engleski

The effect of stable and unstable lifting conditions on muscle power and fatigue rate during resistance exercises

BACKGROUND: This study evaluates the effect of fatigue on mean power in the acceleration and throughout the entire concentric phase of resistance exercises on stable and unstable surfaces. METHODS: A group of 24 fit young men performed a set of 25 repetitions of chest presses on a bench or on a Swiss ball, and squats on a stable support base or on a BOSU® ball (both with 70% of 1RM). While exercising, basic biomechanical and cardiorespiratory parameters were monitored. RESULTS: Outcomes showed that mean power during both exercises was significantly higher on the stable than on the unstable surface. However, mean power in the acceleration (46.1% and 29.3%, respectively ; P=0.009) and during the entire concentric phase of repeated chest presses (44.9% and 33.1%, respectively ; P=0.012) decreased more profoundly under stable than unstable conditions. Furthermore, the oxygen uptake during active lifting intervals was significantly higher during unstable than stable chest presses (2.11±0.22 L/min and 1.69±0.19 L/min, respectively ; P=0.033), whereas its values did not differ significantly during unstable and stable squats (2.13±0.21 L/min and 2.01±0.17 L/min, respectively ; P=0.27). It may be concluded that fatigue in the final repetitions of a set of chest presses impairs the ability to produce power more profoundly when performed on the bench than on a Swiss ball. Contrary to this, there were no significant differences in power decline during squats on the stable support base and a BOSU ball. CONCLUSIONS: These findings indicate that unstable lifting conditions may stimulate power potentiation mechanisms and consequently reduce power decline in fatigue. However, this effect depends on the type of exercise and instability devices used.

ostural balance ; Muscle strength ; Resistance training

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