Fundamentals of Exercise Physiology and Biomechanics: Effect of Force Generated in a Push and Pull Pattern

Introduction

The reason for this lab report is to inform how Newton’s laws of motion can detail human movement. Analysing and understanding movement is important for sports science movement is the effect of force generated in a push and pull pattern between two objects. Forces can change speed or direction of an object. Within this report I will evaluate the findings of counter movement jumps while applying Newtons laws. Newton’s first law, Inertia uses no uses of units therefore this is described as a body in motion stays in motion and a body at rest stays at rest unless acted upon by an unbalanced external force (McCaw 2014).

The formula for newton’s 2nd law F=MA

F = Force

M = Mass

A = Acceleration

Newton’s second law is the law of acceleration which is described as an unbalanced force applied to a body causes an acceleration of the body with a magnitude proportional to the unbalanced force and inversely proportional to the body’s mass. This law expresses the cause effect relationship between force mass and motion (McCaw 2014).

The last law of Newton is termed Equal and opposite action, reaction. This law is when two bodies interact to produce a force, the force on one body is equal in magnitude and opposite in direction to the force on the other body (McCaw 2014)

Force plates examine the ground reaction force acting on a body. This may be at rest or in motion. It measures force in terms of magnitude and direction. If mass of a body is known as the Kinetic (Force) the data can be used to inform Kinematics of the body’s centre of mass in terms of acceleration, velocity and displacement. (Brodt, Wagner and Heath, 2008)

Countermovement jumps (CMJ) begin in a upright position and it is the simplest and reliable method to measure lower body power. (CMJ) can be used in a sports science way setting by using clients to perform a countermovement jump, force plates, accelerometers, high-speed cameras, and infrared platforms have all been shown to provide a valid and reliable measure of (CMJ) performance. Force platforms are considered as the best standard, this is because it measures Peak force (N), Relative peak force (N·kg-1), Peak power (W), Peak velocity (M·s-1), Rate of force development (N·s-1) and Impulse (N·s). This will allow the performer to receive results recorded from the force plate and other equipment used to analyse the jump. Sports scientist may use a force plate to measure a basketball players vertical jump to measure if its below or above average. This informs strength on athlete because it will enable them hand over results to clients and strength and conditioning coaches to guide the athlete to improve by creating a plan for a session that’ll improve power in the lower body.

There are six phases to the (CMJ). The first phase is the weighing phase, this is where an athlete is told to stand still for the force plate to measure the athlete body weight. The second phase is the unweighing phase, this is when the athlete begins the stages of the (CMJ). The third phase is the breaking phase, when the athlete starts to decelerate (brakes) their centre of mass. The fourth phase is the thrust phase, this is known as the concentric phase (push off phase) when the athlete pushes their centre of mass vertically. The fifth phase is the flight phase, this is when the athlete takes off from the force plate trying to attain max positive centre of mass. The sixth and final phase is known as the landing phase, this is when the athlete applies net force that will match propulsion force to decrease their centre of mass. (McMahon, Suchomel, Lake & Comfort, 2018).

Methodology

Participants

Two participants (one male: age: 20 years, height: 185cm, body mass: 78.2kg; one female: age: 20 years, height: 162cm, body mass: 59.8kg) with no history of musculoskeletal impairments gave written consent to participate in this study. Ethical approval was sought and granted from the University Research Ethics Committee.

Procedures

Prior to data collection, participants performed a dynamic warm-up and were familiarised with all procedures (Needham, Morse, & Degens, 2009). Participants were instructed to stand with the feet positioned shoulder width apart and to place the hands on the pelvis. Participants had to squat to a self-selected depth and to perform the CMJ as fast and as high as possible (McMahon, Murphy, Rej, Comfort, 2016; McMahon, Rej, & Comfort, 2017).

Data collection

The CMJ’s were recorded using two force plates (Advanced Mechanical Technology, Inc., MA, USA) with a sampling frequency of 1000 Hz (Street et al., 2011). Body weight was determined prior to the commencement of the CMJ. Raw vertical force-time data were exported and analysed using a Microsoft Excel spreadsheet (version 2016, Microsoft Corp., Redmond, WA, USA).

Data analysis

The data was analysed through excel spreadsheet (version 2016, Microsoft Corp., Redmond, WA, USA). Both participants calculated to work out acceleration, (net force/mass=acceleration). Calculate velocity (Time x acceleration/2 = velocity) and workout displacement, (Time x velocity/2 = displacement).

Results

There is a difference between participant 1 and 2 shown in table 1. as you can see there is a 6.36% difference between the participants peak force (N/KG), a 11.24% difference in acceleration (m/s-2) and a 28.62% difference in velocity (m/s-1). There is barely a difference in displacement.

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Table 1. Results of participates 1 and 2

Figure 1. – ( Male, P1) Figure 2. (Female, P2)

Countermovement jump phase interpretation based on acceleration-time (solid blue line) and displacement-time (dotted red line) curve data.

Countermovement jump phase interpretation based on force-time (solid black line) and velocity-time (dotted green line) curve data.

Discussion

Within this discussion the out come of the results from both participates will be seen. Furthermore, a comparison of the results from the research will be seen using Newton’s laws. Using Newtons first law called Inertia clearly shows in figure 1 and figure 2 an understanding of a body in motion stays in motion and a body at rest stays at a constant rest unless an external force is acted upon it. This is evident in figure 1 and 2 where the black solid line represents a negative downwards force is applied, you’ll get a negative downwards velocity which is also evident represented as the green line. The only way to stop it moving down is if an upwards force is applied to change the velocity. Constant velocity equals constant force.

Using Newtons 2nd Law of acceleration it is clear the acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object. Therefore, As the force acting upon an object is increased, the acceleration of the object is increased. As the mass of an object is increased, the acceleration of the object is decreased. Throughout the CMJ the force is not continuous it is unbalanced. Acceleration follows the direction of force, as you can see from the blue line in figures 1 and 2. Both participants have different masses, even if the same amount of force is applied there will be a difference in acceleration to both participants as you can see from figures above. P1(Male) has a higher mass, therefore their acceleration will be a lot slower compared to P2(Female), as they have a lower mass.

Lastly Newton’s final law is evident as during the (CMJ). When pushing down, ground force will push up equal and opposite force up. This is stated when both participants push down into the ground during breaking and propulsive phrase. The ground responds by pushing upwards and it is understandable by velocity increasing and displacement decreasing creating the equal and opposite reaction.

In comparison to the study done by Christopher Thomas, Irene Kyriakidou, Thomas Dos’Santos and Paul A. Jones. Differences in Vertical Jump Force-Time Characteristics between Stronger and Weaker Adolescent Basketball Players the purpose of this study was to explore differences in CMJ and DJ force-time characteristics between stronger and weaker adolescent male basketball players. Sixteen adolescent male basketball players performed the IMTP to assess measures of peak force (IMTP PF), whereas CMJ and DJ calculated a range of kinetic and kinematic variables.

Comparison of IMTP force-time characterises between stronger and weaker players. Standardized difference was interpreted as: trivial 2.0. Differences in CMJ-PF demonstrated almost certain increases, and there was a possible increase in CMJ-PP between stronger and weaker players.

Comparison of CMJ force-time charactericts between stronger and weaker players. Standardized difference was interpreted as: trivial 2.0.

Comparison of DJ force-time charactericts between stronger and weaker players. Standardized difference was interpreted as: trivial 2.0

The purpose of this study was to explore differences in CMJ and DJ force-time characteristics between stronger and weaker adolescent male basketball players. This study progressed on previous research examining the influence of maximum strength on CMJ [42] and DJ [14,27] performance. There were differences in CMJ-PF between stronger and weaker players. Also, stronger players demonstrated superior DJ-PP than weaker players. However, this study has been unable to find

Sports 2017,5, 63 7 of 10differences in CMJ-JH and DJ-JH between stronger and weaker players.

Conclusion

Overall this lab report informed how Newton’s laws of motion can detail human movement. Analysing and understanding movement is important for sports science movement is the effect of force generated in a push and pull pattern between two objects. This study also showed the benefits of the (CMJ) and the use of force plates and why they’re effective. For a basketball player it’ll be effective for them to use (CMJ) to measure power because they perform a lot of vertical jump movements.

The errors that needed to be improved throughout the whole report was the amount of participants that were involved throughout the research and the amount of jumps performed by each performer. This doesn’t allow the results to be accurate because it has nothing to compare to.