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Stretch-shorten cycle compared with isometric preload: contributions to enhanced muscular performance
A D Walshe1, G J Wilson, G J Ettema
1School of Exercise Science and Sports Management, Southern Cross University, Lismore, New South Wales, Australia. awalshe@scu.edu.au
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 6, 1998
Summary
Muscle contraction history significantly impacts concentric work output. Preceding muscle stretch or isometric preload enhances performance more than concentric-only contractions, suggesting improved muscle activation states.
Area of Science:
- Biomechanics
- Exercise Physiology
- Muscle Physiology
Background:
- Understanding the influence of prior muscle activity on subsequent performance is crucial for optimizing training and athletic endeavors.
- The stretch-shorten cycle (SSC) and isometric preload (IS) are common pre-contraction strategies.
- Isolating the specific mechanisms behind performance enhancement from these histories remains an area of interest.
Purpose of the Study:
- To investigate the effect of different muscular contraction histories on concentric work output.
- To differentiate the contributions of pre-stretch muscle state versus contractile element potentiation to performance enhancement.
Main Methods:
- Forty trained male subjects performed three isokinetic concentric squat conditions: concentric-only (CO), isometric preload (IS), and stretch-shorten cycle (SSC).
- Work output was measured during the initial 300 ms of the concentric phase for each condition.
- Normalized, integrated electromyogram (EMG) was assessed to evaluate muscle activation levels.
Main Results:
- Both SSC and IS conditions demonstrated significantly greater work output in the first 300 ms compared to the CO squat (P < 0.001).
- Work output during the initial 300 ms was significantly higher following the SSC protocol than the IS protocol (P < 0.05).
- No significant differences in normalized EMG were observed across the three conditions.
Conclusions:
- Concentric performance enhancement from a preceding stretch is primarily attributed to achieving a higher active muscle state before the concentric movement begins.
- Contractile element potentiation is also hypothesized to be a significant factor in stretch-induced muscular performance enhancement.