Endurance training increases fatty acid turnover, but not fat oxidation, in young men.
- 1 June 1999
- journal article
- clinical trial
- Published by American Physiological Society in Journal of Applied Physiology
- Vol. 86 (6), 2097-2105
- https://doi.org/10.1152/jappl.1999.86.6.2097
Abstract
We examined the effects of exercise intensity and a 10-wk cycle ergometer training program [5 days/wk, 1 h, 75% peak oxygen consumption (V˙o 2 peak)] on plasma free fatty acid (FFA) flux, total fat oxidation, and whole body lipolysis in healthy male subjects ( n= 10; age = 25.6 ± 1.0 yr). Two pretraining trials (45 and 65% ofV˙o 2 peak) and two posttraining trials (same absolute workload, 65% of oldV˙o 2 peak; and same relative workload, 65% of newV˙o 2 peak) were performed by using an infusion of [1-13C]palmitate and [1,1,2,3,3-2H]glycerol. An additional nine subjects (age 25.4 ± 0.8 yr) were treated similarly but were infused with [1,1,2,3,3-2H]glycerol and not [1-13C]palmitate. Subjects were studied postabsorptive for 90 min of rest and 1 h of cycling exercise. After training, subjects increasedV˙o 2 peak by 9.4 ± 1.4%. Pretraining, plasma FFA kinetics were inversely related to exercise intensity with rates of appearance (Ra) and disappearance (Rd) being significantly higher at 45 than at 65%V˙o 2 peak(Ra: 8.14 ± 1.28 vs. 6.64 ± 0.46, Rd: 8.03 ± 1.28 vs. 6.42 ± 0.41 mol ⋅ kg−1 ⋅ min−1) ( P ≤ 0.05). After training, when measured at the same absolute and relative intensities, FFA Ra increased to 8.84 ± 1.1, 8.44 ± 1.1 and Rd to 8.82 ± 1.1, 8.35 ± 1.1 mol ⋅ kg−1 ⋅ min−1, respectively ( P ≤ 0.05). Total fat oxidation determined from respiratory exchange ratio was elevated during exercise compared with rest, but did not differ among the four conditions. Glycerol Ra was elevated during exercise compared with rest but did not demonstrate significant intensity or training effects during exercise. Thus, in young men, plasma FFA flux is increased during exercise after endurance training, but total fat oxidation and whole-body lipolysis are unaffected when measured at the same absolute or relative exercise intensities.Keywords
This publication has 16 references indexed in Scilit:
- Training-induced alterations of carbohydrate metabolism in women: women respond differently from menJournal of Applied Physiology, 1998
- Training-induced alterations of glucose flux in men.Journal of Applied Physiology, 1997
- Fuel selection, muscle fibreProceedings Of The Nutrition Society, 1995
- The 1993 Merck Frosst Award. Acetyl-CoA carboxylase: an important regulator of fatty acid oxidation in the heartCanadian Journal of Physiology and Pharmacology, 1994
- Skeletal muscle substrate utilization during submaximal exercise in man: effect of endurance training.The Journal of Physiology, 1993
- Hormonal and metabolic responses of untrained, moderately trained, and highly trained men to three exercise intensitiesMetabolism, 1989
- Biochemical adaptation of mitochondria, muscle, and whole-animal respiration to endurance trainingArchives of Biochemistry and Biophysics, 1981
- Fat Metabolism in Heavy ExerciseClinical Science, 1980
- Generalized equations for predicting body density of menBritish Journal of Nutrition, 1978
- Training induced adaptation of skeletal muscle and metabolism during submaximal exerciseThe Journal of Physiology, 1977