Common methods to prescribe exercise intensity are based on fixed percentages of maximum rate of oxygen uptake (V˙O2max), peak work rate (WRpeak), maximal HR (HRmax). However, it is unknown how these methods compare to the current models to partition the exercise intensity spectrum. Purpose Thus, the aim of this study was to compare contemporary gold-standard approaches for exercise prescription based on fixed percentages of maximum values to the well-established, but underutilized, “domain” schema of exercise intensity. Methods One hundred individuals participated in the study (women, 46; men, 54). A cardiopulmonary ramp-incremental test was performed to assess V˙O2max, WRpeak, HRmax, and the lactate threshold (LT), and submaximal constant-work rate trials of 30-min duration to determine the maximal lactate steady-state (MLSS). The LT and MLSS were used to partition the intensity spectrum for each individual in three domains of intensity: moderate, heavy, and severe. Results V˙O2max in women and men was 3.06 ± 0.41 L·min−1 and 4.10 ± 0.56 L·min−1, respectively. Lactate threshold and MLSS occurred at a greater %V˙O2max and %HRmax in women compared with men (P < 0.05). The large ranges in both sexes at which LT and MLSS occurred on the basis of %V˙O2max (LT, 45%–74%; MLSS, 69%–96%), %WRpeak (LT, 23%–57%; MLSS, 44%–71%), and %HRmax (LT, 60%–90%; MLSS, 75%–97%) elicited large variability in the number of individuals distributed in each domain at the fixed-percentages examined. Conclusions Contemporary gold-standard methods for exercise prescription based on fixed-percentages of maximum values conform poorly to exercise intensity domains and thus do not adequately control the metabolic stimulus.

The oxygen uptake (V̇O2) at the respiratory compensation point (RCP) closely identifies with the maximal metabolic steady state. However, the power output (PO) at RCP cannot be determined from contemporary ramp-incremental exercise protocols. Purpose This study aimed to test the efficacy of a “step–ramp–step” (SRS) cycling protocol for estimating the PO at RCP and the validity of RCP as a maximal metabolic steady-state surrogate. Methods Ten heathy volunteers (5 women; age: 30 ± 7 yr; V̇O2max: 54 ± 6 mL·kg−1·min−1) performed in the following series: a moderate step transition to 100 W (MOD), ramp (30 W·min−1), and after 30 min of recovery, step transition to ~50% POpeak (HVY). Ventilatory and gas exchange data from the ramp were used to identify the V̇O2 at lactate threshold (LT) and RCP. The PO at LT was determined by the linear regression of the V̇O2 versus PO relationship after adjusting ramp data by the difference between the ramp PO at the steady-state V̇O2 from MOD and 100 W. Linear regression between the V̇O2–PO values associated with LT and HVY provided, by extrapolation, the PO at RCP. Participants then performed 30-min constant-power tests at the SRS-estimated RCP and 5% above this PO. Results All participants completed 30 min of constant-power exercise at the SRS-estimated RCP achieving steady-state V̇O2 of 3176 ± 595 mL·min−1 that was not different (P = 0.80) from the ramp-identified RCP (3095 ± 570 mL·min−1) and highly consistent within participants (bias = −26 mL·min−1, r = 0.97, coefficient of variation = 2.3% ± 2.8%). At 5% above the SRS-estimated RCP, four participants could not complete 30 min and all, but two exhibited non–steady-state responses in blood lactate and V̇O2. Conclusions In healthy individuals cycling at their preferred cadence, the SRS protocol and the RCP are capable of accurately predicting the PO associated with maximal metabolic steady state.

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.

During exhaustive ramp-incremental cycling tests, the incidence of O2 uptake (V̇O2) plateaus is low. To verify the attainment of maximum V̇O2 (V̇O2max), it is recommended that a trial at a power output (PO) corresponding to 110% of the ramp-derived peak (POpeak) is performed. It remains unclear whether verification trials set at this PO can be tolerated for long enough to allow attainment of V̇O2max. Eleven recreationally-trained individuals performed five ramp tests of varying slope (5, 10, 15, 25, 30 W·min-1), each followed, in series, by two verification trials: the 1st at 110%POpeak of the 25 W·min-1 ramp and the 2nd at 110% POpeak attained in the preceding ramp test. Exercise duration of the 1st verification trial was on average 81±15 s (CV=9±3%) versus 162±32, 121±24, 103±15, and 73±10 s for the 2nd verification trials at 110% of POpeak of the 5, 10, 15, and 30 W·min-1 ramp tests, respectively (P<0.05). Compared to the highest V̇O2 recorded during ramp tests, V̇O2 from the subsequent verification trials were not different for the 5, 10, and 15 W·min-1 ramp tests (P>0.05), but lower for the 25 and 30 W·min-1 ramp tests (P<0.05). Verification trials at 110%POpeak of rapidly-incrementing ramp tests (i.e., 25 W·min-1) were not sustained for long enough to allow the attainment of V̇O2max. With commonly used rapidly-incrementing ramp tests engendering exhaustion within 8-12 min, verification trials <POpeak should be preferred as they can be sustained sufficiently long to allow the attainment of V̇O2max.

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