Kazushige Goto

Muscular adaptations to combinations of high- and low-intensity resistance exercises.

Acute and long-term effects of resistance-training regimens with varied combinations of high- and low-intensity exercises were studied. Acute changes in the serum growth hormone (GH) concentration were initially measured after 3 types of regimens for knee extension exercise: a medium intensity (approximately 10 repetition maximum [RM]) short interset rest period (30 s) with progressively decreasing load (“hypertrophy type‘’); 5 sets of a high-intensity (90% of 1RM) and low-repetition exercise (“strength type‘’); and a single set of low-intensity and high-repetition exercise added immediately after the strength-type regimen (“combi-type‘’). Postexercise increases in serum GH concentration showed a significant regimen dependence: hypertrophy-type > combi-type > strength-type (p < 0.05, n = 8). Next, the long-term effects of periodized training protocols with the above regimens on muscular function were investigated. Male subjects (n = 16) were assigned to either hypertrophy/combi (HC) or hypertrophy/strength (HS) groups and performed leg press and extension exercises twice a week for 10 weeks. During the first 6 weeks, both groups used the hypertrophy-type regimen to gain muscular size. During the subsequent 4 weeks, HC and HS groups performed combi-type and strength-type regimens, respectively. Muscular strength, endurance, and cross sectional area (CSA) were examined after 2, 6, and 10 weeks. After the initial 6 weeks, no significant difference was seen in the percentage changes of all variables between the groups. After the subsequent 4 weeks, however, 1RM of leg press, maximal isokinetic strength, and muscular endurance of leg extension showed significantly (p < 0.05) larger increases in the HC group than in the HS group. In addition, increases in CSA after this period also tended to be larger in the HC group than in the HS group (p = 0.08). The results suggest that a combination of high- and low-intensity regimens is effective for optimizing the strength adaptation of muscle in a periodized training program.

Evaluations of cooling exercised muscle with MR imaging and 31P MR spectroscopy.

PURPOSE To investigate the effects of cooling human skeletal muscle after strenuous exercise using 31P MR spectroscopy and MR imaging. METHODS 14 male subjects (mean age +/- SD, 23.8 +/- 2.3 yr) were randomly assigned to the normal (N = 7) or the cooling group (N = 7). All subjects performed the ankle plantar flexion exercise (12 repetitions, 5 sets). Localized 31P-spectra were collected from the medial gastrocnemius before and after exercise (immediately, 30, 60 min, 24, 48, 96, and 168 h) to determine the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular pH. Transaxial T2-weighted MR images of the medial gastrocnemius were obtained to calculate T2 relaxation time (T2), indicative of intramuscular water level, before and after exercise (24, 48, 96, and 168 h). In addition, the muscle soreness level was assessed at the same time as 31P-spectra measurements. Fifteen-minute cold-water immersion was administered to the cooling group after exercise and initial postexercise measurements. RESULTS The control group showed significantly increased T2 from rest at 48 h after exercise (P < 0.05), but the cooling group showed no significant change in T2 throughout this study. Both groups showed a significantly decreased intracellular pH immediately after exercise (P < 0.05). After that, the cooling group showed a significantly greater value than the value at rest or the control group at 60 min after exercise (P < 0.05). For the Pi/PCr, no significant change was observed in both groups throughout this study. The muscle soreness level significantly increased immediately and at 24-48 h after exercise in both groups (P < 0.05). CONCLUSION The findings of this study suggest that cooling causes an increase in intracellular pH and prevents the delayed muscle edema.

Resistance exercise induces a greater irisin response than endurance exercise

OBJECTIVE We determined detailed time-course changes in the irisin response to acute exercise using different exercise modes. METHODS In experiment 1, seven healthy males rested for 12h (8:00-20:00) to determine the diurnal variation in plasma irisin concentration. In experiment 2, 10 healthy males conducted three exercises to clarify time-course changes in plasma irisin concentration over 6h, using a randomized crossover design. The resistance exercise (R) trial consisted of eight exercises of 12 repetitions with 3-4 sets at 65% of one repetition maximum (1RM). The endurance exercise (E) trial consisted of 60 min of pedaling at 65% of maximal oxygen uptake (VO2max). In the combined mode (R+E) trial, 30 min of endurance exercise was preceded by 30 min of resistance exercise. RESULTS In experiment 1, no significant changes in plasma irisin concentration were observed over 12h. In experiment 2, the R trial showed a marked increase in plasma irisin concentration 1h after exercise (P<0.05), but not in the E or R+E trials. The area under the curve (AUC) for irisin concentrations for 6h after exercise was significantly higher in the R trial than in the R+E trial (P<0.05). The AUC for irisin concentrations was significantly correlated with AUC values for blood glucose, lactate, and serum glycerol (r=0.37, 0.45, 0.45, respectively. P<0.05). CONCLUSIONS Resistance exercise resulted in significantly greater irisin responses compared with endurance exercise alone, and resistance and endurance exercises combined.

Substrate utilization during exercise and recovery at moderate altitude.

Recent studies have shown that exercise training at moderate altitude or in moderate hypoxia improved glycemic parameters. From these data, it has been supposed that endurance exercise in moderate hypoxia affects substrate utilization and that exposure to moderate hypoxia in combination with exercise may be utilized as part of metabolic or diabetes prevention program. However, the influence of exercise at moderate hypoxia on circulating metabolites and hormones in terms of substrate utilization is unclear. The purpose of this study was to elucidate the influence of exercise in moderate hypoxia on substrate utilization. We determined cardiorespiratory, metabolic, and hormonal parameters during exercise and postexercise recovery at a simulated moderate altitude of 2000 m, and then we compared these variables with values obtained at sea level. Seven men participated in this study; subjects reported to the laboratory on 4 occasions. Two maximal exercise tests were performed to estimate peak oxygen uptake at the simulated 2000-m altitude and sea level on different days. Afterward, submaximal exercise tests were carried out at a simulated altitude of 2000 m or sea level, separated by 1 week. Subjects performed submaximal exercise at the same relative exercise intensity (50% peak oxygen uptake) at a simulated altitude of 2000 m and at sea level for 30 minutes. The tests were performed in random order, and subjects were blinded to the respective altitudes. Venous blood samples and expired gases were obtained before, during exercise (15 and 30 minutes), and during postexercise recovery periods (15, 30, 45, and 60 minutes). The respiratory exchange ratio during exercise and recovery at moderate altitude was greater than at sea level. The epinephrine and norepinephrine concentrations during exercise and recovery were higher (P < .05) at moderate altitude than at sea level. Free fatty acids and glycerol concentrations during recovery were lower (P < .05) at moderate altitude than at sea level. These results suggest that carbohydrate utilization is increased during exercise and postexercise recovery period in moderate hypoxia as compared with normoxia. It is also suggested that moderate hypoxia influences the changes in circulating metabolites and hormones in terms of substrate metabolism during exercise and the recovery.

MRI determination of muscle recruitment variations in dynamic ankle plantar flexion exercise

Yanagisawa O, Niitsu M, Yoshioka H, Goto K, Itai Y: Magnetic resonance imaging determination of muscle recruitment variations in dynamic ankle plantar flexion exercise. Am J Phys Med Rehabil 2003;82:760–765. Objective The purpose of this study was to investigate the muscle recruitment variations in the dynamic ankle plantar flexion. Design A total of 17 subjects participated in this study and performed the ankle plantar flexion exercise. Magnetic resonance T2-weighted images were obtained from the calf before and immediately after exercise to calculate each T2 relaxation time in the medial and lateral gastrocnemius, soleus, tibialis posterior, flexor digitorum/hallucis longus, peroneus longus, and dorsiflexors. Results All the muscles except the dorsiflexors showed significantly increased T2 relaxation time and signal intensity on T2-weighted images after exercise. Above all, both gastrocnemius muscles showed significantly greater postexercise T2 relaxation time than the soleus, tibialis posterior, flexor digitorum/hallucis longus, and dorsiflexors. In addition, the peroneus longus had a tendency to show the greatest T2 relaxation time next to the gastrocnemius, but there was no significant difference between them. Conclusions The present study may suggest that the gastrocnemius muscle, especially the medial side, was best recruited in the dynamic ankle plantar flexion exercise. In addition, it is possible that the peroneus longus was most recruited next to the gastrocnemius in this exercise mode.

Whole body, regional fat accumulation, and appetite-related hormonal response after hypoxic training.

The present study was conducted to determine change in regional fat accumulation and appetite‐related hormonal response following hypoxic training. Twenty sedentary subjects underwent hypoxic (n = 9, HYPO, FiO2 = 15%) or normoxic training (n = 11, NOR, FiO2 = 20·9%) during a 4‐week period (3 days per week). They performed a 4‐week training at 55% of maximal oxygen uptake ( V· O2max) for each condition. Before and after the training period, V· O2max, whole body fat mass, abdominal fat area, intramyocellular lipid content (IMCL), fasting and postprandial appetite‐related hormonal responses were determined. Both groups showed a significant increase in V· O2max following training (P<0·05). Whole body and segmental fat mass, abdominal fat area, IMCL did not change in either group. Fasting glucose and insulin concentrations significantly reduced in both groups (P<0·05). Although area under the curve for the postprandial blood glucose concentrations significantly decreased in both groups (P<0·05), the change was significantly greater in the HYPO group than in the NOR group (P<0·05). Changes in postprandial plasma ghrelin were similar in both groups. A significant reduction of postprandial leptin response was observed in both groups (P<0·05), while postprandial glucagon‐like peptide‐1 (GLP‐1) concentrations increased significantly in the NOR group only (P<0·05). In conclusion, hypoxic training for 4 weeks resulted in greater improvement in glucose tolerance without loss of whole body fat mass, abdominal fat area or IMCL. However, hypoxic training did not have synergistic effect on the regulation of appetite‐related hormones.

Glycerophosphocholine enhances growth hormone secretion and fat oxidation in young adults

OBJECTIVE α-Glycerophosphocholine (GPC) is a putative acetylcholine precursor that potentially increases growth hormone secretion through the action of acetylcholine-stimulated catecholamine. The aim of this study was to investigate acute physiologic responses to a single intake of GPC. METHODS Eight healthy male subjects (25 ± 1 y old) ingested GPC 1000 mg or a placebo in a double-blind randomized crossover study. Fasting blood samples were obtained before the administration of GPC (baseline) and 60 and 120 min after administration. All subjects repeated the identical protocol using the placebo. RESULTS Plasma free choline levels significantly increased at 60 and 120 min after GPC administration. Plasma growth hormone secretion was increased significantly 60 min after taking GPC, whereas no significant change was observed with the placebo. In addition, the serum free fatty acid was increased 120 min after GPC ingestion, but no changes were seen with the placebo. Moreover, serum acetoacetate and 3-hydroxybutyrate levels, which are indices of hepatic fat oxidation, were increased at 120 min after taking GPC, whereas the placebo had no effect. CONCLUSION These findings suggest that a single dose of GPC increases growth hormone secretion and hepatic fat oxidation, with concomitant increases in choline levels, in young adults.

Effect of sprint training on resting serum irisin concentration — Sprint training once daily vs. twice every other day

OBJECTIVE Exercise twice every other day has been shown to lead to increasing peroxisome proliferator receptor γ coactivator-1α (PGC-1α) expression (up-stream factor of irisin) via lowered muscle glycogen level during second of exercise compared with exercise once daily. This study determined the influence of 4weeks of sprint training (training once daily vs. twice every other day) on the serum irisin concentration. MATERIALS AND METHODS Twenty healthy males (20.9±1.3years) were assigned randomly to either the SINGLE or REPEATED group (n=10 per group). The subjects in the SINGLE group participated in a sprint training session once daily (5days per week), whereas those in the REPEATED group performed two consecutive training sessions on the same day with a 1-h rest between sessions (2-3days per week). Both groups completed 20 training sessions over 4weeks. Each training session consisted of three consecutive 30-s maximal pedaling exercises with a 10-min rest between sets. Blood samples were collected before and after training period (48h after completing the last training session). RESULTS The serum irisin concentration decreased significantly after training in each group (SINGLE, 338.5±77.8 to 207.6±64.6ng/mL; REPEATED, 329.5±83.9 to 234.2±72.8ng/mL, p<0.05). The plasma interleukin-6 (IL-6) concentration tended to be lower after training in both groups (main effect for period, p=0.054). However, there was no significant difference in the serum irisin or plasma IL-6 concentration between groups after training. The serum high-molecular-weight adiponectin concentration did not change significantly after training in either group. CONCLUSION Sprint training for 4weeks significantly decreased the resting serum irisin concentration, despite different training programs (training once daily vs. twice every other day).

Growth Hormone Receptor Antagonist Treatment Reduces Exercise Performance in Young Males

CONTEXT The effects of GH on exercise performance remain unclear. OBJECTIVE The aim of the study was to examine the effects of GH receptor (GHR) antagonist treatment on exercise performance. DESIGN Subjects were treated with the GHR antagonist pegvisomant or placebo for 16 d. After the treatment period, they exercised to determine exercise performance and hormonal and metabolic responses. PARTICIPANTS Twenty healthy males participated in the study. INTERVENTION Subjects were treated with the GHR antagonist (n = 10; 10 mg/d) or placebo (n = 10). After the treatment period, they performed a maximal oxygen uptake (VO(2 max)) test and a prolonged exercise test, consisting of 60 min of submaximal cycling followed by exercise to fatigue at 90% of VO(2 max). MAIN OUTCOME MEASURES VO(2 max) was measured before and after the treatment period. Hormonal and metabolic responses and time to exhaustion during prolonged exercise were determined. RESULTS Resting serum IGF-I concentration decreased by 20% in the GHR antagonist-treated group (P < 0.05), whereas no change was observed in the placebo group. Conversely, resting serum GH concentration was significantly higher in the treatment group compared with the placebo group (P < 0.01). VO(2 max) did not change significantly in either group after the treatment period. Time to exhaustion at 90% of VO(2 max) was significantly shorter in the treatment group (P < 0.05). No significant differences were observed between the groups in terms of changes in serum free fatty acids, glycerol, VO(2), or relative fat oxidation. CONCLUSION GH might be an important determinant of exercise capacity during prolonged exercise, but GHR antagonist did not alter fat metabolism during exercise.

A single versus multiple bouts of moderate-intensity exercise for fat metabolism

This study compared the fat metabolism between ‘a single bout of 30‐min exercise’ and ‘three bouts of 10‐min exercise’ of the same intensity (60% maximal oxygen uptake) and total exercise duration (30 min). Nine healthy men participated in three trials: (1) a single 30‐min bout of exercise (Single), (2) three 10‐min bouts of exercise, separated by a 10‐min rest (Repeated) and (3) rest (Rest). Each exercise was performed with a cycle ergometer at 60% of maximal oxygen uptake, followed by 180‐min rest. Blood lactate concentration increased significantly after exercise in the Single and Repeated trials (P<0·05), but the Single trial showed a significantly higher value during the recovery period (P<0·05). No significant difference was observed in the responses of plasma glycerol concentration. The Repeated trial produced a smaller increase in the ratings of perceived exertion during the exercise (P<0·01). During the exercise, no significant difference was observed in respiratory exchange ratio (RER) between the Single and Repeated trials. However, the RER values during the recovery period were significantly lower in the Repeated trial than in the Single and Rest trials (P<0·05), indicating higher relative contribution of fat oxidation in the Repeated trial (P<0·05). These results suggest that the repetition of 10‐min of moderate exercise can contribute to greater exercise‐induced fat oxidation compared with a single 30‐min bout of continuous exercise.