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- El-Khoury, Antoine E, et al.
(författare)
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Moderate exercise at energy balance does not affect 24-h leucine oxidation or nitrogen retention in healthy men
- 1997
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Ingår i: American Journal of Physiology. - 0002-9513 .- 2163-5773. ; 273:2, s. E394-E407
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Tidskriftsartikel (refereegranskat)abstract
- Short-term metabolic experiments have revealed that physical exercise increases the oxidation of leucine, which has been interpreted to indicate an increased requirement for dietary protein in physically active subjects. Because it may be inaccurate to extrapolate measurements of amino acid oxidation made over a few hours to the entire day, we have carried out a continuous 24-h intravenous [1-13C]leucine/[15N]urea tracer study in eight healthy adult men. Their diet supplied 1 g protein.kg-1.day-1, and exercise (mean maximal O2 consumption 46%) was for 90 min during the 12-h fast and 12-h fed periods of the day. Subjects were adapted to the diet and exercise regimen for 6 days. Then, on day 7, they were dressed in the University of Uppsala energy metabolic unit's direct calorimeter suit, were connected to an open-hood indirect calorimeter, and received the tracers. Exercise increased leucine oxidation by approximately 50 and 30% over preexercise rates for fast and fed periods, respectively. This increase amounted to approximately 4-7% of daily leucine oxidation. Subjects remained in body leucine equilibrium (balance -4.6 +/- 10.5 mg.kg-1.day-1; -3.6 +/- 8.3% of intake; P = not significant from zero balance). Therefore, moderate exercise did not cause a significant deterioration in leucine homeostasis at a protein intake of 1 g.kg-1.day-1. These findings underscore the importance of carrying out precise, continuous, 24-h measurements of whole body leucine kinetics; this model should be of value in studies concerning the quantitative interactions among physical exercise, energy/protein metabolism, and diet in humans.
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| 2. |
- Sjödin, Anders M, et al.
(författare)
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The influence of physical activity on BMR
- 1996
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 28:1, s. 85-91
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Tidskriftsartikel (refereegranskat)abstract
- In addition to factors such as fat free mass, hormonal status, genetics and energy balance, previous physical activity has been shown to influence energy turnover during resting (RMR = resting metabolic rate) or basal conditions(BMR = basal metabolic rate). This article presents data on BMR from elite endurance athletes (4 female and 4 male), at least 39 h after their last training session, in comparison with sedentary nonathletic controls matched for sex and fat free mass (FFM). Comparisons with theoretical calculations of BMR were also made. The athletes were shown to have a significantly higher BMR than was expected from calculations based on body mass (16%, P < 0.05) or body composition (12%, P < 0.05). There were no corresponding differences found in the nonathletic control group. The athletes had a 13% higher (P < 0.001) BMR than controls if related to FFM and 16% (P = 0.001) if related to both FFM and fat mass (FM). The athletes were also found to have 10% lower R-values (P < 0.01) indicating higher fat oxidation. The conformity of these findings with the present literature and the possible mechanisms behind them as well as its influence on theoretical calculations of energy turnover (ET) based on activity factors expressed as multiples of RMR are further discussed.
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| 4. |
- Andersson, Agneta, et al.
(författare)
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Effects of physical exercise on phospholipid fatty acid composition in skeletal muscle
- 1998
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Ingår i: American Journal of Physiology. Endocrinology and Metabolism. - 0193-1849 .- 1522-1555. ; 274:37, s. E432-E438
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Tidskriftsartikel (refereegranskat)abstract
- The effects of low-intensity exercise on the fatty acid composition in skeletal muscle and in serum were studied in 19 sedentary, middle-aged Swedish men. During a 10-wk period, all subjects were given a standardized diet with an identical fat composition. After 4 wk on this diet, they were randomly allocated to a daily exercise program (55% peak oxygen uptake) or to continue to live a sedentary life for the remaining 6 wk. Aerobic capacity (submaximal bicycle test) and peripheral insulin sensitivity (hyperinsulinemic euglycemic clamp) improved with training, whereas the body weight as well as the body composition (underwater weighing and bioimpedance) were unchanged. The proportions of palmitic acid (16:0) and linoleic acid [18:2(n-6)] and the sum of n-6 fatty acids [18:2(n-6), 20:3(n-6), 20:4(n-6)] were decreased in skeletal muscle phospholipids, whereas the proportion of oleic acid [18:1(n-9)] was increased, by training. The fatty acid profile in skeletal muscle triglycerides remained unchanged. We conclude that regular low-intensity exercise influences the fatty acid composition of the phospholipids in skeletal muscle, which hypothetically may contribute to changes of the skeletal muscle membrane fluidity and influence the peripheral insulin sensitivity.
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