PESTA Launch and Inaugural PE Conference 2011

Eunice Yeo and Dr John Tan

National Institute of Education

Nanyang Technological University

Standing Broad Jump:

Countermovement vs Squat Jump technique

Standing broad jump (SBJ)

• National Physical Fitness Award test (NAPFA)

• Individual Physical Proficiency test (IPPT)

• Explosive leg power

• High number of failures observed

Countermovement-stretch shorten cycle

In a countermovement jump:

• When a person squats down

Quadriceps muscles-eccentric stretch

• When he immediately take-off

Quadriceps muscles-concentric contraction

• Stretch shorten cycle

What is stretch shorten cycle (SSC)?

• Quick stretch of an active muscle followed immediately by shortening of the muscle

• When a muscle is stretched, it causes eccentric tension (developing elastic energy)

• When a muscle contracts, concentric

contraction (shortening tension) + elastic recoil occurs

Countermovement jump

Squat jump

Effects of SSC

• Increase total jump height in vertical jumps by

12% (Asmussen & Bonde-Petersen, 1974)

• Can account for 19% more of the weight lifted

in bench press. (Wilson et al. 1991)

Elastic structures

• Two types:

1) Series elastic component (SEC)

2) Parallel elastic component (PEC)

Series elastic components (SEC)

Characteristics of SSC

• Stretch must be actively resisted –eccentric

• The delay between eccentric and concentric phases should not be more than 4 seconds.

(Wilson, Elliot and Wood (1991) reported that by delaying 1 second at the bottom of a bench press would decrease the advantage gained from the stretch shorten cycle by 55%.)

Characteristics of SSC

The longer the delay the greater the loss!

1 second delay 55% lost

2 seconds delay 80% lost

4 seconds delay 100% lost

Question

• Can stretch shorten cycle be used to enhance

standing broad jump?

Purpose

• Compare performance variables of two

techniques: countermovement jump vs squat

jump

Method

• Three subjects were asked to perform three

maximum-effort jumps with each of the

techniques.

• A 2D video analysis procedure used to process

the variables of the jumps.

Silicon Coach

Take-off angle

Take-off height

Measurements

• Three kinematic variables: take-off speed,

take-off angle, take-off height

• The distance jumped was measured.

Results

• Take-off angle and take-off height were almost

similar with two jumping techniques

• Little significance

Performance variables Countermovement

Jump

Squat Jump

Mean take-off angles 38.8° 37.1°

Mean take-off height 0.84m 0.85m

Results

Subject Jump distance (cm) Take-off speed (ms-1)

Counter-

movement

jump

Squat jump diff (cm) Counter-

movement

jump

Squat jump

1 174 169 5 3.90 2.40

2 228 216 12 3.94 3.69

3 184 174 10 3.48 3.17

• Take-off speed influenced jump distance

Results

• A paired sample T-test was conducted.

• Subject 3, 10 CJ and 10 SJ

• Mean of CJ = 180cm and Mean of SJ = 170cm

• It also showed that the countermovement approach yields a significantly (p<0.05) longer distance than the squat jump.

Discussion

• Greater take-off speed, greater jump distance

• Elastic recoil

• Holding the jump resulted in less jump

distance

Conclusion

• Countermovement jump yields a better jump

distance than squat jump. (average of 9cm)

Recommendation

• Teach the countermovement jump to students

to improve jump distance

Not recommended

Encouraged technique

• Squat cannot be slow

Limitations

• Only 3 subjects studied

• More subjects recruited to increase validation

• Sophisticated equipment can be used to yield

more accurate results

References

• Asmussen, E., and Bonde-Petersen, F. (1974). Storage of elastic energy in

skeletal muscles in man. Acta Physiologica Scandinavica, 91(3): 385-92.

• Komi, P. V. (2000). Stretch-shortening cycle: a powerful model to study

normal and fatigued muscle. Journal of Biomechanics, 33, 1197-1206.

• Wilson, G., Elliott, B., Wood G., (1991). The effect on performance of

imposing a delay during a stretch shorten cycle movement. Medicine and

Science in Sports and Exercise 23(3) , 364-70.

• Winter, D.A. (1990). Biomechanics and motor control of human

movement. 2nd edition. NY: John Wiley & Sons.

Thank you!