Collector Transit and Sweat Lactate Timing during Intermittent Exercise

Abstract

During intermittent exercise, an electronic sweat-lactate timestamp can fall in a different work or recovery interval from the entry of the sampled liquid. This article examines collector transit, reservoir carryover and the precision of sweat-derived physiological endpoints. This study examined nine human exercise investigations. Participant counts, sampling sites, exercise intervals, blood comparisons and prediction errors were evaluated alongside conservation-of-volume and solute-balance equations for plug transport and a mixed reservoir. In 40 men, sweat-minus-blood threshold timing had a mean difference of +19.3 s and individual agreement limits of −126.2 to +164.7 s. In 24 swimmers, four sweat thresholds could not be determined during interrupted testing. For a calculated 10-μL plug path supplied at 4 and 0.25 μL min⁻¹ during alternating 2-min work and recovery intervals, liquid entering at the first work onset reaches the sensor at 4.375 min, during the second effort. A separate 10-μL mixed reservoir retains 7.81% of its starting contents after 12 min and reaches 95% replacement at 13.114 min. That replacement fraction limits residual error to 5% of a concentration step, rather than 5% of total measurement error. Individual-bout interpretation requires sensing-path flow, the upstream liquid volume and an inlet-time interval, followed by independent testing of the concentration, threshold or prediction endpoint.