Coherence Between Power Production during Counter Movement Jump in a Smith Machine and Free Standing with External Loading

Abstract

The purpose of this study was to evaluate the coherence of power production during a Counter Movement Jump (CMJ) performed in a Smith Machine (SM) and Frees Standing (FS). Two female athletes performed 10 test sessions with three days in between. Each test session included two-legged CMJ performed in a SM and FS with external loads. Variables analyzed were Average Power (AP), Average Force (AF) and Average Velocity (AV). The correlation between the results from CMJ performed in a SM and FS was high (r p =0.87-1.0, p<0.001). The results showed a good test-retest reliability for all indices, for both CMJ performed in a SM and FS with Coefficient of Variance (CV) for AP (CV SM =3.1- 3.5 %; CVFS=2.9-4.8 %), AF (CVSM=1.6-1.9 %; CVFS=1.6-2.1 %), and AV (CVSM =1.7-2.7 %; CVFS =1.8-2.9 %). Though significantly higher values were seen during FS CMJ analyzed by Bland-Altman plots with AP (Bias: 13.7 W; LOA -19.1 to 46.5 W), AF (Bias: 2.7 N; LOA -7.0 to 12.4 N) and AV (Bias: 0.03 m/s; LOA -0.05 to 0.11 m/s). In conclusion, athletes and coaches are able to use both SM and FS CMJ to evaluate training progress, but they should be aware about the differences between SM and FS CMJ.