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

Abstract

Athletes lose water and electrolytes as a consequence of thermoregulatory sweating during exercise and it is well known that the rate and composition of sweat loss can vary considerably within and among individuals. Many scientists and practitioners conduct sweat tests to determine sweat water and electrolyte losses of athletes during practice and competition. The information gleaned from sweat testing is often used to guide personalized fluid and electrolyte replacement recommendations for athletes; however, unstandardized methodological practices and challenging field conditions can produce inconsistent/inaccurate results. The primary objective of this paper is to provide a review of the literature regarding the effect of laboratory and field sweat-testing methodological variations on sweating rate (SR) and sweat composition (primarily sodium concentration [Na+]). The simplest and most accurate method to assess whole-body SR is via changes in body mass during exercise; however, potential confounding factors to consider are non-sweat sources of mass change and trapped sweat in clothing. In addition, variability in sweat [Na+] can result from differences in the type of collection system used (whole body or localized), the timing/duration of sweat collection, skin cleaning procedure, sample storage/handling, and analytical technique. Another aim of this paper is to briefly review factors that may impact intra/interindividual variability in SR and sweat [Na+] during exercise, including exercise intensity, environmental conditions, heat acclimation, aerobic capacity, body size/composition, wearing of protective equipment, sex, maturation, aging, diet, and/or hydration status. In summary, sweat testing can be a useful tool to estimate athletes’ SR and sweat Na+ loss to help guide fluid/electrolyte replacement strategies, provided that data are collected, analyzed, and interpreted appropriately.

Soft, Skin‐Interfaced Microfluidic Systems with Wireless, Battery‐Free Electronics for Digital, Real‐Time Tracking of Sweat Loss and Electrolyte Composition

“…In both cases, exercise induces higher rates of sweating than sauna exposure, and the chloride concentrations are proportional to sweat rate. These trends are similar to those published previously using other approaches . Figure f–i compares regional sweating on four subjects.…”

Human Sweat Analysis Using a Portable Device Based on a Screen‐printed Electrolyte Sensor

“…and Baker, et al. . The rise in sweat rate is also consistent to the visible observation during the ergometer tests in our work.…”

Effects of humidity on skin friction against medical textiles as related to prevention of pressure injuries

“…These results were probably obtained because of the relatively high mineral content in saline and sweat. Specifically, the sweat that we used was collected from athletes during the first 30 minutes of practice and was hence characterised by a higher mineral content compared with subsequent sweat samples . When water evaporates from the skin surface, the remaining salts generate a thin textured layer, which contributes to a higher COF compared with liquids with lower mineral content .…”