A 30-day forearm work protocol increases maximal forearm blood flow

To evaluate the local circulatory changes that accompany chronic localized work, we studied the effects of a 4-wk handgrip work protocol on maximal forearm work-related blood flow (ml · min^-1 · 100 ml^-1) in the nondominant forearms of six normal subjects. The reactive hyperemic blood flow response (RHBF) was also evaluated pre- and posttraining in both forearms of each subject to determine whether maximal vasodilatory capacity would be enhanced. In addition, maximal O₂ consumption (V̇(O₂max)) was measured. We found that chronic handgrip work led to an increase in work-related blood flow (before, 22.4; after, 32.1; P < 0.05); a drop in work-related minimal resistance (R) (before, 6.4; after, 4.1; P < 0.05). RHBF rose in the chronically exercised extremity by 30% (before, 33.5; after, 43.7; P < 0.05) as minimal R fell (before, 3.2; after, 2.2; P < 0.05). RHBF and R in the unstimulated dominant forearm remained unchanged (blood flow: before, 33.5; after, 31.0; NS; R before, 3.2; after, 3.2; NS). V̇(O₂max) (ml·kg^-1·min^-1) did not change (before, 35.7; after, 34.0). These findings show that localized skeletal muscle forearm work is associated with a localized increase in vasodilation (RHBF). Thus the vascular system appears to be an independent integral partner in the training process.