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Muscular and metabolic responses to moderate‐intensity short‐term training
Author(s) -
GEOF R. J.,
McCUTCHEON L JILL,
SHEN HUA
Publication year - 1999
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/j.2042-3306.1999.tb05240.x
Subject(s) - citrate synthase , endurance training , glycogenolysis , medicine , horse , lactate dehydrogenase , vo2 max , heart rate , endocrinology , succinate dehydrogenase , interval training , zoology , chemistry , glycogen , biology , biochemistry , enzyme , blood pressure , paleontology
Summary The objectives of this study were to determine the effects of 10 consecutive days of moderate‐intensity training on 1) the muscular metabolic response to exercise at 100% of the pre‐training maximum rate of oxygen consumption (V̇ o 2max ); and 2) mitochondrial enzyme markers (citrate synthase, CS; succinate dehydrogenase, SDH; 3‐hydroxy‐acyl‐CoA dehydrogenase, HAD) of oxidative capacity in middle gluteal muscle. Six mature, unfit Thoroughbred horses completed both incremental (for determination of V̇ o 2max ) and high‐intensity exercise protocols before (HI1) and after (HI2) training. Training consisted of 10 consecutive days of running at 55% V̇ o 2max for 60 min per day (13–14 km/day). For the HI, horses completed a 10 min warm‐up, followed by exercise at 100% of pre‐training V̇ o 2max (mean speed 9.8 m/s) until fatigue. Training resulted in an 8.9% increase in V̇ o 2max (Pre: 142 ± 4 ml/kg bwt/min; Post: 155 ± 4 ml/kg bwt/min) and a 24% increase in run time to fatigue during HI. Whereas V̇ o 2 during HI was not altered by training, peak values for V̇ co 2 and R were significantly lower following training. Compared to HI1, there was a 45% reduction in the net rate of muscle glycogenosis during HI2. Peak (end exercise) values for plasma and muscle lactate concentrations decreased by 22 and 23%, respectively, after training. Training also attenuated the exercise‐associated increase in plasma norepinephrine, but there was no effect on plasma epinephrine concentrations. Maximal activities of CS, SDH, and HAD were unaltered by training. We conclude that 10 days of moderate‐intensity exercise results in decreases in muscle glycogenosis and anaerobic metabolism during high‐intensity exercise at the same absolute workload. Furthermore, development of measurable increases in mitochondrial oxidative potential may not be required for expression of these metabolic adaptations in early training.