Essay: Countermovement: adding weights to the subject’s arm swing cannot improve their jump height

Countermovement jump test have been around the health and fitness business for a long time. They are used to test fitness level from beginners to elite level athletes; specifically, in sports such as basketball and volleyball. Countermovement jump testing can estimate power and determine jump heights. When the subject includes the arm swing in the vertical jump this will cause their center of mass to move higher throughout their body due to the increase of mass concentration. This in turn increases jump height because the velocity during the takeoff phase is greater (Zettle, 2019). Performing a vertical jump with no weights will still put a stress on the body where some level of force production is required to perform this moment with maximal effort. Therefore, can adding a handheld weight be detrimental to the jump? This lab was conducted to test vertical jump performance and whether holding weights would be detrimental to the jump height. the vertical jump would be affected in a positive or negative manner performing an arm swing in the jump with and without weights. Two parts of this lab were conducted one to test the arm mechanics during the vertical jump and the second was to test the ground force reaction with force plates during a vertical jump; unweighted and weighted jump. There is a lot of studies on whether an arm swing during a vertical jump can be a positive or a negative factor while in sport or in general. According to a study published in the Journal of Human Kinetics, wants to know if the arm swing will perform vertical jump for volleyball players. At the end, it is conducted that the jump height with performing the arm swing while jumping improved by 38% compared to no arm swing. The arm swing not only increased height but the increased the average force produced during the acceleration phase (Frantisek et al., 2016). Which in turn would increase the takeoff velocity. In the lab, the subject performed the jump maintaining her arms as straight as possible through the whole jump. The motion of the arm is very important as if is not performed the same throughout then the results may have an error. Ideally when jumping following through the shoulders range of motion, the arms should be extending back first then following through into flexion. Frantisek et al, performed this procedure in their experimented and found it was the most efficient (2016).  The arm swing is supported by the kinetic energy build up which arises from three main foundations. The first is the potential energy from the arms, the second is the work performed by the elbow and shoulder joints and muscles. Finally the third factor the work done by the trunk of the body while loading the legs during the jump (Lees, Vanrenterghem & Clercq, 2004).
According to Newton’s second law which is F=MA, with greater mass and acceleration, the greater the force will be. For the purpose of the lab, the mass is the handheld weights but as well as the subject’s mass. The mechanics of the arm swing with the hand held weights are the same as the non-weighted jump expect by increasing the mass it will increase the force. Adding handheld weights to the subject, even their own body mass alone is also dependent on the subject’s strength and explosiveness. If they are not as strong as one individual then adding the mass to their vertical jump may not get the results hoped for. According to Kraska et al, the possible reasons the subject’s vertical jump is dependent on their current strength was due to the optimization in  neural drive which could also be referred to as their isometric rate of force development (ISFD). ISFD is test of how fast a subject can develop force and their explosive strength, this can also be compared with the adaptations of the subject’s contractile skeletal muscle. Therefore, the subjects who may be stronger than the others who may have higher level of strengths could be due to their nervous system capabilities in turn have higher vertical jumps due to their greater force production (2009). Jumping consists of a contact and flight phase which uses a certain kinematics to produce a dynamic force. Jumping frequencies are performed usually between 1-4 Hz that be said the ground reaction force that is being generated is 2-4.5 times greater than the body mass of the individual. Research by McDonald and Živanovic ́ supports that the acceleration of the body’s center of mass and the subject’s mass were multiplied it would determine the ground reaction force. Alternatively, the ground reaction force can be found by adding all the inertia forces together (2017).
The purpose of this lab was to understand the benefits or risks of an arm swing during a vertical jump. As well as, by adding hand held weights to the subject’s arm swing would it have made the jump height increase or decrease. The second part of the lab was to look at the ground reaction forces in the vertical jump and see if the handheld weights would have produced more force which in turn would allow the subject to jump higher. My hypothesis of this lab is, by increasing or adding weight, the jumpers force will increase and in turn increase their jump height by at least 10%.
Methods
The first part is Lab 1: Arm Mechanics in Vertical Jump Performance. Before starting the jumping trial the 60 Hz camera and tripod was set up perpendicular to the right side of the subject which was shown in the sagittal plane. Two markers were placed on the subject at the proximal shoulder joint (acromioclavicular joint) and the distal wrist joint (ulnar process). Our subject was a 20 year old female who weighed in at 68.18 kg and was 152.4 cm tall. For each trial a scale was included in the video where a meter stick was aligned in the sagittal plane of the subject. The subject performed two different type of jumps, a normal jump with no weight. The second jump was a weighted jump , the subject held one 1kg weight in each hand. After the setup, the participant practiced the movement. A total of three practice jumps were performed. The same jump trials were performed for the second lab which was where ground reaction force was looked at.
The jumps had to be the subject’s maximal effort and the trials were recorded twice for the normal and weighted jump with a 30 second break in between. After the two types of jump were filmed, they were then uploaded to be analyzed on Logger Pro Software; the first step was to set the scale. Where the ruler scale was dragged along the meter stick. Before digitizing the start frame had to be identified. The start frame was selected where the subject’s arm is in full extension and the next part was to digitize the shoulder marker. The digitizing was stopped when it was at least five frames past the top of the jump. After the digitizing was complete the data columns were renamed the position and velocity “RAW”. The same step were completed for digitizing the wrist marker including renaming the data columns. As well as for the weighted jump.
The next was the kinematic data analysis and this is done on Logger Pro. To find subject’s jump height, the shoulder marker standing height was found first. This is when the subject is standing fully upright, prior to the jump. Next was to find the shoulder max jump height, by plotting the shoulder height which allowed you to find the max vertical position of the shoulder. Finally, to calculate the jump height, max shoulder jump height was minused by the standing shoulder height. For the data analysis, it was completed on Logger Pro, first was the x and y velocity for the wrist which was done using the function “low pass filter”. After the finding the velocity of the wrist, the wrist acceleration for the x and y values were found using the derivative function. Next, calculation was the total arm COM motion; the anthropometric table was required for the COM proximal ratio. To solve this the x position of the wrist and shoulder were needed. Next was the arm COM for the x and y velocity, this was done using the derivative function. After the calculation, the arm COM had to be filtered using the low pass filter. Next after finding the arm COM velocity was the acceleration of the x and y; this was done using the derivative function from the arm COM velocity. Once this was completed, the arm segment angle was found; using the trigonometric function. For the wrist/weight acceleration the same steps were completed as the arm. The next calculations were arm movement for inverse dynamics. The first one is shoulder joint moment which is moment due to gravity acting on the arm COM about the shoulder. The second one is linear acceleration about the shoulder which is moment of the arm COM. The third one is arm moment of inertia at the shoulder which is multiplied by arm angular acceleration. The next three are for the weighted jumps only, the first one is the weight on the hand and which is done for the X and then Y forces. After the moment of weight forces about the shoulder were calculated. The last one was moment of inertia at the shoulder which is multiplied by arm angular acceleration. Shoulder power is the next to calculate which is moment of shoulder. The final one to calculate is the arm & handheld weight vertical momentum. For the weighted jump, the wrist velocity plus the handheld weight must be accounted for.
The next part is lab 2: Ground Reaction Forces in Vertical Jump Performance The same subject was used during lab one and the same procedure was followed for setup and the completing the jumps. The only difference was that the subject was jumping off a force plate to determine force, impulse-momentum, work/energetics and power. The one precaution was to make sure the forces do not exceed 3500 N. These were all completed on Logger Pro. These steps were completed for the normal and weighted jump.
After the jumps were collected the next step was the data processing for jump impulse and timing, bottom of countermovement, maximum downward velocity and jump force and timing. Calculating the jump impulse was done using the integral function, using the square brackets the first one was put at time zero and the second was at take-off point. The bottom of countermovement was calculated where the right bracket was moved left until Ft equals zero. Using the examine function record the time and force for the bottom countermovement. Next for max downward velocity; keeping the first bracket still at zero, move the right bracket left more till the force return from negative to zero. The value and time for max negative impulse was recorded. The final one was the jump force and the time, this was used to complete the table for all the above analysis.
Next was the manual calculations, the first one was max downward velocity. For the no weight trial, the max negative impulse was divided by the subject’s mass. For the weighted trial, follow the same steps but add the handheld mass to the subject’s weight. For the takeoff velocity, the jump impulse was divided by the subject’s mass for the no weight trial. For the weighted trial, same step was completed as before by adding the handheld weight to the subject’s mass. For the jump height, the takeoff velocity was used to determine the height for no weight and weighted trial. Final manual calculation was for average power. This was done over two intervals, the whole jump duration (start to take off) and the upward phase (bottom of countermovement to take off). The next calculations will be done on Logger Pro and they are done to find the instantaneous power; each calculation is done for both no weight and weighted jump. The first one is whole-body vertical velocity which is done using the integral function, make sure to add the handheld weight for the weighted jump. Next one is ground reaction force this is force plus the force created by the subject. Same steps is done for weighted with force created by subject plus handheld weight. The final calculation is for instantaneous power which is GRF times whole body vertical velocity.
Results
Jump Height
From figure 1, it is clear the kinematic jump heights are much higher than kinetics lab. For the kinematics part of lab, the normal jump without weight had a jump height was 0.532m and the weighted jump height was 0.602 m. The percent difference between the two for the kinematics lab was 13% therefore the difference is significant. For that kinetics lab, the normal jump was 0.165 m and the weighted jump was 0.14 m. The percent difference between the two was a decrease of 86% therefore the difference is significant. Jump heights for the two different labs were very different, the kinematics lab the jump height was much higher than the kinetics lab. For the kinematics lab, the jump height increase during the weighted jump while in the kinetics lab the jump height decreased.
Arm Angular Velocity
Figure 2 illustrates the arm angular velocity for both the normal and weighted of the countermovement jump. For the bar and the angular velocity during the normal jumped the peak forward/upswing velocity was 19.51 rad/s at 0.1 s and for the weighted jump it was 14.67 rad/s at 0.1 s as well. The percent difference between the two jumps is 33% therefore the difference is significant. For the weighted jump the angular velocity stays somewhat constant after the peak velocity. The normal jump has a steeper fall after the peak velocity.
Shoulder Moment
Figure 3 illustrates the shoulder moment over time for both the normal and weighted jump of the countermovement jump. When comparing the two graphs they two jumps did not have the same pattern which may have occurred due to error when collecting data in the lab. As shown on the graph, the weighted jump hit extremely high and low numbers to the point where the normal jump points can no longer be seen on the graph.  For the normal jump, shoulder moment increased to its peak much earlier than the weighted jump. For the normal jump, the maximum peak was 180 Nm at ~0.1 s and the minimum was -100 Nm at ~0.2 s. For the weighted jump (collection error), the maximum peak was ~2000000 Nm at ~0.3 s and the minimum was -2E+08 Nm at ~0.1s. The percent difference between the two is ~99% therefore the difference is significant.
Shoulder Power
In figure 4, the peak forward/upswing power as well as the breaking phase of the jump was displayed graphically. The normal jump had a peak upward swing earlier in the jump just before 0.1 s while the weighted jump hit its peak 0.3s. The normal jump’s peak for the power was 2400 W and the weighted jump was 1E+10 W. The percent difference for the two jumps is -99% therefore the difference is significant. For the weighted jump the peak and the braking phase is greater than the normal jump. The breaking phase for the normal jump occurred at ~0.2 s and was -1900 W although for the weighted jump it occurred at 0.2 s and it was -2E+10 W. the percent difference between the two is -46% therefore the difference is significant.
Vertical Arm Momentum
In figure 5, vertical arm momentum of maximum upward momentum is displayed for both normal and weighted jumps. The two graphs are not quite as similar in shape but the time variables for when the maximum momentum occurs is similar. The maximum for the normal jump was 50 kgm/s occurring after 0.1 s and peaked early than the weighted jump where its maximum was 10000 kgm/s occurring at 0.2 s. The curve for the weighted jump is much wider compared the normal jump where its curve is much longer. The percent difference between the two jumps is 199% therefore the difference is significant.
Ground Reaction Force
Figures 6 displays the ground reaction force and time. The weighted jump produced a smaller force compared to the normal jump. The maximum force for the normal jump was 635 N while the weighted jump was 520 N. The percent difference between the two results is -18%; therefore, the difference is significant. The jump impulse for the normal jump produced a longer impulse than the weighted jump which tells us the body was under tension for a longer period during the jump; which is the body’s way to produce more force for the jump. The normal jump impulse was 124.6 Ns while the weighted jump impulse was 116.7 Ns. The percent difference for the jump impulse was -6%; therefore, the difference is significant. The maximum negative impulse for the weighted jump produced a bigger impulse than the normal jump. The normal jump had a maximum negative impulse of -44.55 Ns at 0.35 seconds while the weighted jump had a maximum negative impulse of -48.15 Ns at 0.40 seconds. The percent difference between the two was 44%; therefore the difference is significant. The average power for the whole jump for the normal jump was greater than the weighted jump. As well as the upward phase, the normal jump’s average power was greater than the weighted jump. For the whole jump, the normal jump’s average power was 107.17 W and the weighted jump was 62.44 W. The percent difference for the two jumps is 61% therefore the difference is significant. For the upward phase, the normal jump’s average power was 718.89 W and the weighted jump was 647.58 W. the percent difference between the two jumps is -9% therefore the difference is significant.
Instantaneous Power
In figure 7, instantaneous power was displayed for both the normal and weighed jumps. For both graphs for have similar patterns for maximum instantaneous power. Both normal and weighted jump reach their maximum power around 1 second and immediately decrease. For the normal jump the maximum power was ~2400 W and occurred at 1.5 seconds. The weighted jump the maximum power was reached just before 1.0 second and it was ~4000 W. The percent difference between the two jumps was 66% therefore the difference is significant.
Discussion
The purpose of this lab was to understand how the arm swing affects the jump height with no weight and with handheld weights. Furthermore, if the adding the weights would influence the countermovement for the vertically jump positively. Inclined to what we learned in class with regards to Newton’s Laws and as well as the results from previous studies. It would be assumed that adding specific weight would increase the forces at the shoulder in turn increase overall kinetic energy in the body which would lead to an overall increase in jump height. With the results from the lab the main one that proved in favour of my hypothesis was the kinematic jump heights. The weighted jump for the kinematic lab’s jump height was bigger than the normal jump. My hypothesis was by adding weights to the arm swing, the jumpers force will increase and in turn increase their jump height by at least 10%. The findings did not agree enough with my hypothesis due to the lack of results. The difference in the jump heights were significant due to such a big difference between the values. One reason the jump heights did not have an impact because the handheld weights that were being used were standard amongst every participant in lab. If the handheld weight was specially chosen for each subject the results may have been more in favour of the hypothesis. Looking at figure 6 which is vertical ground reaction force, when comparing the two graphs they do appear to look the same graphically. The normal weight jump was able to produce a greater force by 100 N than the weighted jump and it was able to do it quicker by 0.5 s.
Arm Swing Performance
The arm swing performance was maintained by the subject where she did not have issues with performing the motion. However, figure 2 where arm angular velocity is displayed it is clear that the velocity decreased during the weighted jump. The handheld weight did make up for the loss in velocity for the increase in shoulder power and the vertical momentum. Yet, when looking at figure 3 which is shoulder moment there is increase in momentum but the there is also a big decrease. This could be due to the subject not having the strength to adjust to the extra weight being applied to the shoulder; causing a big decrease.
Whole Body Performance (Ground Reaction Force Kinetic Data)
Analyzing figure 5-7, it provides the subject’s overall whole body performance which are vertical momentum, ground reaction force and instantaneous power. At a glance the graphs for their respected figure appear to be graphically similar to each other (the normal and weighted countermovement jumps). It was hypothesized that by increasing weight the vertical momentum would increase; figure 5 supported the hypothesis. For the weighted jump for the vertical arm momentum it had a greater momentum compared to the normal jump. When looking at Newton’s second law, F=ma the weighted graph for figure 6 had a smaller force than the normal jump which does not follow what he hypothesized based on Newton’s Law. This could be due to the subject not feeling comfortable using the weight while jumping either because it was too heavy or even too light.
Kinematic and Kinetic Lab Results
The kinematic jump heights and the kinetic jump did not report the same values as hoped. From basic physics laws, we understand when additional mass is given it was increase the force which will increase kinetic energy and potentially jump height. In figure 1, the kinetics portion of the lab did not prove this idea. The jump height in the kinetics lab with the weight was smaller than without the weight. However, the kinematics lab did prove this point because the weighted jump had a bigger jump height compared to the normal jump. A reason for the such big differences between the kinematic and kinetic lab was perhaps due to the subject having to jump off the force plate in the kinetics lab. For the kinematics lab the subject is jumping off the floor and landing back on the floor so there is not adjusting the body needs to do because it is the same surface. For the kinetics lab the subject is jumping off of the force plate, where it is to different surfaces and there is a slight drop decrease in height from the force plate and the floor. This loads the joints differently where it may cause the subject not to jump as high vertically during the jump.
Assumptions and Limitations of the study
Two limitations with the equipment/protocol was one was the 60 Hz camera being used. It was not one of the best cameras because in certain frames it was hard to see the markers because they were not visible throughout all the frames. If a better camera with higher hertz was used it was would have been more clear to see the markers on the video when digitizing on Logger Pro. The second limitation with the equipment/software, Logger Pro. A time the software would glitch and cause some data to be misplaced. Which conversely could mess up some of the data causing an error. During the lab a few times, we had to redo steps because the program would freeze.
Two assumptions that occurred during the lab is the subject throughout the all the trials maintained straight arm swings and did not bend her arms. This would cause concern because all the calculations would be incorrect and make the results in accurate. The second assumption being made is that the subject is jumping vertically throughout all the trials. However, since the subject was instructed to jump off the force plate, technically it is not a complete vertical jump and the motion moving forward was not factored in.
A Follow-Up Study
An ideal follow-up study would be using the same protocol but more specific to lower body joints and the mechanics. Targeting specific sports like volleyball players, to find an efficient jump pattern or style. Where its produces the greatest force and positive outcomes for higher jump height but is conscious on lower body joints. This study would not involve handheld weights but would pay more attention to different jumping styles with an arm swing. From the studies, I have read, the arm swing has always produces a positive outcome for jump height but it was never looked at the negative effects of jumping and if the extra force being produced can cause a concern for future injury. As the sport is demanding on the lower body as well, a lot of athletes obtain lower body injuries; more so at the major joints (hip, knee and ankle). This follow up study would tell the readers what the most effective way of jumping in a vertical motion is to prevent lower body injury but as well still produce a good jump height to be successful in the sport. This can also be applied to other jump demanding sports such as gymnastics and track and field athletes such as high jumpers. There is a lot of research that can be done in the field.
Similar Research to the Findings
Research by Frantisek et al., published their study in the Journal of Human Kinetics. This paper helps explain the effect of an arm swing on countermovement of the vertical jump. This study showed that including an arm swing in the vertical jump improved the mechanics and increased the jumped height by 38% compared to jumping with no arm swing. The arm swing also increased the average force that was produced during the acceleration phase and the accelerating impulse of the jump. Their study also confirmed that the body position at the accelerating phase either affected or had no change to the jump with an arm swing. The arm swing was best when it downward to the ground which decreased pressure on the surface. Optimally the best position was standing up naturally (2016). Which was the same as the study we conducted. Our subject performed the arm swing the same way, where the arm swing followed the direction of the jump. Where the arms started downwards and as the subject jumped followed upwards with the body. The study by Kraska et al., also supported our findings where adding the handheld weight increased our acceleration during the kinematics lab. This principle followed Newton’s Second Law, F=ma (2009).
Conclusion
Thus, based on the results completed in this lab, adding weights to the subject’s arm swing cannot improve their jump height. Due to some limitations in the lab such as, the subject not have the proper weight specifically for them could affect the optimal countermovement jump performance. As well as jumping off of the force plate onto a different surface could have off balanced the subject also decreasing their jump height performance. Nonetheless, if the above factors are ignored because of the percent difference between the kinematic and kinetic lab the results are trivial. Thus, further proving the circumstance that adding the additional weights cannot improve vertical jump height.