Electromyographic activity and 15RM load during resistance exercises on stable and unstable surfaces.

Abstract

The purpose of this study was to compare electromyographic (EMG) activity and a 15-maximum repetition (15RM) load in bench press (BP) and free squat (FS) on a stable surface (SS) and an unstable surface (US). Nineteen healthy men (age 24.65 ± 3.48 yrs) volunteered for five testing sessions. The load value for the FS on the SS was higher than on the US (83.9 ± 18.67 kg vs. 70.3 ± 10.07 kg, P=0.001). No significant difference was observed between BP on either surface to load value (66 ± 10.15 kg vs. 64.2 ± 8.63 kg, P=0.231). For EMG, no significant differences were observed in the anterior deltoid (0.52 ± 0.13 vs. 0.65 ± 0.42, P=0.06), pectoralis major (0.40 ± 0.44 vs. 0.30 ± 0.21, P=0.14), biceps femoris (0.09 ± 0.08 vs. 0.08 ± 0.06, P=0.50), or vastus lateralis (0.34 ± 0.21 vs. 0.34 ± 0.22, P=0.76) between conditions. Thus, the findings indicate that an US produces similar muscle activation as a SS produce using lower loads.