Enhancement of muscle activation during squat exercise: evaluation with magnetic resonance imaging.

We evaluated whether vibration augmented muscle use during squat exercise with magnetic resonance imaging, with two methods: spin-spin relaxation time (T2 mapping), and volume analysis.Male participants (n = 13) visited the facility on two occasions. During the first visit, each participant completed a resistance exercise (RE) comprising four sets of 12 repetitions of triple extension squats. Before and immediately after completion of the exercise, magnetic resonance imaging of their thigh and calf muscles was performed. During the second visit, participants performed resistance vibration exercise (RVE) using the same protocol, but standing on a vibration plate that provided a whole-body vibration stimulus (20 Hz, 3.5 mm amplitude) during the exercise.RE promoted increased T2 in vastus lateralis, vastus medialis and vastus intermedius muscles (p < 0.0001). The same activation was observed for RVE, with no differences compared to RE. The volumetric method was less effective in assessing muscle activation. Only the vastus medialis and vastus intermedius muscle volumes were significantly greater post-exercise compared to pre-exercise for both RE (both muscles: p = 0.0009) and RVE (respectively: p = 0.005 and p = 0.009). No muscular activation was detected for calf either with T2 or volumetric method.Resistance exercise increased T2 and volume of some muscles of the thigh. The addition of whole-body vibration to resistance exercise does not enhance T2 relaxation time or volume accumulation.