Effect of instability and resistance on unintentional squat lifting kinetics

Eric J Drinkwater, Erica J. Pritchett, David G. Behm

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    Resistance training while using an instability training device is known to increase activation of stabilizing muscle groups while decreasing the force generated by the prime movers during isometric contractions. Purpose: To investigate differences in squat kinetics during dynamic resistance training in an increasingly unstable training environment. Methods: Fourteen active males participated in this study. In each testing session, each participant performed three repetitions of squats with a 10 repetition maximum (RM) resistance, 40% of their 10 RM resistance or 20.45 kg. The three testing session consisted of standing on a stable floor, foam pads or BOSU balls. All repetitions were recorded with an optical encoder to record barbell kinetics. Results: The transition from stable (floor) to very unstable (BOSU) resulted in high likelihoods (>75%) of clinically meaningful differences ranging from small to large (ES 0.31 ' 1.73) in factors relating to concentric kinetics, eccentric power, and squat depth, regardless of the resistance being trained. There were also likely differences at the heaviest resistance in peak concentric power (stable to foam: ES 2.06; foam to BOSU: ES 0.38), eccentric power (stable to foam: ES 1.88; foam to BOSU: ES 0.74), and squat depth (stable to foam: ES 0.50; foam to BOSU: ES 0.67). Conclusions: Resistance training in an unstable environment at an intensity sufficient to elicit strength gains of the prime movers results in deleterious effects in concentric squat kinetics and squat technique. Such observations are particularly evident on very unstable platforms.
    Original languageEnglish
    Pages (from-to)400-413
    Number of pages14
    JournalInternational Journal of Sports Physiology and Performance
    Issue number4
    Publication statusPublished - Dec 2007

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