Low-volume strength and endurance training prevent the decrease in exercise hyperemia induced by non-dominant forearm immobilization.

We examined the effect of 3-week upper limb immobilization on conduit artery cross-sectional area and peak hyperemia (BF(peak)) after exhaustive dynamic handgrip exercise (Ex(dyn)), and that of low-volume strength and endurance training during immobilization. Healthy volunteers (n = 21; mean age, 22 years) were divided into 3 groups: immobilization only (IMM; n = 7), immobilization with training (STR + END; n = 7), and control (no immobilization or training, CNT; n = 7). Endurance training comprised Ex(dyn) at 30% maximum voluntary contraction (MVC) (duration of each session, ~60 s; twice weekly). Strength training involved intermittent isometric handgrip exercise at 70% MVC (duration of each session, 40 s; twice weekly), repeated 10 times. We used ultrasound methods to measure the brachial artery cross-sectional area and the BF(peak) after Ex(dyn) for 5 min pre- and post-immobilization. We found a significant group by time interaction in BF(peak) (p < 0.05). A significant decrease was found in BF(peak) in the IMM (p < 0.05) between pre- and post-immobilization and a protective effect in the STR + END. The 3-week upper limb immobilization did not influence the baseline artery cross-sectional area. In conclusion, BF(peak) decreased after 3-week upper limb immobilization and a combination of strength training and endurance training preserved the blunted BF(peak).

Unchanged muscle deoxygenation heterogeneity during bicycle exercise after 6 weeks of endurance training.

The purpose of this study was to examine the changes in muscle oxygen saturation (SmO(2)) level and its heterogeneity after 6 weeks of endurance training using multi-channel near infrared spatially resolved spectroscopy (NIR(SRS)). Nine healthy subjects participated in this study (Male = 6, Female = 3, age: 27 +/- 5 years, height: 168.7 +/- 7.4 cm, weight: 62.4 +/- 12.4 kg). The subjects performed a 30 W ramp incremental bicycle exercise test until exhaustion before and after endurance training. The NIR(SRS) probe was attached to the left vastus lateralis muscle along the direction of the long axis. The subjects performed bicycle exercise for 30 min/day, 3 days/week for 6 weeks. The work rate during training was set at 60%V(O)(2peak) and increased every 5%V(O)(2peak) when the subjects could maintain the work rate three times consecutively. After training, V(O)(2peak) was significantly increased (Pre: 42.7 +/- 9.9 ml/kg/min, Post: 52.3 +/- 7.2 ml/kg/min, p < 0.001) and the mean SmO(2) within measurement sites at was significantly decreased (Pre: 56.1 +/- 1.1 %, Post: 53.3 +/- 2.2 %, p < 0.05). Conversely, the heterogeneity of the SmO(2) during exercise was not changed by training. These results suggest that the functional heterogeneity of O(2) balance did not change due to endurance training, and the O(2) balance heterogeneity may not interfere with O(2) exchange in the activating muscle in healthy individuals.

Decreased muscle oxygenation and increased arterial blood flow in the non-exercising limb during leg exercise.

We evaluated arterial blood flow, muscle tissue oxygenation and muscle metabolism in the non-exercising limb during leg cycling exercise. Ten healthy male volunteers performed a graded leg cycling exercise at 0, 40, 80, 120 and 160 watts (W) for 5 min each. Tissue oxygenation index (TOI) of the non-exercising left forearm muscle was measured using a near-infrared spatially resolved spectroscopy (NIR(SRS)), and non-exercising forearm blood flow ((NONEX)FBF) in the brachial artery was also evaluated by a Doppler ultrasound system. We also determined O(2) consumption of the non-exercising forearm muscle (NONEXV(O)(2mus)) by the rate of decrease in O(2)Hb during arterial occlusion at each work rate. TOI was significantly decreased at 160 W (p < 0.01) compared to the baseline. The (NONEX)V(O)(2mus) at each work rate was not significantly increased. In contrast, (NONEX)FBF was significantly increased at 120 W (p < 0.05) and 160 W (p < 0.01) compared to the baseline. These results suggest that the O(2) supply to the non-exercising muscle may be reduced, even though (NONEX)FBF increases at high work rates during leg cycling exercise.

A study of passive weight-bearing lower limb exercise effects on local muscles and whole body oxidative metabolism: a comparison with simulated horse riding, bicycle, and walking exercise.

BACKGROUND: We have developed an exercise machine prototype for increasing exercise intensity by means of passively exercising lower limb muscles. The purpose of the present study was to compare the passive exercise intensity of our newly-developed machine with the intensities of different types of exercises. We also attempted to measure muscle activity to study how these forms of exercise affected individual parts of the body. METHODS: Subjects were 14 healthy men with the following demographics: age 30 years, height 171.5 cm, weight 68.3 kg. They performed 4 types of exercise: Passive weight-bearing lower limb exercise (PWLLE), Simulated horse riding exercise (SHRE), Bicycle exercise, and Walking exercise, as described below at an interval of one week or longer. Oxygen uptake, blood pressure, heart rate, and electromyogram (EMG) were measured or recorded during exercise. At rest prior to exercise and immediately after the end of each exercise intensity, the oxygenated hemoglobin levels of the lower limb muscles were measured by near-infrared spectroscopy to calculate the rate of decline. This rate of decline was obtained immediately after exercise as well as at rest to calculate oxygen consumption of the lower limb muscles as expressed as a ratio of a post-exercise rate of decline to a resting one. RESULTS: The heart rate and oxygen uptake observed in PWLLE during maximal intensity were comparable to that of a 20-watt bicycle exercise or 2 km/hr walking exercise. Maximal intensity PWLLE was found to provoke muscle activity comparable to an 80-watt bicycle or 6 km/hr walking exercise. As was the case with the EMG results, during maximal intensity PWLLE, the rectus femoris muscle consumed oxygen in amounts identical to that of an 80-watt bicycle or a 6 km/hr walking exercise. CONCLUSION: Passive weight-bearing lower limb exercise using our trial machine could provide approximately 3 MET of exercise and the thigh exhibited muscle activity equivalent to that of 80-watt bicycle or 6 km/hr walking exercise. Namely, given the same oxygen uptake, PWLLE exceeded bicycle or walking exercise in muscle activity, thus PWLLE is believed to strengthen muscle power while reducing the load imposed on the cardiopulmonary system.

Hemodynamic relationships among upper-abdominal aorta and femoral arteries: basis for measurement of arterial blood flow to abdominal-pelvic organs.

BACKGROUND: Arterial blood flow (BF) to all abdominal-pelvic organs (AP) is a potentially useful indicator of splanchnic circulatory dysfunction or various stress-induced AP flow distributions. BFAP can be measured by subtracting BF in the "peripheral" bilateral limb left/right-femoral arteries (FA) from the "central" upper abdominal aorta (Ao) above the celiac trunk according to the formula: BFAP = BFAo-both BFFAs. It is necessary to understand the hemodynamics of the three-conduit arteries to determine physiological BFAP. The aim was to examine 1) basal hemodynamic parameters such as vessel diameter (VD), blood velocity (BV), and BF and their relationship to Ao and FAs and 2) how both BFAo and BFFAs influence the magnitude of BFAP. MATERIAL/METHODS: Fifty healthy males with a wide range of body weights were evaluated while seated following a 12-hour fast. Hemodynamics in three-conduit arteries was measured by pulsed Doppler with spectral analysis. RESULTS: Positive linear relationships in VD, BV, and BF were observed between Ao and both FAs (r value range: 0.399-0.529) and between BFAo and limb BFFAs (sum of both BFFAs; r=0.544, p<0.0001). BFAP was more strongly proportional to BFAo (r=0.966, p<0.0001) than BFFAs (r=0.303, p=0.0327 in LFA, r=0.281, p=0.0482 in RFA). BFAP was thus expressed as: BFAP (l/min) = 0.85 x BFAo-0.19. CONCLUSIONS: Under basal conditions, biological proportion and close hemodynamic relationship were observed between Ao and FAs. Consequently, BFAP was more strongly influenced by BFAo than by BFFAs. BFAP may be potentially evaluated by BFAo to determine single arterial hemodynamics using the above formula.

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

PURPOSE: The 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. METHODS: Ten 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). RESULTS: There 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. CONCLUSION: The training programs during immobilization period used in this experiment were effective in preventing a decline in muscle oxidative function, endurance and strength.

Arterial blood flow of all abdominal-pelvic organs using Doppler ultrasound: range, variability and physiological impact.

The pulsed Doppler method theoretically enables human arterial blood flow (BF) to be determined in all of the abdominal-pelvic organs (BF(AP)) by subtracting the bilateral proximal femoral arterial BF from the upper abdominal aorta BF above the coeliac trunk. Evaluation of BF(AP) is a potentially useful indicator of exercise or food intake related flow distribution to organs; however, there is a lack of information regarding the physiological significance of BF(AP), and the measurements are yet to be validated. The aims of the present study are to examine the range in BF(AP) among subjects, monitor physiological day-to-day variability in BF(AP) over three different days and then determine whether mean BF(AP) (averaged over the three different measurement days) is related to body surface area (BSA). Forty healthy males (19-39 years) with a wide range of body weights (51-89 kg) were evaluated in a sitting position following a 12 h fast. The above-mentioned three conduit arteries were measured to determine BF(AP) using pulsed Doppler with spectral analysis. The mean BF(AP) was 2078 +/- 495 ml min(-1) (mean +/- SD) (range, 1153-3285 ml min(-1)), which is in agreement with a previous study that measured the sum of BF in the major part of the coeliac, mesenteric and renal arteries. The physiological day-to-day variability (mean coefficient of variation) was 14.5 +/- 10.0%. Significant (p < 0.05) positive linear relationships were observed between BF(AP) and BSA as well as body weight, which is in good agreement with the results of a previous study. The present data suggest that BF(AP) determined by three-conduit arterial hemodynamics may be a valid measurement that encompasses physiologic flow to multiple abdominal-pelvic organ systems.