Effects of Plyometric Exercises on Power Production

This activity is the critical driving force of muscle contraction. The stream of action potentials along the muscle fiber surface is terminated as Acetylcholine at the neuromuscular junction is broken down by acetyl cholinesterase. The release of Calcium ions is ceased. The action of the myosin molecule heads is obstructed because of the change in the configuration of troponin and tropomyosin due to the absence of calcium ions. This will eventually cause the contraction to be ceased. Together with these physical processes, an external stretching force such as gravity pulls the muscle back to its normal length.

Introduction: According to the “Human Physiology Laboratory Manual “,BIOL 282 ,page 31 , the reason of performing this experiment is to learn how the muscle contraction occurs based on the molecular level and what kind of factors are involved .As a matter of fact, skeletal muscles contain a lot of nuclei because of the cell fusion while being developed and are made of cylindrical cells that have myofibrils. The myofibrils contain sarcomeres and the

Martini, F. H., Nath, J. L., and Bartholomew, E. F. “Muscle Tissue.” Anatomy & Physiology. 9th

Actin and myosin are contractile proteins that are essential for muscle contraction (Powers). A contraction is triggered by a series of events called the crossbridge cycle. In a muscle fiber, the functional unit of contraction is called a sarcomere (Powers). A sarcomere contains myofibrils, which consist of actin and myosin myofilaments. The sarcomere shortens when myosin heads and thick myofilaments form crossbridges with actin molecules and thin myofilaments. The formation of a crossbridge is initiated when calcium ions released from the sarcoplasmic reticulum bind to troponin. An action potential triggers this release of these ions. The binding of calcium ions causes troponin to change shape. Tropomyosin moves away from the myosin binding cites on actin, allowing the myosin head to bind actin and form a crossbridge. When ATP on the myosin head has not been hydrolyzed yet, the myosin head is inactivated, or in the uncocked position. The myosin head has to be activated before a crossbridge cycle can begin (Powers). This occurs when ATP binds to the myosin head and is hydrolyzed to Adenosine Diphosphate (ADP) and an inorganic phosphate. The enzyme that breaks this ATP down is called myosin ATPase, which is located on the myosin head. The energy from the hydrolysis activates the myosin head putting it into the cocked position. The activated myosin head binds to actin forming a crossbridge. Then inorganic

O B J E C T I V E S 1. To define these terms used in describing muscle physiology: multiple motor unit summation, maximal stimulus, treppe, wave summation, and tetanus. 2. To identify two ways that the mode of stimulation can affect muscle force production. 3. To plot a graph relating stimulus strength and twitch force to illustrate graded muscle response. 4. To explain how slow, smooth, sustained contraction is possible in a skeletal muscle. 5. To graphically understand the relationships between passive, active, and total forces. 6. To identify the conditions under which muscle contraction is isometric or isotonic. 7. To describe in terms of length and force the

Actin and Myosin proteins serve the primary role of producing muscle contraction. Myosin molecules will create pressure in the skeletal muscle, where ATP hydrolysis causes Myosin to bind to Actin. A conformational change of the molecule then result in Myosin being

Based on the unique arrangement of myosin and actin in skeletal muscle sarcomere, the active force varies with changes in the muscle’s resting length because the active force is created from myosin thick filaments, which bind to the thin actin filaments. This starts the cross bridge cycle and the hydrolysis of ATP. Active force changes when the resting length of the muscle changes. When the resting length is decreased, the active force increases. The shorter the resting length, more myosin filaments will be bound to actin filaments. The active force change is caused by the amount of myosin that binds to the actin.

Plyometrics are all about trying to produce the maximum force available in the quickest time possible. So they are not about overall strength or overall speed, but the best combination of the two. People talk about this in terms of "power".

Plyometric exercises are powerful, fast and enhance body control and power (Miller, Herniman, Ricard, Cheatham & Michael, 2006, p. 458). They link speed and strength, to produce power (Miller et al., 2006, p. 458). These types of exercises involve eccentric contractions followed by concentric contractions. Eccentric contractions occur when the muscle lengthens while producing force (Miller et al., 2006, p. 458). An eccentric contraction generally occurs when weight is being lowered. A concentric contraction, occurs when the muscle shortens as it produces force (Miller et al., 2006, p. 458). This is generally the lifting phase of the movement. Plyometric exercises can involve starting, stopping and changing direction (Miller et al., 2006, p. 458). These types of exercises assist in developing agility, which is the ability to control and maintain body position while changing direction during explosive

For this study one of the top high school Varsity and Jr varsity division in Gwinnett County is used. The teams have a total of 30 students between the ages of 12- 19 years old. Only the top ten students from each team were selected. Legal consent from the school board, the coaches, the students’ parents/legal guardian, and the students must be obtained prior to starting the study. This study will last for eight weeks with four meetings a week prior to the start of the normal practice season. Each session will last two hours and a screening done by a sports physician and a certified strength and conditioning coach will take place in other to determine who is eligible to participate eligibility. Exclusions are made if a player has had an injury or a surgery involving either leg prior the study. The top ten picks are then divided randomly in two groups, group A and group B, with five participants in each. Their age, height, and body mass are collected in a data sheet created on excel. Participants are required to be present for all warmups and training sessions in order to participate in the study. Each group has to have 10 minutes of standardized neuromuscular warm-up, with 5 minutes of submaximal running followed by a dynamic stretch routine consisting of functional exercises:

Plyometric practice alludes to those exercises that empower a muscle to achieve maximal drive in the most limited conceivable time. A plyometric action is isolated into three stages: 1) the eccentric preload stage, 2) the amortization stage, and 3) the concentric contraction. The eccentric preload is the stage in which elastic energy is stored in the series elastic components (SEC) of the muscle. The amortization stage is depicted as the time between the eccentric preload stage and the concentric contraction. The shorter the amortization stage, the more prominent the work yield in the concentric stage because of ideal use of the stored elastic energy. The third and last stage is the actual muscle contraction. This arrangement of three stages is known as the stretch shortening cycle [13]. (Chimera et al.,

The myosin head provide the powerstroke by ATP hydrolysis move the actin filaments toward to the centre of sarcomere known as active force. This process is regulated by Ca2+ and the stimulus from the nerve (Sawatari 2016). The strength of active force is determine by powerstroke from the crossbridge, thus in the hypothesis the more the myosin head crossbridge to actin filaments, the greater active force would be generated theoretically (figure 2). The muscle length generate the maximum active force which known as the optimal muscle length (Sawatari 2016). Figure 2 also show that when the muscle length sketch beyond the optimal muscle length, the active force should start decrease due to less myosin head crossbridge to actin(Silverthorn et al. 2013). On the other hand, the passive force (generated by the intrinsic elastic properties of the muscle without stimulation) would increase when the muscle length increase, then increase significantly when muscle is sketched beyond optimal length, the sum up between passive and active force will become the total force product to the muscle (figure 3). Resting muscle length is different with optimal muscle length. It is a length at passive force just begin to develop in the absence of stimulation of the muscle. In first practical (Syd1.kuracloud.com 2016), we aimed for measure the

Myosin is the protein that moves beside the actins filaments that is within the sarcomere of muscle fibers, in which will create a contraction as it slides past one another. Myosin and actins makes up actomyosin, which is a protein complex found in muscle fibers. Before a contraction occurs, stimulation or sensory excitement must be present with a potential action of a nerve that connects to a muscle. However, the nerve connected to the muscle does not exhilarate fully, but to a few muscle fibers. It reacts to a sensory excitement in each sarcomere that is between the actin and myosin as the impulses reach the muscle fibers. When the muscles are being utilized, myosin will need large amounts of ATP. Once the sacromeres shorten, the muscles contract. Without the skeletal muscle tissue contractions, humans wouldn’t be able to walk, bite, or carry

During a stretch when the muscle is under contraction the myosin pulls the actin to the centre of the sarcomere, this is the basic concept of contraction. The myosin and actin overlap causing them to become bigger as the stretch carries on, refer to figure 4 for the contracted muscles diagram. The overlap between the myosin and actin becomes slacker and the fibres are able to elongate. Figure 4 demonstrate this exact action as the muscle becomes relaxed and elongates. When a muscle is stretched, it is extended to its maximum length: sarcomere to sarcomere, the muscle fibres will reach its maximum resting length, which causes additional tension. The connective tissue which is the tissue that surrounds the fascicles take up the slack, spreading tension throughout the muscle creating a line of tension. The disarranged muscle fibres straighten up in the line of tension, figure 4 displays the stretched form the muscle through a diagram with labelling. This is curial to the restoration of tissue in the specific muscle targeted for

Neuromuscular electrostimulation is a popular way to relieve pain and rejuvenate sore muscles. Neuromuscular electrostimulation is the elicitation of muscle contraction using electrical impulses. In sports medicine, neuromuscular electrostimulation has been used for muscle strengthening, maintenance of muscle mass and strength during periods of prolonged immobilization, selective muscle retraining, and the control of edema. But what will the effects be of neuromuscular electrostimulation and plyometric training on the vertical jump height of teenage athletes? Will the vertical jump height increase, decrease, or stay the same after an eight-week period of using neuromuscular electrostimulation to rejuvenate and strengthen muscles after plyometric training sessions.