Effects of combined ß-hydroxy-ß-methylbutyrate (HMB) and whey protein ingestion on symptoms of eccentric exercise-induced muscle damage.

BACKGROUND: The purpose of this study was to examine the effects of combined ß-hydroxy-ß-methylbutyrate (HMB) and whey protein ingestion on muscle strength and damage following a single bout of eccentric exercise. METHODS: Eighteen untrained male subjects were assigned to HMB and Whey protein (HMB + Whey; 3 g/day HMB and 36.6 g/day whey protein, n = 6), HMB (3 g/day, n = 6), or whey protein (36.6 g/day, n = 6) groups. Ingestion commenced 7 days before non-dominant elbow flexor eccentric exercise (30 deg/sec, 6 reps × 7 sets) and continued until 4 days post-exercise. The maximal isometric strength, muscle soreness, plasma creatine kinase (CK), lactate dehydrogenase (LDH) were assessed pre-exercise, and at 1, 2, 3, and 5 days after exercise. RESULTS: The change scores of maximal isometric strength significantly decreased at day 1, 2, and 5 in the whey protein group compared to pre value and that in HMB + Whey protein and HMB groups decreased at day 1 and 5. The muscle soreness significantly increased in the whey and HMB + Whey protein groups at day 3 compared to pre value (p < 0.05). CK and LDH significantly increased (time effect: p < 0.05) after exercise. However, all data were not significant difference among the groups. CONCLUSIONS: These results suggest that ingestion of combined HMB and whey protein does not have a role to inhibit muscle strength loss and soreness, and decrease in muscle damage markers after eccentric exercise in comparison with HMB and whey protein alone.

Relationship between performance test and body composition/physical strength characteristic in sprint canoe and kayak paddlers.

OBJECTIVE: Canoe sprint is divided into canoe and kayak. The difference between the two competitions is in physical performance. The aim of the present study was to compare and investigate the relationship between physical characteristics and fitness between the two canoe sprint competitors. METHODS: Subjects were 11 canoe paddlers (C) and 12 kayak paddlers (K). They underwent anthropometric characteristics, body composition and fitness tests, and 120 s all-out tests using a canoe and kayak ergometer. The unpaired t-test was used to test for significant differences between disciplines, while Pearson's correlation coefficient was used to examine the association between each measurement item and the performance test. RESULTS: The age, height, body mass, body mass index, and total body fat were, C: 20.6±0.9 yr, 172.8±5.2 cm, 70.8±7.8 kg, 23.7±1.9, 14.4%±3.5%; and K: 19.7±1.2 yr, 172.8±5.3 cm, 69.5±7.8 kg, 23.2±2.1, 12.1%±3.6%, respectively. No significant differences were seen in any of the items for physical characteristics or fitness between C and K. A correlation analysis of performance tests and each measurement item revealed a positive correlation with low-speed isokinetic knee extension and flexion strength for C only (extension: r=0.761; flexion: r=0.784; P<0.01). In addition, performance tests were positively correlated with the circumference of arm (upper arm: r=0.876; forearm: r=0.820; P<0.01) and lower limb (thigh: r=0.781; calf: r=0.753; P<0.01) in C and with height (r=0.549, P<0.05), arm span (r=0.639, P<0.05), and leg length (r=0.621, P<0.01) in K. CONCLUSION: We suggest that the factors correlating with the performance test differ depending on the competitions.

Temporal evolution of neural activity underlying auditory discrimination of frequency increase and decrease.

Discriminating a direction of frequency change is an important ability of the human auditory system, although temporal dynamics of neural activity underlying this discrimination remains unclear. In the present study, we recorded auditory-evoked potentials when human subjects explicitly judged a direction of a relative frequency change between two successive tones. A comparison of two types of trials with ascending and descending tone pairs revealed that neural activity discriminating a direction of frequency changes appeared as early as the P1 component of auditory-evoked potentials (latency 50 ms). Those differences between the ascending and descending trials were also observed in subsequent electroencephalographic components such as the N1 (100 ms) and P2 (200 ms). Furthermore, amplitudes of the P2 were significantly modulated by behavioral responses (upward/downward judgments) of subjects in the direction discrimination task, while those of the P1 were not. Those results indicate that, while the neural responses encoding a direction of frequency changes can be observed in an early component of electroencephalographic responses (50 ms after the change), the activity associated (correlated) with behavioral judgments evolves over time, being shaped in a later time period (around 200 ms) of the auditory processing.