Fumiko Ohmori

Low-volume muscular endurance and strength training during 3-week forearm immobilization was effective in preventing functional deterioration

PurposeThe purpose of this study was to determine whether endurance and strength hand grip exercises during 3-week upper limb immobilization preserve muscle oxidative capacity, endurance performance and strength.MethodsTen healthy adult men underwent non-dominant forearm immobilization by plaster cast for 21 days. Five healthy adult subjects were designated as the immobilization (IMM) group and five were designated as the immobilization + training (IMM+TRN) group. Grip strength, forearm circumference, dynamic handgrip endurance and muscle oxygenation response were measured before and after the 21 day immobilization period. Using near-infrared spectroscopy (NIRS), muscle oxygen consumption recovery (VO2mus) was recorded after a submaximal exercise and the recovery time constant (TcVO2mus) was calculated. Reactive hyperemic oxygenation recovery was evaluated after 5 minutes ischemia. Two training programs were performed by the IMM+TRN group twice a week. One exercise involved a handgrip exercise at 30% maximum voluntary contraction (MVC) at a rate of 1 repetition per 1 second until exhaustion (about 60 seconds). The other involved a handgrip exercise at 70% MVC for 2 seconds with a 2 second rest interval, repeated 10 times (40 seconds).ResultsThere was a significant group-by-time interaction between the IMM and IMM+TRN groups in the TcVO2mus (p = 0.032, F = 6.711). A significant group-by-time interaction was observed between the IMM and IMM+TRN groups in the MVC (p = 0.001, F = 30.415) and in grip endurance (p = 0.014, F = 9.791). No significant group-by-time interaction was seen in forearm circumference and reactive hyperemic oxygenation response either in IMM or IMM+TRN group.ConclusionThe training programs during immobilization period used in this experiment were effective in preventing a decline in muscle oxidative function, endurance and strength.

Exercise-induced blood flow in relation to muscle relaxation period

BackgroundDynamic 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.MethodsSeven 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.ResultsIn 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).ConclusionThe 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.