Effect of induced metabolic alkalosis on sweat composition in men

Abstract

To determine whether induced metabolic alkalosis affects sweat composition, 10 males cycled for 90 min at 62.5 ± 1.3% peak oxygen uptake, on two separate occasions. Subjects ingested either empty capsules (placebo) or capsules containing NaHCO3– (0.3 g kg–1 body mass; six equal doses) over a 2-h period, which commenced 3 h prior to exercise. Arterialized-venous blood samples were drawn prior to and after 15, 30, 60 and 90 min of exercise. Sweat was aspirated at the end of exercise from a patch located on the right scapula region. NaHCO3– ingestion elevated blood pH, [HCO3–] and serum [Na+], whereas serum [Cl–] and [K+] were reduced, both at rest and during exercise (P < 0.05). Sweat pH was greater in the NaHCO3– trial (6.24 ± 0.18 vs. 6.38 ± 0.18; P < 0.05), whereas sweat [Na+] (49.5 ± 4.8 vs. 50.2 ± 4.3 mEq L–1), [Cl–] (37.5 ± 5.1 vs. 39.3 ± 4.2 mEq L–1) and [K+] (4.66 ± 0.19 vs. 4.64 ± 0.34 mEq L–1) did not differ between trials (P > 0.05). Sweat [HCO3–] (2.49 ± 0.58 vs. 3.73 ± 1.10 mEq L–1) and [lactate] (8.92 ± 0.79 vs. 10.51 ± 0.32 mmol L–1) tended to be greater after NaHCO3– ingestion, although significance was not reached (P=0.07 and P=0.08, respectively). These data indicate that induced metabolic alkalosis can modify sweat composition, although it is unclear whether the secretory coil, reabsorptive duct, or both are responsible for this alteration.