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( Colin R. Carriker ),( Roger A. Vaughan ),( Trisha A. Vandusseldorp ),( Kelly E. Johnson ),( Nicholas M. Beltz ),( James J. Mccormick ),( Nathan H. Cole ),( Ann L. Gibson ) 한국운동영양학회 2016 Physical Activity and Nutrition (Phys Act Nutr) Vol.20 No.4
[Purpose] To examine the effect of a 4-day NO<sub>3</sub>- loading protocol on the submaximal oxygen cost of both low fit and high fit participants at five different exercise intensities. [Methods] Eleven (6 high fit, VO<sub>2max</sub> 60.1 ± 4.6ml/kg/min; 5 low fit, VO<sub>2max</sub> 42.4 ± 3.2ml/ kg/min) participants were initially assigned to a placebo (PL; negligible NO<sub>3</sub>-) or inorganic nitrate-rich (NR; 6.2 mmol nitrate/day) group using a double-blind, placebo-controlled, crossover design. Participants completed three trials (T1, T2 and T3). T1 included a maximal aerobic capacity (VO<sub>2max</sub>) treadmill test. A 6-day washout, minimizing nitrate consumption, preceded T2. Each of the four days prior to T2 and T3, participants consumed either PL or NR with the final dose 2.5 hours prior to exercise. A 14-day washout followed T2. T2 and T3 consisted of 5-minute submaximal treadmill bouts (45, 60, 70, 80 and 85% VO<sub>2max</sub>) determined during T1. [Results] Low fit nitrate-supplemented participants consumed less oxygen (p<0.05) at lower workloads (45% and 60% VO<sub>2max</sub>) compared to placebo trials; changes were not observed in high fit participants. The two lowest intensity workloads of 45 and 60% VO<sub>2max</sub> revealed the greatest correlation (r=0.54, p=0.09 and r=0.79, p<0.05; respectively) between VO<sub>2max</sub> and change in oxygen consumption. No differences were found between conditions for heart rate, respiratory exchange ratio or rating of perceived exertion for either fitness group. [Conclusion] Nitrate consumption promotes reduced oxygen consumption at lower exercise intensities in low fit, but not high fit males. Lesser fit individuals may receive greater benefit than higher fit participants exercising at intensities <60% VO<sub>2max</sub>.
Jamie K. Schnuck,Kyle L. Sunderland,Matthew R. Kuennen,Roger A. Vaughan 한국운동영양학회 2016 Physical Activity and Nutrition (Phys Act Nutr) Vol.20 No.2
Background: β-alanine is a common component of numerous sports supplements purported to improve athletic performance through enhanced carnosine biosynthesis and related intracellular buffering. To date, the effects of β-alanine on oxidative metabolism remain largely unexplored. This work investigated the effects of β-alanine on the expression of proteins which regulate cellular energetics. Methods: C2C12 myocytes were cultured and differentiated under standard conditions followed by treatment with either β-alanine or isonitrogenous non-metabolizable control D-alanine at 800μM for 24 hours. Metabolic gene and protein expression were quantified by qRT-PCR and immunoblotting, respectively. Glucose uptake and oxygen consumption were measured via fluorescence using commercially available kits. Results: β-alanine-treated myotubes displayed significantly elevated markers of improved oxidative metabolism including elevated peroxisome proliferator-activated receptor β/δ (PPARβ/δ) and mitochondrial transcription factor a (TFAM) which led to increased mitochondrial content (evidenced by concurrent increases in cytochrome c content). Additionally, β-alanine-treated cells exhibited significantly increased oxygen consumption compared to control in a PPARβ/δ-dependent manner. β-alanine significantly enhanced expression of myocyte enhancer factor 2 (MEF-2) leading to increased glucose transporter 4 (GLUT4) content. Conclusion: β-alanine appears to increase cellular oxygen consumption as well as the expression of several cellular proteins associated with improved oxidative metabolism, suggesting β-alanine supplementation may provide additional metabolic benefit (although these observations require in vivo experimental verification).