IndexIntroductionMethodologyParticipantsProceduresData collectionData analysisResultsDiscussionConclusionIntroductionCountermovement jumping (CMJ) has become a commonly used indicator for assessing an individual's "fitness", especially of lower extremity power and strength that has been utilized by both the general population and high-performance sports.” Vertical jump height is measured as the variance between the position of the individual's center of gravity in the starting position (a standing position) and his or her position at maximum height. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay There are numerous methods to collect data from the CMJ, but one widely accepted and reliable way requires the use of a force plate that uses ground reaction forces to calculate variables such as peak power, maximum rate of force development and jump height. “Force plates are highly sensitive to errors in the magnitude of force and the location of the center of pressure and are also used to evaluate foot positioning and its variability during human walking, again with high sensitivity to errors” . This equipment also measures force produced over time, how much force occurs and when it occurs, and "if the body of a mass is known, the kinetic data can be used to inform the kinematics of the body's center of mass in terms of acceleration , velocity and displacement.” “On the other hand, it has emerged that center of gravity models can cause errors that disqualify their use as a validation criterion for kinetic parameters.” There have been several studies that have attempted to explain force graphs -time derived from the CMJ, but with mixed results regarding sex differences. For example, Laffaye (2014) attributed sex differences in CMJ height to the ability of men to demonstrate greater relative peak concentric strength (vs. to body mass), along with a greater rate of mean absolute and relative eccentric force development (RFD). However, in contrast to this, Ebben (2007) found no sex differences in CMJ RFD or movement time. Similarly, Rice (2017) reported no sex differences in peak force or RFD calculated from the CMJ. To begin analytical research and coaching from the statistics and information provided, it is essential that Newton's laws are understood and used to explain how individuals control their movements with force. Newton devised three laws that perfectly describe the relationship between force and motion. The aim of the present study, therefore, is to distinguish the relationship between Newton's three laws and the CMJ and use these laws to explain force changes across the CMJ. Methodology Participants Two participants (one male: age: 20 years, height : 185 cm, body mass: 78.2 kg; one female: age: 20 years, height: 162 cm, body mass: 59.8 kg) without history of musculoskeletal disorders gave written consent to participate in this study. Ethical approval was sought and granted by the University Research Ethics Committee. Procedures Prior to data collection, participants performed a dynamic warm-up and were familiarized with all procedures. Participants were asked to stand with their feet positioned shoulder-width apart and place their hands on their pelvis. Participants were required to squat to a self-selected depth and perform the CMJ as fast and as high as possible. Data collection The CMJs wererecorded using two force plates with a sampling rate of 1000 Hz. Body weight was determined before the start of the CMJ. The raw vertical force-time data were exported and analyzed using a Microsoft Excel spreadsheet. Data analysis Data were analyzed using an Excel spreadsheet (version 2016, Microsoft Corp., Redmond, WA, USA). Net force was calculated by subtracting the participant's weight from the original force. Acceleration was then resolved by dividing the net force by body mass; velocity was calculated via the trapezoid rule (integration) using acceleration data versus time; the displacement is then calculated based on velocity versus time. Results The overall results from this lab suggest that males can produce more strength overall and more force per kg of their body weight. The male also achieved greater acceleration and speed but had a lower displacement than the female. Although the male's displacement was smaller, they still achieved a higher jump than the female, suggesting that there is a relationship between normalized force and jump height. Discussion There are three phases in CMJ; lightening phase, braking phase and propulsion phase. Each can be explained via Newton's laws of motion. Newton's first law of inertia explains the loosening of weight by stating that "Every body continues in its state of rest, or of uniform motion along a straight line, unless forced to change that state by forces impressed upon it." of it" (Newton, 1987) . As seen from Figures 1 and 2, both individuals cause a negative external force, breaking their resting state of inertia and resulting in a negative velocity. Peak downward velocity is reached at the end of the weight-release phase, so an upward force must be applied to bring the velocity back to zero, as seen in Figures 1 and 2 during the braking phase where a massive amount of force is applied. Furthermore, throughout the entire movement, Newton's first law is always in effect because there is a constant change in velocity which must mean that a constant force is being applied on the body weight. Newton's 2nd law states that "the acceleration of an object depends directly on the overall force acting on an object and inversely on the mass of the object." As seen from Figures 1 and 2, there is a proportional change in shape in the acceleration as there is a change in the force which explains that 'F = M x A'. Furthermore, when one of the subjects applies a downward force, a negative acceleration occurs, and when a positive force is applied, a positive acceleration occurs. Newton's 2nd law also says that "acceleration for a given force is inversely proportional to mass." The peak force produced by participant 2 is approximately 1400 N which causes an acceleration of 15 m/s². However, looking at the results of the participant, who has the greatest mass, the acceleration produced at 1400 N is less than 10 m/s², which further supports Newton's 2nd law. The braking phase consists in the fact that the subject continues to descend and does not end until the subject stops and has zero speed, i.e. when the enormous peak of force applied can be seen since this is the point where the subject applies a positive force for change. their movement from bottom to top. Towards the end of the braking phase, when the subject stops and reaches zero speed, this is the moment when the peak force is maximum. This increase in force can be explained by Newton's third law which states that "when two bodies interact to produce a force, the force on.