Carbohydrate ingestion influences skeletal muscle cytokine mRNA and plasma cytokine levels after a 3-h run.

Sixteen experienced marathoners ran on treadmills for 3 h at approximately 70% maximal oxygen consumption (Vo(2 max)) on two occasions while receiving 1 l/h carbohydrate (CHO) or placebo (Pla) beverages. Blood and vastus lateralis muscle biopsy samples were collected before and after exercise. Plasma was analyzed for IL-6, IL-10, IL-1 receptor agonist (IL-1ra), IL-8, cortisol, glucose, and insulin. Muscle was analyzed for glycogen content and relative gene expression of 13 cytokines by using real-time quantitative RT-PCR. Plasma glucose and insulin were higher, and cortisol, IL-6, IL-10, and IL-1ra, but not IL-8, were significantly lower postexercise in CHO vs. Pla. Change in muscle glycogen content did not differ between CHO and Pla (P = 0.246). Muscle cytokine mRNA content was detected preexercise for seven cytokines in this order (highest to lowest): IL-15, TNF-alpha, IL-8, IL-1beta, IL-12p35, IL-6, and IFN-gamma. After subjects ran for 3 h, gene expression above prerun levels was measured for five of these cytokines: IL-1beta, IL-6, and IL-8 (large increases), and IL-10 and TNF-alpha (small increases). The increase in mRNA (fold difference from preexercise) was attenuated in CHO (15.9-fold) compared with Pla (35.2-fold) for IL-6 (P = 0.071) and IL-8 (CHO, 7.8-fold; Pla, 23.3-fold; P = 0.063). CHO compared with Pla beverage ingestion attenuates the increase in plasma IL-6, IL-10, and IL-1ra and gene expression for IL-6 and IL-8 in athletes running 3 h at 70% Vo(2 max) despite no differences in muscle glycogen content.

The effects of a multimedia system in supermarkets to alter shoppers' food purchases: nutritional outcomes and caveats.

A randomized-control test of a multimedia nutrition intervention-the Nutrition for a Lifetime System (NLS©)- utilized supermarket receipts to examine effects of NLS treatment on the daily per person nutritional content of participants' supermarket purchases. In regression analyses controlling for background variables, baseline purchases and trends toward increased purchasing, NLS treatment contributed to lower levels of total fat and to higher levels of total fiber and servings of fruits and vegetables at post-test. Redemption of NLS coupons contributed to greater decreases in fat and increases in servings of fruits and vegetables in users' purchases. Implications for future interventions promoting healthier food choices include tailoring program content and addressing broader lifestyle issues such as caloric intake and expenditure.

Dietary carbohydrate as an ergogenic aid for prolonged and brief competitions in sport.

Reduction of body stores of carbohydrate and blood glucose is related to the perception of fatigue and the inability to maintain high-quality performance. This has been clearly shown with aerobic, endurance events of moderate intensity of over 90 min duration. Carbohydrate intake may also have relevance for athletes involved in short, high-intensity events, especially if body weight control is an issue. Prevention of carbohydrate depletion begins with a high-carbohydrate training diet of about 60-70% carbohydrate. If possible, carbohydrate beverages should be consumed during the event at the rate of 30-70 g/hr to reduce the chance of body carbohydrate depletion. Finally, replacement of body carbohydrate stores can be achieved most rapidly if 40-60 g of carbohydrate is consumed as soon as possible after the exercise and at repeating 1-hr intervals for at least 5 hr after the event.

Diet and weight changes of female bodybuilders before and after competition.

This study assessed nutritional and body weight patterns in 6 female bodybuilders approximately a month before and after a competition. The women kept dietary and body weight records and two of them also agreed to collect morning urine samples to provide information about their menstrual cycle. All women lost weight before and gained weight after competition. Energy intake was modestly restricted and the subjects consumed a moderate-protein, low-fat, high-carbohydrate diet just prior to competition. Energy intake doubled, and total grams of fat increased approximately tenfold just after competition. Urinary data indicated that the cycle following competition was prolonged, with reduced reproductive hormone concentrations. In summary, the women practiced extreme dietary control while preparing for a competition but followed the event with a higher energy and fat intake. These changes in diet and body weight may contribute to the disturbances previously observed in the menstrual cycle of these athletes.

Response of beta-endorphin and estradiol to resistance exercise in females during energy balance and energy restriction.

The acute effect of weightlifting on beta-endorphin and estradiol was studied in experienced female recreational weightlifters. Five eumenorrheic females completed two months of testing, each with a different sequence of testing conditions (SEQ1 and SEQ2). In SEQ1, a week of weight maintenance diet and prescribed exercise (3 d.wk-1, 3 sets, approximately 85% 1 RM, 10-12 reps, eight lifts) beginning on d 11 of their menstrual cycle was followed by measurement of hormone response to a weightlifting bout during energy balance (EBAL) on d 18. This included blood sampling via a catheter before, just after, and at 15 and 30 min of recovery. The women consumed 500 kcal per day for the next 48 hrs and then repeated the weightlifting test during negative energy balance (NEBAL). SEQ2 was similar except that the 48 hrs of NEBAL preceded the EBAL test condition. Estradiol and beta-endorphin increased from baseline to immediately post exercise under both dietary conditions but was significant only during NEBAL. Estradiol increased 1.6 fold and beta-endorphin 3.7 fold by the end of the resistance exercise bout during NEBAL. Both hormones were also elevated for a longer time during recovery in the NEBAL condition. Since estradiol and beta-endorphin can suppress gonadotropin release, it is possible that repeated elevations in these hormones during weightlifting, especially concurrent with energy restriction, could contribute to disruption of the menstrual cycle.

Opioid antagonism, perceived exertion and tolerance to exercise-thermal stress.

In an attempt to investigate the physiological responses to opioid receptor blockade during exercise in the heat, five male volunteers completed two bouts of stationary cycling at 70% VO2max in a hot (33 degrees C765% RH) environment. Exercise was conducted following the administration of either naloxone or saline (4 mg i.v.) five minutes prior to exercise. A second 4 mg dose was administered at 25 minutes of exercise. Performance time was 11% shorter (p = 0.06), and RPE response was significantly higher at test termination on naloxone. No drug effect was observed on rectal or mean skin temperature during exercise. Forearm blood flow (FBF) was higher on naloxone, while exercise heart rates were lower on the drug versus saline. No significant changes were observed in estimated mean arterial pressure or gross sweat responses to exercise. Plasma immunoreactive beta-endorphin was significantly elevated in the naloxone trial only. Thus, while opioids may play some hemodynamic role during exercise in the heat, it appears that opioid mediation of the perceived stress of exercise contributes more to an individual's thermal tolerance. Additionally, the results suggest that perceptual and hemodynamic/cardiovascular responses that may be mediated by these peptides are dissociable phenomena.