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Mechanisms underlying the reduced performance measures from using equipment with a counterbalance weight system
Harsh H Buddhadev1, Jakob L Vingren, Anthony A Duplanty
1Department of Kinesiology, Applied Physiology Laboratory, Health Promotion and Recreation, University of North Texas, Denton, Texas, USA.
Journal of Strength and Conditioning Research
|December 23, 2011
Summary
Counterbalanced Smith machines underestimate upper-body power during explosive movements. Using a counterbalance increases the net external load, leading to inaccurate performance testing.
Area of Science:
- Biomechanics
- Exercise Physiology
- Sports Performance
Background:
- Bench press throws on a Smith machine are used to assess upper-body power.
- Counterbalanced Smith machines may reduce performance measures, but the reasons are unclear.
Purpose of the Study:
- To investigate the physiological and biomechanical factors behind reduced performance on counterbalanced Smith machines.
- To determine if counterbalance systems affect force and velocity measurements in bench press throws.
Main Methods:
- Twenty-four men performed Smith machine bench press throws at 30% of 1-repetition maximum.
- Four conditions were tested: rebound/counterbalance, rebound/no counterbalance, concentric-only/counterbalance, and concentric-only/no counterbalance.
- Peak power, force, and velocities were measured using accelerometers and force plates.
Main Results:
- Counterbalance significantly reduced peak accelerometer-based force (-21.2% rebound, -17.0% concentric-only).
- Counterbalance increased peak ground reaction force (5.3% rebound, 3.2% concentric-only).
- Discrepancies suggest an increased net external load with counterbalance.
Conclusions:
- Counterbalance systems on Smith machines increase net external load during the concentric phase.
- This leads to an underestimation of actual upper-body power and performance capability.
- Counterbalance systems should be avoided for performance testing of explosive movements.
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