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Lower-Extremity Joint Function During a Drop Jump: Relationships to Performance and Maximal Strength
Michael H Haischer1,2, Nayun Ahn3, Kristof Kipp1
1Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin.
Journal of Strength and Conditioning Research
|July 27, 2026
Summary
Stronger athletes demonstrate enhanced knee motor function during drop jumps, leading to improved jump height and performance. This highlights how greater relative strength boosts mechanical energy generation for better athletic outcomes.
Area of Science:
- Biomechanics
- Human movement science
- Sports performance
Background:
- Humans adjust joint stiffness based on stretch-shortening cycle (SSC) demands.
- The SSC enhances jumping performance by increasing vertical impulse through eccentric loading.
- Joints have diverse roles (strut, spring, motor, damper) during locomotion, but their specific contributions to SSC performance and strength are unclear.
Purpose of the Study:
- To analyze lower-extremity joint function during drop jumps.
- To determine the relationship between joint function, jump performance (jump height, ground contact time [GCT], reactive strength index [RSI]), and maximal strength.
Main Methods:
- Forty-five athletes performed drop jumps from a 12-inch box.
- Motion capture and ground reaction force data were collected.
- Joint functional indices (JFI) were calculated for ankle, knee, and hip; maximal strength was assessed via isometric midthigh pull.
Main Results:
- The rank order of joint function was strut, spring, motor, and damper across all joints.
- Stronger athletes showed increased knee motor function.
- Greater knee motor function correlated with shorter GCT, higher jump height, and better RSI.
Conclusions:
- Maximal strength positively impacts jump performance.
- Enhanced knee motor function, linked to greater strength, is crucial for optimizing SSC task performance.
- This suggests strength training can improve jump mechanics and outcomes.
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