Sodium citrate ingestion and muscle performance in acute hypobaric hypoxia |
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Authors: | C Hausswirth A-X Bigard R Lepers M Berthelot C -Y Guezennec |
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Institution: | (1) Département de Physiologie Systémique, Centre d'Etudes et de Recherches de Médecine Aérospatiale, BP 73, F-91223 Brétigny sur Orge Cedex, France |
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Abstract: | Eight subjects were studied on four occasions following ingestion of a 300-ml solution containing either sodium citrate (C, 0.4g · kg–1 body mass) or placebo (P, sodium chloride 0.045 g · kg–1 body mass), at local barometric pressure (N, P
B approximately 740 mmHg, 98.7 kPa) or hypobaric hypoxia (HH, P
B = 463 mmHg, 61.7 kPa). At 2 h after ingestion of the solution, the subjects performed prolonged isometric knee-extension at 35% of the maximal voluntary contraction (MVC) measured either in N or HH. Results showed that ingestion of C led to an improvement in muscle endurance (P < 0.01). However, this increase in endurance time for knee extensor muscles was only significant in N ( +22%, P < 0.05, compared to + 15%, NS, at N and HH, respectively). Following ingestion of sodium citrate, pre-exercise bicarbonate concentrations and pH levels were significantly higher than those measured after P ingestion. A significant treatment effect was observed for blood lactate concentrations with values higher for C than for P after 4, 6 and 10 min of recovery (P < 0.05). Electromyographic signals (EMG) were obtained from the vastus lateralis muscle during the prolonged isometric contraction at 35% MVC. The mean power frequency (MPF) significantly decreased in time under both N-P and N-C conditions. In HH, no significant decrease in MPF was observed with time. The results suggest that C ingestion was an ergogenic aid enhancing endurance during a sustained isometric contraction. In addition, it is suggested that fatigue during prolonged isometric contraction in HH was not directly related to factors determining the EMG signs of fatigue. |
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Keywords: | Alkalising agent Muscle fatigue Melectric power spectrum Simulated high altitude |
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