Sweat Rates, Sweat Sodium Concentrations, and Sodium Losses in 3 Groups of Professional Football Players

Abstract

Context: Sweat sodium losses have never been reported in a large cohort of American football players.Objective: To compare sweat rates (SwtRs), sweat sodium concentrations (SwtNa + ), and sodium losses in 3 groups of players (backs and receivers [BK], linebackers and quarterbacks [LB/QB], and linemen [LM]) to determine if positional differences and, therefore, size differences exist.Design: Observational study. Setting: Data were collected during practices in the second week of 2 consecutive training camps. The wet bulb globe temperature was 78.56F 6 3.56F (25.96C 6 1.96C).Patients or Other Participants: Eighteen BK, 12 LB/QB, and 14 LM volunteered.Intervention(s): Sterile sweat patches were applied to the right forearm after the skin was appropriately cleaned. The patches were removed during practice, placed in sterile tubes, centrifuged, frozen, and later analyzed by flame photometry.Main Outcome Measure(s): Sweat rate, SwtNa + , and sodium loss. We calculated SwtR by change in mass adjusted for urine produced and fluids consumed divided by practice time in hours.Results: Other than age, physical characteristics were different among groups (P , .001). The SwtR was different among groups (F 2,41 5 7.3, P 5 .002). It was lower in BK (1.42 6 0.45 L/h) than in LB/QB (1.98 6 0.49 L/h) (P , .05) and LM (2.16 6 0.75 L/h) (P , .01), but we found no differences between SwtRs for LB/QB and LM. The SwtNa + was not different among groups (BK 5 50 6 16 mEq/L, LB/QB 5 48.2 6 23 mEq/L, and LM 5 52.8 6 25 mEq/L) and ranged from 15 to 99 mEq/L. Sweat sodium losses ranged from 642 mg/h to 6.7 g/ h, and findings for group comparisons approached significance (P 5 .06). On days when players practiced 4.5 hours, calculated sodium losses ranged from 2.3 to 30 g/d.Conclusions: The BK sweated at lower rates than did the midsized LB/QB and large LM, but LB/QB sweated similarly to LM. Sweat sodium concentration and daily sodium losses ranged considerably. Heavy, salty sweaters require increased dietary consumption of sodium during preseason.

Sweating Is Greater in NCAA Football Linemen Independently of Heat Production

“…Furthermore, despite heat production per unit BSA being the same and heat production per unit mass actually being ~25% lower in linemen (6.0 ± 0.5 Wkg ') in comparison with backs (8.2 + 0.8 Wkg ') by virtue of their significantly lower surface area-to-mass ratio, Ttorc was in fact ~0.5°C higher in linemen at the end of 60 min of exercise. Although previous research with both NFL and NCAA football programs have demonstrated greater wholebody sweating and larger elevations in Tcore in linemen (12,13,15,16), the experimental eonditions were such that previous studies could not identify whether different levels of heat stress were simply due to differences in metabolic heat produetion or also differences in the potential for heat dissipation. Our data suggest that football linemen have a compromised potential for heat dissipation independently of any difference in metabolic heat production.…”

Sweating Rate and Sweat Sodium Concentration in Athletes: A Review of Methodology and Intra/Interindividual Variability

“…As this and other studies have shown, WBSR typically ranges from approximately 0.5 to approximately 2.0 L/h [2, 24, 96]. WBSR can be >3.0 L/h [9, 15, 96, 137–141] but this is relatively rare (approximately 2% of athletes in Fig. 1a) and is usually associated with extreme circumstances (related to environment, exercise intensity, and/or large body mass) [96].…”

Physiology of sweat gland function: The roles of sweating and sweat composition in human health

“…According to normative data, a forearm sweat [Na] of 80 mmol/L is approximately two standard deviations above average [156] (Figure 5). "Salty sweat" has been observed in both healthy individuals [151,263,266,268,269] and cystic fibrosis patients [174][175][176]259,263,267,270]. Regardless of the underlying cause of the high sweat [Na] and [Cl], case reports and theoretical models alike demonstrate that excessive electrolyte losses through sweating can contribute to the development of Na and Cl imbalances.…”