The purpose of experiments 1 and 3 were to determine the relationship between the intensity of EMG activity of a muscle contraction in the dominant and non-dominant arm of the subject. As the consecutive squeezes were stronger, the both the absolute integral of EMG activity and muscle force increases. This is because there is a linear relationship between the absolute integral of force and EMG, however, this is only true when the muscles are activated isometerically (true for this experiment). There are many types of contractions, two main ones are: when the muscle length changes (isotonic), and when it stays the same (isometric). The force produced by muscles depend on its length, velocity of movement and frequency, and when a contraction …show more content…
The refractory period of muscle fibers are 1-2 milliseconds (Sherwood et al., 2016). The short refractory period allows contractions to reach tetanus, which is caused by the frequent stimulation of the muscle fibers (Silverthorn et al., 2013).
The increase in amplitude of the absolute integrals of EMG and muscle force as seen in table 1 and table 2 is caused by both the number of motor units recruited and the frequency of the contracting fiber. The lowest relative grip strength recruits less motor units, but as the strength increases, more motor units are recruited, and because the muscle fibers are constantly being restimulated, the muscle force is able to reach tetanus for a period of time (seen in figure 1.0 and 1.1) for each relative strength.
Comparing the results from table 1 and 2, and figure 1.1 and 1.2, the dominant forearm is slightly stronger than the non-dominant forearm. The percent difference in the maximum grip strength is 11%. The stronger forearm has a higher ratio of average maximum grip strength compared to the area of the EMG absolute integral than the weaker forearm. The percent difference between in the slope of the force-EMG graphs is also
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.
In this lab, I took two recordings of my heart using an electrocardiogram. An electrocardiogram, EKG pg. 628 Y and pg. 688 D, is a recording of the heart's electrical impulses, action potentials, going through the heart. The different phases of the EKG are referred to as waves; the P wave, QRS Complex, and the T wave. These waves each signify the different things that are occurring in the heart. For example, the P wave occurs when the sinoatrial (SA) node, aka the pacemaker, fires an action potential. This causes the atria, which is currently full of blood, to depolarize and to contract, aka atrial systole. The signal travels from the SA node to the atrioventricular (AV) node during the P-Q segment of the EKG. The AV node purposefully delays
According to Neumann, a force can be considered a push or pull that can produce, arrest or modify movement and can be measured as F=ma (Neumann, 2010). Force can also be considered the load. In regards to muscle contraction force relative to the joint, the force can be the internal force produced by the muscle itself, the force of gravity or the force of the particular load/weight. Torque is a cross product between force and the distance of the force from the fulcrum and is the ability of a force to cause rotation on a lever. Torque is a measure of how much a force acting on an
Cardiovascular Activity And How it Influences the body. Introduction: Cardiovascular fitness is a form of aerobic fitness (Neporent and Egan 1997). There are many different ways of evaluating the amount of oxygen used during cardiovascular fitness and one the methods involved is called VO2 Max. VO2 Max is the maximum amount of oxygen that the body can hold.
While the precise progression of force varies significantly (especially the extensive gap between soft control and deadly force) among different agencie...
Kinesiology: The Mechanics & Pathomechanics of Human Movement (Second ed.). Glenside, Pennsylvania: Lippincott Williams & Wilkins. Qiao T, Liu C and Ran F. (2005) The impact of gastrocnemius muscle cell changes in chronic venous insufficiency. Eur J Vasc Endovase Surg 30; 430-436.
The purpose of this experiment was to gather data on how the amount of time spent active impacts the speed of heart rate in beats per minute. The hypothesis stated that if the amount of time active is lengthened then the speed of the heart rate is expected to rise because when one is active, the cells of the body are using the oxygen quickly. The heart then needs to speed up in order to maintain homeostasis by rapidly providing oxygen to the working cells. The hypothesis is accepted because the data collected supports the initial prediction. There is a relationship between the amount of time spent active and the speed of heart rate: as the amount of time spent active rose, the data displayed that the speed that the heart was beating at had also increased. This relationship is visible in the data since the average resting heart rate was 79 beats per minutes, while the results show that the average heart rate after taking part in 30 seconds of activity had risen to 165 beats per minute, which is a significantly larger amount of beats per minute compared to the resting heart rate. Furthermore, the average heart rates after 10 and 20 seconds of activity were 124 and 152 beats per minute, and both of which are higher than the original average resting heartbeat of 79.
Dunn, George et al. National Strength and Conditioning Association. National Strength and Conditioning Association Journal. 7. 27-29. 1985.
AIM: - the aim of this experiment is to find out what the effects of exercise are on the heart rate. And to record these results in various formats. VARIABLES: - * Type of exercise * Duration of exercise * Intensity of exercise * Stage of respiration
There are quantitative differences in the skeletal muscle action potentials and its duration potentials that is up to five times longer than the duration of myelinated nerve fibers. Significantly lower than the velocity of conduction in the nerve fibers that innervate muscle fibers is the velocity of conduction in skeletal muscle fibers. The stretching of the tendon attached to the muscle activates specialized receptors in the muscle that send signals to motorneurons through one synapse. The impulse from the motorneuron causes the muscle fibers to depolarize and
Muscular Strength: This works with muscular endurance to be able produce force for a short period of
Manoel, Mateus E; Harris-Love, Michael OAuthor Information; Danoff, Jerome VAuthor Information; Miller, Todd AAuthor Information. Journal of Strength and Conditioning Research; Champaign Vol. 22, Iss. 5, (Sep 2008): 1528-34.
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.