Energy metabolism in human calf muscle performing isometric plantar flexion superimposed by 20-Hz vibration.

Vibration training is commonly expected to induce an active muscle contraction via a complex reflex mechanism. In calf muscles of 20 untrained subjects, the additional energy consumption in response to vibration superimposed on an isometric contraction was examined by (31)P magnetic resonance spectroscopy and by near infrared spectroscopy. Subjects performed 3 min of isometric plantar flexion exercise at 40% MVC under four conditions: with (VIB) and without (CON) superimposed 20 Hz vibration at +/-2 mm amplitude, both combined with or without arterial occlusion (AO). After contraction under all conditions, the decreases in oxygenated haemoglobin were not significantly different. After VIB + AO consumption of ATP was increased by 60% over CON + AO, visible by significant decreases in [PCr] and intracellular pH (P < 0.05). The additional energy consumption by vibration was not detectable under natural perfusion. Probably without AO the additional energy consumption by vibration was compensated by oxidative phosphorylation enabled by additional perfusion.