Protein and Overtraining: Potential Applications for Free-Living Athletes

Despite a more than adequate protein intake in the general population, athletes have special needs and situations that bring it to the forefront. Overtraining is one example. Hard-training athletes are different from sedentary persons from the sub-cellular to whole-organism level. Moreover, competitive, "free-living" (less-monitored) athletes often encounter negative energy balance, sub-optimal dietary variety, injuries, endocrine exacerbations and immune depression. These factors, coupled with "two-a-day" practices and in-season demands require that protein not be dismissed as automatically adequate or worse, deleterious to health. When applying research to practice settings, one should consider methodological aspects such as population specificity and control variables such as energy balance. This review will address data pertinent to the topic of athletic protein needs, particularly from a standpoint of overtraining and soft tissue recovery. Research-driven strategies for adjusting nutrition and exercise assessments will be offered for consideration. Potentially helpful nutrition interventions for preventing and treating training complications will also be presented

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients

Low-protein vegetarian diet does not have a short-term effect on blood acid¿base status but raises oxygen consumption during submaximal cycling

Background. Acid–base balance refers to the equilibrium between acids and bases in the human body. Nutrition may affect acid–base balance and further physical performance. With the help of PRAL (potential renal acid load), a low-protein vegetarian diet (LPVD) was designed to enhance the production of bases in body. The aim of this study was to investigate if LPVD has an effect on blood acid–base status and performance during submaximal and maximal aerobic cycling. Methods. Nine healthy, recreationally active men (age 23.5 ± 3.4 yr) participated in the study and were randomly divided into two groups in a cross-over study design. Group 1 followed LPVD for 4 days and group 2 ate normally (ND) before performing a cycle ergometer test. The test included three 10-min stages at 40, 60 and 80% of VO2max. The fourth stage was performed at 100% of VO2max until exhaustion. After 10–16 days, the groups started a second 4-day diet, and at the end performed the similar ergometer test. Venous blood samples were collected at the beginning and at the end of both diet periods and after every stage cycled. Results. Diet caused no significant difference in venous blood pH, strong ion difference (SID), total concentration of weak acids (Atot), partial pressure of CO2 (pCO2) or HCO3- at rest or during cycling between LPVD and ND. In the LPVD group, at rest SID significantly increased over the diet period (38.6 ± 1.8 vs. 39.8 ± 0.9, p=0.009). Diet had no significant effect on exercise time to exhaustion, but VO2 was significantly higher at 40, 60 and 80% of VO2max after LPVD compared to ND (2.03 ± 0.25 vs. 1.82 ± 0.21 l/min, p=0.035; 2.86 ± 0.36 vs. 2.52 ± 0.33 l/min, p<0.001 and 4.03 ± 0.50 vs. 3.54 ± 0.58 l/min, p<0.001; respectively). Conclusion. There was no difference in venous blood acid–base status between a 4-day LPVD and ND. VO2 was increased during submaximal cycling after LPVD suggesting that the exercise economy was poorer. This had no further effect on maximal aerobic performance. More studies are needed to define how nutrition affects acid–base balance and performance.peerReviewe

Human ankle plantar flexor muscle–tendon mechanics and energetics during maximum acceleration sprinting

Tendon elastic strain energy is the dominant contributor to muscle–tendon work during steady-state running. Does this behaviour also occur for sprint accelerations? We used experimental data and computational modelling to quantify muscle fascicle work and tendon elastic strain energy for the human ankle plantar flexors (specifically soleus and medial gastrocnemius) for multiple foot contacts of a maximal sprint as well as for running at a steady-state speed. Positive work done by the soleus and medial gastrocnemius muscle fascicles decreased incrementally throughout the maximal sprint and both muscles performed more work for the first foot contact of the maximal sprint (FC1) compared with steady-state running at 5 m s(−1) (SS5). However, the differences in tendon strain energy for both muscles were negligible throughout the maximal sprint and when comparing FC1 to SS5. Consequently, the contribution of muscle fascicle work to stored tendon elastic strain energy was greater for FC1 compared with subsequent foot contacts of the maximal sprint and compared with SS5. We conclude that tendon elastic strain energy in the ankle plantar flexors is just as vital at the start of a maximal sprint as it is at the end, and as it is for running at a constant speed

Effect of sodium bicarbonate and beta-alanine supplementation on maximal sprint swimming

Background. This study examined the effect of simultaneous supplementation of extracellular buffer sodium bicarbonate (SB) and intracellular buffer beta-alanine (BA) on maximal sprint swimming. Methods. Thirteen competitive male swimmers completed 4 different treatments (placebo [PL], SB, BA + PL, and BA + SB) in a crossover procedure. PL or SB supplementation (0.3 g/kg body weight) was ingested 60 min before two maximal 100-m freestyle swims that were performed with a passive recovery of 12-min between each swim. Because of the known long washout period for carnosine, four weeks of BA supplementation (4.8 g per day) was started after the first week of PL or SB supplementation and performance testing. Results. The first maximal swims were similar, but the increase in time of the second versus the first 100-m swimming time was 1.5 s more (p < 0.05) in PL than in SB. Blood pH values were significantly (p < 0.05) greater in the SB and in the BA + SB groups compared to the PL and BA + PL values. There were no differences in peak blood lactate between the treatments. Conclusion. Supplementing with SB prior to performing maximal sprint swimming with repetitions under 60 s improves performance. However, co-supplementation with SB and BA did not confer any added benefit on maximal swim performance.peerReviewe

The role of the extrinsic thoracic limb muscles in equine locomotion

Muscles have two major roles in locomotion: to generate force and to absorb/generate power (do work). Economical force generation is achieved by short-fibred pennate muscle while the maximum power output of a muscle is architecture independent. In this study we tested the hypothesis that there is an anatomical and structural separation between the force-generating anti-gravity muscles and the propulsive (limb/trunk moving) muscles of the equine forelimb. Muscle mass and fascicle length measurements were made on the thoracic limb extrinsic muscles of six fresh horse cadavers. Physiological cross-sectional area and maximum isometric force were then estimated. Maximum power was estimated from muscle volume and published contraction velocity data. The majority of extrinsic forelimb muscles were large with long fascicles arranged in parallel to the long axis of the muscle. Muscles arranged in this way are optimised for doing work. The architecture of serratus ventralis thoracis (SVT) was unique. It had short (48 ± 17 mm) fascicles, arranged at about 45° to the long axis of the muscle, which would suggest a force-generating, anti-gravity role. The muscle belly of SVT was sandwiched between two broad, thick sheets of aponeurosis. Hence, SVT could make a significant contribution to the overall elastic properties of the thoracic limb