Force production during squats performed with a rotational resistance device under stable versus unstable conditions

[Purpose] Force production during a squat action on a rotational resistance device (RRD) under stable and unstable conditions. [Subjects and Methods] Twenty-one healthy males were asked to perform six sets of six repetitions of squats on an RRD on either stable or unstable surfaces. The stable and unstable sets were performed on different days. Muscular outputs were obtained from a linear encoder and a strain gauge fixed to a vest. [Results] Overall, the results showed no significant differences for any of the dependent variables across exercise modes. Force(mean) outputs were higher in the concentric phase than in the eccentric phase for each condition, but there were no differences in velocity, time or displacement. The force(peak) was similar in the eccentric and concentric phases of movement under both stable and unstable conditions. There were no significant differences in force(mean) between sets per condition or between conditions. [Conclusion] These results suggest that performing squats with a RRD achieves similar force(mean) and force(peak) under stable and unstable conditions. The force(peak) produced is also similar in concentric and eccentric phases.