# Comparison of pilocarpine‐ versus exercise‐induced sweat sodium concentration across exercise intensities in trained athletes

## TL;DR

This study compares sodium levels in sweat collected during exercise and at rest using pilocarpine in trained athletes, finding that the method is most accurate at moderate exercise intensity.

## Contribution

The study establishes intensity-dependent agreement between pilocarpine-induced and exercise-induced sweat sodium concentrations in trained athletes.

## Key findings

- Pilocarpine overestimates exercise sodium at low intensity and underestimates at high intensity.
- Pilocarpine sodium remains stable across multiple testing sessions.
- The method is most accurate at moderate exercise intensity.

## Abstract

Pilocarpine‐induced sweat testing offers a laboratory‐based method for assessing sweat composition, but its comparability to exercise sweating remains unclear. Establishing a relationship between this resting test and exercise sweating is important for practitioners when in‐exercise sampling is impractical. This study compared sweat sodium concentration ([Na+]) between pilocarpine‐ and exercise‐induced sweat across exercise intensities. 15 well‐trained athletes (10 male, 5 female) performed 3 × 20 min cycling bouts (low [LO], moderate [MOD], and high [HI] intensity) and 4 pilocarpine sweat tests. Sweat was collected from the forearm using pilocarpine iontophoresis at rest, and a macroduct collector during exercise. Exercise [Na+] increased with intensity (LO = 44.5 ± 15.6, MOD = 54.9 ± 16.9, HI = 61.3 ± 21.3 mmol·L−1; p < 0.001) alongside sweat rate (LO = 0.62 ± 0.2, MOD = 1.26 ± 0.3, HI = 1.92 ± 0.6 L·h−1). Pilocarpine [Na+] overestimated exercise [Na+] at LO, matched at MOD, and underestimated at HI. Pilocarpine [Na+] was stable across four visits (p = 0.263, coefficient of variation 5.5%). In trained athletes, pilocarpine testing shows intensity‐dependent agreement with exercise [Na+]: closest at moderate workloads, with predictable bias at the extremes. Under standardized conditions, it provides a practical alternative for hydration planning when exercise testing is not feasible.