Sweat composition: comparison of collection methods and effects of exercise intensity

Abstract

SummaryThe objectives of this study were to compare sweat collection techniques and determine effect of low and high intensity exercise on the composition and osmolality of equine sweat in exercise trained Thoroughbred horses. Sweat collection sites included the neck and thorax, bilaterally and behind the girth ventrally. Sweat was collected in cotton gauze, either exposed to the air or contained within a plastic pouch, from sealed pouches, with or without application of vaseline to the skin, and as it dripped off the skin behind the girth (free catch). There were differences in the ionic composition of sweat collected by different techniques during and after low (50% OOzmax) and after high (90% OOZ,,,~~) intensity exercise. These changes were most consistent where collection technique minimised evaporative losses. With regard to collection method, ionic concentrations and osmolality were lowest in samples obtained from sealed pouches without vaseline on the skin. In samples obtained from cotton gauze and by free catch, osmolality, [Na] and [Cl] were significantly increased when compared with sweat collected from sealed pouches. In samples collected from sealed pouches during low intensity exercise, osmolality increased 11 %, [Na] and [Cl] increased 26% and 9%, respectively and [K] decreased 14%. Osmolality and the concentrations of these ions did not change during recovery. In contrast, osmolality increased by 12% in the first 5 min following high intensity exercise. After both intensities of exercise, there was a significant decrease in the concentration of protein in sweat collected by all methods. Results indicate that collection technique had a marked effect on composition of sweat as demonstrated by increased osmolality and increased concentrations of Na and CI in sweat collected in cotton gauze and by free catch.

Effects of Different Oral Doses of Sodium Chloride on the Basal Acid-Base and Mineral Status of Exercising Horses Fed Low Amounts of Hay

“…Since equine sweat is rich in sodium, potassium and chloride [3], [4], [5], [6], [7], [8], diets marginal in these electrolytes may cause disturbances of fluid and mineral homeostasis and therefore potentially health problems in exercised horses [9]. However, recently the value of supplementing, especially in the non-endurance horse, at the currently recommended levels has been questioned and this topic has become highly controversial [10].…”

“…Spooner et al [18] observed a comparatively low sodium content in the sweat of Arabian horses. Evaporation of water during sweat collection may lead to an overestimate of the electrolyte content of sweat [5]. In addition, sweat losses show considerable variation, and they are not very closely linked to the intensity of work but also to other factors such as environmental temperature and individual horse [19].…”

Sweat composition in Arabian horses performing endurance exercise on forage‐based, low Na rations

“…1995b). Comparing Ca and Mg to values reported by McCutcheon et al . (1995b), Ca values obtained here are greater (6.6–12 mmol/l vs. 4.8 mmol/l), while Mg is quite similar (1.6–3.3 mmol/l vs. 3.3 mmol/l).…”

“…Comparing the sweat concentrations of Na, K, and Cl to those previously reported (Table 3), the Na concentration we observed (88–104 mmol/l depending on diet) in this study was clearly lower than the previously reported range (range 110–249). This may be the result of a difference in collection method, as some of the previous studies technique may have allowed sweat to evaporate which would have falsely increased the concentrations reported (McCutcheon et al . 1995b).…”

“…Concentrations decreased early on in the exercise test, with significant changes occurring from after bout 1 (the completion of 15 km) to after bout 2 (completion of 30 km); Mg further decreased by the end of the exercise bout. Both sweat Ca and Mg concentrations have previously been shown to decrease over the course of an exercise bout (McCutcheon et al . 1995b).…”