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This study aimed to investigate the effects of caffeine ingestion by chewing gum (GUMCAF) combined with priming exercise on pulmonary oxygen uptake ( V ˙ O 2 ) and near-infrared spectroscopy-derived muscle oxygen extraction (HHb + Mb) kinetics during cycling performed in a severe-intensity domain. Fifteen trained cyclists completed four visits: two under a placebo gum (GUMPLA) and two under GUMCAF ingestion. Each visit consisted of two square-wave cycling bouts at Δ70 intensity (70% of difference between the V ˙ O 2 at first ventilatory threshold and V ˙ O 2 max) with duration of 6 min each and 5 min of passive rest between the bouts. The GUMPLA or GUMCAF (400 mg) was chewed for 5 min, 12 min before the first Δ70 bout in a randomized double-blind procedure. The fundamental phase and slow component of HHb + Mb and V ˙ O 2 kinetics were evaluated. For HHb + Mb kinetics, regardless of ingested gum, priming exercise effects occurred on the time constant (GUMCAF 16.0 ± 4.0 vs. 13.9 ± 2.9 s; GUMPLA 15.7 ± 6.1 vs. 13.2 ± 2.5 s), amplitude, slow component, time delay, and mean response time parameters (p ≤.032). For V ˙ O 2 kinetics, there were significant effects of bouts on the amplitude, slow component, end V ˙ O 2 , and the gain kinetics parameters (p <.017). Baseline V ˙ O 2 was higher during GUMCAF than GUMPLA (p =.020). No significant effects occurred for the interaction between gum and bout in any parameter of V ˙ O 2 or HHb + Mb kinetics. Therefore, unlike the priming exercise in severe-intensity exercise, GUMCAF is not an effective strategy for improving V ˙ O 2 or HHb + Mb kinetics acceleration. [ABSTRACT FROM AUTHOR]

Purpose: To examine the capacity of physiological variables and performance to predict peak oxygen consumption (peak VO[subscript 2]) in children and adolescents living with HIV. Method: Sixty-five children and adolescents living with HIV (30 boys) aged 8-15 years, participated in the study. Peak VO[subscript 2] was measured by breath-by-breath respiratory exchange during an incremental cycle ergometer until volitional exhaustion. Information on the time to exhaustion, maximal power output (Pmax), and peak heart rate (peak HR) were also recorded. Results: Predictive models were developed and all equations showed the ability of performance variables to predict peak VO[subscript 2]. However, Model 1 was based only on Pmax by following equation: Y = 338.8302 + (Pmax [W] * 11.16435), R[superscript 2] = 0.90 and standard error of estimation ("SEE") = 180 ml[dot]min[superscript -1]. Conclusion: The VO[subscript 2] peak can be predicted simply by the Pmax obtained from the incremental cycle ergometer test. This protocol is a valid and useful tool for monitoring the aerobic fitness of children and adolescents living with HIV, especially in resource-limited settings.

This study aimed to verify the effects of 4 weeks of high-intensity interval training (HIIT), heavy (HRT) and explosive (ERT) resistance training on aerobic, anaerobic and neuromuscular parameters and performance of well-trained runners. Twenty-six male athletes were divided into HIIT (n = 10), HRT (n = 7) and ERT (n = 9) groups. Maximal oxygen uptake ($V{O_2}\max $ V O 2 max) and the corresponding velocity ($vV{O_2}\max $ vV O 2 max), anaerobic threshold (AT), running economy (RE), oxygen uptake kinetics, lower-body strength (1RM) and power (CMJ), and the 1500m and 5000m time-trial (TT) were determined. Improvements were observed in $vV{O_2}\max $ vV O 2 max (mean difference (Δ): 2.6%; effect size (ES): 0.63) with HIIT, while AT was incresead in ERT (Δ: 4.3%; ES: 0.73) and HRT (Δ: 6.9%; ES: 0.72) groups. The CMJ performance was increased in ERT (Δ: 13.8%; ES: 1.03), HRT (Δ: 6.9%; ES: 0.55) and HIIT (Δ: 5.4%; ES: 0.34), whereas 1RM increase in HRT (Δ: 38.1%; ES: 1.21) and ERT (Δ: 49.2%; ES: 0.96) groups. HIIT improved the 1500m (Δ: −2.3%; ES: −0.62) and both HRT (Δ: −1.6%; ES: −0.32) and ERT (Δ: −1.7%; ES: −0.31) the 5000m TT. Despite performance adaptations were dependent on the training characteristics, both RT and HIIT model constitute an alternative for training periodization. [ABSTRACT FROM AUTHOR]

The purpose of this study was to verify the heart rate variability (HRV) and heart rate (HR) kinetics during the fundamental phase in different intensity domains of cycling exercise. Fourteen males performed five exercise sessions: (1) maximal incremental cycling test; (2) two rest-to-exercise transitions for each intensity domain, that is, heavy (Δ30) and severe (Δ60) domains. HRV markers (SD1 and SD2) and HR kinetics in the fundamental phase were analyzed by first-order exponential fitting. There were no significant differences in amplitude values between SD1Δ30 (8.98 ± 3.52 ms) and SD1Δ60 (9.44 ± 3.24 ms) and SD2Δ30 (24.93 ± 9.16 ms) and SD2Δ60 (25.98 ± 7.29 ms). Significant difference was observed between HRΔ30 (52 ± 7 bpm) and HRΔ60 (63 ± 8 bpm). The time constant (τ) values were significantly different between SD1Δ30 (17.61 ± 6.26 s) and SD1Δ60 (13.86 ± 5.90 s), but not between SD2Δ30 (20.06 ± 3.73 s) and SD2Δ60 (19.47 ± 6.03 s) or HRΔ30 (56.75 ± 18.22 s) and HRΔ60 (58.49 ± 15.61 s). However, the τ values for HRΔ30 were higher and significantly different in relation to SD1Δ30 and SD2Δ30, as well as for HRΔ60 in relation to SD1Δ60 and SD2Δ60. The kinetics of the autonomic variable (SD1 marker) was accelerated by the increased intensity. Moreover, significant differences were found for the τ values, with faster HRV markers than HR, in both intensities of Δ30 and Δ60, which suggests that these variables indicate distinct and specific cardiac autonomic response times during different intensity domains in cycling. HIGHLIGHTS The application of HRV to optimize exercise prescription at different effort intensities is extremely important to obtain assertive and effective results. Analysis of the kinetic responses of HRV is a useful tool for the evaluation of exercise performance and health status. A faster kinetics was found for HRV markers in comparison to HR, for both intensities analysed, which suggests that these variables indicate distinct and specific cardiac autonomic response times during different intensity domains in cycling. [ABSTRACT FROM AUTHOR]

Near-infrared spectroscopy (NIRS) has been utilized as a noninvasive method to evaluate skeletal muscle mitochondrial function in humans, by calculating muscle V O2 (V O2m) recovery (off-) kinetics following short light-intensity plantar flexion exercise. The aim of the present study was to determineV O2m 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 V O2 (V O2p; HEAVY). V O2p and vastus lateralis muscle fractional O2 extraction by NIRS [deoxy(HbMb)]) were recorded continuously. Transient arterial occlusions were carried out at rest and during the recovery for V O2m calculation. All subjects tolerated the repeated occlusions protocol without problems. The quality of the monoexponential fitting for V O2m off-kinetics analysis was excellent (0.93≤r2≤0.99). According to interclass correlation coefficient, the test-retest reliability was moderate to good. V O2m 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 V O2m 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 V O2m off-kinetics. Only following MODERATE theV O2m off-kinetics were faster than the V O2p off-kinetics. V O2m 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. [ABSTRACT FROM AUTHOR]

Purpose: To examine the capacity of physiological variables and performance to predict peak oxygen consumption (peak V˙ O2) in children and adolescents living with HIV.Method: Sixty-five children and adolescents living with HIV (30 boys) aged 8-15 years, participated in the study. Peak V˙ O2 was measured by breath-by-breath respiratory exchange during an incremental cycle ergometer until volitional exhaustion. Information on the time to exhaustion, maximal power output (Pmax), and peak heart rate (peak HR) were also recorded.Results: Predictive models were developed and all equations showed the ability of performance variables to predict peak V˙ O2. However, Model 1 was based only on Pmax by following equation: Y = 338.8302 + (Pmax [W] * 11.16435), R2 = 0.90 and standard error of estimation (SEE) = 180 ml ⋅ min-1.Conclusion: The V˙ O2 peak can be predicted simply by the Pmax obtained from the incremental cycle ergometer test. This protocol is a valid and useful tool for monitoring the aerobic fitness of children and adolescents living with HIV, especially in resource-limited settings. [ABSTRACT FROM AUTHOR]

A link between muscle fatigue, decreased efficiency and the slow component of oxygen uptake (VO2sc) has been suggested. However, a cause-effect relationship remains to be elucidated. Although alterations in VO2 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 VO2 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 VO2 and time constant (τ) were significantly higher in M-VH compared to U-VH, the fundamental amplitude and the VO2 slow component (VO2sc) 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 VO2 kinetics parameters (p > 0.05). The alterations in VO2 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. [ABSTRACT FROM AUTHOR]

Background: We aimed to investigate the effect of a priming ischemia-reperfusion (IR) model on the kinetics of pulmonary oxygen uptake (VO2) and cardiopulmonary parameters after high-intensity exercise. Our primary outcome was the overall VO2 kinetics and secondary outcomes were heart rate (HR) and O2 pulse kinetics. We hypothesized that the IR model would accelerate VO2 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 VO2 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 VO2 kinetics parameters (VO2 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 (MRT180s 67.3 ± 6.0 vs. 71.3 ± 6.1 s; P = 0.54) and O2 pulse kinetics (MRT180s 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 VO2, HR, and O2 pulse kinetics during high-intensity cycling exercise. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the physiological responses during the time limit at the intensity of the peak velocity of the Carminatti's test (T-CAR). Ten professional futsal players (age, 27.4 ± 5.8 years, body mass, 78.8 ± 8.5 kg, body height, 175.8 ± 6.8 cm, body fat mass, 14.1 ± 2.6%) took part in the study. The players performed three tests, with an interval of at least 48 hours, as follows: the T-CAR to determine the peak velocity and the maximal heart rate; an incremental treadmill protocol to determine the maximal physiological responses; and a time limit running test at the peak velocity reached in the T-CAR. During the last two tests, a portable gas analyzer was used for direct measurement of cardiorespiratory variables. It was shown that the peak velocity was not significantly different from the maximal aerobic speed achieved in the laboratory (p = 0.213). All athletes reached their maximum oxygen uptake during the time limit test. The maximum oxygen uptake achieved during the time limit test was not different from that observed in the laboratory condition (51.1 ± 4.7 vs. 49.6 ± 4.7 ml.kg-1.min-1, respectively, p = 0.100). In addition, Bland and Altman plots evidenced acceptable agreement between them. On average, athletes took ~140 s to achieve maximum oxygen uptake and maintained it for ~180 s. Therefore, the peak velocity intensity can be used as an indicator of maximal aerobic power of futsal athletes and the time limit can be used as a reference for training prescription. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Kineanthropometry & Human Performance is the property of Brazilian Journal of Kineanthropometry & Human Performance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Kineanthropometry & Human Performance is the property of Brazilian Journal of Kineanthropometry & Human Performance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Kineanthropometry & Human Performance is the property of Brazilian Journal of Kineanthropometry & Human Performance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: The muscle oxygen uptake ( m V ˙ O 2 ) kinetics following exercise, measured by near-infrared spectroscopy, has been used as a functional evaluation of muscle oxidative metabolism. This study aimed to determine the m V ˙ O 2 off-kinetics and verify the relationship of the recovery rate of m V ˙ O 2 ( k ) with time-trial performance and different aerobic parameters in trained rowers. Methods: Eleven male rowers (age: 20 ± 3 years; V ˙ O 2 m a x : 4.28 ± 0.35 L·min -1 ) used a rowing ergometer to perform (I) an incremental test to determine the maximal oxygen uptake ( V ˙ O 2 m a x ) and peak power output (P peak ); (II) several visits to determine maximal lactate steady state (MLSS); and (III) a 2000-m rowing ergometer performance test. Also, one test to determine m V ˙ O 2 off-kinetics of the vastus lateralis muscle using a repeated arterial occlusions protocol. Results: The m V ˙ O 2 generated a good monoexponential fit ( R 2  = 0.960 ± 0.030; SEE = 0.041 ± 0.018%.s -1 ). The k of m V ˙ O 2 (2.06 ± 0.58 min -1 ) was associated with relative V ˙ O 2 m a x ( r = 0.79), power output at MLSS ( r = 0.76), and P peak ( r = 0.83); however, it was not related with 2000-m rowing performance ( r = -0.38 to 0.52; p > .152). Conclusion: These findings suggest that although not associated with rowing performance, the m V ˙ O 2 off-kinetics determined after a submaximal isometric knee extension may be a practical and less-exhaustive approach than invasive responses and incremental tests to assess the muscle oxidative metabolism during a training program.

Near-infrared spectroscopy (NIRS) has been utilized as a noninvasive method to evaluate skeletal muscle mitochondrial function in humans, by calculating muscle V̇o 2 (V̇o 2 m ) recovery (off-) kinetics following short light-intensity plantar flexion exercise. The aim of the present study was to determine V̇o 2 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 V̇o 2 (V̇o 2 p ; HEAVY). V̇o 2 p and vastus lateralis muscle fractional O 2 extraction by NIRS (Δ[deoxy(Hb+Mb)]) were recorded continuously. Transient arterial occlusions were carried out at rest and during the recovery for V̇o 2 m calculation. All subjects tolerated the repeated occlusions protocol without problems. The quality of the monoexponential fitting for V̇o 2 m off-kinetics analysis was excellent (0.93≤ r 2 ≤0.99). According to interclass correlation coefficient, the test-retest reliability was moderate to good. V̇o 2 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 V̇o 2 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 V̇o 2 m off-kinetics. Only following MODERATE the V̇o 2 m off-kinetics were faster than the V̇o 2 p off-kinetics. V̇o 2 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 V̇o 2 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 V̇o 2 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.

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.