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Comparison of Muscle Activation between Variable Resistance Training and Free Weight Training: A Systematic Review
Jie Li1, Zongwei Chen2,3, Mingjun Gong1
1School of Sports Training, Tianjin University of Sport, Tianjin, China.
Journal of Human Kinetics
|May 29, 2026
Summary
Variable resistance training (VRT) enhances muscle activation during the concentric phase compared to free weight training (FWT). Higher loads in VRT further increase muscle activation, offering potential performance benefits.
Area of Science:
- Sports Science
- Biomechanics
- Exercise Physiology
Background:
- Free weight training (FWT) has biomechanical limitations.
- Variable resistance training (VRT) may overcome these limitations and enhance performance.
- The impact of VRT on muscle activation requires further investigation.
Purpose of the Study:
- To compare muscle activation between VRT and FWT.
- To analyze the effect of variable resistance load proportions in VRT.
- To examine the influence of contraction phases on muscle activation in VRT.
Main Methods:
- Systematic review of studies on healthy adults with resistance training experience.
- Muscle activation measured using surface electromyography (sEMG).
- Meta-analysis using random-effects model to calculate Standardized Mean Differences (SMD).
Main Results:
- No significant overall difference in muscle activation between VRT and FWT (SMD = 0.07; p = 0.493).
- VRT demonstrated greater muscle activation during the concentric phase compared to the eccentric phase (SMD = 1.40; p < 0.001).
- VRT showed significantly greater concentric muscle activation than FWT (SMD = 0.32; p = 0.033).
- Higher variable resistance load proportions in VRT led to greater activation than FWT at equivalent loads (SMD = 0.38; p = 0.036).
Conclusions:
- Variable resistance training (VRT) significantly enhances concentric-phase muscle activation compared to free weight training (FWT).
- Optimizing variable resistance load proportions in VRT can further amplify muscle activation benefits.
- VRT presents a promising training modality for improving muscle activation, particularly during the concentric phase of movements.
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