International SportMed Journal - Volume 8, Issue 2, 2007
Volume 8, Issue 2, 2007
Source: International SportMed Journal 8, pp 43 –53 (2007)More Less
Creatine supplementation is a widely used and heavily studied ergogenic aid. Athletes use creatine to increase muscle mass, strength, and muscle endurance. While the performance and muscle-building effects of creatine supplementation have been well documented, the mechanisms responsible for these muscular adaptations have been less studied.
Objective: The purpose of this review is to examine studies of the mechanisms underlying muscular adaptations to creatine supplementation.
Data sources: PubMed and SPORTDiscus databases were searched from 1992 to 2007 using the terms creatine, creatine supplementation, creatine monohydrate, and phosphocreatine.
Study selection: Studies of creatine supplementation in healthy adults were included.
Data extraction: Due to the small number of studies identified, a meta-analysis was not performed.
Data synthesis: Several potential mechanisms underlying muscular adaptations to creatine supplementation were identified, including: metabolic adaptations, changes in protein turnover, hormonal alterations, stabilization of lipid membranes, molecular modifications, or as a general training aid. The mechanisms with the greatest amount of support (metabolic adaptations, molecular modifications, and general training aid) may work in concert rather than independently.
Conclusions: Creatine supplementation may alter skeletal muscle directly, by increased muscle glycogen and phosphocreatine, faster phosphocreatine resynthesis, increased expression of endocrine and growth factor mRNA, or indirectly, through increased training volume.
Muscle damage and amino acid supplementation : does it aid recovery from muscle damage? : review articleAuthor Kazunori NosakaSource: International SportMed Journal 8, pp 54 –67 (2007)More Less
Following unaccustomed exercise consisting of lengthening (eccentric) contractions, delayed onset muscle soreness (DOMS) develops together with muscle weakness, and these symptoms persist for several days. DOMS and the impairment of muscle function due to muscle damage affect training and athletic performance; thus effective measures to prevent or reduce muscle damage, or enhance recovery from damage, are important. Since it is known that amino acid supplementation stimulates the transport of amino acids into the skeletal muscles, and administration of exogenous amino acids after exercise increases protein synthesis while reducing protein breakdown, it is plausible that amino acid supplementation is effective for reducing muscle damage and / or enhancing recovery from muscle damage. Several studies have investigated the effects of amino acid supplementation on DOMS and other markers of muscle damage, and some of them found positive effects while others did not. It should be noted that few studies found a positive effect of amino acid supplementation on recovery of muscle function, and no previous studies have investigated whether amino acid supplement facilitates regeneration of damaged contractile and / or non-contractile elements. It cannot be concluded from currently available information that amino acid supplementation is effective for recovery from muscle damage. However, it appears that the effects of amino acid supplementation on muscle damage, if any, are affected by the timing and amount of supplementation, the magnitude and cause of muscle damage, composition of amino acids in the supplement, and other food intake in addition to the supplement. These should be investigated further before concluding whether amino acid supplementation contributes to attenuation of muscle damage and enhances recovery of muscle function after damaging exercise.
HMB use and its relationship to exercise-induced muscle damage and performance during exercise : review articleSource: International SportMed Journal 8, pp 68 –77 (2007)More Less
Objective: Literature review of the ergogenic aid β-hydroxy-β-methylbutyrate (HMB) and it effects on exercise-induced muscle damage.
Data sources: Medline, Ovid, SportDISCUS and relevant bibliographies were reviewed in February, 2007 using the following terms: HMB, beta-hydroxy-beta-methylbutyrate, muscle damage, CPK, creatine phosphokinase, exercise, delayed-onset muscle soreness.
Study selection: Relevant studies were limited to human investigations which were randomized, blinded, and placebo-controlled, and included an objective measurement of muscle damage. A total of eleven studies met the criteria for the review.
Data extraction: Relevant literature was identified and reviewed.
Data synthesis and conclusions: HMB is a nutritional supplement proposed to function as an anti-catabolic agent which decreases muscle protein breakdown and cell damage brought about by intense exercise. Previous research has claimed to support this hypothesis with findings of significantly reduced markers of muscle catabolism from HMB supplementation. Critical review of this literature reveals limitations in the assessments of these studies as evidenced by two main flaws in the basic premise behind HMB and muscle damage: (1) No rigorous scientific literature has verified the proposed mechanism through which HMB reduces muscle breakdown; (2) The use of muscle-specific enzymes is likely a labile and insensitive method to indicate muscle damage. Based on the literature to date, the effect of HMB on preventing exercise-induced muscle damage is likely transient and of little physiological significance. Further research to clarify the mechanism of HMB and precisely evaluate its role in protein turnover is needed.
A comparison of injury rates in organised sports, with special emphasis on American bull riding : review articleSource: International SportMed Journal 8, pp 78 –86 (2007)More Less
Objective: The authors set out to determine which sport in the literature has the highest injury rates.
Data sources: A systematic review of sports injury studies was performed using the PubMed database on the National Library of Medicine website, using the key words: ''Injury Incidence'' in combination with each of the sports: ''boxing,'' ''football,'' ''hockey,'' ''rodeo,'' ''rugby,'' and ''soccer.''
Study section: Using a 3-round selection process, 2021 papers were reviewed. Those papers that did not report injury rates as a function of time were excluded.
Data extraction: Each paper underwent an independent review by two authors. Injury rates from the papers reporting the top 5 injury rates for each sport were recorded and placed into an electronic spreadsheet for comparison. All selected studies reported injury rates as a function of time, although the unit of time was not always the same; therefore, simple extrapolation was made for all studies to make the unit of time in hours.
Data synthesis: The injury rate in bull riding was found to be 1440 injuries/1000 exposure hours; 1.56 times greater than amateur boxing, 1.75 times greater than semi-professional rugby, 10.3 times greater than American football, and 13.3 times greater than ice hockey.
Conclusions: The authors conclude that injury rates vary widely between contact sports and that American bull riding is the most dangerous organised, spectator sport in the world.
Influence of anthropometry on race performance in ultra-endurance triathletes in the longest triathlon in North America : clinical case seriesSource: International SportMed Journal 8, pp 87 –96 (2007)More Less
Background: Little is known about the effects of anthropometry on race performance in ultra-endurance athletes.
Research question: The investigation of the influence of anthropometric parameters on race performance in ultra-endurance triathletes in the longest triathlon in North America.
Type of study: Descriptive field study.
Methods: Body mass, body height, length of lower limbs, skinfold thicknesses, circumferences of extremities (as well as calculation of BMI), percent skeletal muscle mass (%SM) and percent body fat (%BF) were determined in the 8 male starters of the Virginia Triple Iron Triathlon 2006 in the USA. This race is the longest triathlon in North America, where athletes have to perform a 11.4 km swim, 540 km cycle ride and 126.6 km run within 68 hours. The measured and calculated anthropometric parameters were correlated with race performance in order to find factors that influence race performance in ultra-endurance triathletes.
Results: In the 5 successful finishers of the race, race time was not significantly influenced by the directly measured anthropometric properties of body height, length of limbs, body mass, average skinfold thickness, and the limb perimeters of thigh, calf and upper arm (p>0.05). Furthermore, no significant influence was observed between race time and the calculated parameters BMI, %BF and %SM (p>0.05).
Conclusions: In the Virginia Triple Iron Triathlon 2006, no influence was observed from body mass, body height, length of limbs, skinfold thickness, perimeters of extremities, BMI, %SM and %BF on race performance in the only 5 successful finishers.