Establishing the V̇o₂ versus constant-work-rate relationship from ramp-incremental exercise: simple strategies for an unsolved problem

Abstract

The dissociation between constant work rate of O2 uptake (V̇o2) and ramp V̇o2 at a given work rate might be mitigated during slowly increasing ramp protocols. This study characterized the V̇o2 dynamics in response to five different ramp protocols and constant-work-rate trials at the maximal metabolic steady state (MMSS) to characterize 1) the V̇o2 gain (G) in the moderate, heavy, and severe domains, 2) the mean response time of V̇o2 (MRT), and 3) the work rates at lactate threshold (LT) and respiratory compensation point (RCP). Eleven young individuals performed five ramp tests (5, 10, 15, 25, and 30 W/min), four to five time-to-exhaustions for critical power estimation, and two to three constant-work-rate trials for confirmation of the work rate at MMSS. G was greatest during the slowest ramp and progressively decreased with increasing ramp slopes (from ~12 to ~8 ml·min−1·W−1, P < 0.05). The MRT was smallest during the slowest ramp slopes and progressively increased with faster ramp slopes (1 ± 1, 2 ± 1, 5 ± 3, and 10 ± 4, 15 ± 6 W, P < 0.05). After “left shifting” the ramp V̇o2 by the MRT, the work rate at LT was constant regardless of the ramp slope (~150 W, P > 0.05). The work rate at MMSS was 215 ± 55 W and was similar and highly correlated with the work rate at RCP during the 5 W/min ramp ( P > 0.05, r = 0.99; Lin’s concordance coefficient = 0.99; bias = −3 W; root mean square error = 6 W). Findings showed that the dynamics of V̇o2 (i.e., G) during ramp exercise explain the apparent dichotomy existing with constant-work-rate exercise. When these dynamics are appropriately “resolved”, LT is constant regardless of the ramp slope of choice, and RCP and MMSS display minimal variations between each other. NEW & NOTEWORTHY This study demonstrates that the dynamics of V̇o2 during ramp-incremental exercise are dependent on the characteristics of the increments in work rate, such that during slow-incrementing ramp protocols the magnitude of the dissociation between ramp V̇o2 and constant V̇o2 at a given work rate is reduced. Accurately accounting for these dynamics ensures correct characterizations of the V̇o2 kinetics at ramp onset and allows appropriate comparisons between ramp and constant-work-rate exercise-derived indexes of exercise intensity.

Menstrual and oral contraceptive cycle phases do not affect submaximal and maximal exercise responses

“…From a submaximal perspective, ventilatory thresholds corresponding to GET and RCP, which are important markers of exercise intensities, were also unaffected by the menstrual and oral contraceptive cycle phases. Previous literature examining these thresholds are limited in number when investigating within the menstrual and oral contraceptive cycles, yet the present study is in agreement with the few studies showing no menstrual cycle phase effects on GET and RCP …”

Fractal Correlation Properties of Heart Rate Variability: A New Biomarker for Intensity Distribution in Endurance Exercise and Training Prescription?

“…Whether this is related to underlying differences in biologic mechanism or simply from protocol variation is unclear (Plowman and Smith, 2017 ). Finally, both gas exchange and lactate testing strongly depend on exercise test protocol, which may or may not produce threshold values equivalent to constant load exercise (Iannetta et al, 2019 ). Even if correction methods are applied, transfer of results measured by laboratory treadmill or cycle ergometry to actual trail running, skiing or road cycling may be altered through changes in biomechanical efficiency (Beneke et al, 2011 ).…”

Constant Load Exercise at Gas Exchange Threshold is Accompanied by a Distinct Elevation in Blood Lactate Level

“…It is known that for a stepwise initiation of CL-exercise, there is a delay in the increase of VO 2 , which is known as the mean response time. This delay in the response to VO 2 increases with exercise intensity [32,33]. Therefore, when the work rate at the GET VO 2 is taken as the GET work rate, it may result in overestimation of the GET work rate because the work rate is, in a sense, ahead of VO 2 .…”