科研之友
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摘要
Introduction/Purpose Upright resistance exercise causes large transient fluctuations in blood pressure during and immediately after the performance. We examined the effect of resistance load and the number of repetitions on the middle cerebral artery blood flow velocity (MCAv) response during and after upright squatting exercise. Methods Healthy males (n = 12; mean +/- SD: 26 +/- 5 yr) completed 30%, 60%, and 90% of their six-repetition maximum load, completing two and six repetitions of these loads during two visits (order randomized). Beat-to-beat MCAv, blood pressure, and continuous end-tidal PCO2 during exercise, at nadir, and during recovery are reported as the change from preexercise standing baseline. Results During exercise, MCAv(mean) increased 31% +/- 16% (P %26lt; 0.001) across all loads (P = 0.74) and repetitions (P = 0.89), whereas mean arterial pressure (MAP) increased (all P %26lt; 0.05) as load and repetitions increased (e.g., 122 +/- 9 (two repetitions) vs 135 +/- 11 mm Hg (six repetitions) and 128 +/- 13 vs 143 +/- 14 mm Hg, at 30% and 60%, respectively). Within the six-repetition sets, peak MCAv(mean) remained unchanged across the set (P = 0.61), whereas MAP increased (P = 0.003). The 90% load produced the lowest MCAv(mean) nadir (pooled means, -18 +/- 6 vs -10 +/- 7 cm center dot s(-1), P %26lt; 0.001 vs 30%) and MAP nadir (-34 +/- 7 and -43 +/- 5 mm Hg, for two and six repetitions, respectively; P %26lt; 0.001) after exercise. Postexercise MCAv(mean) reductions occurred via a selective, load-dependent (P %26lt; 0.001) decrease in diastolic MCAv. MCAv(mean) remained below baseline for the longest period after the 90% six-repetition set (10 s postexercise, P %26lt; 0.01) and took the longest to recover (14.8 +/- 6.9 s, P = 0.002). Conclusion These data indicate that higher relative loads produce a greater postexercise hypotension and result in a proportionate reduction in MCAv(mean).
- 出版日期2014-3
