Chihoko Ueda

Deterioration of muscle function after 21-day forearm immobilization.

PURPOSE Although it is well known that immobilization causes muscle atrophy, most immobilization models have examined lower limbs, and little is known about the forearm. The purpose of this study was to determine whether forearm immobilization produces changes in muscle morphology and function. METHODS Six healthy males (age: 21.5 +/- 1.4, mean +/- SD) participated in this study. The nondominant arm was immobilized with a cast (CAST) for 21 d, and the dominant arm was measured as the control (CONT). The forearm cross-sectional area (CSA) and circumference were measured as muscle morphology. Maximum grip strength, forearm muscle oxidative capacity, and dynamic grip endurance were measured as muscle function. Magnetic resonance (MR) imaging was used to measure CSA, and 31phosphorus MR spectroscopy was used to measure time constant (Tc) for phosphocreatine (PCr) recovery after submaximal exercise (PCr-Tc). Grip endurance was expressed by the number of handgrip contractions at 30% maximum grip strength load. All measurements were taken before and after the immobilization. RESULTS After the 21-d forearm immobilization, no changes were seen for each measurement in CONT. CSA and the circumference showed no significant changes in CAST. However, maximum grip strength decreased by 18% (P < 0.05), PCr-Tc was prolonged by 45% (P < 0.05), and the grip endurance at the absolute load was reduced by 19% (P < 0.05) for CAST. CONCLUSION In this model, 21-d forearm immobilization caused no significant changes in forearm muscle morphology, but the muscle function showed remarkable deterioration ranging from 18 to 45%.

Noninvasive monitoring of deterioration in skeletal muscle function with forearm cast immobilization and the prevention of deterioration

BackgroundIn this research inactivity was simulated by immobilizing the forearm region in a plaster cast. Changes in skeletal muscle oxidative function were measured using near-infrared spectroscopy (NIRS), and the preventative effect of the training protocol on deterioration of skeletal muscle and the clinical utility of NIRS were examined.MethodsFourteen healthy adult men underwent immobilization of the forearm of the non-dominant arm by plaster cast for 21 days. Eight healthy adult subjects were designated as the immobilization group (IMM) and six were designated as the immobilization + training group (IMM+TRN). Grip strength, forearm circumference and dynamic handgrip exercise endurance were measured before and after the 21-day immobilization period. Using NIRS, changes in oxidative function of skeletal muscles were also evaluated. Muscle oxygen consumption recovery was recorded after the completion of 60 seconds of 40% maximum voluntary contraction (MVC) dynamic handgrip exercise 1 repetition per 4 seconds and the recovery time constant (TcVO2mus) was calculated.ResultsTcVO2mus for the IMM was 59.7 ± 5.5 seconds (average ± standard error) before immobilization and lengthened significantly to 70.4 ± 5.4 seconds after immobilization (p < 0.05). For the IMM+TRN, TcVO2mus was 78.3 ± 6.2 seconds before immobilization and training and shortened significantly to 63.1 ± 5.6 seconds after immobilization and training (p < 0.05).ConclusionsThe training program used in this experiment was effective in preventing declines in muscle oxidative function and endurance due to immobilization. The experimental results suggest that non-invasive monitoring of skeletal muscle function by NIRS would be possible in a clinical setting.

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.

A practical indicator of muscle oxidative capacity determined by recovery of muscle O 2 consumption using NIR spectroscopy

We examined the relationship between the time constant (Tc) for muscle oxygen consumption (VO 2mus) recovery after exercise, as measured by near-infrared continuous wave spectroscopy (NIRcws), and the Tc for phosphocreatine (PCr) recovery as an index of muscle oxidative capacity. Eight healthy male subjects performed a dynamic handgrip exercise, and the VO2mus recovery after exercise was measured with NIRcws by repeated arterial occlusion. VO2mus was determined from the rate of deoxygenation during arterial occlusion, and muscle oxidative capacity was calculated from the Tc for PCr recovery using 31 phosphorus-magnetic resonance spectroscopy. VO2mus increased 8.9 ± 4.9 (mean ± SD) fold of resting after exercise and thereafter decreased exponentially. The Tc for VO2mus recovery and the Tc for PCr recovery were 33.1 ± 9.0 and 35.0 ± 8.5 s, respectively. The Tc for VO2mus recovery was significantly correlated to the Tc for PCr recovery (r = 0.92, p < .01).

Muscle Reoxygenation Difference Between Superficial and Deep Regions of the Muscles During Static Knee Extension

UNLABELLED The purpose of this study was to test the hypothesis that differences in vertical spatial difference in reoxygenation after exercise exists, reflecting heterogeneity of muscle oxygenation during exercise might be due to the difference in dominantly recruited muscle fiber type. METHODS Ten healthy female subjects performed 1 min static knee extension exercise at low (30%) and high (60%) fraction of maximal voluntary contraction (MVC). Muscle oxygenation in the vastus lateralis (VL) was monitored using multi channel near-infrared spectroscopy. Half time reoxygenation (T(1/2)reoxy) after exercise was calculated from oxygenated hemoglobin in the eight channels which changed the distance between light source and detector distances at 2,3,4,5 cm. Blood flow (BF) in the femoral artery was measured by Doppler ultrasound. Mean arterial blood pressure (BP) at the end of the exercise was assessed by a Finometer device. RESULTS BF during exercise did not differ significantly during exercise at low and high intensity, whereas BP was elevated at high intensity. T(1/2)reoxy tended to be prolonged at high intensity. It would be due to a transition of muscle fiber recruitment from type I toward type II fiber dominance, and/or insufficient oxygen supply for increased demand in the muscle. T(1/2)reoxy in different light source and detector distances was not different among them. CONCLUSION This study demonstrated that the reoxygenation in the superficial region did not differ from that in the deeper region, including superficial, even when exercise intensity was high.

The Effects of Food Intake on Muscle Oxygen Consumption

Diet-induced thermogenesis (DIT) is the energy expended in excess of resting metabolic rate for digestion, absorption, transport, metabolism, and storage of foods. Despite a large number of studies on human DIT (Bahr et al., 1991; Burkhard-Jagodzinska et al., 1999; Pittet et al., 1974; Segal et al., 1990; Sekhar et al., 1998; Van Zant et al., 1992; Westerterp et al., 1999), it is not clear in which tissues DIT mainly takes place. Although Astrup et al. (1985, 1986) have shown the possible involvement of skeletal muscle with DIT in humans, rather than brown adipose tissue, there have been few studies examining DIT in skeletal muscle. Furthermore, the effects of various kinds of food, especially sympathetic nervous system (SNS) stimulating agents such as cayenne pepper, on human skeletal muscle metabolism are not fully understood.

Food Intake Increases Resting Muscle Oxygen Consumption As Measured By Near-infrared Spectroscopy

The purpose of this study was to quantitatively examine the changes in muscle oxygen consumption (VO2mus) after food intake as measured by near-infrared continuous wave spectroscopy (NIRcws). Six healthy male subjects were given a meal with a calculated total energy content of 10 kcal/kg body. VO2mus was measured from 15 min to 150 min after they finished eating. VO2mus in the finger flexor muscles was estimated by the rate of deoxygenation during arterial occlusion using NIRcws. The absolute value of VO2mus was calculated using each subjects resting metabolic rate measured by 31Phosphorus-magnetic resonance spectroscopy (31P-MRS). Deep tissue temperature (TD) was also monitored in the forearm same area. The control experiment followed the same protocol but without meal. There was a significant increase in VO2mus: pre-meal value was 1.47 ± 0.17 μM O2/s, post-meal peak value (post 120 min) was 2.31 ± 0.38 μM O2/s (p < .05 vs. pre). In contrast, the control experiment did not show any increase. There was no significant difference in TD between the two experiments. The results indicate that food intake induced a significant increase in VO2mus. NIRcws can be used to provide specific information about changes in localized muscle metabolism elicited by food intake.