The influence of backrest support and handgrip contractions on acute metabolic, respiratory, and cardiovascular responses were evaluated in 13 healthy men during exposure to whole-body vibration (WBV).
Following assessment of aerobic fitness during arm cranking, subjects were exposed to frequencies 3, 4.5, and 6 Hz with 0.9 g(r.m.s) acceleration magnitude on a vibrating base in randomized order, on separate days. Each exposure included 6 min baseline without WBV, 8 min of WBV exposure either 'with' or 'without' backrest, 4 min recovery, followed by 8 min of WBV with opposite backrest condition, and 4 min recovery. During the final minute of WBV, subjects performed right hand maximal rhythmic handgrip contractions for one minute. During baseline and before completion of WBV session 'with' and 'without' backrest, cardiac output was estimated indirectly by carbon dioxide rebreathing.
At 3 and 4.5, and 3 and 6 Hz, absolute and relative oxygen uptake demonstrated significantly greater responses during sitting 'without' backrest than 'with' backrest (P