Isometric contractions at around 15-20% of maximal voluntary isometric contraction (MVIC) can result in increased intramuscular pressures that are sufficient to reduce muscle blood flow [19, 20]. However, muscle blood flow is stopped completely at higher intensities [19, 20], with the result that the muscle acts as a closed system and the active muscle fibres are solely dependent upon anaerobic energy provision [21]. Isometric endurance hold time is dependent upon the intensity of the muscle contraction with higher percentages of MVIC causing shorter hold times [22]. At fatigue, the maximal accumulation of Lac- in the knee extensor muscles, and therefore

decrement in muscle pH, is caused by a moderate rate of lactate production (~1.1 mmol·kg-1 dm·s-1) accumulated over a moderate time period. The optimal exercise intensity Sepantronium mw to accumulate lactate is around 45% of MVIC [23]. The Rohmert equation [22] predicts that a constant isometric

contraction of the knee extensors will fail to maintain 45% MVIC after approximately 78 s [24]. Therefore, Linsitinib mouse we aimed to examine the effect of β-alanine supplementation on isometric endurance of the knee extensor muscles at 45% of MVIC. Our hypothesis was that isometric hold times at 45% MVIC would be 78 s before supplementation and that these hold times would be increased with β-alanine but not with placebo. Method Participants Sixteen physically active males volunteered and were split into a β-alanine and a placebo group. However, 3 participants dropped out of the study (2 from the placebo group and 1 from the β-alanine group) due to sports related injuries sustained during the period of supplementation. As a result, only thirteen participants completed both XMU-MP-1 trials with 6 and 7 being supplemented with placebo and β-alanine, respectively (Table 1). All participants were considered healthy according to a health screening questionnaire and the health screening procedure was repeated prior to each laboratory visit to ensure the health

status of the participants had not changed. Participants had not taken any supplement in the 3 months prior to the study and had not supplemented with β-alanine for nearly at least 6 months. Participants were also requested to maintain similar levels of physical activity and dietary intake for the duration of the study and compliance with this request was verbally confirmed with participants prior to commencement of the study. None of the participants were vegetarian and would have consumed small amounts of β-alanine in their diet, typically 50 to 400 mg per day. The study was approved by the institutions Ethical Advisory Committee and all participants provided informed consent. Table 1 Participant characteristics     Age (y) Height (m) Body Mass (kg)     Week 0 Week 4 β-alanine Mean 24 1.81 81.6 81.9 n = 7 SD 7 0.04 10.9 10.8 Placebo Mean 21 1.79 80.3 80.1 n = 6 SD 4 0.06 10.9 11.