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Introduction

Jumping is a complex human movement that requires complex motor coordination between upper and lower body segments. The propulsive action of the lower limbs during a vertical jump has been considered particularly suited for evaluating explosive characteristics of sedentary individuals and elite athletes. Also since performance in most individual and team sports depends on the athlete’s ability to produce force quickly, the use of reliable and valid testing procedure is beneficial for monitoring the effects of training and for talent selection purposes

The Vertical Jump is a Test for leg power, it is used by many athletes from different sports.

Vertical jumps are used to measure an athlete’s performance in various sports(i.e Basketball, volleyball and track and field). And it is measured by how high one athlete is able to lift/elevate off the ground from a standstill position using as much power from their lower body as possible.

This test also helps to test the whole body’s explosiveness which could be effective in that sport they are participating in.

The three phases of the vertical jump are the preparatory phase, takeoff phase and the landing phase. The different muscle groups contract eccentrically and concentrically to power a vertical jump.

In the preparatory phase where an individual prepares to jump, there is flexion at the hip and joint. The tibialis anterior at the ankle dorsi-flexes. When he or she squats lower to jump up, knee and hip flexion causes the ankle joint to contract eccentrically. The muscles around the hip sartorius, rectus femoris and bicep femoris power the phase of the jump.

The next phase of the jump is the takeoff phase. In this phase the knee and hip joint extend and the ankle joint plantar flexes. The gluteus maximus, semitendinosus, long head of the bicep femoris, adductor magnus and the semimembranosus also extends as the body powers upwards. The extension of the hips causes the quadriceps muscles to fire to perform knee extension simultaneously. At the peak of the jump the ankle joint plantar-flexes.

            The final phase of the jump is known as the landing phase. In this phase the muscle involvement follows the reverse order seen in the takeoff phase. In order to maintain balance and the effect spinal position there is compression in the rectus abdominis and iliocostalis thoracis.

The aim is to find out the most effective method of jumping to achieve the highest vertical jump height.

 

Methods

One subject was enrolled in this study: Active male (exercise 3 to 5 days a week), BMI 22.5, 32years old. Subject was asked to perform 3 trials of squat jumps and countermovement jumps each. Subject was allowed to warm up for 5 minutes before the start of the first trial. The vertical jump height was measured from the starting position marked ‘X’ to a red marker on the subjects foot.

A Sony HDR-PJ30E digital camera with 1920×1080 resolution and shutter speed 25 frames per second was set up perpendicular to the plane of motion with the camera standpoint 5 meters away from the subject. Red markers were placed over the subjects ankle, knee and hip.

 

Results

Table 1: Results Generated for Squat Jump and Countermovement Jump Trials

 

            The results shown on Table 1 reveal that the CMJ was superior in all 3 aspects calculated. The average angular velocity of the subjects knee extension during the CMJ was 1.3089935 rad/s faster than that of the SJ and the takeoff velocity of the CMJ was 1.295 m/s faster than that of the SJ. Overall this resulted in an average height difference of 6.34 cm in favour of the CMJ.

Discussion and Conclusion

            From the results, it can be concluded that the CMJ was more effective in achieving a higher vertical jump height than the SJ. The angular velocity of the knee extension and takeoff velocity indicate that a higher force was generated during the CMJ than the SJ. However, a greater forced developed does not fully explain the CMJs effectiveness. Further research identified the deciding factor to be the Stretch-Shortening Cycle (SSC). The SSC of muscles is derived from the cycle of concentric and eccentric muscle contractions during human movement and can allow for a height jump height due to the combination of 4 factors. (Winkelman, 2011)

Firstly, Potentiation. The eccentric stretching of pre-activated muscles has been shown to produce 2 times the force that that of a non-activated muscle. In the case of the SJ, where there is not eccentric downward phase, the absence of potentiation can be a contributing factor to the lower jump height. Furthermore, increasing the speed of the downward phase as well as decreasing the time taken between the downward phase and take-off phase would increase force production during take-off. (Wilson, Elliott & Wood, 1991) Secondly, an increase in muscle activity state during the CMJ allows greater hip angular velocity of the knee and hip extension and ultimately, greater concentric force and velocity during take-off. Thirdly and lastly, storage and re-utilisation of strain energy and stretch reflex. One study found that the same amount of strain energy was delivered between the CMJ and the SJ therefore would not explain the performance difference in vertical jump height but rather the energy efficiency of the jump. (Anderson & Pandy, 1993)

In conclusion the aim of this study is to find out the more effective method of jumping to achieve the highest vertical jump height. The finding suggest that the countermovement jump is the more effective method of the achieving the highest vertical jump height.

 

 

References

 

Bobbert, MF and Casius, LJ. Is the effect of a countermovement on

jump height due to active state development? Med Sci Sports Exerc

37: 440–446, 2005.

 

Miller, DI. A biomechanical analysis of the contribution of the trunk

to standing vertical jump take-offs. In: Physical Education, Sports

and the Science. J. Broekhoff, ed. Microform Publications, Eugene,

Oregon, USA, 1976. pp. 355–373.

http://aclprevention.blogspot.sg/2014/01/squat-jump-vs-counter-jump-squat-as.html

 

 

One study also showed that muscle strength characteristics of lower limb joints were the main determinant of vertical jump performance, rather than jump technique.