Biomedical subjects

J W Rankin

Publications and source records attributed to J W Rankin.

9 recordsLinked to original sources

PubMed2001

Creatine supplementation affects muscle creatine during energy restriction.

INTRODUCTION: Anaerobic performance and body protein may decrease with energy restriction practiced by some athletes for weight loss. METHODS: This investigation examined the effects of creatine (Cr) supplementation during energy restriction on muscle Cr, exercise performance (10 sprints of 6 s, with 30-s rest), nitrogen balance, and body composition in male resistance trainers. Creatine supplemented (CrS, 20 g x d(-1) of Cr) and those given a placebo (P1) consumed a formula diet of 75.3 kJ (18 kcal) x kg(-1) x d(-1) (54.7% C, 21.3% P, 24% F) for 4 d. A control group was unsupplemented and continued their normal diet. There were no changes in body composition or performance of the control group. RESULTS: CrS and P1 demonstrated similar decreases in body weight and percent body fat. The percent change in fat-free mass was more for P1 (2.4+/-0.3% reduction) than CrS (1.4+/-0.4%), but urinary nitrogen losses were similar. Significant increases in muscle total Cr and CrP of 15-16% were demonstrated by CrS over the energy restriction period, whereas P1 had no changes in muscle Cr. Total work done during the sprints expressed per body weight tended to be 3.8% higher in CrS and 0.5% less in P1 after the energy restriction (P = 0.058). CONCLUSION: It was concluded that Cr supplementation increased muscle Cr during short-term energy restriction but did not affect body fat or protein loss. The change in muscle creatine was reflected in a tendency for higher total sprint work for the Cr group.

Adipose Tissue↗

PubMed1999

Role of protein in exercise.

Most research confirms that the body's increased use of protein, as a "fuel" and for repair, increases with aerobic exercise, especially during high intensity and long duration activity. Protein intake higher than the United States Food and Drug Administration's Recommended Dietary Allowance (RDA), with additional energy and resistance training, results in optimal protein status for participants in strength training. Although many active individuals interpret this research to mean that they need to consume extra protein foods or supplements to perform optimally, most people in the United States already consume protein at a level well above the RDA. Physicians should be aware that low energy consuming individuals (e.g., women, those dieting for weight loss, the elderly) may be at risk for low protein intake, and thus protein status, if they are active.

Dietary Proteins↗

PubMed1999

Acute carbohydrate consumption does not influence resistance exercise performance during energy restriction.

The effect of acute carbohydrate consumption on performance and metabolism of resistance-trained males was determined. Twenty-two subjects, assigned to either carbohydrate (C, n = 8), placebo (P, n = 8), or control (N, n = 6), performed standardized workouts every other day for a week prior to testing and throughout the testing period. Three of these workouts (T1, T2, and T3) were the performance test in that the last bouts of leg extension and bench press were done to failure at 80% of 10 repetition maximum. A carbohydrate or placebo beverage was consumed 30 min prior to T3. Blood samples were drawn before and after T2 and T3. There was no effect of carbohydrate or energy restriction on number of repetitions done during the leg extension performance test. Carbohydrate intake prior to a resistance exercise bout done in negative energy balance state did not affect performance or evidence of muscle damage.

Adult↗

PubMed1996

Effect of weight loss and refeeding diet composition on anaerobic performance in wrestlers.

Collegiate wrestlers (N = 12) consumed a formula, hypoenergy diet (18 kcal.kg-1, 60% carbohydrate) without dehydration for 72 h. For the next 5 h, the athletes were fed either a 75% (HC) or a 47% (MC) carbohydrate formula diet of 21 kcal.kg-1. Each wrestler performed three anaerobic arm ergometer performance tests (TEST1, before weight loss; TEST2, after weight loss; TEST3, after refeeding). Blood withdrawn just before and after each test was analyzed for pH, bicarbonate, base excess, glucose, and lactate. Both groups had a similar significant reduction in total work done during TEST2 (92.4% of TEST1). Work done in TEST3 by HC was 99.1% of TEST1 while MC did 91.5% of their initial work (P = 0.1). Peak power was unaffected by the treatment. Plasma lactate significantly increased during the performance test from 1.72 to 21.91 mmol.l-1 as did plasma glucose from 4.88 to 5.25 mmol.l-1 when groups and trials were collapsed. Lactate accumulation was diminished during TEST2 compared with the other tests. Although the exercise bout reduced pH, bicarbonate, and base excess, there was no difference in the effect by group. In conclusion, weight loss by energy restriction significantly reduced anaerobic performance of wrestlers. Those on a high carbohydrate refeeding diet tended to recover their performance while those on a moderate carbohydrate diet did not. The changes in performance were not explained by the acid/base parameters measured.

Adult↗

PubMed1984