Acidosis
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Data on spectroscopy detailed by G. Layec and co-authors
2009 JUL 21 - (NewsRx.com) -- "The effects of a priming exercise bout on both muscle energy production and the pattern of muscle fibre recruitment during a subsequent exercise bout are poorly understood. The purpose of the present study was to determine whether a prior exercise bout which is known to increase O-2 supply and to induce a residual acidosis could alter energy cost and muscle fibre recruitment during a subsequent heavy-intensity knee-extension exercise," scientists writing in the journal Experimental Physiology report. "Fifteen healthy subjects performed two 6 min bouts of heavy exercise separated by a 6 min resting period. Rates of oxidative and anaerobic ATP production, determined with P-31-magnetic resonance spectroscopy, and breath-by-breath measurements of pulmonary oxygen uptake were obtained simultaneously. Changes in muscle oxygenation and muscle fibre recruitment occurring within the quadriceps were measured using near-infrared spectroscopy and surface electromyography. The priming heavy-intensity exercise increased motor unit recruitment (P < 0.05) in the early part of the subsequent exercise bout but did not alter muscle energy cost. We also observed a reduced deoxygenation time delay, whereas the deoxygenation amplitude was increased (P < 0.01). These changes were associated with an increased oxidative ATP cost after similar to 50 s (P < 0.05) and a slight reduction in the overall anaerobic rate of ATP production (0.11 +/- 0.04 mm min(-1) W-1 for bout 1 and 0.06 +/- 0.11 mm min(-1) W-1 for bout 2; P< 0.05). We showed that a priming bout of heavy exercise led to an increased recruitment of motor units in the early part of the second bout of heavy exercise," wrote G. Layec and colleagues. The researchers concluded: "Considering the increased oxidative cost and the unaltered energy cost, one could suggest that our results illustrate a reduced metabolic strain per fibre.." Layec and colleagues published their study in Experimental Physiology (Effects of a prior high-intensity knee-extension exercise on muscle recruitment and energy cost: a combined local and global investigation in humans. Experimental Physiology, 2009;94(6):704-719). Additional information can be obtained by contacting D. Bendahan, Faculty Med Marseille, CNRS, Center Resonance Magnet Biology & Medical, UMR 6612, 27 Blvd. Jean Moulin, F-13005 Marseille, France. The publisher of the journal Experimental Physiology can be contacted at: Wiley-Blackwell Publishing, Inc., Commerce Place, 350 Main St., Malden 02148, MA, USA. Keywords: France, Marseille, Acidosis, Magnetic Resonance, Physiology, Spectroscopy, Surgery. This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2009, Life Science Weekly via NewsRx.com.
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