Application of V̇o 2 to the Critical Power Model to Derive the Critical V̇o 2

Abstract

Succi, PJ, Dinyer, TK, Byrd, MT, Voskuil, CC, and Bergstrom, HC. Application of V Ȯ2 to the critical power model to derive the critical V Ȯ2 . J Strength Cond Res 36(12): 3374-3380, 2022-The purposes of this study were to (a) determine whether the critical power (CP) model could be applied to V Ȯ2 to estimate the critical V Ȯ2 (CV Ȯ2 ) and (b) to compare the CV Ȯ2 with the V Ȯ2 at CP (V Ȯ2 CP), the ventilatory threshold (VT), respiratory compensation point (RCP), and the CV Ȯ2 without the V Ȯ2 slow component (CV Ȯ2 slow). Nine subjects performed a graded exercise test to exhaustion to determine V Ȯ2 peak, VT, and RCP. The subjects performed 4 randomized, constant power output work bouts to exhaustion. The time to exhaustion (T Lim ), the total work (W Lim ), and the total volume of oxygen consumed with (TV Ȯ2 ) and without the slow component (TV Ȯ2 slow) were recorded during each trial. The linear regressions of the TV Ȯ2 vs. T Lim , TV Ȯ2 slow vs. T Lim , and W Lim vs. T Lim relationship were performed to derive the CV Ȯ2 , CV Ȯ2 slow, and CP, respectively. A 1-way repeated-measures analysis of variance (p # 0.05) with follow-up Sidak-Bonferroni corrected pairwise comparisons indicated that CV Ȯ2 (42.49 6 3.22 ml•kg 21 •min 21 ) was greater than VT (30.80 6 4.66 ml•kg 21 •min 21 ; p , 0.001), RCP (36.74 6 4.49 ml•kg 21 •min 21 ; p 5 0.001), V Ȯ2 CP (36.76 6 4.31 ml•kg 21 •min 21 ; p , 0.001), and CV Ȯ2 slow (38.26 6 2.43 ml•kg 21 •min 21 ; p , 0.001). However, CV Ȯ2 slow was not different than V Ȯ2 CP (p 5 0.140) or RCP (p 5 0.235). Thus, the CP model can be applied to V Ȯ2 to derive the CV Ȯ2 and theoretically is the highest metabolic steady state that can be maintained for an extended period without fatigue. Furthermore, the ability of the CV Ȯ2 to quantify the metabolic cost of exercise and the inefficiency associated with the V Ȯ2 slow component may provide a valuable tool for researchers and coaches to examine endurance exercise.

Metabolic and Perceptual Responses to Constant Heart Rate Exercise at Vigorous Intensities in Women

“…Although the desired exercise intensities are identified based on a metabolic (oxygen consumption ( VO 2 )) rate, percentages of HR peak or the corresponding ratings of perceived exertion (RPE) are commonly used to prescribe exercise intensities because they are more practical than measuring VO 2 during an exercise bout (1,2). These exercise recommendations include a range of very light to moderate (30%-59% VO 2 R or HR R , <57%-76% HR peak , <37%-63% VO 2peak , RPE <9-13), vigorous (60%-89% VO 2 R or HR R , 77%-95% HR peak , 64%-90% VO 2peak , RPE [14][15][16][17], and near maximal (≥90% VO 2 R or HR R , ≥91% VO 2peak , ≥96% HR peak ) exercise intensities that are performed most days of the week at an intensity low enough to be sustained for 20 to 60 min, but high enough to elicit metabolic and cardiovascular adaptations (1,2). Although exercise prescriptions using the % VO 2 R or HR R may be more appropriate for deconditioned individuals, the use of relative maximal values (% HR peak ) is more common in training applications (2).…”

“…Therefore, during exercise anchored or fixed to HR, power output or running speed is reduced to maintain the designated HR, and VO 2 tracks these reductions in work rate, whereas RPE increases throughout the exercise trials (10,11,15,16). The magnitude of changes in these parameters is likely dependent on the relative intensity of the HR or RPE anchor (11,(15)(16)(17). Previous research has utilized the critical HR and GET to examine constant HR exercise during treadmill running and cycle ergometry (11,(15)(16)(17).…”

“…The magnitude of changes in these parameters is likely dependent on the relative intensity of the HR or RPE anchor (11,(15)(16)(17). Previous research has utilized the critical HR and GET to examine constant HR exercise during treadmill running and cycle ergometry (11,(15)(16)(17). Evidence from these studies (11,16,17) demonstrated average decreases in VO 2 of 8% to 22% from the start to the end as the speed or power output was reduced to maintain the designated HR, which ranged from 88% to 94% HR peak .…”

“…Previous research has utilized the critical HR and GET to examine constant HR exercise during treadmill running and cycle ergometry (11,(15)(16)(17). Evidence from these studies (11,16,17) demonstrated average decreases in VO 2 of 8% to 22% from the start to the end as the speed or power output was reduced to maintain the designated HR, which ranged from 88% to 94% HR peak . Importantly, the ranges of relative VO 2 changes from the start to the end of these exercise trials were 95% to 87% VO 2peak during treadmill running (16) at a relative HR of 94% HR peak , and 81% to 64% VO 2peak during cycle ergometry at 91% HR peak .…”

“…A secondary aim was to examine these responses relative to the exercise intensity domains (moderate, heavy, and severe). It was hypothesized that 1) the average VO 2 and RPE responses for the HR trials would be within the recommended range for vigorous exercise (64%-90% VO 2peak , RPE [14][15][16][17] at the start of the trials at HR L , HR M , and HR H , but these responses would become dissociated throughout the trials such that VO 2 would track decreases in power output and transition from a vigorous to moderate intensity for HR L , but remain vigorous for HR M and HR H ; 2) there would be more pronounced increases in the VO 2 /power output ratio at HR H and HR M than HR L that would reflect a lower metabolic efficiency; 3) the HR L would be sustained for 60 min for most subjects, but T lim would vary at the HR M between 20 and 60 min, and HR H would not be sustainable for 20 min for most subjects; and 4) the trial at HR H would begin in the severe domain and traverse to the heavy domain for most subjects, whereas the HR M and HR L would be in the heavy domain at the start of the trials and traverse to the moderate domain for most subjects.…”