Abstract
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.
Highlights
Physical activity declines with aging and illness, and inactivity decreases various functions of varying organs
Measurements were made over 2 days for both IMM and immobilization + training (IMM+TRN) groups before and after the 21-day immobilization; circumference, reactive hyperemic response and maximum voluntary contraction (MVC) of the grip in day 1, and recovery time constant of muscle oxygen consumption (TcVO2mus) and endurance performance in day 2
For all the measurements made before immobilization, there was no significant difference observed between IMM and IMM+TRN groups
Summary
Physical activity declines with aging and illness ( long-term hospitalization), and inactivity decreases various functions of varying organs. There are several reports on the influence of disuse on the blood vessel system measured by reactive hyperemic blood flow. Reactive hyperemic blood flow in the superficial femoral artery decreased by 28% after 52 days of bed rest [3]. A trend towards a decrease in hyperemic flow was present after 4 weeks of unilateral lower limb suspension [4]. These reports suggest that hyperemic blood flow, which is a marker for vasodilator capacity of resistance vessel, may be decreased after periods of inactivity
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