Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review

The leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been extensively used as an ergogenic aid; particularly among bodybuilders and strength/power athletes, who use it to promote exercise performance and skeletal muscle hypertrophy. While numerous studies have supported the efficacy of HMB in exercise and clinical conditions, there have been a number of conflicting results. Therefore, the first purpose of this paper will be to provide an in depth and objective analysis of HMB research. Special care is taken to present critical details of each study in an attempt to both examine the effectiveness of HMB as well as explain possible reasons for conflicting results seen in the literature. Within this analysis, moderator variables such as age, training experience, various states of muscle catabolism, and optimal dosages of HMB are discussed. The validity of dependent measurements, clustering of data, and a conflict of interest bias will also be analyzed. A second purpose of this paper is to provide a comprehensive discussion on possible mechanisms, which HMB may operate through. Currently, the most readily discussed mechanism has been attributed to HMB as a precursor to the rate limiting enzyme to cholesterol synthesis HMG-coenzyme A reductase. However, an increase in research has been directed towards possible proteolytic pathways HMB may operate through. Evidence from cachectic cancer studies suggests that HMB may inhibit the ubiquitin-proteasome proteolytic pathway responsible for the specific degradation of intracellular proteins. HMB may also directly stimulate protein synthesis, through an mTOR dependent mechanism. Finally, special care has been taken to provide future research implications

Associations of sport participation with selfperception, exercise self-efficacy and quality of life among children and adolescents with a physical disability or chronic disease—a cross-sectional study.

Background: Little evidence is available about how sports participation influences psychosocial health and quality of life in children and adolescents with a disability or chronic disease. Therefore, the aim of the current study is to assess the association of sports participation with psychosocial health and with quality of life, among children and adolescents with a disability. Methods: In a cross-sectional study, 195 children and adolescents with physical disabilities or chronic diseases (11% cardiovascular, 5% pulmonary, 8% metabolic, 8% musculoskeletal/orthopaedic, 52% neuromuscular and 9% immunological diseases and 1% with cancer), aged 10–19 years, completed questionnaires to assess sports participation, health-related quality of life (DCGM-37), self-perceptions and global self-worth (SPPC or SPPA) and exercise self-efficacy. Results: Regression analyses showed that those who reported to participate in sports at least twice a week had more beneficial scores on the various indicators compared to their peers who did not participate in sport or less than twice a week. Those participating in sports scored better on all scales of the DCGM-37 scale, on the scales for feelings of athletic competence and children but not adolescents participating in sports reported greater social acceptance. Finally, we found a strong association between sport participation and exercise self-efficacy. Conclusions: This study provides the first indications that participating in sports is beneficial for psychosocial health among children and adolescents with a disability. However, more insight is needed in the direction of the relationships. (aut. ref.