The highest work rate associated with a predominantly aerobic contribution coincides with the highest work rate at which VO2max can be attained

PURPOSE

To estimate the highest power output at which predominant energy contribution is derived from the aerobic system (aerobic limit power: ALP) and to compare ALP with the upper boundary of the severe intensity exercise domain.

METHODS

Fifteen male individuals participated in this study. The upper boundary was estimated using i) linear relationship between time to achieve V ˙ O2max and time to task failure (PUPPERBOUND), ii) hyperbolic relationships between time to achieve V ˙ O2max vs. power output, and time to task failure vs. power output (PUPPERBOUND´), and iii) precalculated V ˙ O2max demand (IHIGH). ALP was estimated by aerobic, lactic, and phospholytic energy contributions using V ˙ O2 response, blood [lactate] response, and fast component of recovery V ˙ O2 kinetics, respectively.

RESULTS

ALP was determined as the highest power output providing predominant aerobic contribution; however, anaerobic pathways became the predominant energy source when ALP was exceeded by 5% (ALP + 5%) (from 46 to 52%; p = 0.003; ES:0.69). The V ˙ O2 during exercise at ALP was not statistically different from V ˙ O2max (p > 0.05), but V ˙ O2max could not be attained at ALP + 5% (p < 0.01; ES:0.63). ALP was similar to PUPPERBOUND and PUPPERBOUND´ (383 vs. 379 and 384 W; p > 0.05). There was a close agreement between ALP and PUPPERBOUND (r: 0.99; Bias: - 3 W; SEE: 6 W; TE: 8 W; LoA: - 17 to 10 W) and PUPPERBOUND´ (r: 0.98; Bias: 1 W; SEE: 8 W; TE: 8 W; LoA: - 15 to 17 W). ALP, PUPPERBOUND, and PUPPERBOUND´ were greater than IHIGH (339 ± 53 W; p < 0.001).

CONCLUSION

ALP may provide a new perspective to intensity domain framework.

Acute Oxygen Consumption Response to Fast Start High-Intensity Intermittent Exercise

The current investigation compared the acute oxygen consumption (VO2) response of two high-intensity interval exercises (HIIE), fast start (FSHIIE), and steady power (SPHIIE), which matched w prime (W') depletion. Eight cyclists completed an incremental max test and a three-minute all-out test (3MT) to determine maximal oxygen consumption (VO2max), critical power (CP), and W'. HIIE sessions consisted of 3 X 4 min intervals interspersed by 3 min of active recovery, with W' depleted by 60% (W'target) within each working interval. SPHIIE depleted the W'target consistently throughout the 3 min intervals, while FSHIIE depleted the W'target by 50% within the first minute, with the remaining 50% depleted evenly across the remainder of the interval. The paired samples t-test revealed no differences in the percentage of training time spent above 90% of VO2max (PT ≥ 90% VO2max) between SPHIIE and FSHIIE with an average of 25.20% and 26.07%, respectively. Pairwise comparisons indicated a difference between minute 1 peak VO2, minute 2, and minute 3, while no differences were present between minutes 2 and 3. The results suggest that when HIIE formats are matched based on W' expenditure, there are no differences in PT ≥ 90% VO2max or peak VO2 during each interval.

Peak Running Velocity vs. Critical Speed: Which One Is Better to Prescribe Endurance Training to Recreational Runners?

ABSTRACT

Figueiredo, DH, Figueiredo, DH, Manoel, FA, and Machado, FA. Peak running velocity vs. critical speed: which one is better to prescribe endurance training to recreational runners? J Strength Cond Res 37(9): 1783-1788, 2023-This study aimed to evaluate the effects of 5 weeks of training prescribed by peak running velocity obtained on the track (Vpeak_TR) and their respective time limit (Tlim), as well as by critical speed (CS), on physiological and endurance performance parameters in recreational runners. Twenty-two male runners were distributed into a Vpeak_TR group (GVP) and CS group (GCS) with a predefined program, alternating moderate-intensity continuous training and high-intensity interval training. Maximum oxygen uptake (V̇O2max), and its respective velocity (vV̇O2max), Vpeak_TR, Tlim at 100% Vpeak_TR, 5-km running performance, CS, and D' (maximum distance covered above CS) were assessed at pretraining and posttraining period. There was a significant increase from pretraining to posttraining in Vpeak_TR (GVP = 4.5 ± 3.1% vs. GCS = 7.5 ± 4.2%), vV̇O2max (GVP = 3.9 ± 3.8% vs. GCS = 8.6 ± 6.7%), and mean velocity 5-km (GVP = 5.6 ± 3.3% vs. GCS = 7.3 ± 3.5%) and decrease in 5-km time (GVP = -5.1 ± 3.0% vs. GCS = -6.8 ± 3.0%). CS and V̇O2max significantly improved in GCS (9.3 ± 8.4% and 6.0 ± 6.8%, respectively), with no difference for GVP (2.8 ± 5.6% and 1.3 ± 8.4%, respectively). No differences were observed between groups for all variables. These findings give further supports to the notion that both variables obtained on the track are valid tools to prescribed training in recreational runners.

Body Composition Is Related to Maximal Effort Treadmill Test Time in Firefighters

Firefighting tasks may require near maximal levels of cardiorespiratory fitness. Previous research has indicated that body fat percentage (BF%) and aerobic capacity (VO_2peak) are related to the performance of firefighting tasks. Since a standard submaximal treadmill test for firefighters is terminated at 85% of maximal heart rate (MHR), key performance information relating to maximal cardiorespiratory effort may not be measured in a submaximal test. The purpose of this study was to examine the relationships between body composition and time spent running at intensities greater that 85% MHR. Height, weight, body mass index (BMI; kg/m²), BF%, MHR (bpm), VO_2peak (mL/kg/min), predicted VO_2peak (P-VO_2peak; mL/kg/min), submaximal treadmill test time (WFI_sub Test Time; min), and maximal treadmill test time (WFI_max Test Time; min) were collected in fifteen active-duty firefighters. The results indicated that significant relationships (p < 0.05) existed between BF% and VO_2peak, BF% and WFI_max Test Time, BF% and T_diff, and VO_2peak and WFI_max Test Time. P-VO_2peak was not significantly different than VO_2peak, and the WFI_max Test Time was significantly longer than the WFI_sub Test Time. These results indicate that a submaximal treadmill test may reasonably predict VO_2peak, but key information about physiological work at intensities greater than 85% MHR may be missed when using submaximal effort tests.

Application of V̇ o2 to the Critical Power Model to Derive the Critical V̇ o2

ABSTRACT

Succi, PJ, Dinyer, TK, Byrd, MT, Voskuil, CC, and Bergstrom, HC. Application of V̇ o2 to the critical power model to derive the critical V̇ o2 . 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 V̇ o2 to estimate the critical V̇ o2 (CV̇ o2 ) and (b) to compare the CV̇ o2 with the V̇ o2 at CP (V̇ o2 CP), the ventilatory threshold (VT), respiratory compensation point (RCP), and the CV̇ o2 without the V̇ o2 slow component (CV̇ o2 slow). Nine subjects performed a graded exercise test to exhaustion to determine V̇ o2 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 (TV̇ o2 ) and without the slow component (TV̇ o2 slow) were recorded during each trial. The linear regressions of the TV̇ o2 vs. T Lim , TV̇ o2 slow vs. T Lim , and W Lim vs. T Lim relationship were performed to derive the CV̇ o2 , CV̇ o2 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 CV̇ o2 (42.49 ± 3.22 ml·kg -1 ·min -1 ) was greater than VT (30.80 ± 4.66 ml·kg -1 ·min -1 ; p < 0.001), RCP (36.74 ± 4.49 ml·kg -1 ·min -1 ; p = 0.001), V̇ o2 CP (36.76 ± 4.31 ml·kg -1 ·min -1 ; p < 0.001), and CV̇ o2 slow (38.26 ± 2.43 ml·kg -1 ·min -1 ; p < 0.001). However, CV̇ o2 slow was not different than V̇ o2 CP ( p = 0.140) or RCP ( p = 0.235). Thus, the CP model can be applied to V̇ o2 to derive the CV̇ o2 and theoretically is the highest metabolic steady state that can be maintained for an extended period without fatigue. Furthermore, the ability of the CV̇ o2 to quantify the metabolic cost of exercise and the inefficiency associated with the V̇ o2 slow component may provide a valuable tool for researchers and coaches to examine endurance exercise.

Grey Zone: A Gap Between Heavy and Severe Exercise Domain

ABSTRACT

Ozkaya, O, Balci, GA, As, H, Cabuk, R, and Norouzi, M. Grey zone: A gap between heavy and severe exercise domain. J Strength Cond Res 36(1): 113-120, 2022-The aim of this study was to determine a critical threshold (CT) interpreted as "the highest exercise intensity where V̇o2 can be stabilized before reaching 95% of V̇o2max (V̇o2peak)" and compare it with commonly used anaerobic threshold indices. Ten well-trained male cyclists volunteered for this study. Ventilatory threshold (VT) was determined from incremental tests. Multisession constant-load trials were performed to reveal V̇o2max. Mathematically modeled critical power (CP) was estimated through the best individual fit parameter method. Maximal lactate steady state (MLSS) was detected by 30-minute constant-load exercises. The individual CT load of each cyclist was tested by constant-load exercises to exhaustion with +15 W intervals until minimal power output to elicit V̇o2peak. The results showed that work rate corresponding to CT (329.5 ± 41.5 W) was significantly greater than that of the MLSS (269.5 ± 38.5 W; p = 0.000), VT (279.6 ± 33 W; p = 0.000), and CP (306.3 ± 39.4 W; p = 0.000), and CP overestimated both VT and MLSS (p = 0.000). There was no significant V̇o2 difference between the 10th and 30th minute of MLSS and MLSS + 15 W exercise (0.36-0.13 ml·min-1·kg-1; p = 0.621). Exercising V̇o2 response of MLSS + 15 W could not exceed the level of 95% V̇o2max (57.02 ± 3.87 ml·min-1·kg-1 and 87.2 ± 3.1% of V̇o2max; p = 0.000), whereas V̇o2 responses greater than 95% of V̇o2max were always attained during exercises performed at CT + 15 W (64.52 ± 4.37 ml·min-1·kg-1 and 98.6 ± 1% of V̇o2max; p > 0.05). In conclusion, this study indicates that there is a "grey zone" between heavy and severe exercise domain. This information may play a key role in enhancing athletic performance by improving the quality of training programs.

Relationship of critical speed derived from a 10-minute submaximal treadmill test to 5-km and 10-km running performances

It has been shown that the critical speed (CS) predicted from a perceptually self-regulated 10-min submaximal treadmill test (T10) is reliable and closely matches the CS estimated from conventional methods. To assess the relationship between the T10 and 5-km and 10-km running performances, 36 recreational runners (mean SD: age: 32.2 ± 6.2 years, height: 173.2 ± 7.3 cm, weight: 70.9 ± 8.8 kg, V̇O2max: 53.3 ± 6.1 mL.kg-1.min-1) performed a ramp incremental test and two T10 tests (the first as a familiarization trial). Results showed that the T10 CS (3.9 ± 0.44 m.s-1) was significantly correlated with runners' last 6 months best performances in 5-km (20.3 ± 2.7 min; r = -0.90) and 10-km (42.7 ± 5.7 min; r = -0.91), the V̇O2max (r = 0.75), the speed associated with the gas exchange threshold (vGET: 3.38 ± 0.36 m.s-1; r = 0.76), the speed associated with the second ventilatory threshold (vVT2: 4.15 ± 0.49 m.s-1; r = 0.84), and the speed associated with the V̇O2max (vV̇O2max: 4.78 ± 0.54 m.s-1; r = 0.87). Moreover, 79% and 83% of the variance in 5-km and 10-km performances could be explained solely by the CS predicted from the T10. Results evidenced the strong relationship and practical performance relevance of the T10 CS test. Novelty: • Critical speed derived from a 10-min submaximal treadmill test (T10) is significantly correlated with 5-km and 10-km running performances • The T10 critical speed test may represent a useful tool for assessing running performance capabilities.

A submaximal treadmill test to predict critical speed

We assessed the reliability and validity of a 10-min submaximal treadmill test (T10) to predict critical speed (CS). Forty-two runners completed a familiarization trial plus two experimental trials (T10 test and T10 retest). Reliability between the T10 test and T10 retest was assessed using coefficient of variation (CoV), limits of agreement (LoA) and intraclass correlation (ICC). For validity, the speed from the T10 retest was compared with the CS determined from 3 runs on separate days on a running track over 1200, 2400, and 3600 m (field test). Reliability between the T10 test and T10 retest showed a CoV of 3.4%, LoA of 0.05 ± 0.39 m.s^-1, and an ICC of 0.93. Validity showed that speed (m.s^-1) (T10 retest: 3.86 ± 0.51; field test: 3.88 ± 0.55) did not differ between trials. The T10 retest was highly correlated with the field test, r = 0.93, and the standard error for the estimate of CS using the T10 retest was 0.06 m.s^-1, and the LoA was 0.02 ± 0.40 m.s^-1. A submaximal 10-min treadmill test (T10) provides a practical and accessible method to estimate CS.

Applying the Critical Power Model to a Full-Body Resistance-Training Movement

PURPOSE

To determine if the mathematical model used to derive critical power could be used to identify the critical resistance (CR) for the deadlift; compare predicted and actual repetitions to failure at 50%, 60%, 70%, and 80% 1-repetition maximum (1RM); and compare the CR with the estimated sustainable resistance for 30 repetitions (ESR30).

METHODS

Twelve subjects completed 1RM testing for the deadlift followed by 4 visits to determine the number of repetitions to failure at 50%, 60%, 70%, and 80% 1RM. The CR was calculated as the slope of the line of the total work completed (repetitions × weight [in kilograms] × distance [in meters]) vs the total distance (in meters) the barbell traveled. The actual and predicted repetitions to failure were determined from the CR model and compared using paired-samples t tests and simple linear regression. The ESR30 was determined from the power-curve analysis and compared with the CR using paired-samples t tests and simple linear regression.

RESULTS

The weight and repetitions completed at CR were 56 (11) kg and 49 (14) repetitions. The actual repetitions to failure were less than predicted at 50% 1RM (P < .001) and 80% 1RM (P < .001) and greater at 60% 1RM (P = .004), but there was no difference at 70% 1RM (P = .084). The ESR30 (75 [14] kg) was greater (P < .001) than the CR.

CONCLUSIONS

The total work-vs-distance relationship can be used to identify the CR for the deadlift, which reflected a sustainable resistance that may be useful in the design of resistance-based exercise programs.

Different durations within the method of best practice affect the parameters of the speed-duration relationship

The aim of the study was to determine whether estimates of the speed-duration relationship are affected using different time-trial (TT) field-based testing protocols, where exhaustive times were located within the generally recommended durations of 2-15 min. Ten triathletes (mean ± SD age: 31.0 ± 5.7 years; height: 1.81 ± 0.05 m; body mass: 76.5 ± 6.8 kg) performed two randomly assigned field tests to determine critical speed (CS) and the total distance covered above CS (D́). CS and D́ were obtained using two different protocols comprising three TT that were interspersed by 60 min passive rest. The TTs were 12, 7, and 3 min in Protocol I and 10, 5, and 2 min in Protocol II. A linear relationship of speed vs. the inverse of time (s = D́ × 1/t + CS) was used to determine parameter estimates. Significant differences were found for CS (p = 0.026), but not for D́ (p = 0.123). The effect size for CS (d = 0.305) was considered small, while that for D́ was considered moderate (d = 0.742). CS was significantly correlated between protocols (r = 0.934; p < 0.001), however, no correlation was found for D́ (r = 0.053; p = 0.884). The 95% limits of agreement were ±0.28m s^-1 and ±73.9 m for CS and D́, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations results in different estimates of CS and D́, and thus protocols cannot be used interchangeably. The use of a consistent protocol is therefore recommended, when investigating or monitoring the speed-duration relationship estimates in well-trained athletes.