Hiroshi Ohshima

Intravenous pamidronate prevents femoral bone loss and renal stone formation during 90-day bed rest

Long‐term bed rest has potential risks of bone loss and renal stone formation. We examined the effects of resistive exercise and intravenous pamidronate on BMD, bone turnover, urinary calcium, and renal stone formation in 25 healthy males during 90‐day bed rest. Pamidronate prevented femoral bone loss and renal stone formation, but resistive exercise showed little effects.

Effect of short-duration spaceflight on thigh and leg muscle volume.

PURPOSE Human skeletal muscle probably atrophies as a result of spaceflight, but few studies have examined this issue. Thus, little is known about the influence of microgravity upon human skeletal muscle, nor is it possible to assess the validity of ground based models of spaceflight. This study tested the hypothesis that the magnitude of spaceflight induced muscle atrophy would be a function of flight duration and greater than that of bed rest. METHODS Three astronauts flew 9, 15, and 16 d in space. Volume of the knee extensor (quadriceps femoris), knee flexor (hamstrings, sartorius, and gracilis), and plantar flexor (triceps surae) muscle groups was measured using magnetic resonance imaging before and after spaceflight and during recovery. The volume of each muscle group in each image was determined by multiplying cross-sectional area by slice thickness. These values were subsequently summed to calculate muscle volume. RESULTS Volume changes in the knee extensor, knee flexor, and plantar flexor muscle groups ranged from -15.4 to -5.5, -14.1 to -5.6, and -8.8 to -15.9%, respectively. Muscle volume decreases normalized by flight duration ranged from 0.62 to 1.04% x d(-1). These relative changes appeared to be greater than those that we have reported previously for bed rest (Akima et al., J. Gravitat. Physiol. 4:15-22, 1997). CONCLUSIONS These results suggest that atrophy as a result of at least 2 wk of spaceflight varied among individuals and muscle groups and that the degree of atrophy appeared to be greater than that induced by 20 d of bed rest.

Effect of Physical Inactivity on the Oxidation of Saturated and Monounsaturated Dietary Fatty Acids: Results of a Randomized Trial

Objectives: Changes in the way dietary fat is metabolized can be considered causative in obesity. The role of sedentary behavior in this defect has not been determined. We hypothesized that physical inactivity partitions dietary fats toward storage and that a resistance exercise training program mitigates storage. Design: We used bed rest, with randomization to resistance training, as a model of physical inactivity. Setting: The trial took place at the Space Clinic (Toulouse, France). Participants: A total of 18 healthy male volunteers, of mean age ± standard deviation 32.6 ± 4.0 y and body mass index 23.6 ± 0.7 kg/m2, were enrolled. Interventions: An initial 15 d of baseline data collection were followed by 3 mo of strict bed-rest alone (control group, n = 9) or with the addition of supine resistance exercise training every 3 d (exercise group, n = 9). Outcome measures: Oxidation of labeled [d31]palmitate (the main saturated fatty acid of human diet) and [1-13C]oleate (the main monounsaturated fatty acid), body composition, net substrate use, and plasma hormones and metabolites were measured. Results: Between-group comparisons showed that exercise training did not affect oxidation of both oleate (mean difference 5.6%; 95% confidence interval [95% CI], −3.3% to 14.5%; p = 0.20) and palmitate (mean difference −0.2%; 95% CI, −4.1% to 3.6%; p = 0.89). Within-group comparisons, however, showed that inactivity changed oxidation of palmitate in the control group by −11.0% (95% CI, −19.0% to −2.9%; p = 0.01) and in the exercise group by −11.3% (95% CI, −18.4% to −4.2%; p = 0.008). In contrast, bed rest did not significantly affect oleate oxidation within groups. In the control group, the mean difference in oleate oxidation was 3.2% (95% CI, −4.2% to 10.5%; p = 0.34) and 6.8% (95% CI, −1.2% to 14.7%; p = 0.08) in the exercise group. Conclusions: Independent of changes in energy balance (intake and/or output), physical inactivity decreased the oxidation of saturated but not monounsaturated dietary fat. The effect is apparently not compensated by resistance exercise training. These results suggest that Mediterranean diets should be recommended in sedentary subjects and recumbent patients.

Effects of a Low-Volume Aerobic-Type Interval Exercise on V˙O2max and Cardiac Mass

PURPOSE The aim of this study was to compare the effects of time-efficient, low-volume interval exercises on cardiorespiratory capacity and left ventricular (LV) mass with traditional continuous exercise in sedentary adults. METHODS Forty-two healthy but sedentary male subjects (age 26.5 ± 6.2 yr) participated in an 8-wk, five times per week, supervised exercise intervention. They were randomly assigned to one of three exercise protocols: sprint interval training (SIT, 5 min, 100 kcal), high-intensity interval aerobic training (HIAT, 13 min, 180 kcal), and continuous aerobic training (CAT, 40 min, 360 kcal). Cardiorespiratory capacity (V˙O2max) and LV mass (3T-MRI) were measured preintervention and postintervention. RESULTS We observed significant (P < 0.01) increases in V˙O2max in all three groups, and the effect of the HIAT was the greatest of the three (SIT, 16.7% ± 11.6%; HIAT, 22.5% ± 12.2%; CAT, 10.0% ± 8.9%; P = 0.01). There were significant changes in LV mass, stroke volume (SV), and resting HR in both the SIT (LV mass, 6.5% ± 8.3%; SV, 5.3% ± 8.3%; HR, -7.3% ± 11.1%; all P < 0.05) and HIAT (LV mass, 8.0% ± 8.3%; SV, 12.1% ± 9.8%; HR, -12.7% ± 12.2%; all P < 0.01) but not in the CAT (LV mass, 2.5% ± 10.1%; SV, 3.6% ± 6.6%; HR, -2.2% ± 13.3%; all P > 0.05). CONCLUSIONS Our study revealed that V˙O2max improvement with the HIAT was greater than with the CAT despite the HIAT being performed with a far lower volume and in far less time than the CAT. This suggests that the HIAT has potential as a time-efficient training mode to improve V˙O2max in sedentary adults.

Effects of low-intensity resistance exercise with blood flow restriction on coagulation system in healthy subjects

Recent studies have demonstrated that even a low‐intensity resistance exercise can effectively induce muscle hypertrophy and strength increase when combined with moderate blood flow restriction (BFR) into the exercising muscle. Although serious side effects of low‐intensity resistance exercise with BFR have not been reported, a concern of thrombosis has been suggested, because this type of exercise is performed with restricted venous blood flow and pooling of blood in extremities. Thus, the purpose of this study was to investigate the effects of low‐intensity resistance exercise with BFR on coagulation system in healthy subjects. Ten healthy men (25·1 ± 2·8 year) performed four sets of leg press exercises with and without BFR (150–160 mmHg) at an intensity of 30% of one‐repetition maximum (1RM). In each exercise session, one set with 30 repetitions was followed by three sets with 15 repetitions. Blood samples were taken before, and 10 min, 1, 4 and 24 h after the exercise. Prothrombin fragment 1 + 2 (PTF) and thrombin–antithrombin III complex (TAT) were measured as markers of thrombin generation, whereas D‐dimer and fibrin degradation product (FDP) were measured as markers of intravascular clot formation. Changes in plasma volume (PV) were calculated from haemoglobin and hematocrit values. PV reduction was significantly greater after the exercise with BFR than without (P<0·05). However, neither markers of thrombin generation nor intravascular clot formation increased after the exercises. These results suggest that low‐intensity resistance exercise with BFR does not activate coagulation system in healthy subjects.

Risk of renal stone formation induced by long-term bed rest could be decreased by premedication with bisphosphonate and increased by resistive exercise

Objectives:  To clarify the influence of long‐term bed rest on renal stone formation and to analyze the mechanism of bed‐rest‐induced stone formation and prevention by bisphosphonate and bed‐rest exercise.

A hexokinase from fish liver with wide specificity for nucleotides as phosphoryl donor

The liver of rainbow trout contains two hexokinases (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1) designated C and D from the elution pattern in DEAE-cellulose column chromatography. Hexokinase D has been purified about 50-fold from the liver of rainbow trout by chromatography with DEAE-cellulose and Sephadex G-200, and by isoelectric focusing. The properties of hexokinase D were similar to those of mammalian hexokinase III with respect to the Km values for ATP and glucose and the substrate inhibition by glucose at high concentration. However, the enzyme showed a wide specificity for nucleotides as the phosphoryl donor. Although it has been reported that the only effective nucleotide as the phosphoryl donor for hexokinase from various origin in ATP, and that ADP, a reaction product, inhibits the enzyme, hexokinase D from the rainbow-trout liver was found to be able to form glucose 6-phosphate (Glc-6-P) from glucose and various nucleotides such as ATP, ADP, CTP, GTP, UTP and UDP. The reaction products from ADP and glucose, Glc-6-P and AMP, were identified by chromatography on ion-exchange resin column and paper. The enzyme D was not inhibited by ADP but was strongly inhibited by AMP, which is a reaction product from ADP.

Physical Training for Long-Duration Spaceflight.

INTRODUCTION Physical training has been conducted on the International Space Station (ISS) for the past 10 yr as a countermeasure to physiological deconditioning during spaceflight. Each member space agency has developed its own approach to creating and implementing physical training protocols for their astronauts. We have divided physical training into three distinct phases (preflight, in-flight, and postflight) and provided a description of each phase with its constraints and limitations. We also discuss how each member agency (NASA, ESA, CSA, and JAXA) prescribed physical training for their crewmembers during the first 10 yr of ISS operations. It is important to understand the operational environment, the agency responsible for the physical training program, and the constraints and limitations associated with spaceflight to accurately design and implement exercise training or interpret the exercise data collected on ISS. As exploration missions move forward, resolving agency differences in physical training programs will become important to maximizing the effectiveness of exercise as a countermeasure and minimizing any mission impacts.

Cardiorespiratory fitness level correlates inversely with excess post-exercise oxygen consumption after aerobic-type interval training

BackgroundThe purpose of this study was to reveal any association between cardiorespiratory fitness level and excess post-exercise oxygen consumption (EPOC) using three cycling protocols with varying degrees of exercise intensity, i.e., sprint interval training (SIT), high-intensity interval aerobic training (HIAT), and continuous aerobic training (CAT).FindingsTen healthy men, aged 20 to 31 years, attended a cross-over experiment and completed three exercise sessions: SIT consisting of 7 sets of 30-s cycling at 120% VO2max with a 15-s rest between sets; HIAT consisting of 3 sets of 3-min cycling at 80~90% VO2max with a 2-min active rest at 50% VO2max between sets; and CAT consisting of 40 min of cycling at 60~65% VO2max. During each session, resting VO2, exercise VO2, and a 180-min post-exercise VO2 were measured. The net exercise VO2 during the SIT, HIAT, and CAT averaged 14.7 ± 1.5, 31.8 ± 4.1, and 71.1 ± 10.0 L, and the EPOCs averaged 6.8 ± 4.0, 4.5 ± 3.3, and 2.9 ± 2.8 L, respectively. The EPOC with SIT was greater than with CAT (P < 0.01) and HIAT (P = 0.12). Correlation coefficients obtained between subjects’ VO2max and the ratio of EPOC to net exercise VO2 for SIT, HIAT, and CAT were −0.61 (P = 0.06), -0.79 (P < 0.01), and −0.42 (P = 0.23), respectively.ConclusionsOur data suggest that cardiorespiratory fitness level correlates negatively with the magnitude of EPOC, especially when performing aerobic-type interval training.

An exercise protocol designed to control energy expenditure for long-term space missions.

INTRODUCTION Astronauts experience weight loss during spaceflight. Future space missions require a more efficient exercise program not only to maintain work efficiency, but also to control increased energy expenditure (EE). When discussing issues concerning EE incurred through exercise, excess post-exercise energy expenditure (EPEE) must also be considered. The aim of this study was to compare the total EE, including EPEE, induced by two types of interval cycling protocols with the total EE of a traditional, continuous cycling protocol. METHODS There were 10 healthy men, ages 20 to 31 yr, who completed 3 exercise sessions: sprint interval training (SIT) consisting of 7 sets of 30-s cycling at 120% VO2max with a 15-s rest between each bout; high-intensity interval aerobic training (HIAT) consisting of 3 sets of 3-min cycling at 80-90% VO2max with a 2-min active rest at 50% VO2max; and continuous aerobic training (CAT) consisting of 40 min of cycling at 60-65% VO2max. During each session, resting metabolic rate, exercise EE, and a 180-min post-exercise EE were measured. RESULTS The EPEEs during the SIT, HIAT, and CAT averaged 32 +/- 19, 21 +/- 16, and 13 +/- 13 kcal, and the total EE for an entire exercise/ rest session averaged 109 +/- 20, 182 +/- 17, and 363 +/- 45 kcal, respectively. While the EPEE after the CAT was significantly less than after the SIT, the total EE with the CAT was the greatest of the three. DISCUSSION The SIT and HIAT would be potential protocols to control energy expenditure for long space missions.