Exercise-induced blood flow in relation to muscle relaxation period

BACKGROUND: Dynamic exercise is characterized by relaxation periods between contractions. The relaxation period should be considered as a causal factor for determining the magnitude of blood flow during dynamic exercise. The purpose of this study was to investigate the effect of muscle relaxation periods determined by the response of each subject on the exercise-induced blood flow response. METHODS: Seven healthy female subjects performed dynamic plantar flexions twice in succession; the duration of each flexion was 1-s and they were performed at an intensity of 15%, 30% and 50% of the maximal voluntary contraction (MVC). Based on the blood flow response after a single contraction, we set up intervals between two successive contractions; the intervals corresponded to 50% (pre-Tpeak), 100% (Tpeak), and 150% (post-Tpeak) of the time required to reach peak blood flow. RESULTS: In all the conditions, upon cessation of the contraction, there was a progressive, beat-by-beat increase in the blood flow through the popliteal artery that peaked by the 5th cardiac cycle. Peak values of blood flow achieved after exercise were significantly higher at pre-Tpeak than at Tpeak and post-Tpeak (p < 0.05). CONCLUSION: The result indicate that at three intervals based on the time taken to reach the peak value, the highest blood flow value was obtained at the pre-Tpeak interval.