Kaoru Takamatsu

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.

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.

Hormone and Recovery Responses to Resistance Exercise with Slow Movement

This study examined acute hormone and recovery responses to resistance exercise with slow movements. Six men performed three types of exercise regimens (five sets of knee extension exercise): (1) high-intensity resistance exercise with normal movement (HN; 1 s for lifting action, 1 s for lowering action), (2) low-intensity resistance exercise with slow movement (LS; 3 s for lifting action, 3 s for lowering action), and (3) low-intensity resistance exercise with normal movement (LN; 1 s for lifting action, 1 s for lowering action). The intensity in the first set was set at approximately 80% of 1RM for HN and 40% of 1RM for LS and LN. In the HN and LS, the subjects performed each exercise set until exhaustion. In the LN, both intensity and number of repetitions were matched with those for LS. The total work volume in the HN showed approximately double the value of LS and LN (P < 0.05). Electromyography (EMG) data indicated that LS showed sustained EMG signals throughout the exercise. During the exercise, the HN and LS showed lower muscle oxygenation levels. After the exercise, LS caused significantly greater norepinephrine and free testosterone responses (delta value) than in the HN and LN (P < 0.05). However, no significant difference was observed in the recovery of maximal isometric strength, isokinetic strength, and jump performance between the HN and LS. These results indicate that slow movements during the resistance exercise are important for the enhancement of hormonal responses, especially catecholamine and free testosterone, but they do not affect muscle strength recovery.

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.

Hormonal responses to resistance exercise after ingestion of carnosine and anserine.

Goto, K, Maemura, H, Takamatsu, K, and Ishii, N. Hormonal responses to resistance exercise after ingestion of carnosine and anserine. J Strength Cond Res 25(2): 398-405, 2011-Intramuscular carnosine buffers protons (H+) in skeletal muscle. We examined the effects of supplementation with chicken breast meat extract (CBEX) containing carnosine and anserine on hormonal responses to resistance exercise. Twenty-two men were assigned to a CBEX drink group (CBEX containing total 2 g of carnosine and anserine) (n = 14) or a placebo drink group (n = 8). The subjects ingested the prescribed drink (100 mL) twice daily for 30 days without physical training. Before and after the supplementation period, the subjects completed 5 sets of bilateral knee extension exercises (with a 90-s rest between sets). The magnitude of the increase in exercise-induced free testosterone did not change significantly after supplementation in either group. The blood lactate response to exercise was attenuated after supplementation in both groups (p < 0.05). In the CBEX group, the plasma epinephrine and norepinephrine concentrations after exercise were significantly lower after supplementation (p < 0.05). The serum growth hormone response to exercise was also reduced in the CBEX group after supplementation (delta value: 5.4 ± 1.9 ng/mL [pre] vs. 1.6 ± 0.5 ng/mL [post], p = 0.05). No significant differences in exercise-induced strength reduction (fatigue index) were observed in the 2 groups after supplementation. These results suggest that short-term supplementation with CBEX attenuates the exercise-induced epinephrine, norepinephrine, and growth hormone responses.