Skeletal muscle atrophy is known to occur in various conditions, and is commonly the result of prolonged disuse of the muscle. However, no therapeutic treatment to date has been shown to completely prevent this problem. Numerous studies suggest that prevention of inactivity-related oxidative stress can delay or attenuate the progression of disuse muscle atrophy in rodents. Based on this evidence, many researchers have tested the hypothesis that dietary supplementation with antioxidants would be an effective countermeasure for disuse muscle atrophy. We have recently demonstrated that oral supplementation with astaxanthin, a potent natural antioxidant known as a carotenoid pigment found in marine organisms, might protect against disuse muscle atrophy, in part by preventing myonuclear apoptosis and myofibrillar protein degradation. Although the precise mechanisms underlying these processes are not completely understood, it appears that astaxanthin supplementation might be an effective and potential therapeutic countermeasure to protect against disuse skeletal muscle atrophy. This review summarizes the potential protective role of astaxanthin against skeletal muscle disuse, providing a novel insight into prevention of disuse-induced skeletal muscle atrophy.
It is well known that excessively elevated core body temperature owing to prolonged exercise in high temperatures causes heat-related illness and has a negative impact on exercise performance. Many articles have been published about effective cooling methods to avoid such impacts on physiological functions in the heat. Ice slurry ingestion has been used by many athletes as a practical and effective cooling strategy. Ice slurry can easily be used on sports fields. Moreover, ice slurry reduces core body temperature more effectively than water alone. Thus, ingestion of ice slurry may be one of the best cooling strategies in hot temperatures. This article provides an overview of the effects of ice slurry ingestion on core body temperature, thermal perception, and exercise performance, and offers practical recommendations in the field that can be adopted by athletes and coaches.
The purpose of this study was to clarify the tackling characteristics of tacklers relationship causing concussion based on match video records in the collegiate rugby union. Twenty-three tackling situations leading to concussion were identified based on injury data and video records. Additionally, 94 tackling situations in which concussion did not occur were extracted from the same matches. Overall, one hundred and seventeen tackling situations were analyzed in detail, and categorized into three tackle phases and outcomes. Logistic regression analysis was performed to clarify which tackling characteristics in the tackler relationship had a higher chance of concussion. The chance of concussion occurring to a tackler was significantly higher for collision tackle (odds ratio [OR] 84.00, 95% CI 8.27–853.11), making initial contact with tackler’s head/neck (OR 23.47, 95% CI 4.80–114.71), no arm usage by tackler (OR 3.54, 95% CI 1.23–10.20) and tackle break by ball-carrier (OR 5.76, 95% CI 1.67–19.85). Conversely, tacklers were significantly less likely to suffer concussion when the ball-carrier performed a side step before initial contact (OR 0.11, 95% CI 0.01–0.85). In conclusion, tackles leading to concussion were related to various factors in the time period before and after tackle as well as in the moment of tackle. The results of this study suggest that further research needs to be done, given the relationship between each tackling characteristic. Moreover, we consider that players and coaching staff should improve tackle skill safety by clarifying the common contributing factors to both suffering concussion and tackle performance.
The aim of this study was to investigate the effects of bright-light exposure immediately prior to sleep on the human urine metabolome. Eight young and healthy men were exposed to dim light (control condition) or bright-light (10000 lux) 3 hours before sleep (Bright-light condition: BL). Objective sleep quality was recorded by polysomnography, and subjective sleep quality was evaluated by the Oguri-Shirakawa-Azumi sleep inventory MA version (OSA-MA). Urine samples were collected after waking up under both the BL and control conditions. Polysomnographic analysis showed that sleep latency was significantly increased in BL compared to the control condition. OSA-MA score of refreshing was significantly lower in BL. Moreover, body temperature was significantly higher at times around sleep onset in BL (23:30, 0:00, and 0:30). Together, these results suggest that exposure to bright-light prior to sleep can alter sleep and circadian rhythms. According to analysis of the urine metabolome, the level of Allothreonine was significantly higher and the levels of N-acetylleucine, ornithine, 5-hydroxylysine, carnosine, and 4-amino-3-hydroxybutyric acid were significantly lower in BL (P < 0.05). In addition, the levels of adenosine tended to be higher (P < 0.08) and those of glucosamine, 5-aminovaleric acid, suberic acid, and anserine divalent tended to be lower in BL (P < 0.09). Our findings indicate that exposure to bright-light before sleep impacts metabolites.
We investigated factors correlated with cognitive decline in elderly adults by measuring aerobic fitness, physical activity, and cognitive function. Participants were community-dwelling adults aged 65 years or older (N = 455; 130 men and 325 women). Aerobic fitness was assessed in an incremental exercise test using a cycle ergometer; physical activity was determined with step counts using a uniaxial accelerometer. Cognitive function was examined using Urakami’s screening test for Alzheimer’s disease (AD). We analyzed the results for 287 participants (71 men and 216 women) with no missing data. The maximum possible score for cognitive function was 15; impairment was defined as scores of ≤ 12. The χ2 and t-test were used to compare data between participants with impairment and controls. Male and female participants were analyzed separately. After adjusting for age, BMI, and diabetes, we performed analysis of covariance. Of the total, 29 participants (10.1%) were categorized as impaired on screening. For aerobic fitness and physical activity, there were no significant differences between men with impairment and controls. However, aerobic fitness was significantly lower (p < 0.002) and physical activity was not significantly different for women with impairment than for controls by t-test. After adjustment, significant differences were also found for aerobic fitness (p < 0.001) between the groups in women. The impairment group had a significantly higher ratio of women with diabetes than the control group (p < 0.05). Our results suggest that decline in aerobic fitness is obviously associated with decline in cognitive function among women.
Recently, it was suggested that the angle at which the maximum muscle strength improves depends on the load of training. This is inconsistent with the principle of specificity of joint angle, which indicates that the improvement of muscle strength is obtained when a similar joint angle as the trained angle is used. The present study investigated the angle at which maximum muscle strength increases with low-load hip abductor isometric training. Sixteen healthy men (24.8 ± 3.2 years of age) were randomly divided into an intervention group or a control group. The intervention group performed isometric resistance training for hip abductor muscle at a low intensity of 30% of the maximum voluntary contraction (MVC) at 25° hip abduction three days a week for four weeks. In pre- and post-training, isometric hip abduction MVCs were measured every 10° through the range of hip joint positions from 15° adduction to 35° abduction (i.e. 6 hip angles). A significant interaction was shown only at the hip position of 15° abduction (F = 4.84). At 15° abduction, there was a significant increase in MVC between pre- and post-training for the intervention group (p = .03, d = .53), but not for the control group. Our results indicate that, in low-load hip abductor isometric training, the improvement of the MVC did not follow the specificity of the joint angle. Instead, the low-load training improved the MVC at a joint angle where the muscle is extended further than that during training.