KINETIC ANALYSIS OF IMPACT ABSORPTION AT LANDING DURING JUMPING MOTION: COMPARISON WITH AND WITHOUT AWARENESS

¹Teikyo Heisei University, Department of Physical Therapy, Tokyo, Japan

Background: A large impact force is transmitted to the body at landing during jumping, which often cause injuries. Few studies have reported the differences in human motion with and without the awareness of shock absorption during jumping motion.

Purpose: The objective of this study was to characterize the human motion with and without our awareness of shock absorption during jumping motion.

Methods: We enrolled 16 healthy young adults for the study. A three-dimensional motion analysis system ( sampling frequency: 100 Hz ) and a force plate ( sampling frequency: 1,000 Hz ) were used. The subjects stood with their right leg on the force plate. For the first trial, the individuals jumped vertically with their maximum efforts without awareness of shock absorption. However, for the second trial, we instructed each individual to maximize efforts at jumping, similar to the first trial, and landing softly with self-awareness of shock absorption. Jump height, the time during a jumping motion, vertical floor reaction force, and the extent of length change between the anterior superior iliac spine to the lateral malleolus were all measured while jumping with and without awareness of shock absorption. Statistical analyses were performed using Wilcoxon single-rank test at a 5% significance level.

Results: The following results were obtained ( expressed as median ± quartile deviation ):
1) Both jump height and fall speed, with and without the awareness of shock absorption showed no significant difference.
2) The maximum vertical floor reaction force with the awareness of shock absorption ( 742.3 ± 200.4 N ) was significantly lesser than that without the awareness of shock absorption ( 1405.4 ± 570.2 N ).
3) The time between jumping to the highest point and starting to bend the lower limbs, with the awareness of shock absorption ( 0.26 ± 0.03 s ) was significantly shorter than that without the awareness of shock absorption ( 0.29 ± 0.03 s ).
4) During a jump motion, the extent of length decrease ratio between the anterior superior iliac spine to the lateral malleolus, with the awareness of shock absorption ( 44.4 ± 9.8 % ) was significantly greater than that without awareness of shock absorption ( 28.2 ± 6.6 % ).
5) The impact time, which is calculated from the relationship between momentum and impulse with the awareness of shock absorption ( 0.11 ± 0.02 s ) was significantly greater than that without the awareness of shock absorption ( 0.06 ± 0.02 s ).
6) Spring constant with the awareness of shock absorption ( 2.9 ± 1.8 N / mm ) was significantly lesser than that without the awareness of shock absorption ( 6.0 ± 2.3 N / mm ).

Conclusions: While jumping with the awareness of shock absorption, the legs start bending earlier to absorb the impact, the impact absorption time is longer, and the spring constant is lesser than while jumping without the awareness of shock absorption. In addition, the maximum vertical floor reaction force is lesser, even if the jump height is the same.

Implications: We believe these results may be applicable for patients’ education to prevent injuries.

Funding acknowledgements: This work was not supported by any foundation.

Keywords:
Jumping motion
Impact absorption
Awareness

Topics:
Research methodology, knowledge translation & implementation science
Occupational health & ergonomics
Sport & sports injuries

Did this work require ethics approval? Yes

Institution: Teikyo Heisei University

Committee: Teikyo Heisei University

Ethics number: R01-078