The effect of a standardized verbal encouragement protocol on peak oxygen uptake during incremental treadmill testing in healthy individuals: A randomized cross-over trial

Peak oxygen uptake (VO2peak) is considered a vital indicator of health and physical fitness that is often measured during incremental exercise testing. While previous research has shown that the attained VO2peak during exercise testing can be influenced by verbal encouragement, no or limited details were provided on the verbal encouragement protocol, hereby hampering implementation in clinical practice or research. Moreover, it remains unknown whether motivation modulates the effect of verbal encouragement. This study aimed to develop and examine the influence of a standardized verbal encouragement protocol on the achieved VO2peak, time to exhaustion (TTE), peak heart rate (HRpeak), and peak respiratory exchange ratio (RERpeak) during incremental treadmill testing. As a secondary aim, we investigated whether motivation modulated the effect of verbal encouragement on VO2peak. 24 healthy volunteers performed two incremental treadmill runs with 1 week in between and received verbal encouragement during only one of the tests. Motivation toward exercise was measured using the behavioral regulation in exercise questionnaire-2 (BREQ-2) questionnaire. VO2peak (Delta 2.10 mL/kg/min, p < 0.001) and RERpeak (Delta 2%, p = 0.042) were significantly higher with verbal encouragement. In contrast, HRpeak (Delta 1.5 beats/min, p = 0.225) and TTE (Delta 1.5%, p = 0.348) were not significantly different between conditions. Exercise motivation showed a weak and nonsignificant association with the change in VO2peak between tests (r -0.19, R-2 0.037, SEE 2.88, and p = 0.367). These findings show that verbal encouragement leads to higher physiological outcomes during incremental treadmill testing, but the magnitude of this effect is not higher for individuals with lower levels of pretest motivation.