Lab Recruitment and Isotonic and Isometric Contractions

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Predictions 1. When the arm goes from resting to flexing, the amplitude and frequency of sEMG spikes will increase. 2. During flexion, the amplitude and frequency of sEMG spikes will ___ during extension be greater than 3. Recruitment of motor units will be greatest when the load is 5 pounds. Materials and Methods Comparison of motor unit activation during muscle tone and concentric and eccentric isotonic contractions 1. Dependent Variable. amplitude and frequency of sEMG spikes 2. Independent Variable. muscle movement 3. Controlled Variables. total number of motor units present in muscle; subject’s physical condition Recruitment during isometric contractions 1. Dependent Variable. amplitude and frequency of sEMG spikes 2. Independent Variable. muscle load 3. Controlled Variables. total number of motor units present in muscle; muscle movement; subject’s physical condition 4. What does the acronym sEMG stand for? Surface Electromyography. 5. During a muscle contraction, what is recorded on a sEMG? Amplitude and frequency of sEMG spikes. 6. Spike numbers were measured during a ____msec period. Spike numbers were measured during a 200 msec period. Results Table 3. Muscle Tone (Resting) and Isotonic Contractions Amplitude (mV) Spike Numbers (per 0.2 sec time period) Rest Concentric Eccentric Rest Concentric Eccentric Subject 1 0.13 0.48 0.32 1 20 19 Subject 2 0.1 0.43 0.39 1 20 19 Subject 3 0.11 0.49 0.3 1 20 20 Amplitude (mV) Spike Numbers (per 0.2 sec time period) Rest Concentric Eccentric Rest Concentric Eccentric average 0.11 0.47 0.34 1 20 19.33 Graph 1. sEMG Amplitudes and Frequencies at Rest and During Isotonic Contractions 1. When the biceps brachii was at rest, were motor units activated as indicated by amplitude and frequency of sEMG spikes? Yes, but the normal resting muscles exhibit muscle tone in low rate because the

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