Sweat rate and fluid turnover in American football players compared with runners in a hot and humid environment

Abstract

Objectives: To determine sweat rate (SwR) and fluid requirements for American footballers practicing in a hot, humid environment compared with cross country runners in the same conditions. Methods: Fifteen subjects, 10 footballers and five runners, participated. On the 4th and 8th day of preseason two a day practices, SwR during exercise was determined in both morning and afternoon practices/runs from the change in body mass adjusted for fluids consumed and urine produced. Unpaired t tests were used to determine differences between groups. Results: Overall SwR measured in litres/h was higher in the footballers than the cross country runners (2.14 (0.53) v 1.77 (0.4); p,0.01). Total sweat loss in both morning (4.83 (1.2) v 1.56 (0.39) litres) and afternoon (4.8 (1.2) v 1.97 (0.28) litres) practices/runs, and daily sweat losses (9.4 (2.2) v 3.53 (0.54) litres) were higher in the footballers (p,0.0001). The footballers consumed larger volumes of fluid during both morning and afternoon practices/runs (23.9 (8.9) v 5.5 (3.1) ml/min and 23.5 (7.3) v 13.6 (5.6) ml/min; p,0.01). For complete hydration, the necessary daily fluid consumption calculated as 130% of daily sweat loss in the footballers was 12.2 (2.9) litres compared with 4.6 (0.7) litres in the runners (p,0.0001). Calculated 24 hour fluid requirements in the footballers ranged from 8.8 to 19 litres. Conclusions: The American footballers had a high SwR with large total daily sweat losses. Consuming large volumes of hypotonic fluid may promote sodium dilution. Recommendations for fluid and electrolyte replacement must be carefully considered and monitored in footballers to promote safe hydration and avoid hyponatraemia.

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

“…Although daily sodium intake is likely adequate for most athletes in the United States, this may not hold true for football players who are known to lose up to 15 L of sweat per day during preseason training. 11 Investigators have reported on SwtNa + and sodium losses during training and games in European football (soccer) players 13,[16][17][18][19] and on SwtRs and sweat losses in endurance athletes, such as runners 3,20 ; however, few data on American football players are available. We have reported differences in SwtRs between LM and BK, but we have not studied the midsized players, such as linebackers, fullbacks, and quarterbacks (LB/QB).…”

“…Mean daily sweat losses of between 8 and 10 L/d were reported in a series of studies [3][4][5]9 involving both professional and collegiate football players. Using average sweat sodium concentrations (SwtNa + ) (approximately 50 mEq/ L), 13 calculated daily sodium losses in excess of 10 g/d have occurred in some of these players.…”

“…N Football players need to be educated about the dangers of overdrinking. R ecent field investigations [1][2][3][4][5][6][7][8][9][10][11] of intestinal temperatures, sweat rates (SwtRs), sweat losses, serum electrolytes, and urinary measures of hydration have vastly improved our understanding of thermoregulation and fluid balance in American football players during preseason training. Higher core temperatures and greater SwtRs have been documented 5,9,10 in large interior linemen (LM) than in running and defensive backs and wide receivers (BK).…”

Loaded and Unloaded Marching: Implications for Fluid Replacement

“…Average sweat rate during physical activity can vary from 0.5 L·h -1 to more than 2.5 L·h -1 [5,6] however these results portray a variety of exercise types, intensities and environmental conditions all of which affect sweat production. It is important to know that there are considerable variations in fluid loss between individuals in different activities and even within the same activity [22][23][24][25]. The sweat loss in the participants in the present study ranged from 0.7 L·h -1 to 1.5 L·h -1 ; factors such as genetic predisposition, heat acclimatization state and metabolic efficiency will influence sweat rates for each individual [6].…”

Research of Interindividual Differences in Physiological Response under Hot-Dry and Warm-Wet Climates

“…The hot-dry and warm-wet climates have a great influence on physiological systems, such as the nervous system, urinary system, digestive system, and immune system [7][8][9][10][11]. When working in the extreme climates, people would have a risk of experiencing the change of physiological parameters, such as increases of body temperature, heart rate, and sweat production [12][13][14][15][16][17]. The high temperature may reduce work efficiency and cause emotional instability, which will lead to the increase of industrial accident rates [18,19], so it is necessary to study the influencing factors on physiological parameters.…”