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

Optimal depth jump height quantified as percentage of athlete stature

Purpose: An individual’s optimal depth jump platform height provides a resistive force which allows an athlete to rebound with substantial velocity resulting in maximum power exertion. The objective of this investigation was to show that the optimal platform height in a depth jump can be quantified as a percentage of individual body stature which can serve as measurable quantified value. Although athlete height is not highly correlated to power ability nor does a universal height exist, this value can provide a basis for a rehabilitation or strength and conditioning program. The desired intensity of a program can be prescribed as a percentage of the individual’s optimal drop height. Methods: Sixteen male participants (age = 21.7 ± 1.54 yrs., height = 177.7 ± 11.4 cm, mass = 77.7 ± 13.6 kg; mean ± SD) were tested in a depth jump through a range of platform heights based on percentage of the individual anthropometric data defined at 0-, 10-, 20-, 30-, 40-, and 50% of the participants’ stature using a 3-D motion capture system (Qualysis) and force plates (Bertec) to calculate power. Results: The optimal drop height was found to be 21.3 (±10.3)% of the participants’ heights for maximum peak power and 27.5 (±15.3)% for maximum average power. Conclusions: These results suggest that an individual optimal drop height does exist as a percentage of stature and could be applied to a rehabilitation or power-based training program using the drop height as a quantified basis allowing an athlete to gradually work toward their individual optimal drop height and exhibit maximum power. Keywords: Kinematics; Kinetics; Lower extremity assessment; Plyometrics; Power

Descriptive Epidemiology of Collegiate Men's Wrestling Injuries: National Collegiate Athletic Association Injury Surveillance System, 1988–1989 Through 2003–2004

Objective: To review 16 years of National Collegiate Athletic Association (NCAA) injury surveillance data for men's wrestling and identify potential areas for injury prevention initiatives