In an effort to evaluate potential peripheral adaptations to training, maximal metabolic vasodilation was studied in the dominant and nondominant forearms of six tennis players and six control subjects. Maximal metabolic vasodilation was defined as the peak forearm blood flow measured after release of arterial occlusion, the reactive hyperemic blood flow (RHBF). Two ischemic stimuli were employed in each subject: 5 min of arterial occlusion (RHBF5) and 5 min of arterial occlusion coupled with 1 min of ischemic exercise (RHBF5ex). RHBF and resting forearm blood flows were measured using venous occlusion strain-gauge plethysmography (ml X min-1 X 100 ml-1). Resting forearm blood flows were similar in both arms of both groups. RHBF5ex was similar in both arms of our control group (dominant, 40.8 +/- 1.2 vs. nondominant, 40.9 +/- 2.1). However, RHBF5ex was 42% higher in the dominant than in the nondominant forearms of our tennis player population (dominant, 48.7 +/- 4.0 vs. nondominant, 34.4 +/- 3.4; P less than 0.05). This intraindividual difference in peak forearm blood flows was not secondary to improved systemic conditioning since the maximal O2 consumptions in the two study groups were similar (controls, 45.4 +/- 3.9 vs. tennis players, 46.1 +/- 1.7). These findings suggest a primary peripheral cardiovascular adaptation to exercise training in the dominant forearms of the tennis players resulting in a greater maximal vasodilatation.