strongest. Recruitment of motor units always occurs in the same sequence, with the slow twitch motor units being first, intermediate being second, and so on. The slow twitch motor units have the lowest threshold and are the first to respond to a stimulus. As the stimulus increases, threshold is reached next for the intermediate twitch motor units, and then, lastly, the fast twitch motor units. This increase in motor unit activity directly corresponds to the electrical activity on the sarcolemma of muscle fibers. As a result, it can be detected by electrodes being placed on the skin during an EMG, which for our purposes, was accomplished virtually using the LearnSmart
BIO 201
Professor Washo-Krupps
February 16, 2017
Motor Unit Recruitment and Muscle Fatigue Lab
Introduction
Human skeletal muscles are made up of hundreds of cylindrically-shaped cells called myofibers, and they are bound together by connective tissue. These muscles are stimulated to contract by somatic motor nerves, or motor neurons, that carry signals in the form of nerve impulses from the brain or spinal cord, to the skeletal muscles. Although a motor neuron can innervate several fibers, each muscle fiber can only be innervated by one motor neuron. This combination of a single motor neuron and all of the muscle fibers is referred to as a motor unit.
Using electromyogram (EMG) technology, I am able to measure the electrical …show more content…
The first part of the lab was conducted in order to observe the recruitment of motor units during a muscle contraction in which increasing grip force was applied using the dynamometer in steps up to 40kg. The second part of the lab dealt with determining the time it took for 50% muscle fatigue to occur when maximum grip force was applied to the same muscle using the dynamometer. All results were recorded in the lab notebook for subsequent analysis.
Results
In Figure 1, we can see that as increasing grip force is applied to the muscle, the number of active motor units also increases. In Figure 2, it is clear that when grip strength is maintained at a maximum, muscle fatigue occurs at the rate of 50% after 54 …show more content…
The slow twitch fibers resist fatigue, but are the weakest of the three, while the fast twitch fibers, although they tire easily, are the strongest. Recruitment of motor units always occurs in the same sequence, with the slow twitch motor units being first, intermediate being second, and so on. The slow twitch motor units have the lowest threshold and are the first to respond to a stimulus. As the stimulus increases, threshold is reached next for the intermediate twitch motor units, and then, lastly, the fast twitch motor units. This increase in motor unit activity directly corresponds to the electrical activity on the sarcolemma of muscle fibers. As a result, it can be detected by electrodes being placed on the skin during an EMG, which for our purposes, was accomplished virtually using the LearnSmart