The procedure for this lab was separated into two sections, one pertaining to the muscle activities and other for nerve activities. In the muscle section, data was acquired through the use of iWorx TA unit in conjunction with LabScribe 3 software. The iWorx TA unit was also connected to stimulating electrodes and a pressure ball. Sticky pads were placed on the forearm and readjusted until optimal motor point was located. A specific software setting and the correct procedure to locate the point can be found on the Muscle lab manual (*-*-*-). The ball must be grasped in a relaxed state with minimal pressure. The pressure on the ball resulting from the contraction is recorded in Volt (V). For each part the provided parameters were set in the software. …show more content…
Part 1 of the section measures the effect of motor unit recruitment on the force of muscle contraction.
The software setting is set as described in the lab manual. The stimulus intensity is initially set to 1 amps and gradually increased until a slight response is observed and recorded. The intensity is now increased by 0.2 amps with an interval of 2-3 seconds until the stair stepping response reaches saturation. Refer to the Muscle lab manual for the correct procedure to record data (*-*-*). Part 2 involved measurement and observation of the shape and strength of single muscle contractions such as latent period, contraction and relaxation. The Amp to 75% of max muscle contraction, 10 stimuli were recorded and 6 were selected to be observed and calculated (*-*-*-). Part 3 was used to measure the effects of frequency of stimulation and motor unit recruitment on the muscle contraction force. The Amp to 15% of the muscle contraction, constant stimulus recordings were taken increasing the frequency initially set to 1, then 2, and then in increments of 2 until maximum plateaued contraction was achieved. The interval of 5 seconds was required for each frequency. Part 4 measured the differences in relaxation rates of a fatigued and non-fatigued
muscle. Parameters were provided for the experiment. After a period of rest, the unfatigued experiment was performed and recorded values for 4 trials. Parameters were set for fatigued stimulation after which the same experiment was performed as unfatigued for 4 trials. Part 5 involved the depletion of nutrients and its effects on muscle fatigue. The blood supply was weakened by a sphygmomanometer cuff inflated to 140 mmHg and trials were performed with and without the cuff. The time that constant beat of 2 Hz is maintained by the student is recorded. In the Nerve section, PowerLab unit in conjunction with Labchart Reader is used. The dissection of a sciatic nerve is performed in accordance with the Nerve lab manual (*-*-*-). The sciatic nerve and the attached gastrocnemius muscle is then placed on the Nerve bath chamber as described in the manual. Ringer solution is added to keep the nerve from drying. Part 1 of this section involved the observation of a CAP produced by the nerve with the provided parameters. Part 2 measured the stimulus intensity and its relation to the duration of the peak. The duration is initially increased until maximum CAP is observed. Then the amplitude is increased until the maximum CAP is observed. In this experiment, the maximum CAP was observed outside the safe range (1 V) of Amplitude. The experiment was halted to avoid damage to the nerve and 1V was recorded as the max. Part 3 involved double stimulation of nerve and the stimulation intervals were increased until the two CAP were equal. Part 4 involved placing the nerve bath chamber on ice and measure its effects on CAP amplitude and conduction speed. The temperature of the bath slowly decreased and a stimulation was presented at a 0.5-degree Celsius decrease in temperature. The nerve bath was halted prematurely as the cold temperature caused the system to malfunction. However, sufficient data was recorded. Results The results for this experiment were acquired from two different sessions, Muscle and Nerve. The muscle section multiple variables were manipulated to receive a broad set of data. Firstly, the relationship between the stimulating amplitude of the human FDS muscle and the muscle contraction of the pressure ball is displayed (Figure 1). The threshold for the minimum contraction was 1.2 mA and the maximum contraction of 1.7 Volt was at 3.0 mA. The relationship between the two variables was linear positively correlated however, the values start to plateau when the intensity was increased (Figure 1). During the individual twitch experiment, the latent time of 33 ms was determined and there was a consistent contraction rate of 13.05 V/s and relaxation rate of 6.34 V/s. The rate of contraction was twice as fast as the relaxation rate. (Table 1). The contraction of the pressure ball and the frequency of the stimulus provided were also positively correlated. However, started decreasing at higher frequencies. The frequency that resulted in maximum contraction of the FDS muscle was in the range of 14-16 Hz (Figure 2). The relaxation time for unfatigued muscle is immensely smaller (332 ms) than the relaxation time for a fatigued muscle (715 ms). These results are consistent over multiple trials. (Table 2). The use of sphygmomanometer cuff resulted in a less time to reach fatigue (60.32 sec) compared to the trials without the cuff (93.36 sec) (Table3). In the Nerve section, the CAP manipulation of various variables leads to varying effects on the recorded data. The figure of CAP shows an initial peak that shoots right after the stimulation is provided. Then its followed by relatively large peak (0.475 ms) and a relatively small peak (1.25ms) and the CAP finishes off with a trough roughly present at (1.7 ms) after the initial stimulation (Figure 3). The second part was to examine how voltage intensity and duration of the stimulus cause change in the CAP amplitude. Figure 4 shows an inverse relationship between duration of stimulus and Voltage required to maintain a constant amplitude of 90 mV. The voltage saturates at 0.24 V after 0.175 ms duration. (Figure 4). Two stimuli are presented to the nerve and the interval between the stimuli is changed and the difference in their amplitude is measured. As the interval increases, the difference between the amplitude of two stimuli decreases. This is shown by an inverse curve on Figure 5. The lowest difference is observed at 5 ms interval thus, the peaks there were almost equal. The data obtained for the relationship and amplitude showed no correlation However, temperature did effect the duration of CAP. A decrease in temperature leads to an increase in CAP duration. The relationship is somewhat linear and negatively correlated. (Figure 5).
In the beginning phases of muscle contraction, a “cocked” motor neuron in the spinal cord is activated to form a neuromuscular junction with each muscle fiber when it begins branching out to each cell. An action potential is passed down the nerve, releasing calcium, which simultaneously stimulates the release of acetylcholine onto the sarcolemma. As long as calcium and ATP are present, the contraction will continue. Acetylcholine then initiates the resting potential’s change under the motor end plate, stimulates the action potential, and passes along both directions on the surface of the muscle fiber. Sodium ions rush into the cell through the open channels to depolarize the sarcolemma. The depolarization spreads. The potassium channels open while the sodium channels close off, which repolarizes the entire cell. The action potential is dispersed throughout the cell through the transverse tubule, causing the sarcoplasmic reticulum to release
The data was recorded for ten minutes. The last segment in the data collection was to analyze the effects of direct electrical stimulation. The hook electrode was disconnected and two electrode needles were inserted about five mm from each end of the gastrocnemius muscle. Starting at the maximum voltage from the first experiment, voltage was slowly increased until a twitch appeared. Then voltage was set to ten times the maximum voltage from the first experiment.
Another weakness in the experimental design was that the reliability of the experiment was very low. As each test subject was only tested against each amount of prior exercise once, the impact of random errors is likely very large, which can be seen by the spread of the data on the graph. Although, this was attempted to be rectified by averaging the results of all four test subjects, it does not improve reliability too much. Conclusion: The results of this investigation indicated that a relationship between the amount of prior exercise and muscle fatigue does exist, however the results are also not conclusive enough to speculate on what the relationship is. This means that the hypothesis “If the amount of time spent performing vigorous exercise prior to the set of repetitions increases, then the physical performance (number of repetitions) will decrease” cannot be supported or rejected due to the inconclusive data.
The subject’s forearm was prepared by cleaning the surface of their skin (the flexor digitorum superficialis muscle) and the bony prominence of their wrist with an alcohol swab, and the EMG adhesive electrodes where placed on the belly of the flexor digitorum superficialis muscle. The positive electrode was placed more proximal to the elbow, while the negative electrode was placed more mid-distally. The grounding (noise reducing) electrode was places on the bony prominence of the wrist, and the force transducer was setup to achieve a stable baseline. The subject was then instructed to the support their forearm over the edge of the table or on their leg with the wrist in a semi-flexed position, and when ready squeeze the force grip transducer as hard as possible. For the first/”fast” time interval of the experiment, the subject made ten squeezes as fast as possible with one second per squeeze intervals, and the force onset, EMG onset, difference between force onset and EMG onset, peak EMG amplitude, and peak force amplitude were observed and recorded. The experiment was then repeated for a medium, three seconds per squeeze, and slow, five seconds per squeeze time intervals with the same variables observed and
When performing manual muscle testing for shoulder flexion and abduction, PTA’s typically place their hand at the wrist verses the mid-extremity because placing their hands at the wrist increases the length of the lever thus testing the muscles ability to resist externally applied force overtime and across the bone-joint lever arm system. Shorter lever arms will provide higher testing scores when compared to using longer lever arms, thus changing the point of force application affects the length of the lever arm and therefore the muscle torque.
Every day we use our skeletal muscle to do simple task and without skeletal muscles, we will not be able to do anything. Szent-Gyorgyi (2011) muscle tissue contraction in rabbit’s muscles and discovered that ATP is a source for muscle contraction and not ADP. He proposed a mechanism to cellular respiration and was later used by Sir Hans Krebs to investigate the steps to glucose catabolism to make ATP. In this paper, I will be discussing the structure of muscle fibers and skeletal muscles, muscle contraction, biomechanics, and how glucose and fat are metabolized in the skeletal muscles.
Discuss the relationship between distribution of muscle fiber type and performance. How might exercise training modify or change a person’s fiber-type distribution?
Muscle fatigue is a decline in ability of a muscle to generate force within any part of the body. Muscular fatigue is a particular response when it comes to an untrained athlete that is starting an intense workout program, and the muscles of the body is not able to respond in an orderly manner as it would respond to an elite athlete. This paper will focus and provide general information about recent studies on peripheral fatigue. Peripheral fatigue is one of the sites for possible fatigue and its where neural, mechanical, or energetic events can hamper tension development. Neural fatigue is a factor of peripheral fatigue, which occurs when the nerves are unable to generate a signal and this reduces the ability of the muscle fiber to contract which is considered to be metabolic fatigue. Neural factors deals with the movement of action potential going through a process to produce a muscle contraction and when this process does not go through the proper steps then fatigue set in because the muscles will not be able to contract. Neural fatigue has two main factors which is, a shortage of...
Muscle endurance is the ability to perform a lot of repetitions against a given resistance for a long period of time. The combination of strength and endurance results in muscle endurance. Muscle endurance is used in may sports such as rowing, swimming, cycling, distance running, field hockey and American football. Normally, an endurance muscle program involves lifting about 12-25 repetitions of moderate loads. In some cases, this is inadequate for many sports such as boxing, canoeing and x-cross skiing.
The muscular system is the set of all the muscles that make up the human body. It is an extensive system of muscles and nervous tissue, which is distributed all through the body. In total, the human body consists of approximately 650 muscles. The muscular system is divided into three types of muscle: cardiac muscle, smooth muscle, and skeletal muscle.
The concept of electrical muscle stimulation is to use technologically advanced science that uses very mild electrical current to exercise your muscles. When one performs any exercise, their brain sends a message down the spinal cord through the nerves innervating all the muscles causing them to contract. An outside electrical source stimulates the nerves to send these signals to your muscle to contract. This is achieved by passing electrical currents through electrode pads placed over a muscle.
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Thibodeau, G., & Patton, K. (1993). Chapter ten: Anatomy of the muscular system. In Anatomy and physiology (1st ed., p. 252). St Louis: MO: Mosby.
Dunn, George et al. National Strength and Conditioning Association. National Strength and Conditioning Association Journal. 7. 27-29. 1985.
The muscular system is a very important part of the human body. It has many components and functions, and is the source of the body’s movement. There are roughly 650 muscles in the human body and are different types of muscles. Muscles can either be voluntary or involuntary which means controlled or uncontrolled movement. Muscles have many reasons and in this paper you will widen your knowledge of muscles and their functions as well their diseases and how they help maintain the body.