Prolonged time spent in sedentary behaviors (i.e., activities performed while sitting or reclining) has been consistently shown as an independent risk factor for increased cardiometabolic risk and all-cause mortality, whereas breaking up sedentary time is associated with improved cardiometabolic profile. However, there is still great controversy with the respect to what would be the optimal or minimum type, intensity, and frequency of physical activity necessary to revenue such positive outcomes in different populations. In this review, we aimed to discuss the available evidence from prospective experimental studies regarding the beneficial effects of breaking up prolonged sitting time on cardiometabolic risk factors, and the influence of intensity, frequency, and volume of the physical activity replacing sitting. A structured computer-based search on the electronic databases PUBMED and SCOPUS was independently conducted by two researchers. Only prospective intervention studies (controlled and uncontrolled) evaluating the effects of explicitly replacing sitting time with physical activity (including standing) on metabolic parameters as outcomes were included. Seventeen studies were included in the review. The currently available prospective experimental studies do advocate that breaking up sitting time and replacing it with light-intensity ambulatory physical activity and standing may be a stimulus sufficient enough to induce acute favorable changes in the postprandial metabolic parameters in physically inactive and type 2 diabetic subjects, whereas a higher intensity or volume seems to be more effective in rendering such positive outcomes in young habitually physically active subjects. Prospective experimental studies provide considerable evidence of the positive effects of breaking up prolonged time spent sitting on metabolic outcomes. However, it seems that the type, intensity, and frequency of physical activity necessary to effectively counteract the detrimental effects of prolonged sitting may differ according to the subjects' characteristics, especially with respect to the subjects' habitual physical activity level.

In this study, we investigated the effects of rapid weight loss followed by a 4-h recovery on judo-related performance. Seven weight-cycler athletes were assigned to a weight loss group (5% body weight reduction by self-selected regime) and seven non-weight-cyclers to a control group (no weight reduction). Body composition, performance, glucose, and lactate were assessed before and after weight reduction (5–7 days apart; control group kept weight stable). The weight loss group had 4 h to re-feed and rehydrate after the weigh-in. Food intake was recorded during the weight loss period and recovery after the weigh-in. Performance was evaluated through a specific judo exercise, followed by a 5-min judo combat and by three bouts of the Wingate test. Both groups significantly improved performance after the weight loss period. No interaction effects were observed. The energy and macronutrient intake of the weight loss group were significantly lower than for the control group. The weight loss group consumed large amounts of food and carbohydrate during the 4-h recovery period. No changes were observed in lactate concentration, but a significant decrease in glucose during rest was observed in the weight loss group. In conclusion, rapid weight loss did not affect judo-related performance in experienced weight-cyclers when the athletes had 4 h to recover. These results should not be extrapolated to inexperienced weight-cyclers.

The aim of this study was to investigate the effects of beta-alanine supplementation on exercise capacity and the muscle carnosine content in elderly subjects. Eighteen healthy elderly subjects (60–80 years, 10 female and 4 male) were randomly assigned to receive either beta-alanine (BA, n = 12) or placebo (PL, n = 6) for 12 weeks. The BA group received 3.2 g of beta-alanine per day (2 × 800 mg sustained-release Carnosyn™ tablets, given 2 times per day). The PL group received 2 × (2 × 800 mg) of a matched placebo. At baseline (PRE) and after 12 weeks (POST-12) of supplementation, assessments were made of the muscle carnosine content, anaerobic exercise capacity, muscle function, quality of life, physical activity and food intake. A significant increase in the muscle carnosine content of the gastrocnemius muscle was shown in the BA group (+85.4%) when compared with the PL group (+7.2%) (p = 0.004; ES: 1.21). The time-to-exhaustion in the constant-load submaximal test (i.e., TLIM) was significantly improved (p = 0.05; ES: 1.71) in the BA group (+36.5%) versus the PL group (+8.6%). Similarly, time-to-exhaustion in the incremental test was also significantly increased (p = 0.04; ES 1.03) following beta-alanine supplementation (+12.2%) when compared with placebo (+0.1%). Significant positive correlations were also shown between the relative change in the muscle carnosine content and the relative change in the time-to-exhaustion in the TLIM test (r = 0.62; p = 0.01) and in the incremental test (r = 0.48; p = 0.02). In summary, the current data indicate for the first time, that beta-alanine supplementation is effective in increasing the muscle carnosine content in healthy elderly subjects, with subsequent improvement in their exercise capacity.