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Blood sodium concentration of tetraplegics during exercise has not been investigated. This study aimed to measure blood sodium changes in relation to fluid intakes and thermal comfort in tetraplegics during wheelchair rugby training. Twelve international male wheelchair rugby players volunteered, and measures were taken during 2 training sessions. Body mass, blood sodium concentration, and subjective thermal comfort using a 10-point scale were recorded before and after both training sessions. Fluid intake and the distance covered were measured during both sessions. The mean (SD) percentage changes in body mass during the morning and afternoon training sessions were +0.4%1 (0.65%) and +0.69% (1.24%), respectively. There was a tendency for fluid intake rate to be correlated with the percentage change in blood sodium concentration (p = .072, r ² = .642) during the morning training session; this correlation reached significance during the afternoon session (p = .004, r ² = .717). Fluid intake was significantly correlated to change in thermal comfort in the morning session (p = .018, r ² = .533), with this correlation showing a tendency in the afternoon session (p = .066, r ² = .151). This is the first study to investigate blood sodium concentrations in a group of tetraplegics. Over the day, blood sodium concentrations significantly declined; 2 players recorded blood sodium concentrations of 135 mmol/L, and 5 recorded blood sodium concentrations of 136 mmol/L. Excessive fluid intake as a means of attenuating thermal discomfort seems to be the primary cause of low blood sodium concentrations in tetraplegic athletes. Findings from this study could aid in the design of fluid-intake strategies for tetraplegics.

Postexercise protein and sodium supplementation may aid recovery and rehydration. Preserved beef provides protein and contains high quantities of sodium that may alter performance related variables in runners. The purpose of this study was to determine the effects of consuming a commercial beef product postexercise on sodium and water balance. A secondary objective was to characterize effects of the supplementation protocols on hydration, blood pressure, body mass, and running economy. Eight trained males (age = 22 ± 3 y, V̇O_2max = 66.4 ± 4.2 ml·kg^-1·min^-1) completed three identical weeks of run training (6 run·wk^-1, 45 ± 6 min·run^-1, 74 ± 5% HRR). After exercise, subjects consumed either, a beef nutritional supplement (beef jerky; [B]), a standard recovery drink (SRD), or SRD+B in a randomized counterbalanced design. Hydration status was assessed via urinary biomarkers and body mass. No main effects of treatment were observed for 24 hr urine volume (SRD, 1.7 ± 0.5; B, 1.8 ± 0.6; SRD+B, 1.4 ± 0.4 L·d^-1), urine specific gravity (1.016 ± 0.005, 1.018 ± 0.006, 1.017 ± 0.006) or body mass (68.4 ± 8.2, 68.3 ± 7.7, 68.2 ± 8.1 kg). No main effect of treatment existed for sodium intake—loss (-713 ± 1486; -973 ± 1123; -980 ± 1220 mg·d^-1). Mean arterial pressure (81.0 ± 4.6, 81.1 ± 7.3, 83.8 ± 5.4 mm Hg) and average exercise running economy (V̇O₂: SRD, 47.9 ± 3.2; B, 47.2 ± 2.6; SRD+B, 46.2 ± 3.4 ml·kg-¹·min^-1) was not affected. Urinary sodium excretion accounted for the daily sodium intake due to the beef nutritional supplement. Findings suggest the commercial beef snack is a viable recovery supplement following endurance exercise without concern for hydration status, performance decrements, or cardiovascular consequences.

Weight categorized athletes use a variety of techniques to induce rapid weight loss (RWL) in the days leading up to weigh in. This study examined the fluid and electrolyte balance responses to 24-hr fluid restriction (FR), energy restriction (ER) and fluid and energy restriction (F+ER) compared with a control trial (C), which are commonly used techniques to induce RWL in weight category sports. Twelve subjects (six male, six female) received adequate energy and water (C) intake, adequate energy and restricted water (~10% of C; FR) intake, restricted energy (~25% of C) and adequate water (ER) intake or restricted energy (~25% of C) and restricted (~10% of C) water intake (F+ER) in a randomized counterbalanced order. Subjects visited the laboratory at 0 hr, 12 hr, and 24 hr for blood and urine sample collection. Total body mass loss was 0.33% (C), 1.88% (FR), 1.97% (ER), and 2.44% (F+ER). Plasma volume was reduced at 24 hr during FR, ER, and F+ER, while serum osmolality was increased at 24 hr for FR and F+ER and was greater at 24 hr for FR compared with all other trials. Negative balances of sodium, potassium, and chloride developed during ER and F+ER but not during C and FR. These results demonstrate that 24 hr fluid and/or energy restriction significantly reduces body mass and plasma volume, but has a disparate effect on serum osmolality, resulting in hypertonic hypohydration during FR and isotonic hypohydration during ER. These findings might be explained by the difference in electrolyte balance between the trials.

To determine the effectiveness of 3 commonly used beverages in restoring fluid and electrolyte balance, 8 volunteers dehydrated by 1.94% ± 0.17% of body mass by intermittent exercise in the heat, then ingested a carbohydrate-electrolyte solution (Gatorade), carbonated water/apple-juice mixture (Apfelschorle), and San Benedetto mineral water in a volume equal to 150% body-mass loss. These drinks are all are perceived to be effective rehydration solutions, and their effectiveness was compared with the rehydration effectiveness of Evian mineral water, which is not perceived in this way by athletes. Four hours after rehydration, the subjects were in a significantly lower hydration status than the pretrial situation on trials with Apfelschorle (–365 ± 319 mL, P = 0.030), Evian (–529 ± 319 mL, P < 0.0005), and San Benedetto (–401 ± 353 mL, P = 0.016) but were in the same hydration status as before the dehydrating exercise on Gatorade (–201 ± 388 mL, P = 0.549). Sodium balance was negative on all trials throughout the study; only with Apfelschorle did subjects remain in positive potassium balance. In this scenario, recovery of fluid balance can only be achieved when significant, albeit insufficient, quantities of sodium are ingested after exercise. There is a limited range of commercially available products that have a composition sufficient to achieve this, even though the public thinks that some of the traditional drinks are effective for this purpose.