Fatigue and Performance Rates as Decision-Making Criteria in Pacing Control During CrossFit®.

We investigated fatigue and performance rates as decision-making criteria in pacing control during CrossFit®. Thirteen male regional-level competitors completed conditions of all-out (maximum physical work from beginning to end) and controlled-split (controlled physical work in the first two rounds but maximum work in the third round) pacing throughout the Fight Gone Bad workout separated by one week. We assessed benchmarks, countermovement jumps and ratings of fatigue after each round. Benchmarks were lower in round 1 (99 vs. 114, p < .001) but higher in rounds 2 (98 vs. 80, p < .001) and 3 (97 vs. 80, p < .001) for controlled-split compared with all-out pacing. Reductions in countermovement jumps were higher after rounds 1 (-12.6% vs. 1.6%, p < .001) and 2 (-12.7% vs. -4.0%, p = .014) but similar after round 3 (-13.2% vs. -11.3%, p = .571) for all-out compared with controlled-split pacing. Ratings of fatigue were higher after rounds 1 (7 vs. 5 a.u., p < .001) and 2 (8 vs. 7 a.u, p = .023) but similar after round 3 (9 vs. 9 a.u., p = .737) for all-out compared with controlled-split pacing. During all-out pacing, countermovement jump reductions after round 2 correlated with benchmark drops across rounds 1 and 2 (r = .78, p = .002) and rounds 1 and 3 (r = -.77, p = .002) and with benchmark workout changes between pacing strategies (r = -.58, p = .036), suggesting that the larger the countermovement jump reductions the higher the benchmark drops across rounds and workouts. Therefore, benchmarks, countermovement jumps and ratings of fatigue may assess exercise-induced fatigue as decision-making criteria to improve pacing strategy during workouts performed for as many repetitions as possible.

Ischemic preconditioning increases spinal excitability and voluntary activation during maximal plantar flexion contractions in men.

The enigmatic benefits of acute limb ischemic preconditioning (IP) in enhancing muscle force and exercise performance have intrigued researchers. This study sought to unravel the underlying mechanisms, focusing on increased neural drive and the role of spinal excitability while excluding peripheral factors. Soleus Hoffmann (H)-reflex /M-wave recruitment curves and unpotentiated supramaximal responses were recorded before and after IP or a low-pressure control intervention. Subsequently, the twitch interpolation technique was applied during maximal voluntary contractions to assess conventional parameters of neural output. Following IP, there was an increase in both maximum normalized force and voluntary activation (VA) for the plantar flexor group, with negligible peripheral alterations. Greater benefits were observed in participants with lower VA levels. Despite greater H-reflex gains, soleus volitional (V)-wave and sEMG amplitudes remained unchanged. In conclusion, IP improves muscle force via enhanced neural drive to the muscles. This effect appears associated, at least in part, to reduced presynaptic inhibition and/or increased motoneuron excitability. Furthermore, the magnitude of the benefit is inversely proportional to the skeletal muscle's functional reserve, making it particularly noticeable in under-recruited muscles. These findings have implications for the strategic application of the IP procedure across diverse populations.

Reliability and Validity of Cycling Sprint Performance at Isolinear Mode Without Torque Factor: A Preliminary Study in Well-Trained Male Cyclists.

Purpose: This study aimed to compare the performance-derived parameters utilizing isolinear (ISOLIN) and isovelocity (ISOVEL) sprint cycling modes. Method: For that, 20 male trained cyclists performed 2 sprints of 7 s on an electromagnetically braked cycle ergometer in ISOLIN and six sprints in ISOVEL mode with cadences between 90 and 180 rpm, each separated by 3-min. A linear function modeled the sprints within each mode to extrapolate maximal cadence (CMAX) and torque (TMAX), and a quadratic function was used to extrapolate the apex defined as optimal cadence power (OPTCAD) and peak power output (PMAX). Fifteen subjects performed another 4 sprints at ISOLIN mode on different days to verify the reliability. Results: The measures from the power-cadence relationship were not different between the ISOLIN and ISOVEL modes. Although significant differences were detected in the T-C relationship, TMAX was greater at ISOLIN than ISOVEL (p = .006). On the other hand, CMAX was higher at ISOVEL than ISOLIN (p < .001). The correlation between parameters was large to very large (r = 0.51 to 0.89). However, high limits of agreement were verified. The ISOLIN presented consistency during the trials, and the random errors were acceptable (CV = 5.3% to 11.5%). Conclusion: Using the power-cadence relationship, PMAX and OPTCAD could be detected similarly between the two sprint modes (ISOLIN and ISOVEL). Thus, the findings demonstrated that a single ISOLIN sprint test could be a suitable tool for quantifying the time course of muscle fatigue during and after cycling exercises in well-trained male cyclists.

Prediction of Exercise Tolerance in the Severe and Extreme Intensity Domains by a Critical Power Model.

This study aimed to assess the predictive capability of different critical power (CP) models on cycling exercise tolerance in the severe- and extreme-intensity domains. Nineteen cyclists (age: 23.0 ± 2.7 y) performed several time-to-exhaustion tests (Tlim) to determine CP, finite work above CP (W'), and the highest constant work rate at which maximal oxygen consumption was attained (IHIGH). Hyperbolic power-time, linear power-inverse of time, and work-time models with three predictive trials were used to determine CP and W'. Modeling with two predictive trials of the CP work-time model was also used to determine CP and W'. Actual exercise tolerance of IHIGH and intensity 5% above IHIGH (IHIGH+5%) were compared to those predicted by all CP models. Actual IHIGH (155 ± 30 s) and IHIGH+5% (120 ± 26 s) performances were not different from those predicted by all models with three predictive trials. Modeling with two predictive trials overestimated Tlim at IHIGH+5% (129 ± 33 s; p = 0.04). Bland-Altman plots of IHIGH+5% presented significant heteroscedasticity by all CP predictions, but not for IHIGH. Exercise tolerance in the severe and extreme domains can be predicted by CP derived from three predictive trials. However, this ability is impaired within the extreme domain.

Effects of Photobiomodulation Therapy on Performance in Successive Time-to-Exhaustion Cycling Tests: A Randomized Double-Blinded Placebo-Controlled Trial.

The goal of this study was to investigate the effects of photobiomodulation therapy (PBMT) on performance, oxygen uptake (VO2) kinetics, and lower limb muscle oxygenation during three successive time-to-exhaustions (TTEs) in cyclists. This was a double-blind, randomized, crossover, placebo-controlled trial study. Sixteen cyclists (~23 years) with a cycling training volume of ~460 km/week volunteered for this study. In the first session, cyclists performed a maximal incremental test to determine maximal oxygen uptake and maximal power output (POMAX). In the following sessions, cyclists performed three consecutive TTEs at POMAX. Before each test, PBMT (135 J/thigh) or a placebo (PLA) was applied to both thighs. VO2 amplitude, O2 deficit, time delay, oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (tHb) were measured during tests on the right vastus lateralis. The PBMT applied before three successive TTE increased performance of the first and second TTE (~10-12%) tests, speed of VO2 and HHb kinetics during the first test, and increased peripheral muscle oxygenation (increase in HHb and tHb) in the first and second exhaustion tests. However, the PBMT effects were attenuated in the third TTE, as performance and all the other outcomes were similar to the ones from the PLA intervention. In summary, PBMT application increased the first and second successive TTEs, speed of VO2, and muscle oxygenation.

Acute Effects of a Practical Blood Flow Restriction Device During Swimming Exercise.

Purpose: The present study aimed to analyze: 1) the reliability of the tissue saturation index (TSI) and ratings of perceived discomfort (RPD) responses wearing a neoprene practical cuff (PrC), comparing with the responses from traditional (TrC) pneumatic cuffs (study I); 2) the effects of PrC on metabolic (blood lactate concentration, BLC), perceptual (rate of perceived effort, RPE) and kinematic responses at sub-maximal swimming velocities (study II). Methods: Study I; 1) PrC test-retest at rest and during swimming ergometer exercise; 2) BFR at rest with TrC inflated to different percentages of the minimum arterial occlusion pressure (MAOP; 60, 80, 100, 120 and 140%). Test-retest reliability of TSI and RPD was assessed by the intraclass correlation coefficient (ICC) and comparisons among conditions were analyzed by one-way repeated-measures ANOVA. Study II; 1) 50, 200 and 400 m swimming performances; 2) sub-maximal incremental swimming protocol with and without PrC. Two-way repeated measures ANOVA was used to compare all variables during sub-maximal velocities. Results: TSI (ICC = 0.81; 95%CI 0.62-0.91) and RPD (ICC = 0.97; 95%CI 0.94-0.99) were reliable under restricted exercise using PrC. TSI during restricted exercise was lower (p <.001) compared to unrestricted exercise (6.8 ± 6.1% vs. 21.6 ± 8.2% of physiological normalization). PrC showed higher BLC only at or above 91% of critical velocity (p < .03), while stroke rate and RPE were higher (p < .005), and stroke length was lower (p < .03) during all swimming velocities. Conclusion: This easy-to-handle and affordable practical BFR device increased physiological stress at sub-maximal efforts which could be an additional training tool for swimmers.

Modeling the expenditure and reconstitution of distance above critical speed during two swimming interval training sessions.

In swimming, the speed-time relationship provides the critical speed (CS) and the maximum distance that can be performed above CS (D'). During intermittent severe intensity exercise, a complete D' depletion coincides with task failure, while a sub-CS intensity is required for D' reconstitution. Therefore, determining the balance D' remaining at any time during intermittent exercise (D'BAL) could improve training prescription. This study aimed to 1) test the D'BAL model for swimming; 2) determine an equation to estimate the time constant of the reconstitution of D' (τD'); and 3) verify if τD' is constant during two interval training sessions with the same work intensity and duration and recovery intensity, but different recovery duration. Thirteen swimmers determined CS and D' and performed two high-intensity interval sessions at a constant speed, with repetitions fixed at 50 m. The duration of passive recovery was based on the work/relief ratio of 2:1 (T2:1) and 4:1 (T4:1). There was a high variability between sessions for τD' (coefficient of variation of 306%). When τD' determined for T2:1 was applied in T4:1 and vice versa, the D'BAL model was inconsistent to predict the time to exhaustion (coefficient of variation of 29 and 28%). No linear or nonlinear relationships were found between τD' and CS, possibly due to the high within-subject variability of τD'. These findings suggest that τD' is not constant during two high-intensity interval sessions with the same recovery intensity. Therefore, the current D'BAL model was inconsistent to track D' responses for swimming sessions tested herein.

Muscle Fatigue Is Attenuated When Applying Intermittent Compared With Continuous Blood Flow Restriction During Endurance Cycling.

PURPOSE: The aim of this study was to identify a blood-flow-restriction (BFR) endurance exercise protocol that maximizes metabolic strain and minimizes muscle fatigue. METHODS: Twelve healthy participants accomplished 5 different interval cycling endurance exercises (2-min work, 1-min rest) in a randomized order: (1) control, low intensity with unrestricted blood flow (CON30); (2) low intensity with intermittent BFR (i-BFR30, ∼150 mm Hg); (3) low intensity with continuous BFR (c-BFR, ∼100 mm Hg); (4) unloaded cycling with i-BFR0 (∼150 mm Hg); and (5) high intensity (HI) with unrestricted blood flow. Force production, creatine kinase activity, antioxidant markers, blood pH, and potassium (K+) were measured in a range of 5 minutes before and after each cycling exercise protocol. RESULTS: HI showed the highest reduction (Δ = -0.26 [0.05], d = 5.6) on blood pH. Delta pH for c-BRF30 (Δ = -0.02 [0.03], d = 0.8) and Δ pH for i-BRF30 (Δ = -0.04 [0.03], d = 1.6) were different from each other, and both were higher compared with CON30 (Δ = 0.03 [0.03]). There was significant before-to-after force loss following HI (Δ = 55 [40] N·m-1, d = 1.5) and c-BFR30 (Δ = 27 [21] N·m-1, d = 0.7) protocols only, which were accompanied by significant increases in K+ (HI: Δ = 0.94 [0.65] mmol·L-1, d = 1.8; c-BFR30: Δ = 0.72 [0.85] mmol·L-1, d = 1.2). Moreover, all BFR conditions elicited slight increases in plasma creatine kinase, but not for HI and CON30. Glutathione changes from before to after were significant for all BFR conditions and HI, but not for CON30. CONCLUSIONS: The attenuation in fatigue-induced reductions in maximal force suggests that i-BFR exercise could be preferable to c-BFR in improving exercise capacity, with considerably less biologic stress elicited from HI exercises.

Near-infrared spectroscopy-derived muscle V̇O2${\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ kinetics after moderate running exercise in healthy males: reliability and associations with parameters of aerobic fitness.

NEW FINDINGS: What is the central question of this study? What is the reliability of near-infrared spectroscopy-derived muscle oxygen uptake ( mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ ) kinetics following running exercise and what is the relationship between the time constant of mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ off-kinetics and parameters of aerobic fitness? What is the main finding and its importance? The time constant of mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ kinetics in gastrocnemius following moderate running exercise presents good to excellent reliability. In addition, it was well correlated with parameters of aerobic fitness, such as maximal speed of an incremental test, ventilatory threshold and pulmonary V̇O2${\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ on-kinetics. Therefore, near-infrared spectroscopy-derived muscle oxidative capacity together with other physiological measurements may allow a concomitant local and systemic analysis of the components of the oxidative system. ABSTRACT: Near-infrared spectroscopy-derived muscle oxygen uptake ( mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ ) kinetics following single-joint exercise has been used to assess muscle oxidative capacity. However, little evidence is available on the use of this technique following whole-body exercise. Therefore, this study aimed to assess the reliability of the NIRS-derived mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ kinetics following running exercise and to investigate the relationship between the time constant of mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ off-kinetics ( τmV̇O2$\tau {\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ ) and parameters of aerobic fitness. After an incremental test to determine V̇O2max${\dot{V}_{{{\rm{O}}_{\rm{2}}}{\rm{max}}}}$ , first (VT1 ) and second (VT2 ) ventilatory thresholds, and maximal speed (Smax ), 13 males (age = 21 ± 4 years; V̇O2max${\dot{V}_{{{\rm{O}}_{\rm{2}}}{\rm{max}}}}$  = 55.9 ± 3.4 ml kg-1  min-1 ) performed three sets (two on the first day and one on a subsequent day) of two repetitions of 6-min running exercise at 90%VT1 . The pulmonary V̇O2${\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ ( pV̇O2${\rm{p}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ ) on-kinetics and mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ off-kinetics in gastrocnemius were assessed. τmV̇O2$\tau {\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ presented no systematic change and satisfactory reliability (the standard error of the measurement (SEM) and intraclass correlation coefficient of 4.21 s and 0.49 for between transitions; and 2.65 s and 0.74 averaging τmV̇O2$\tau {\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ within each time set), with no difference (P > 0.3) between the within- (SEM = 2.92 s) and between-day variability (SEM = 2.78 s and 2.19 s between first vs. third set, and second vs. third set, respectively). τmV̇O2$\tau {\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ (28.5 ± 4.17 s) correlated significantly (P < 0.05) with Smax (r = -0.66), VT1 (r = -0.64) and time constant of the p V̇O2${\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ on-kinetics (r = 0.69). These findings indicate that NIRS-derived mV̇O2${\rm{m}}{\dot{V}_{{{\rm{O}}_{\rm{2}}}}}$ kinetics in the gastrocnemius following moderate running exercise is a useful and reliable parameter to assess muscle oxidative capacity.

Relationship between peripheral muscle strength, exercise capacity and body composition in children and adolescents with cystic fibrosis.

STUDY DESIGN: This was a transversal analytical study. BACKGROUND: Exercise capacity is usually decreased in cystic fibrosis, impacting the disease prognosis. As well, peripheral muscle strength and nutritional status seem to be related to exercise capacity (EC). OBJECTIVE: To verify the relationship between peripheral muscle strength, pulmonary function and body composition with EC in children and adolescents with CF. METHODS: The study included CF children/adolescents that were clinically stable. The disease's severity was classified according to the Schwachman-Doerschuk score. Initially the subjects underwent bioimpedance and spirometry tests. Quadriceps muscle strength (QMS) and handgrip strength (HG) were evaluated by dynamometry. The Modified Shuttle Walk Test (MSWT) was conducted along with gas analysis in order to measure EC. RESULTS: Twenty-five children/adolescents (10.30 ± 2.33 years old) participated in the survey. 72% were eutrophic, with a mean FEV1 of 68.55%, predicted percentage of the MSWT walked distance (%WD) was 70.91%, and QMS 65.80%. QMS presented significant correlations with absolute WD (r = 0.54), oxygen peak consumption (r = 0.72), lean body mass (LM) (r = 0.83), and body mass index (BMI) (r = 0.69). HG was related with BMI (r = 0.45) and LM (r = 0.65). There was a difference in the %WD between the groups with higher/lower strength (p = .02). CONCLUSION: There was no correlation between HG and EC in this studied sample. Early involvement of QMS was observed even in individuals with low disease severity. This finding reinforces the importance of including this QMS assessment in CF reference centers to monitor, prevent and prescribe adequate exercise training for these individuals.

"Test-retest reliability and minimal detectable change in TGlittre-P test in children and adolescents with cystic fibrosis".

OBJECTIVE: to provide test-retest reliability for the TGlittre-P in children and adolescents with cystic fibrosis (CFG) and healthy controls (HCG), to establish the minimal detectable change for time in TGlittre-P and comparing the performance in the TGlittre-P test between these populations. METHOD: A cross-sectional study evaluated 36 children and adolescents aged 6 to 13. Anthropometric and spirometric evaluation was performed, as well as, on the same day, two TGlittre-P tests with a 30-minute interval between them. RESULTS: TGlittre-P time test-retest reliability was excellent for both groups (CFG: intraclass correlation coefficient [ICC] = 0.849, p < 0.001 and HCG: ICC = 0.913, p < 0.001). As concerning absolute reliability, the time spent presented a small variability with a standard error of measurement of 8.4 s (s) to CFG and 5.3 s to HCG. The minimal detectable change at 95% confidence level (MDC95) was 23.2 s and 14.6 s, respectively. There was no difference between the groups regarding performance in the TGlittre-P test (CFG 179.1 s ± 25.7 s vs. HCG 174.7 s ± 22.3 s) p = 0.589. CONCLUSION: The TGlittre-P is a reliable tool in children and adolescents with CF and healthy controls. The TGlittre-P appears not to be sensitive enough to discriminate a group of children and adolescents with mild cystic fibrosis from healthy counterparts.IMPLICATIONS FOR REHABILITATIONTGlittre-P is a multitasking test that has been used to assess the functional capacity of children and adolescents with chronic diseases.TGlittre-P has excellent reliability in children and adolescents with and without CF.TGlittre-P differences time greater than 12% could indicate changes in the functional capacity of children and adolescents with CF.Other functional capacity tests may be preferred to detect continuous increases in functional capacity through rehabilitation or training, whether children and adolescents obtain performance values close to 100% of predicted.

A-Mode Ultrasound Reliability in Fat and Muscle Thickness Measurement.

ABSTRACT: Ribeiro, G, de Aguiar, RA, Penteado, R, Lisbôa, FD, Raimundo, JAG, Loch, T, Meira, Â, Turnes, T, and Caputo, F. A-mode ultrasound reliability in fat and muscle thickness measurement. J Strength Cond Res 36(6): 1610-1617, 2022-This study aimed to verify the reliability of the BodyMetrix portable A-mode ultrasound in measuring fat and muscle tissue thickness. Thirty physically active men participated in daily body composition evaluations. The evaluations comprised 2 techniques: (a) graphic technique (GTBM), which measured the fat thickness at 9 body sites (abdomen, axillary, biceps brachii, calf, chest, subscapular, suprailiac, thigh, and triceps brachii), and (b) imaging technique (ITBM), which simultaneously measured the fat and muscle thickness of 6 body surfaces (abdomen, biceps brachii, chest, thigh, trapezius, and triceps brachii). Regarding GTBM, relative reliability was moderate to excellent (intraclass correlation coefficient [ICC]: 0.81-0.98), whereas absolute reliability was acceptable for abdomen, calf, chest, subscapular, suprailiac, and triceps brachii (coefficient of variation [CV]: 6.9-8.8%) but high for axillary, biceps brachii, and thigh (CV: 12.0-17.4%) in measuring fat thicknesses. Concerning ITBM, relative reliability was good to excellent (ICC: 0.93-0.99 and 0.90-0.98), whereas absolute reliability was acceptable (CV: 3.0-9.2% and 3.5-5.9%) in measuring fat and muscle thickness, respectively. These findings suggest that the, GTBM was only reliable in measuring fat thickness of abdomen, calf, chest, subscapular, suprailiac, and triceps brachii, whereas ITBM was reliable in measuring both fat and muscle thickness in all regions, but showed better reliability values in measuring muscle than fat thickness.

Effects of Time of Day on Race Splits, Kinematics, and Blood Lactate During a 50-m Front Crawl Performance.

ABSTRACT: Lisbôa, FD, Raimundo, JAG, Pereira, GS, Ribeiro, G, de Aguiar, RA, and Caputo, F. Effects of time of day on race splits, kinematics, and blood lactate during a 50-m front crawl performance. J Strength Cond Res 35(3): 819-825, 2021-This study aimed to investigate the performance, race splits, metabolic, and stroke parameters during 2 successive 50-m front crawl under conditions simulating a competition. Eleven competitive male swimmers (20 ± 3 years, 182 ± 5 cm, and 77 ± 5 kg) performed 2 successive 50-m front crawl trials in a 50-m swimming pool at 10 am and 5 pm. Block time (tB), 15-m performance (t.15-m), and 50-m performance (t.50-m) were measured. Velocity (V), stroke rate (SR), stroke length (SL), and stroke index (SI) were measured at 3 time points during the trials. Pre-trial and post-trial blood samples were taken to determine blood lactate accumulation (Δ[Lac]). For t.50-m, the relative difference between 10 am and 5 pm reached 0.1% (p = 0.7; effect size [ES] = 0.02). Furthermore, no differences in tB (p = 0.12; ES = -0.28) and t.15-m (p = 0.39; ES = -0.16) were observed between periods. Both V (p = 0.11; ES = -0.14) and SI (p = 0.16; ES = 0.15) were also similar. Higher values of SR were recorded at 10 am (p = 0.03; ES = -0.32), whereas the morning values of SL were lower (p = 0.04; ES = 0.3). Δ[Lac] was not significantly different between periods (p = 0.07; ES = -0.27). Although time of the day did not impact performance in 2 successive 50-m front crawl performances, different stroke parameters profiles were observed during these trials. This may help coaches design specific warm-up exercises to enhance performance at different times of the day.

The effects of predictive trials on critical stroke rate and critical swimming speed.

BACKGROUND: Critical swimming speed (CSS) and critical stroke rate (CSR) have important practical applications in evaluating endurance capacity and stroke parameters. The CSS and CSR are determined from the linear regression between two or more performance times with the respective predictive distance or "number of stroke cycles," respectively. It is already known that CSS is dependent on the number and duration of the predictive trials chosen, and performance times ranging from 2 to 12 min have been recommended. However, the effects of predictive trials on the CSR have not been reported. It was hypothesized that CSS and CSR determined by different predictive trials lasting 2 to 12 min would elicit similar values. Therefore, the purpose of the present study was to determine the impact of different combinations of predictive trials lasting 2 to 12 min on both CSR and CSS. METHODS: Thirteen swimmers performed three fixed-distance (200, 400, and 800 m) performances. All possible combinations of CSR and CSS with two (CSR200-400/CSS200-400, CSR200-800/CSS200-800, CSR400-800/CSS400-800) and three (CSR200-400-800/CSS200-400-800) trials were determined. RESULTS: No significant differences were found between CSR and CSS determined with different predictive distance tests. In addition, CSR200-800 and CSS200-800 showed the lowest coefficient of variation and highest intraclass correlation coefficients with CSR200-400-800 and CSS200-400-800, respectively. CONCLUSIONS: This study demonstrated that CSR and CSS were not statistically different when determined with different predictive trials located within the recommended durations of 2-12 min. Nevertheless, CSR200-800 and CSS200-800 exhibited the best consistency with CSR200-400-800 and CSS200-400-800, respectively.

Similar maximal oxygen uptake assessment from a step cycling incremental test and verification tests on the same or different day.

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.

Mechanical power during an incremental test can be estimated from 2000-m rowing ergometer performance.

BACKGROUND: This study aimed to identify the relationship between the mean power output of 2000-m rowing ergometer performance with the peak power output obtained during an incremental test, in addition to verifying the possibility of using the 2000-m mean power as an intensity associated with V̇O2max. METHODS: Nineteen rowers (age 25.5±10.6 years; V̇O2peak: 65.4±5.8 mL/kg/min) completed an incremental test followed by a 2000-m familiarization test (day 1) and a 2000-m rowing ergometer test (day 2). During the incremental test, the peak power output (PV̇O2peak) and the exercise intensity thresholds were determined. The maximal oxygen uptake (V̇O2peak) was analyzed in both tests. RESULTS: The PV̇O2peak (284.8±44.7 W) presented the highest correlation coefficient (r=0.978) with 2000-m mean power (284.2±49.9 W) and was the only one included in stepwise regression explaining 96% of 2000-m mean power. V̇O2peak was lower in the incremental test (4.69±0.61 L/min) compared with the 2000-m rowing ergometer test (4.86±0.63 L/min; P=0.01) with a small bias limits of agreement (0.16±0.53 L/min). CONCLUSIONS: 2000-m mean power is a valid tool to estimate the PV̇O2peak and allow the achievement of V̇O2peak. Furthermore, the PV̇O2peak was the most important predictor of performance.

Speeding of oxygen uptake kinetics is not different following low-intensity blood-flow-restricted and high-intensity interval training.

NEW FINDINGS: What is the central question of this study? Can interval blood-flow-restricted (BFR) cycling training, undertaken at a low intensity, promote a similar adaptation to oxygen uptake ( V̇O2 ) kinetics to high-intensity interval training? What is the main finding and its importance? Speeding of pulmonary V̇O2 on-kinetics in healthy young subjects was not different between low-intensity interval BFR training and traditional high-intensity interval training. Given that very low workloads are well tolerated during BFR cycle training and speed V̇O2 on-kinetics, this training method could be used when high mechanical loads are contraindicated. ABSTRACT: Low-intensity blood-flow-restricted (BFR) endurance training is effective to increase aerobic capacity. Whether it speeds pulmonary oxygen uptake ( V̇O2p ), CO2 output ( V̇CO2p ) and ventilatory ( V̇Ep ) kinetics has not been examined. We hypothesized that low-intensity BFR training would reduce the phase 2 time constant (τp ) of V̇O2p , V̇CO2p and V̇Ep by a similar magnitude to traditional high-intensity interval training (HIT). Low-intensity interval training with BFR served as a control. Twenty-four participants (25 ± 6 years old; maximal V̇O2 46 ± 6 ml kg-1  min-1 ) were assigned to one of the following: low-intensity BFR interval training (BFR; n = 8); low-intensity interval training without BFR (LOW; n = 7); or high-intensity interval training without BFR (HIT; n = 9). Training was 12 sessions of two sets of five to eight × 2 min cycling and 1 min resting intervals. LOW and BFR were conducted at 30% of peak incremental power (Ppeak ), and HIT was at ∼103% Ppeak . For BFR, cuffs were inflated on both thighs (140-200 mmHg) during exercise and deflated during rest intervals. Six moderate-intensity step transitions (30% Ppeak ) were averaged for analysis of pulmonary on-kinetics. Both BFR (pre- versus post-training τp  = 18.3 ± 3.2 versus 14.5 ± 3.4 s; effect size = 1.14) and HIT (τp  = 20.3 ± 4.0 versus 13.1 ± 2.9 s; effect size = 1.75) reduced the V̇O2p τp (P < 0.05). As expected, there was no change in LOW ( V̇O2p τp  = 17.9 ± 6.2 versus 17.7 ± 4.3 s; P = 0.9). The kinetics of V̇CO2p and V̇Ep were speeded only after HIT (38.5 ± 10.6%, P < 0.001 and 31.2 ± 24.7%, P = 0.004, respectively). Both HIT and low-intensity BFR training were effective in speeding moderate-intensity V̇O2p kinetics. These data support the findings of others that low-intensity cycling training with BFR increases muscle oxidative capacity.

Comparison of the physiological responses induced by different pediatric exercise field tests in children.

OBJECTIVE: This study aimed to compare the physiological responses induced by the modified shuttle walk test (MSWT), the 6-minute walk test (6MWT), and the pediatric Glittre activities of daily living test for children (TGlittre-P) in healthy children. METHOD: This was an analytical observational cross-sectional study. All subjects underwent an anthropometric evaluation, pulmonary function test, TGlittre-P, 6MWT, and MSWT using a portable gas analyzer. Each test was conducted on the same day, and a maximum period of 15 days was considered for completion of the 3 days of data collection. RESULTS: Overall, 24 subjects were included (mean age, 9.78 ± 1.27 years). The peak oxygen consumption (VO2peak ) during the MSWT (1409.94 ± 285.13 mL/kg/min) was significantly higher than that during the TGlittre-P (982.19 ± 205.95 mL/kg/min) and 6MWT (982.85 ± 257.09 mL/kg/min) (P < .001 for both). There was no difference in VO2peak  as well as most of the physiological variables between the 6MWT and TGlittre-P (P = .987). The MSWT VO2peak correlated with the 6MWT VO2peak (r = 0.67; P = .00) and the TGlittre-P VO2peak (r = 0.43; P = .04). The VO2peak values achieved in the 6MWT and TGlittre-P were also correlated (r = 0.68; P = .00). Unlike in the MSWT, in which the physiological measurements show an incremental response, the VO2 , heart rate, minute ventilation, and respiratory exchange ratio were stabilized in the TGlittre-P and 6MWT. CONCLUSION: The TGlittre-P and 6MWT showed similar physiological responses and required less metabolic, respiratory, and cardiovascular overload than the MSWT. The performance measures and VO2peak values obtained in the three tests were correlated.

Effects of ischemic conditioning on maximal voluntary plantar flexion contractions.

Intermittent blood flow restriction to local or remote vascular beds induces endogenous protection against ischemia-reperfusion injury in several tissues and organs. When applied non-invasively by placing occlusion cuffs on the limbs, this ischemic conditioning has been shown to elicit an acute ergogenic response. However, the underlying mechanisms behind this phenomenon remain unknown. Prior research suggest that ischemic conditioning may operate via improved motor discharges from the central nervous system, thus enhancing the electrochemical activation and force generation of agonist muscles. Here we show that, for healthy individuals performing maximal voluntary contractions of the plantar flexors, the acute benefit elicited by ischemic conditioning on maximal isometric ankle torque production is largely explained by parallel gains in the surface myoelectrical activity of the triceps surae. However, the magnitude of this response appears to vary between individuals. These findings indicate that enhanced levels of agonist activity contribute to the ergogenic effect of ischemic conditioning during maximal efforts, thereby enabling more direct assessments of neural output following the procedure.

The Impact of Preconditioning Strategies Designed to Improve 2000-m Rowing Ergometer Performance in Trained Rowers: A Systematic Review and Meta-Analysis.

PURPOSE: The 2000-m rowing-ergometer test is the most common measure of rowing performance. Because athletes use different intervention strategies for enhancing performance, investigating the effect of preconditioning strategies on the 2000-m test is of great relevance. This study evaluated the effects of different preconditioning strategies on 2000-m rowing-ergometer performance in trained rowers. METHODS: A search of electronic databases (PubMed, Google Scholar, and Web of Science) identified 27 effects of different preconditioning strategies from 17 studies. Outcomes were calculated as percentage differences between control and experimental interventions, and data were presented as mean ± 90% confidence interval. Performance data were converted to the same metrics, that is, mean power. Meta-regression analyses were conducted to assess whether performance level or caffeine dose could affect the percentage change. RESULTS: The overall beneficial effect on 2000-m mean power was 2.1% (90% confidence limit [CL] ±0.6%). Training status affected the percentage change with interventions, with a -1.1% (90% CL ±1.2%) possible small decrease for 1.0-W·kg-1 increment in performance baseline. Caffeine consumption most likely improves performance, with superior effect in higher doses (≥6 mg·kg-1). Sodium bicarbonate and beta-alanine consumption resulted in likely (2.6% [90% CL ±1.5%]) and very likely (1.4% [90% CL ±1.2%]) performance improvements, respectively. However, some preconditioning strategies such as heat acclimation, rehydration, and creatine resulted in small to moderate enhancements in 2000-m performance. CONCLUSIONS: Supplementation of caffeine and beta-alanine is a popular and effective strategy to improve 2000-m ergometer performance in trained rowers. Additional research is warranted to confirm the benefit of other strategies to 2000-m rowing-ergometer performance.