Energy beverages: content and safety.

Exercise is making a resurgence in many countries, given its benefits for fitness as well as prevention of obesity. This trend has spawned many supplements that purport to aid performance, muscle growth, and recovery. Initially, sports drinks were developed to provide electrolyte and carbohydrate replacement. Subsequently, energy beverages (EBs) containing stimulants and additives have appeared in most gyms and grocery stores and are being used increasingly by "weekend warriors" and those seeking an edge in an endurance event. Long-term exposure to the various components of EBs may result in significant alterations in the cardiovascular system, and the safety of EBs has not been fully established. For this review, we searched the MEDLINE and EMBASE databases from 1976 through May 2010, using the following keywords: energy beverage, energy drink, power drink, exercise, caffeine, red bull, bitter orange, glucose, ginseng, guarana, and taurine. Evidence regarding the effects of EBs is summarized, and practical recommendations are made to help in answering the patient who asks, "Is it safe for me to drink an energy beverage when I exercise?"

Physical fitness of industrial firefighters

Firefighting is widely known to be one of the most physically demanding civilian occupations. A subset of this is Industrial Firefighting, which places similarly high physical demands on Industrial Firefighters. Although there are some studies on community firefighters, literature is scant on Industrial Firefighters and their physical fitness. ^ A cross-sectional study of Industrial Firefighters in Petrochemical companies in Texas was carried out in 1996–98 to assess their physical fitness and to develop a set of physical agility criteria useful in their selection and ongoing fitness for duty evaluations. ^ A physical agility criteria and a fitness scorecard was developed based on seven parameters (resting heart rate, diastolic blood pressure, aerobic capacity, muscle strength, muscle endurance, trunk flexibility and total body fat) of musculoskeletal and cardiorespiratory fitness. Each indicator received a minimum of 0 to a maximum of 20 points, based on individual performance. Therefore a minimum and maximum achievable score for the entire battery of tests was 0 and 140 respectively. Of the 111 study subjects, 5 (4.5%) were far above average, 31 (28%) above average, 46 (41.5 %) average, 29 (26%) below average and 0 (0%) far below average as deemed by the physical fitness scorecard. The mean score was 77 (±23) with a minimum and maximum score of 35 and 135 respectively. ^ Following univariate analysis an exploratory factor analysis to group variables and to assess the overall role of constituent variables in total fitness of a firefighter was developed. This was followed by a stepwise linear regression analysis using aerobic capacity as a dependent variable. ^ Finally, a graded implementation strategy was devised, such that all existing Industrial Firefighters would have an opportunity to improve or maintain their physical fitness at or above average level as deemed by the fitness scorecard. ^

Temporal analysis of PI-3kinase and MAPK signal transduction during skeletal muscle overload

Skeletal muscles can adapt to increased mechanical forces (or loading) by increasing the size and strength of the muscle. Knowledge of the molecular mechanisms by which muscle responds to increased loading may lead to the discovery of novel treatment strategies for muscle wasting and frailty. The objective of this research was to examine the temporal associations between the activation of specific signaling pathway intermediates and their potential upstream regulator(s) in response to increased muscle loading. Previous work has demonstrated that focal adhesion kinase (FAK) activity is increased in overloaded hypertrophying skeletal muscle. Thus FAK is a candidate for transducing the loading stimulus in skeletal muscle, potentially by activating phosphatidylinositol 3-kinase (PI3K) and members of the mitogen-activated protein kinase (MAPK) family. However, it was unknown if muscle overload would result in activation of PI3K or the MAPKs. Thus, this work seeks to characterized the temporal response of (1) MAPK phosphorylation (including Erk 2, p38 MAPK and JNK), (2) PI3K activity, and (3) FAK tyrosine phosphorylation in response to 24 hours of compensatory overload in the rat soleus and plantaris muscles. In both muscles, overload resulted in transient Increases in the phosphorylation state of Erk2 and JNK, which peaked within the first hour of overload and returned to baseline thereafter. In contrast, p38 MAPK phosphorylation remained elevated throughout the entire 24-hour overload period. Moreover, overload increased PI3K activity only, in the plantaris and only at 12 hours. Moreover, 24 hours of overload induced a significant increase in total protein content in the plantaris but not the soleus. Thus an increase in total muscle protein content within the 24-hour loading period was observed only in muscle exhibiting increased PI3K activity. Surprisingly, FAK tyrosine phosphorylation was not increased during the overload period in either muscle, indicating that PI3K activation and increased MAPK phosphorylation were independent of increased FAK tyrosine phosphorylation. In summary, increased PI3K activity and sustained elevation of p38 MAPK phosphorylation were associated with muscle overload, identifying these pathways as potential mediators of the early hypertrophic response to skeletal muscle overload. This suggests that stimuli or mechanisms that activate these pathways may reduce/minimize muscle wasting and frailty. ^