Influence of carbohydrate, intense exercise, and rest intervals on hormonal and oxidative changes.

Dept. of Health, Leisure, and Exercise Science, Appalachian State University, Boone, NC 28608, USA.
International journal of sport nutrition and exercise metabolism (Impact Factor: 1.86). 11/2007; 17(5):478-90.
Source: PubMed

ABSTRACT This study compared effects of carbohydrate (CHO) and rest on oxidative stress during exercise. Cyclists (N = 12) completed 4 randomized trials at 64% Wattsmax under 2 conditions (continuous cycling for 2 h [C] and cycling with 3-min rest every 10 min for 2.6 h [R]). Subjects cycled under each condition while receiving 6% CHO and placebo (PLA). CHO and PLA were given preexercise (12 mL/kg) and during exercise (4 mL x kg(-1) x 15 min(-1)). Blood was collected preexercise, postexercise, and 1 h postexercise and assayed for F2-isoprostanes, hydroperoxides (LH), nitrite, antioxidant capacity, glucose, insulin, cortisol, and epinephrine. F2-isoprostanes and LH were lower in CHO. Glucose, cortisol, and epinephrine exhibited significant effects, with postexercise levels of glucose higher and cortisol and epinephrine lower in CHO during the R condition. This pattern was identical in the C condition (21). Oxidative stress during cycling was unaffected by use of short rest intervals but was diminished by CHO.

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    ABSTRACT: Carbohydrate supplementation is a popular nutritional practice used in tennis to enhance physical capacities, motor-skill performance, and delay fatigue. However, the effects of carbohydrate supplementation on physiological and perceptual responses during tennis match play are not established. This double blind, randomized, placebo-controlled crossover study was designed to determine the influence of carbohydrate supplementation (0.5g•kg•h) on glycemia, salivary hormones (cortisol and testosterone) concentration, salivary IgA concentration and ratings of perceived exertion (RPE) during 3 h of tennis match play in 12 well trained tennis players. The only significant difference between the two conditions was a lower salivary cortisol concentration post-match in the carbohydrate trial (p<0.05); however, there was a trend for higher glucose concentration (p = 0.06) and lower session-RPE (p = 0.08) following tennis match play in the carbohydrate condition, which may have some practical implications. There was no change in salivary testosterone, salivary IgA and RPE responses during tennis match play between conditions (p>0.05). These data indicate that carbohydrate ingestion during 3 h of competitive tennis match play helps to maintain glycemia and attenuates the increase in salivary cortisol concentration compared to placebo.
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