Convergent validity of a simplified device and relationship between blood lactate and salivary lactate after a vertical squat jump in healthy non-athletes.

The study used healthy participants only, and the vertical squat jump test included only males, so it does not show what happens in patients or women. Only 4 participants were analysed in the device test and 15 in the vertical squat jump analysis, so the agreement estimates are based on a very small sample. Lactate Pro 2 cannot measure saliva lactate below 0.4 mmol/L or less; 'Lo' readings forced exclusion of 1 of 5 device-test participants and 5 of 20 vertical squat jump participants. The paper says all 20 vertical squat jump participants were analyzed, but it also says 5 were excluded from analysis and Table 4 reports 15 analysed. Absolute saliva values differed between Lactate Pro 2 and the automatic analyzer, so the comparison relied on normalized values rather than raw concentrations. The vertical squat jump was only one exercise task, and the authors note the saliva-blood time lag may depend on the exercise used. No clinical exercise prescription, patient outcome, or treatment effect was tested.

This study was supported by an Intramural Research Grant (26-6) for Neurological and Psychiatric Disorders of the National Center of Neurology and Psychiatry and a Grant-in-Aid for Scientific Research (19K12862 to H.N.). The authors declared no conflict of interest.

Do not use saliva lactate from Lactate Pro 2 as a direct replacement for blood lactate after a vertical squat jump. The device could not measure baseline saliva in 5 of 20 participants, and blood and saliva lactate did not agree at the same time points.