Time Course of Improved Flow-Mediated Dilation after Short-Term Exercise Training

Purpose: The purpose was to determine the influence of a unilateral localized short-term handgrip training protocol on brachial artery flow-mediated dilation (BAFMD) and to examine the time course of such changes. Methods: Fourteen healthy males (age: 26 ± 5.7 yr) underwent high-resolution ultrasonographic brachial artery assessments before (V1), during (V2–V7), and at the end of 4 wk (V8) of 60% maximal voluntary contraction handgrip training (20 min·d-1, 5 d·wk-1) of the nondominant arm. Results: Before training resting diameters were similar between the trained (nondominant) and untrained (dominant) arms. A 2 (trained and untrained arms) × 2 (V1 and V8) repeated measure ANOVA revealed a significant main (P = 0.02 and P = 0.03) and interaction effect (P = 0.05 and P = 0.01) for the percent and absolute change in BAFMD. BAFMD improved 62% and 70%, respectively from V1 to V8, for the percent and absolute change. Subsequent linear orthogonal polynomial contrasts indicate both the percent and absolute change in BAFMD were statistically different at V2 (end of week 1 and 4 training days) from V1. These unilateral changes were not accompanied by changes in resting artery diameter, hemodynamic measures, hematological markers, and indices of heart rate variability suggesting the change may be locally mediated. Conclusions: This study shows a localized short-term exercise-training program resulted in significant improvements in BAFMD in the trained arm compared with the untrained arm and suggests this occurred after only 4 d of training.