Influence of chronic dietary carbohydrate supplementation on plasma cytokine responses to exercise.

This study examined the influence of 28 days of dietary carbohydrate (CHO) supplementation on plasma cytokine responses to cycle ergometry. Sixteen highly trained male cyclists and triathletes (age: 30.6+/-5.6 y; VO2max: 64.8+/-4.7 mL x kg(-1) x min(-1); mean+/-SD) participated in the study. One group (n=8) consumed a higher-CHO (8.5+/-1.7 g x kg(-1) body mass.day (-1)) diet for 28 days; a second group (n=8) consumed a moderate-CHO diet (5.3+/-0.4 g x kg (-1) x day (-1)). Total daily energy intakes were similar between the two groups. Cytokine responses to cycle ergometry were assessed prior to and again following the dietary intervention period. The cycle ergometry protocol involved 100 min steady state cycling at 70% VO2max followed by a time trial of approximately 30 min. Athletes were provided with 15 mL x kg (-1) x h (-1) of water during each trial. Blood samples were collected pre-, immediately post- and 1 h post-exercise for determination of plasma glucose and pro-inflammatory (IL-6, IL-8) and anti-inflammatory (IL-10, IL-1ra) cytokine concentrations. Cytokine responses to cycle ergometry were not substantially altered following the 28-day higher-CHO diet. In contrast, following the 28-day moderate-CHO diet, there were approximately 30-50% reductions (p=0.08-0.11) in anti-inflammatory cytokine responses post-exercise. These findings suggest that increased dietary CHO content alone does not effectively attenuate the pro-inflammatory cytokine response to exercise, however, there may be a small reduction in the anti-inflammatory cytokine response.

Pre-exercise carbohydrate status influences carbohydrate-mediated attenuation of post-exercise cytokine responses.

Most studies investigating the effects of acute carbohydrate (CHO) ingestion on post-exercise cytokine responses have involved fasted athletes. This study characterised the effects of acute CHO beverage ingestion preceded by consumption of a CHO-containing pre-exercise meal. Sixteen highly-trained male cyclists/triathletes (age: 30.6 +/- 5.6 y; V O (2max): 64.8 +/- 4.7 ml . kg . min (-1) [mean +/- SD]) undertook two cycle ergometry trials involving randomised consumption of a 10 % CHO beverage (15 mL . kg (-1) . hr (-1)) or water (H (2)O). Trials were undertaken 2 h after a breakfast providing 2.1 g CHO . kg (-1) body mass (BM) (48 kJ . kg (-1) BM) and consisted of 100 min steady state cycle ergometry at 70 % V O (2max) followed by a time trial of approximately 30 min duration. Blood samples were collected pre-, post- and 1 h post-exercise for measurement of Interleukin (IL)-6, IL-8, IL-10 and IL-1ra. Time-trial performance was not substantially different between CHO and H (2)O trials (4.5 %, p = 0.42). Neither IL-6 nor IL-8 responses were substantially reduced in the CHO compared to the H (2)O trial. There was a substantial reduction in IL-10 (32 %, p = 0.05) and IL-1ra (43 %, p = 0.02) responses at 1 h post-exercise with CHO compared to H (2)O ingestion. In conclusion, the previously shown attenuating effects of CHO ingestion during exercise on cytokine responses appear reduced when athletes consume a CHO-containing pre-exercise meal.

Body mass changes and voluntary fluid intakes of elite level water polo players and swimmers.

Calculated sweat rates (measured by body mass changes) and voluntary fluid intakes were monitored in elite level water polo players and swimmers during normal exercise sessions to determine fluid requirements to maintain fluid balance, and the degree of fluid replacement of these athletes. Data were collected from training and competition sessions for male water polo players (n = 23) and training sessions only for swimmers (n = 20 females; n = 21 males). The calculated average sweat rate and fluid intake rate during training sessions for male water polo players was 287 ml/h and 142 ml/h, respectively, with a rate of 786 ml/h and 380 ml/h during matches. During training sessions for male swimmers, the calculated average sweat rate and fluid intake rate per kilometre was 138 ml/km and 155 ml/km, respectively; and for female swimmers, 107 ml/km and 95 ml/km. There was a wide individual variation in fluid intake and sweat loss of both water polo players and swimmers. Dehydration experienced by athletes in this study was less than typically reported for "land-based" athletes. Errors inherent in the technique used in this study are acknowledged and may be significant in the calculation of reported sweat losses and levels of fluid balance in aquatic athletes.

Guidelines for daily carbohydrate intake: do athletes achieve them?

Official dietary guidelines for athletes are unanimous in their recommendation of high carbohydrate (CHO) intakes in routine or training diets. These guidelines have been criticised on the basis of a lack of scientific support for superior training adaptations and performance, and the apparent failure of successful athletes to achieve such dietary practices. Part of the problem rests with the expression of CHO intake guidelines in terms of percentage of dietary energy. It is preferable to provide recommendations for routine CHO intake in grams (relative to the body mass of the athlete) and allow flexibility for the athlete to meet these targets within the context of their energy needs and other dietary goals. CHO intake ranges of 5 to 7 g/kg/day for general training needs and 7 to 10 g/kg/day for the increased needs of endurance athletes are suggested. The limitations of dietary survey techniques should be recognised when assessing the adequacy of the dietary practices of athletes. In particular, the errors caused by under-reporting or undereating during the period of the dietary survey must be taken into account. A review of the current dietary survey literature of athletes shows that a typical male athlete achieves CHO intake within the recommended range (on a g/kg basis). Individual athletes may need nutritional education or dietary counselling to fine-tune their eating habits to meet specific CHO intake targets. Female athletes, particularly endurance athletes, are less likely to achieve these CHO intake guidelines. This is due to chronic or periodic restriction of total energy intake in order to achieve or maintain low levels of body fat. With professional counselling, female athletes may be helped to find a balance between bodyweight control issues and fuel intake goals. Although we look to the top athletes as role models, it is understandable that many do not achieve optimal nutrition practices. The real or apparent failure of these athletes to achieve the daily CHO intakes recommended by sports nutritionists does not necessarily invalidate the benefits of meeting such guidelines. Further longitudinal studies of training adaptation and performance are needed to determine differences in the outcomes of high versus moderate CHO intakes. In the meantime, the recommendations of sports nutritionists are based on plentiful evidence that increased CHO availability enhances endurance and performance during single exercise sessions.

Effect of fat adaptation and carbohydrate restoration on metabolism and performance during prolonged cycling.

For 5 days, eight well-trained cyclists consumed a random order of a high-carbohydrate (CHO) diet (9.6 g. kg(-1). day(-1) CHO, 0.7 g. kg(-1). day(-1) fat; HCHO) or an isoenergetic high-fat diet (2.4 g. kg(-1). day(-1) CHO, 4 g. kg(-1). day(-1) fat; Fat-adapt) while undertaking supervised training. On day 6, subjects ingested high CHO and rested before performance testing on day 7 [2 h cycling at 70% maximal O(2) consumption (SS) + 7 kJ/kg time trial (TT)]. With Fat-adapt, 5 days of high-fat diet reduced respiratory exchange ratio (RER) during cycling at 70% maximal O(2) consumption; this was partially restored by 1 day of high CHO [0.90 +/- 0.01 vs. 0.82 +/- 0.01 (P < 0.05) vs. 0.87 +/- 0.01 (P < 0.05), for day 1, day 6, and day 7, respectively]. Corresponding RER values on HCHO trial were [0. 91 +/- 0.01 vs. 0.88 +/- 0.01 (P < 0.05) vs. 0.93 +/- 0.01 (P < 0.05)]. During SS, estimated fat oxidation increased [94 +/- 6 vs. 61 +/- 5 g (P < 0.05)], whereas CHO oxidation decreased [271 +/- 16 vs. 342 +/- 14 g (P < 0.05)] for Fat-adapt compared with HCHO. Tracer-derived estimates of plasma glucose uptake revealed no differences between treatments, suggesting muscle glycogen sparing accounted for reduced CHO oxidation. Direct assessment of muscle glycogen utilization showed a similar order of sparing (260 +/- 26 vs. 360 +/- 43 mmol/kg dry wt; P = 0.06). TT performance was 30.73 +/- 1.12 vs. 34.17 +/- 2.48 min for Fat-adapt and HCHO (P = 0.21). These data show significant metabolic adaptations with a brief period of high-fat intake, which persist even after restoration of CHO availability. However, there was no evidence of a clear benefit of fat adaptation to cycling performance.

Safety of commercial air travel following myocardial infarction.

BACKGROUND: Travelers occasionally suffer myocardial infarction (MI) while abroad. Existing guidelines recommend a 4- to 24-week convalescent period following MI before air travel should be permitted. HYPOTHESIS: Air travel may be undertaken safely in the early post-MI period. METHODS: The aeromedical transport records of two international medical assistance companies over a 3-yr period were reviewed. We identified 209 patients who suffered MI; 13 transported by private air ambulance were excluded. We reviewed the aeromedical transports of the remaining 196 adults carried on commercial aircraft between 3-53 d post-MI to investigate the safety of air travel in this group. Data were recorded regarding patient age; sex; location of MI; complications of MI; presence of medical escort; duration of flight(s); use of oxygen, medications, or cardiac monitoring during transport; and development of symptoms in flight. RESULTS: Within 7 d of their acute MI 3 patients (2%) were transported; 87 (44%) between days 8-14 post-MI; 65 (33%) between days 15-21; 27 (14%) between days 22-28; and 14 (7%) more than 28 d post-MI. Some 187 patients (95%) were transported without incident; 9 (5%) patients experienced symptoms requiring evaluation by the escorting physician. Of the 9, 6 problems occurred in patients being transported less than 14 d post-MI. Symptoms resolved spontaneously or immediately after physician intervention in all but one case. CONCLUSION: International aeromedical transport of patients may be safely accomplished 2-3 wk after an acute MI when an accompanying physician is present. Recommendations for delaying travel more than 4 wk after infarction are not supported by clinical experience and should be revised.

Body weight changes and voluntary fluid intakes during training and competition sessions in team sports.

Fluid losses (measured by body weight changes) and voluntary fluid intakes were measured in elite basketball, netball, and soccer teams during typical summer and winter exercise sessions to determine fluid requirements and the degree of fluid replacement. Each subject was weighed in minimal clothing before and immediately after training, weights, and competition sessions; fluid intake, duration of exercise, temperature and humidity, and opportunity to drink were recorded. Sweat rates were greatest during competition sessions and significantly lower during weights sessions for all sports. Seasonal variation in dehydration (%DH) was not as great as may have been expected, particularly in sports played indoors. Factors influencing fluid replacement during exercise included provision of an individual water bottle, proximity to water bottles during sessions, encouragement to drink, rules of the game, duration and number of breaks or substitutions, and awareness of personal sweat rates. Guidelines for optimizing fluid intakes in these three sports are provided.

Delayed presentation of unstable cervical spine injury with minimal symptoms.

Emergency physicians are less likely to suspect the presence of a severe or unstable cervical spine injury in patients who have been ambulatory since the traumatic episode. We present the case of a man with multiple cervical fractures and a 75% anterior subluxation of C6 and C7 who did not seek medical care for six weeks after falling from a height. Previous reports of delayed or occult cervical spine injuries are reviewed. Physicians must aggressively search for injuries whenever a history of neck pain is present or a strong mechanism of injury exists, even if the patient has been ambulatory for days or weeks following the injury.

Acute cholecystitis in the emergency department.

Acute cholecystitis is a frequent consideration in patients presenting to the emergency department with the challenging complaint of upper abdominal pain. It is estimated that 20% of American adults have gallstones, and of these a large percentage (about one-third) will at some point develop acute cholecystitis. The epidemiology and associated risk factors of acute cholecystitis are briefly reviewed along with the pathogenesis and clinical presentation of the disease. Finally, an approach to the diagnosis in the emergency department and suggested management is discussed including a comparison of the strengths and weaknesses of ultrasonography and hepatobilary scintigraphy.