Enhanced exercise performance and anti-fatigue effects following L-citrulline (Cit) intake have been reported in resistance training and endurance exercise, but not in intermittent short-time high-intensity exercise. Therefore, the effect of Cit intake on intermittent short-time high-intensity exercise performance in collegiate athletes was investigated. A double-blind, placebo-controlled crossover trial was performed using nine male collegiate track athletes (age 20.9 ± 1.6 years). Each participant ingested either Cit or a placebo (3 g [grams]/day) for 7 days and underwent Wingate test using a bicycle ergometer on days 0 and 7 performed three times using a pedaling load of 7.5% of the participant’s weight for 30 s (seconds) at full power. As for the results, Cit intake significantly increased the change in mean power output, pedaling speed per 5 s, and power output per 5 s (Δday 7 - 0) during pedaling as well as the change in oxygen consumption derived by analysis of expired gas. The amount of change in the rate of perceived exertion during exercise significantly decreased, and the amount of change in serum nitrite/nitrate (NOx) (Δday 7 - 0) post-exercise was significantly increased compared to that of pre-exercise by Cit intake. These results suggested that Cit intake of 3 g/day for 7 days may have enhanced exercise performance and anti-fatigue effects on intermittent short-time high-intensity exercise in male collegiate track athletes.
The impact of characteristic physical functions on location of arm pain in youth baseball players is unclear. This study aimed to identify the differences in characteristic physical functions between youth baseball players with and without throwing-related arm pain and to clarify these differences according to location of shoulder and elbow pain during pitching. One-hundred nine junior high school baseball players (aged 12-15 years) who participated in a medical checkup underwent clinical assessment, ultrasonography, and physical function measurements. Bilateral passive range of motion (ROM) of the shoulder and elbow were measured. Shoulder muscle tests measured the strength of the throwing arm. Before the examinations, participants completed a questionnaire about their age, gender, years of play, and position in baseball. Participants were divided into 4 groups according to arm pain: non-injured group (no pain), shoulder pain group, medial elbow pain group, and osteochondritis dissecans (OCD) of the humeral capitellum group. Group differences in physical function and baseball exposure variables were analyzed through parametric and nonparametric tests. Twenty-six players sustained throwing-related pain in the shoulder or elbow. Elbow extension and flexion deficits were significantly greater with elbow injury. Our study suggests that dominant elbow extension and flexion ROM may increase the risk of throwing-related elbow pain in junior high school baseball players. We could not clarify the characteristics of shoulder pain in this study; thus, further research is required to improve understanding of these characteristics and their implications.
The effects of high-load resistance training on muscle strength and muscle mass depend on rest periods between sets. However, whether differences in rest period length during low-load resistance exercise (RE) has an influence on improving muscle characteristics remains unclear. Better understanding such effects would enable us to prescribe low-load resistance exercise more safely and effectivity. The purpose of this study was to investigate the acute effects of low-load RE on muscle swelling with different length rest periods between sets. A total of 42 young men (age, 22.9 ± 2.4 years; height, 172.1 ± 5.4 cm; body mass, 65.6 ± 6.5 kg) were recruited to participate in this study. They were assigned to one of three groups with different rest periods between sets (20 s [seconds], 60 s, or 180 s). A total of 12 sets of 10 repetitions of RE with 30% of one repetition maximum on knee extensor muscles were performed. Muscle thickness of the vastus lateralis was measured using ultrasonography as an indicator of muscle swelling every 3 sets. Muscle thickness significantly increased after 3 sets of RE in the 20-s (3.9 ± 3.3%) and 60-s groups (5.9 ± 3.8%), but only after 12 sets in the 180-s group (4.3 ± 3.1%). RE with rest periods shorter than 60 s could result in exercise-induced muscle swelling after fewer sets of RE.
We investigated the characteristics of consecutive adjustment focusing on the phase before relaxing completely compared to discrete adjustment that involves just relaxing completely. Eleven participants were instructed to produce an isometric knee extension force based on their maximum voluntary force (MVF), as quickly and accurately as possible. They conducted discrete and consecutive tasks. For the discrete task, they were asked to relax their force completely from a starting level of 20% or 60% MVF. And for the consecutive task, they were asked to match the target level of 20%, 40%, or 60% MVF after they completely relaxed their force from the starting level of 20% or 60% MVF. Produced force was recorded, and the parameters of quickness (onset time, relaxation time, and rate of force development) were analyzed. Relaxation time was slower in consecutive adjustment than in discrete adjustment in the case of the 20% starting level. On the other hand, the onset time was constant irrespective of the process of adjustment. Our results indicated that the process of consecutive adjustment affects the relaxation time in the case of force control.
The purpose of this study was to investigate the impact of acute exercise and hypoxic exposure on the level of circulating selenoprotein P (SeP), which is known to cause insulin and exercise resistance, and expression of the muscle peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) gene in pre-diabetes rat models. Fifteen week old male Wistar rats (n = 20) were fed with a high-fat diet and water ad libitum for 3 weeks. After the acclimation period, they were assigned to sedentary or exercise groups under normoxic (20.9% O2) and hypoxic (14.5% O2) conditions. Each of the exercise groups (NE and HE) was administered two 30-min no-load swimming exercises with an interval of 5-min rest. The serum, the liver, and the triceps muscle were obtained 3 h after the exercises. Hypoxic exposure did not affect hepatic SeP mRNA, serum SeP protein, and muscle PGC-1α mRNA expression. In contrast, acute swimming exercise reduced circulating SeP concentration and increased PGC-1α mRNA expression in triceps muscle. In conclusion, acute swimming exercise rather than moderate hypoxic exposure might improve insulin and exercise resistance in pre-diabetes conditions for type 2 diabetes.