Comparison of pilocarpine- versus exercise-induced sweat sodium concentration across exercise intensities in trained...

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.