Negative aspects of aging include a decrease in muscle mass/strength and maximal oxygen consumption (VO_2max). The most beneficial and adaptable protocol among the various exercise methods should be explored in older adults. A combination of aerobic and strength training has been recommended as an effective and required exercise program to improve both VO_2max and muscle mass/strength in guidelines. Recently, high-intensity interval training (HIIT) has become a popular and time-efficient way to perform vigorous exercise effectively, potentially improving VO_2max and muscle strength/power as it is rendered as a combination of aerobic and strength exercise training. It is often used by young and middle-aged people with/without chronic disease. However, the adaptation of HIIT in older adults has not been fully established yet. The effects of submaximal HIIT on metabolic, physiological, muscle adaptation, and cognitive abilities have been observed in older adults. In contrast, there is only limited evidence on sprint interval training (supramaximal), which also affects muscle strength/power and VO_2max in older adults. Because some barriers remain to be overcome when implementing HIIT in older adults, the applicable protocols should be explored with stratification by age and physical function. Furthermore, data on safety, clean-up methods, adherence to participation rate, and settled intensity during unsupervised training are still lacking and should be focused on in future studies.

We recently developed a rice fermented beverage (RFB) that contains a wide variety of ergogenic nutrients (e.g. carbohydrates [CHOs], amino acids, and rice-derived phytochemicals). Although we showed a potential for prototype-RFB to promote post-exercise muscle glycogen restoration in rats, it is unclear whether RFB has ergogenic effects on human performance. Therefore, this study aimed to investigate the effect of daily supplementation of RFB on endurance exercise performance in male college student athletes. In this randomized double-blind crossover placebo-controlled study, 14 male college athletes (mean age, 20.2 ± 1.0 year) consumed either RFB or placebo for 3 weeks (100 mL/day) and performed ramp and constant workload cycle exercise tests before and after the supplementation period. The constant exercise test consisted of 40 min of cycling at 90% anaerobic threshold (AT) followed by increasing workload (30% AT every 10 min) until exhaustion. The amount of change in maximum workload and oxygen uptake/workload in the ramp-cycling test after supplementation tended to be higher and lower, respectively, in the RFB than in the placebo group. In the constant exercise test, blood lactate level was significantly lower in the RFB than in the placebo group during the 90% AT exercise period (p < 0.05). Moreover, a moderate positive linear correlation was found between the amount of change in time to exhaustion and Δ_{Exhaustion−90%ATfinal} CHO oxidation when RFB was consumed (r = 0.661, p < 0.05). These results suggest that daily RFB intake may be beneficial for improving endurance exercise performance in trained humans.

This study conducted a secondary survey based on the hypothesis that the “total mechanical activation of fast-twitch fibers in the muscles determines the effects of muscle hypertrophy”, with resistance training of the knee extensor muscles as the target because of its importance in preventing sarcopenia. Using a mathematical model that estimates the mechanical activation of each muscle fiber (fast-twitch and slow-twitch fiber) during exercise, which was developed in a previous study, we estimated the total mechanical activation of fast-twitch fibers in 30 training programs described in 23 selected previous studies on leg extension exercise programs and their muscle hypertrophy effect. With the estimated value and other factors of the training effect described in previous studies (training volume, etc.) as explanatory variables and muscle hypertrophy effect as an objective variable, we performed multiple regression analysis. The results revealed that the training effect was related to total mechanical activation of the fast-twitch fibers (standardized partial regression coefficient: 0.66), training load (standardized partial regression coefficient, 0.29) and number of sets (standardized partial regression coefficient: −0.37). The total mechanical activation of fast-twitch fibers was the strongest determinant of the muscle hypertrophy effect. In addition, we predicted the relationship between the level of the training effect of leg extension exercise and program variables. This study is the first to demonstrate “the relationship between total mechanical activation of fast-twitch fibers and muscle hypertrophy effect” in the field of muscle physiology, and the first to elucidate the association between the program variables and the training effect.

Decreased internal rotation range of motion of the dominant shoulder in baseball pitchers may be due to humeral retrotorsion and posterior shoulder tightness. Measurement of shoulder tightness is generally performed with range of motion; however, this may not be optimal for measuring posterior shoulder tightness in baseball pitchers. Joint stiffness using passive torque should also be used to assess shoulder tightness. The purpose of this study was to compare dominant and non-dominant shoulder humeral retrotorsion and shoulder tightness in baseball pitchers, and dominant and non-dominant shoulder range of motion and shoulder stiffness of the passive torque after correction based on humeral retrotorsion. Twenty-five male college baseball pitchers were included. Humeral retrotorsion, shoulder range of motion (internal rotation, external rotation, total range of motion), and passive torque during shoulder internal rotation (max torque, stiffness) of the dominant and non-dominant sides were measured. Shoulder range of motion and stiffness were corrected on each side using humeral retrotorsion. Humeral retrotorsion, external rotation range of motion, and stiffness were significantly greater on the dominant side than on the non-dominant side. Internal rotation range of motion was reduced on the dominant side compared to the non-dominant side. There were no side-to-side differences in the total range of motion, humeral retrotorsion-corrected range of motion, and humeral retrotorsion-corrected stiffness. In conclusion, healthy college baseball pitchers have decreased internal rotation range of motion in the dominant shoulder due to side-to-side differences in humeral retrotorsion, not joint stiffness.