Microcirculation of skeletal muscle adapts differently to a resistive exercise intervention with and without superimposed whole-body vibrations.

Whole body vibration (WBV) training is commonly practiced and may enhance peripheral blood flow. Here, we investigated muscle morphology and acute microcirculatory responses before and after a 6 week resistive exercise training intervention without (RE) or with (RYE) simultaneous whole body vibrations (20 Hz, 6 nun peak to peak amplitude) in 26 healthy men in a randomized, con trolled parallel design study. Total haemoglobin (tHb) and tissue oxygenation index (TOI) were measured in gastrocnemius muscle (GM) with near infrared spectroscopy (NIRS). Whole body oxygen consumption (VO2) was measured via spirometry, and skeletal muscle morphology was determined in soleus (SOL) muscle biopsies. Our data reveal that exercise induced muscle deoxygenation both before and after 6 weeks training was similar in RE and RYE (P = 0.76), although VO2 was 20% higher in the RYE group (P<0.001). The RYE group showed a 14%-point increase in reactive hyperaemia (P = 0.007) and a 27% increase in blood volume (P<0.01) in GM after 6 weeks of training. The number of capillaries around fibres was increased by 15% after 6 weeks training in both groups (P<0.001) with no specific effect of superimposed WBV (P = 0.61). Neither of the training regimens induced fibre hypertrophy in SOL. The present findings suggest an increased blood volume and vasodilator response in GM as an adaptation to long-term RYE, which was not observed after RE alone. We conclude that RYE training enhances vasodilation of small arterioles and possibly capillaries. This effect might be advantageous for muscle thermoregulation and the delivery of oxygen and nutrients to exercising muscle and removal of carbon dioxide and metabolites.