We hypothesized that prior exercise would attenuate the muscle fatigue accompanied by oxygen uptake slow-component (V̇O2SC) behavior during a subsequent very-heavy (VH)-intensity cycling exercise. Thirteen healthy male subjects performed tests to determine the critical power (CP) and the fixed amount of work above CP ([Formula: see text]) and performed 6 square-wave bouts until 3 or 8 min, each at a work rate set to deplete 70% [Formula: see text] in 8 min, with a maximal isokinetic effort before and after the conditions without (VHCON) and with prior exercise (VHEXP), to measure the cycling peak torque decrement. The V̇O2SC magnitude at 3 min (VHCON = 0.280 ± 0.234, VHEXP = 0.116 ± 0.109 L·min−1; p = 0.04) and the V̇O2SC trajectory were significantly lower for VHEXP (VHCON = 0.108 ± 0.042, VHEXP = 0.063 ± 0.031 L·min−2; p < 0.01), leading to a V̇O2SC magnitude at the eighth minute that was significantly lower than VHCON (VHCON = 0.626 ± 0.296 L·min−1, VHEXP = 0.337 ± 0.179; p < 0.01). Conversely, peak torque progressively decreased from pre-exercise to 3 min (Δtorque = 21.5 ± 7.7 vs. 19.6 ± 9.2 Nm) and to 8 min (Δtorque = 29.4 ± 15.8 vs. 27.5 ± 12.0 Nm) at VHCON and VHEXP, respectively, without significant differences between conditions. Regardless of the condition, there was a significant relationship between Δtorque and the V̇O2SC (R2: VHCON = 0.23, VHEXP = 0.25; p = 0.01). Considering that “priming” effects on the V̇O2SC were not accompanied by the muscle force behavior, these findings do not support the hypothesis of a “causal” relationship between the time-course of muscle fatigue and V̇O2SC.

The contribution of chronological age, skeletal age (Fels method) and body size to variance in peak velocity derived from the Carminatti Test was examined in 3 competitive age groups of Brazilian male soccer players: 10-11 years (U-12, n=15), 12-13 years (U-14, n=54) and 14-15 years (U-16, n=23). Body size and soccer-specific aerobic fitness were measured. Body composition was predicted from skinfolds. Analysis of variance and covariance (controlling for chronological age) were used to compare soccer players by age group and by skeletal maturity status within of each age group, respectively. Relative skeletal age (skeletal age minus chronological age), body size, estimated fat-free mass and performance on the Carminatti Test increased significantly with age. Carminatti Test performance did not differ among players of contrasting skeletal maturity status in the 3 age groups. Results of multiple linear regressions indicated fat mass (negative) and chronological age (positive) were significant predictors of peak velocity derived from the Carminatti Test, whereas skeletal age was not a significant predictor. In conclusion, the Carminatti Test appears to be a potentially interesting field protocol to assess intermittent endurance running capacity in youth soccer programs since it is independent of biological maturity status.

Near-infrared spectroscopy (NIRS) has been utilized as a noninvasive method to evaluate skeletal muscle mitochondrial function in humans, by calculating muscle V̇o2 (V̇o2 m) recovery (off-) kinetics following short light-intensity plantar flexion exercise. The aim of the present study was to determine V̇o2 m off- kinetics following standard cycle ergometer exercise of different intensities. Fifteen young physically active healthy men performed an incremental exercise (INCR) up to exhaustion and two repetitions of constant work-rate (CWR) exercises at 80% of gas exchange threshold (GET; MODERATE) and at 40% of the difference between GET and peak pulmonary V̇o2 (V̇o2 p; HEAVY). V̇o2 p and vastus lateralis muscle fractional O2 extraction by NIRS (Δ[deoxy(Hb+Mb)]) were recorded continuously. Transient arterial occlusions were carried out at rest and during the recovery for V̇o2 m calculation. All subjects tolerated the repeated occlusions protocol without problems. The quality of the monoexponential fitting for V̇o2 m off-kinetics analysis was excellent (0.93≤ r2≤0.99). According to interclass correlation coefficient, the test-retest reliability was moderate to good. V̇o2 m values at the onset of recovery were ~27, ~38, and ~35 times higher (in MODERATE, HEAVY, and INCR, respectively) than at rest. The time constants (τ) of V̇o2 m off-kinetics were lower ( P < 0.001) following MODERATE (29.1 ± 6.8 s) vs. HEAVY (40.8 ± 10.9) or INCR (42.9 ± 10.9), suggesting an exercise intensity dependency of V̇o2 m off-kinetics. Only following MODERATE the V̇o2 m off-kinetics were faster than the V̇o2 p off-kinetics. V̇o2 m off-kinetics, determined noninvasively by the NIRS repeated occlusions technique, can be utilized as a functional evaluation tool of skeletal muscle oxidative metabolism also following conventional cycle ergometer exercise. NEW & NOTEWORTHY This is the first study in which muscle V̇o2 recovery kinetics, determined noninvasively by near-infrared spectroscopy (NIRS) by utilizing the repeated occlusions method, was applied following standard cycle ergometer exercise of different intensities. The results demonstrate that muscle V̇o2 recovery kinetics, determined noninvasively by the NIRS repeated occlusions technique, can be utilized as a functional evaluation tool of skeletal muscle oxidative metabolism also following conventional cycle ergometer exercise, overcoming significant limitations associated with the traditionally proposed protocol.

The present study aimed to compare maximal oxygen uptake of a step incremental test with time to exhaustion verification tests (TLIM) performed on the same or different day. Nineteen recreationally trained cyclists (age: 23 ± 2.7 years; maximal oxygen uptake: 48.0 ± 5.8 mL·kg−1·min−1) performed 3 maximal tests as follows: (i) same day: an incremental test with 3-min stages followed by a TLIM at 100% of peak power output of the incremental test (TLIM-SAME) interspaced by 15 min; and (ii) different day: a TLIM at 100% of peak power output of the incremental test (TLIM-DIFF). The maximal oxygen uptake was determined for the 3 tests. The maximal oxygen uptake was not different among the tests (incremental: 3.83 ± 0.41; TLIM-SAME: 3.72 ± 0.42; TLIM-DIFF: 3.75 ± 0.41 L·min−1; P = 0.951). Seven subjects presented a variability greater than ±3% in both verification tests compared with the incremental test. The same-day verification test decreased the exercise tolerance (240 ± 38 vs. 310 ± 36 s) compared with TLIM-DIFF (P < 0.05). In conclusion, the incremental protocol is capable of measuring maximal oxygen uptake because similar values were observed in comparison with verification tests. Although the need for the verification phase is questionable, the additional tests are useful to evaluate individual variability. Novelty Step incremental test is capable of measuring maximal oxygen uptake with similar values during TLIM on the same or different day. Although the necessity of the verification phase is questionable, it can allow the determination of variability in maximal oxygen uptake.

Purpose. the aim of the study was to examine the differences of the anaerobic speed reserve (ASr) in soccer players according to the playing positions (defenders, midfielders, and forwards). Methods. Overall, 120 elite-level national Brazilian soccer players (46 defenders, 45 midfielders, and 29 forwards) performed a field incremental test to estimate maximal aerobic speed (MAS) and a 30-m sprint to determine maximal sprinting speed (MSS). the difference between MAS and MSS was used to estimate ASr. Players were classified by position and by MAS and MSS performance. For each playing position, they were ranked and divided into higher and lower MSS (MSS-H and MSS-L, respectively) and MAS (MAS-H and MAS-L, respectively) groups. the players' ASr was compared among these groups. Results. the comparison of ASr within playing position showed no difference among defenders, midfielders, or forwards. In addition, a higher ASr was found for the fastest players (MSS-H) in all playing positions as compared with their MSS-L counterparts. When ASr was compared between MASH and MAS-L, a significant difference (p < 0.05) was observed. A high correlation was noted between ASr and MSS (r = 0.72; p < 0.001) and between ASr and MAS (r =-0.63; p < 0.001). Conclusions. MSS is the main index that determines the magnitude of ASr, which should be considered when characterizing the soccer players' running speed profile. However, no difference was found when the playing positions were compared, indicating similar characteristics of the running profile in a large sample of soccer players.

New Findings r What is the central question of this study?Does the rate of utilization of W (the curvature constant of the power-duration relationship) affect fatigue during severe-intensity exercise? r What is the main finding and its importance?The magnitude of fatigue after two severe-intensity exercises designed to deplete the same fraction of W (70%) at two different rates of utilization (fast versus slow) was similar after both exercises. Moreover, the magnitude of fatigue was related to critical power (CP), supporting the contention that CP is a key determinant in fatigue development during high-intensity exercise. Thus, the CP model is a suitable approach to investigate fatigue mechanisms during high-intensity exercise.The depletion of W (the curvature constant of the power-duration relationship) seems to contribute to fatigue during severe-intensity exercise. Therefore, the aim of this study was to determine the effect of a fast versus a slow rate of utilization of W on the occurrence of fatigue within the severe-intensity domain. Fifteen healthy male subjects performed tests to determine the critical power, W and peak torque in the control condition (T CON ) and immediately after two fatiguing work rates (THREE and TEN) set to deplete 70% W in either 3 (T THREE ) or 10 min (T TEN ). The T THREE and T TEN were significantly reduced (F = 19.68, P = 0.01) in comparison to T CON . However, the magnitude of reduction in peak torque (T THREE = −19.8 ± 10.1% versus T TEN = −16.8 ± 13.3%) was the same in the two fatiguing exercises (t = −0.76, P = 0.46). There was a significant inverse relationship between the critical power and the reduction in peak torque during both THREE (r = −0.49, P = 0.03) and TEN (r = −0.62, P = 0.02). In contrast, the W was not significantly correlated with the reduction in peak torque during both THREE (r = −0.14, P = 0.33) and TEN (r = −0.30, P = 0.10). Thus, fatigue following severe-intensity exercises performed at different rates of utilization of W was similar when the same work was done above the critical power (i.e. same amount of W used).

A link between muscle fatigue, decreased efficiency and the slow component of oxygen uptake (VO 2 sc) has been suggested. However, a cause-effect relationship remains to be elucidated. Although alterations in VO 2 kinetics after elevated baseline work rate have previously been reported, to date no study has observed the effect on muscle force production (MFP) behavior considering physiological differences between male and female subjects. This study investigated the effect of elevated baseline work rate on the VO 2 kinetics and MFP in 10 male and 10 female healthy subjects. Subjects performed 4 transitions of very-heavy (VH) intensity cycling in a randomized order after unloaded (U-VH) or moderate (M-VH) exercise. Maximal isokinetic efforts (MIE) were performed before and after each condition at two different cadences (60 or 120 rpm). Whereas baseline VO 2 and time constant (τ) were significantly higher in M-VH compared to U-VH, the fundamental amplitude and the VO 2 slow component (VO 2 sc) were significantly lower in M-VH ( p < 0.05) in both sexes. Blood lactate concentration ([La]) and rate of perceived exertion (RPE) were not influenced by condition or sex ( p > 0.05). The MFP post-exercise was not significantly influenced by condition in both sexes and cadences (Δtorque for males: at 60 rpm in U-VH = 13 ± 10 Nm, in M-VH = 13 ± 9 Nm; at 120 rpm in U-VH = 22 ± 14 Nm, in M-VH = 21 ± 12 Nm; for females: at 120 rpm in U-VH = 10 ± 9 Nm, in M-VH = 12 ± 8 Nm; p > 0.05), with the exception that female subjects presented smaller decreases in M-UH at 60 rpm compared to U-VH (11 ± 13 vs. 18 ± 14 Nm, respectively, p < 0.05). There was no correlation between the decrease in torque production and VO 2 kinetics parameters ( p > 0.05). The alterations in VO 2 kinetics which have been suggested to be linked to changes in motor unit recruitment after elevated baseline work rate did not reflect alterations in MFP and fatigue in both sexes.

Background: We aimed to investigate the effect of a priming ischemia-reperfusion (IR) model on the kinetics of pulmonary oxygen uptake (VO 2 ) and cardiopulmonary parameters after high-intensity exercise. Our primary outcome was the overall VO 2 kinetics and secondary outcomes were heart rate (HR) and O 2 pulse kinetics. We hypothesized that the IR model would accelerate VO 2 and cardiopulmonary kinetics during the exercise. Methods: 10 recreationally active men (25.7 ± 4.7 years; 79.3 ± 10.8 kg; 177 ± 5 cm; 44.5 ± 6.2 mL kg −1 min −1 ) performed a maximal incremental ramp test and four constant load sessions at the midpoint between ventilatory threshold and VO 2 max on separate days: two without IR (CON) and two with IR (IR). The IR model consisted of a thigh bi-lateral occlusion for 15 min at a pressure of 250 mmHg, followed by 3 min off, before high-intensity exercise bouts. Results: There were no significant differences for any VO 2 kinetics parameters (VO 2 base 1.08 ± 0.08 vs. 1.12 ± 0.06 L min −1 ; P = 0.30; τ = 50.1 ± 7.0 vs. 47.9 ± 6.4 s; P = 0.47), as well as for HR (MRT 180s 67.3 ± 6.0 vs. 71.3 ± 6.1 s; P = 0.54) and O 2 pulse kinetics (MRT 180s 40.9 ± 3.9 vs. 48.2 ± 5.6 s; P = 0.31) between IR and CON conditions, respectively. Conclusion: We concluded that the priming IR model used in this study had no influence on VO 2 , HR, and O 2 pulse kinetics during high-intensity cycling exercise.