Shiro Ichimura

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).

Calculation of ventilation threshold using noncontact respirometry

We proposed the calculation method of the ventilation threshold using the noncontact respirometry under pedal stroke motion. By the simultaneous measurement with the expiration gas analyzer, we examined the effectiveness of the proposal method. There was high correlation over 0.8 between ventilation variations calculated by our proposed method and the expiration gas analyzer. On the other hand, the correlation between ventilation thresholds calculated by our proposed method and the expiration gas analyzer is 0.735. In this experiment, the sufficient examination seemed to be difficult on the correlation, since the difference between the systemic aerobic capacities of the examinees is small.

Non-contact Measurement Method of Respiratory Movement under Pedal Stroke Motion

We proposed the non-contact measurement method of the respiratory movement under pedal stroke motion, by the application of optical technique. By the simultaneous measurement with the expiration gas analyzer, we examined the effectiveness of the proposal method. As the results, we clarified that the calculated value obtained by our proposal method is highly correlated with the tidal volume expiration measured by the expiration gas analyzer.

Low-volume muscle endurance training prevents decrease in muscle oxidative and endurance function during 21-day forearm immobilization

Aim:  To examine the effects of low‐volume muscle endurance training on muscle oxidative capacity, endurance and strength of the forearm muscle during 21‐day forearm immobilization (IMM‐21d).

Evaluation of venous return in lower limb by passive ankle exercise performed by PHARAD.

This paper presents evaluation of venous return, i.e., blood flow volume of vein (BF), in the lower limb after passive exercise performed by our developed “parallel link type human ankle rehabilitation assistive device (PHARAD)”. The PHARAD can perform complex passive exercises (plantar flexion/dorsiflexion, inversion/eversion, adduction/abduction, and combination of these motions) by reproducing input motions of a foot plate that is attached to a sole of foot. The passive exercise can be performed for not only rehabilitation but also prevention of deep vein thrombosis (DVT). In this study, we measured the concentration of Total hemoglobin (Total-Hb) using multi-channel near infra-red spectroscopy (NIRS)-based tissue oximeters and calculated a gradient of Total-Hb during a venous occlusion. We defined the gradient as BF and evaluated BF after 3 min passive exercise performed by the PHARAD comparing to BF of resting. Seven healthy young adult people were recruited for the experiment and we assessed passive exercise, active exercise, and walking. Experimental results show that BF after the passive exercises significantly increases compare to BF of resting and this indicates that passive exercises performed by the PHARAD increases BF and has a potential to prevent DVT.

Calculation of Systemic Aerobic Capacity without Contact Using Pattern Light Projection

We proposed the calculation method of the systemic aerobic capacity using the noncontact respiration measurement under pedal stroke motion. By the simultaneous measurement with the expiration gas analyzer, we examined the effectiveness of the proposed method. The correlation between the quasi ventilation thresholds calculated by our proposed method and the ventilation thresholds calculated by the expiration gas analyzer is 0.801. And, the gradient of the regression line between two methods is almost 1. This result indicates the possibility of the calculation of the systemic aerobic capacity without contact by the proposed method.

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.