Comparison of NIRS exercise intensity thresholds with maximal lactate steady state, critical power and rowing performance.

This study aimed to compare the intensity of deoxygenated haemoglobin concentration ([HHb]) and tissue saturation index (TSI) breakpoints ([HHb]-BP and TSI-BP) with maximal lactate steady state (MLSS) and critical power (CP), and to describe their association with 2000-m rowing ergometer performance. Fourteen male rowers performed on a rowing ergometer: I) a discontinuous incremental test with 3-min stages (INC3); II) a continuous incremental test with 1-min stages (INC1); III) constant workload tests to determine MLSS; and IV) performance tests of 500 m, 1000 m, 2000 m and 6000 m to determine CP.CP (257 ± 39 W; 3.79 ± 4.1 L · min-1) was higher than [HHb]-BP3 (205 ± 26 W; 3.48 ± 2.9 L · min-1), [HHb]-BP1 (207 ± 27 W; 3.27 ± 3.2 L · min-1), and TSI-BP3 (218 ± 31 W; 3.51 ± 3.0 L · min-1), but not higher than TSI-BP1 (222 ± 34 W; 3.43 ± 3.2 L · min-1). MLSS (187 ± 26 W; 3.33 ± 3.2 L · min-1) was lower than TSI-BP3 and TSI-BP1 for power output, but not different in any comparison for ⩒O2. The limits of agreement for power output and ⩒O2 suggest poor agreement among these thresholds. The low level of agreement compromises the use of [HHb]-BP and TSI-BP for estimating MLSS and CP; therefore, these thresholds should not be considered interchangeable.

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.

Muscle Oxidative Capacity in Vivo Is Associated With Physiological Parameters in Trained Rowers.

Purpose: The muscle oxygen uptake (mV˙O2) 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 mV˙O2 off-kinetics and verify the relationship of the recovery rate of mV˙O2 (k) with time-trial performance and different aerobic parameters in trained rowers. Methods: Eleven male rowers (age: 20 ± 3 years; V˙O2max: 4.28 ± 0.35 L·min-1) used a rowing ergometer to perform (I) an incremental test to determine the maximal oxygen uptake (V˙O2max) and peak power output (Ppeak); (II) several visits to determine maximal lactate steady state (MLSS); and (III) a 2000-m rowing ergometer performance test. Also, one test to determine mV˙O2 off-kinetics of the vastus lateralis muscle using a repeated arterial occlusions protocol. Results: The mV˙O2 generated a good monoexponential fit (R2 = 0.960 ± 0.030; SEE = 0.041 ± 0.018%.s-1). The k of mV˙O2 (2.06 ± 0.58 min-1) was associated with relative V˙O2max (r = 0.79), power output at MLSS (r = 0.76), and Ppeak (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 mV˙O2 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.

1) The present study showed that the NIRS-derived mV˙O2 off-kinetics from the vastus lateralis can be used as a functional tool of skeletal muscle oxidative metabolism in rowers.2) The results demonstrated that the recovery rate of mV˙O2 was well correlated with important aerobic parameters such as V˙O2max, maximal lactate steady state, and peak power output during an incremental test.

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.

Effects of linear periodization of combined training on quality of life of adults with obesity: a blind randomized controlled trial.

This study aimed to compare the effect of 16-weeks of combining aerobic and strength training with a linear increase or fixed intensity on the health-related quality of life (HRQoL) of obese adults. This single-blinded clinical trial involved adults with obesity (BMI ≥ 30 kg/m2), randomized into control (CG), fixed intensity (FG), or linear increase (LG) groups. The FG and LG performed 16 weeks of combined (aerobic + strength) training for 60 min, three times a week. The FG performed aerobic exercises between 50 and 59% of the heart rate reserve (HRres) and strength at 10-12 maximum repetitions (RM). The LG started with 40-49% of HRres and 12-14 RM and progressively increased the intensity (50-59% and 10-12 RM; 60-69% and 8-10 RM). The HRQoL was assessed using the SF-36 questionnaire. Generalized estimation equations and mean differences (∆) were used. Of the 69 participants (23 per group), 36 completed the intervention (CG = 13, FG = 9, and LG = 14). A significant difference was observed in the time of the physical function, with superiority in the training groups (CG: ∆ = 1.2 vs. FG and LG, respectively: ∆ = 10.0). The mental health component and mental health domain showed significant differences for the FG (∆ = 30.2 and ∆ = 23.1, respectively). In conclusion, the combined training improved physical functioning. Specifically, fixed-intensity training effectively enhanced mental health indicators.Trial Registration: This study is registered at www.ensaiosclinicos.gov.br/ (No. RBR-3c7rt3), Date of registration: 07/02/2018.

Agreement of maximal lactate steady state with critical power and physiological thresholds in rowing.

The aim of this study was threefold: (a) to compare the maximal lactate steady state (MLSS) with critical power (CP); (b) to describe the relationship of MLSS with rowing performances; and (c) to verify the agreement of MLSS with several exercise intensity thresholds in rowers. Fourteen male rowers (mean [SD]: age = 26 [13] years; height = 1.82 [0.05] m; body mass = 81.0 [7.6] kg) performed on a rowing ergometer: (I) discontinuous incremental test with 3 min stages and 30-s recovery intervals (INC3min); (II) continuous incremental test with 60-s stages (INC1min); (III) two to four constant workload tests to determine MLSS; and (IV) performance tests of 500, 1000, 2000 and 6000 m to determine CP. Twenty-seven exercise intensity thresholds based on blood lactate, heart rate and ventilatory responses were determined by incremental tests, and then compared with MLSS. CP (257 [38] W) was higher than MLSS (187 [25] W; p < 0.001), with a very large mean difference (37%), large typical error of estimate (14%) and moderate correlation (r = 0.48). Despite the correlations between MLSS and most intensity thresholds (r > 0.70), all presented low correspondence (TEE > 5%), with a lower bias found between MLSS and the first intensity thresholds (-12.5% to 4.1%). MLSS was correlated with mean power during 500 m (r = 0.65), 1000 m (r = 0.86) and 2000 m (r = 0.78). In conclusion, MLSS intensity is substantially lower than CP and presented low agreement with 27 incremental-derived thresholds, questioning their use to estimate MLSS during rowing ergometer exercise.Highlights MLSS was substantially lower than CP in rowing exercise with a mean difference of 37%, much larger than the difference commonly found in running and cycling exercise (i.e., ?10%).A clear disagreement was reported between MLSS and 27 physiological thresholds determined in different incremental tests.There is a positive association of MLSS with 500, 1000 and 2000 m rowing ergometer performance tests.

Effects of Nonperiodized and Linear Periodized Combined Training on Health-Related Physical Fitness in Adults With Obesity: A Randomized Controlled Trial.

ABSTRACT: Streb, AR, Passos da Silva, R, Leonel, LdS, Possamai, LT, Gerage, AM, Turnes, T, and Del Duca, GF. Effects of nonperiodized and linear periodized combined training on health-related physical fitness in adults with obesity: a randomized controlled trial. J Strength Cond Res 36(9): 2628-2634, 2022-The aim of this randomized controlled trial study was to compare the effects of 16 weeks of linear periodized and nonperiodized combined training (CT) in cardiorespiratory fitness, muscle strength, and body composition indicators of adults with obesity. Thirty-four obese adults of both sexes (36.6 ± 4.4 years; body mass index, 32.9 ± 2.7 kg·m -2 ) were divided into nonperiodized (NG; n = 8), linear periodized (PG; n = 11), and control (CG; n = 15) groups. The NG and PG groups performed 3 weekly sessions of CT over 16 weeks in different ways. Anthropometric measures, maximal strength for leg press and barbell bench press, maximal oxygen uptake (V̇ o2 max), and ventilatory thresholds were determined before and after intervention. The generalized estimation equation was used, with the applied level of significance for the interaction of 0.10 and the isolated effect of time or group or both of 0.05. Significant and similar increases were observed in the 1-repetition maximum test for bench press (NG: 48.8 ± 5.7 to 55.0 ± 6.1 kg; PG: 48.7 ± 5.7 to 53.8 ± 5.9 kg; p = 0.001) and leg press (NG: 235.2 ± 18.7 to 268.3 ± 19.7 kg; PG: 223.1 ± 25.3 to 253.3 ± 23.1 kg; p = 0.05) in trained groups. Relative V̇ o2 max improved only in PG (27.8 ± 1.3 to 32.0 ± 1.4 mL·kg·min -1 ; p = 0.05), while ventilatory thresholds improved in NG and CG ( p = 0.004 and p = 0.06). There was an increase in body mass in CG (97.6 ± 3.4 to 99.1 ± 2.9 kg) and NG (92.5 ± 5.4 to 93.5 ± 5.4 kg; p = 0.05). Combined training improved maximal upper-body and lower-body strength, regardless of periodization. However, for improvement in V̇ o2 max, linear periodization may be superior to nonperiodization in obese adults.

Is Bilateral Deficit in Handgrip Strength Associated With Performance in Specific Judo Tasks?

ABSTRACT: Turnes, T, Silva, BA, Kons, RL, and Detanico, D. Is bilateral deficit in handgrip strength associated with performance in specific judo tasks? J Strength Cond Res 36(2): 455-460, 2022-The aim of this study was to identify the existence of bilateral deficit (BD) on maximal handgrip strength during standing and seated positions in judo athletes and to correlate this with judo-specific tasks. Nineteen male judo athletes (age 22.1 ± 4.6 years) performed unilateral and bilateral handgrip strength tests in seated and standing postures to calculate bilateral index (BI). Athletes then performed the Judogi Grip Strength Test (dynamic and isometric modes) and Special Judo Fitness Test. The comparisons between bilateral and unilateral handgrip strength for each position, weight categories, or training experience (novice <10 years and advanced >10 years) were made by paired and unpaired t-tests. The sum of bilateral forces was significantly lower than unilateral forces at standing (unilateral: 105 ± 20 vs. bilateral: 102 ± 21 kgf, BI: -3.0 ± 5.9%, p = 0.043), but not at seated position (unilateral: 100 ± 19 vs. bilateral: 98 ± 19 kgf, BI: -2.1 ± 7.3%, p = 0.230), indicating BD only at standing position. Pearson coefficient correlations were not significant between judo tests and BI, with similar performance in judo tests between athletes with BD and bilateral facilitation (p > 0.05). Significant BD was observed at standing position in advanced (-4.5 ± 7.1%, p = 0.049) but not in novice athletes (-0.9 ± 3.8%, p = 0.592). We concluded that BI in maximal handgrip strength test was not related with judo-specific tests. However, the BD occurred only at standing position, suggesting that postural stability may contribute for this phenomenon.

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.

Similar Time Near VO2max Regardless of Work Rate Manipulation in Cycling Interval Training.

The current study aimed to compare time spent above 90% V̇O2max (tV̇O2max) during 3 work-matched interval training protocols comprising 8×60-second exercise efforts with decreasing, increasing, or constant work rate distribution within each exercise interval. Ten healthy male subjects (age: 27.6±5.0 years; V̇O2max: 3.82±0.52 L•min-1) performed an incremental test to determine V̇O2max and peak power output (P max). During visits 2, 3, and 4, three work-matched interval training sessions comprising 8×60 s efforts: 60 s active recovery with the power output held constant (100%Pmax; ITCON), decreasing (from 110 to 90%Pmax; ITDEC), or increasing (from 90 to 110%Pmax; ITINC) linearly throughout each work interval. Time sustained above 90% of V̇O2max (tV̇O2max) or HRmax (tHRmax), blood lactate concentrations (BLC) and rating of perceived exertion (RPE) were measured. The tV̇O2max (ITCON: 274±132; ITDEC: 313±102; ITINC: 310±113 s, P=0.37), tHRmax (ITCON: 396±180; ITDEC: 441±207; ITINC: 390±212 s, P=0.47), BLC (P=0.73), and final RPE (P=0.75) were similar among protocols. In conclusion, work-matched interval training induced similar time near V̇O2max and associated physiological responses regardless of work rate manipulation.

Desempenho de corrida e natação de guarda-vidas civis após uma temporada de verão / Running and swimming performance of civilian lifeguards after a summer season

O objetivo do presente estudo foi verificar o desempenho de corrida e natação de guarda-vidas civis após uma temporada de verão em Florianópolis ­ SC. Quatorze guarda-vidas civis (idade: 23.4 ± 5.0 anos; massa corporal: 74.6 ± 8.9 kg; estatura: 176 ± 0.1 cm) realizaram testes de 500m de natação e 1600m de corrida antes e após uma temporada de verão de 5 meses. Não foi realizada nenhuma intervenção na rotina dos guarda -vidas durante esse período. A comparação no desempenho pré e pós temporada foi realizada pelo teste t de Student para dados pareados (bicaudal), enquanto as correlações entre as variáveis foram verificadas pelo coeficiente de correlação de Pearson, com nível de significância de 5% (p < 0.05). Houve piora nos tempos dos testes de 500m de natação (Pré: 501.4 ± 77.9; Pós: 523.1 ± 84.6 s; p < 0.01) e 1600m de corrida (Pré: 371.6 ± 42.3 s; Pós: 393.9 ± 42.7 s; p < 0.01), sem associação entre o tempo de desempenho pré-temporada no teste de natação (r = 0.441, p = 0.115) ou corrida (r = -0.179, p = 0.541) com as magnitudes de piora. Concluiu-se que houve uma piora no desempenho de corrida e natação ao término da temporada de verão nos guarda-vidas civis, o que pode levar a uma perda no rendimento nas atividades que são submetidos rotineiramente. Dessa forma, tornam-se importantes estratégias, como o treinamento sistematizado, para minimizar essa queda no rendimento dos guarda-vidas civis, evitando o risco a si mesmo e a potenciais vítimas.(AU)

: The aim of this study was verify the performance of the running and swimming of civilian lifeguards after a summer season in Florianópolis - SC. Fourteen civilian lifeguards (age: 23.4 ± 5.0 years; body mass: 74.6 ± 8.9 kg; height: 176 ± 0.1 cm) performed tests of 500m swimming and 1600m running before and after a summer season of 5 months. There was no intervention in the routine of the lifeguards during this period. Statistical analysis consisted of a paired t-test (two-tailed) for the pre and post-season comparison, with the correlations between the variables being verified by Pearson's correlation coefficient, with level of significance of 5% (p < 0.05) for all tests. There was an impairment in the 500m swimming test (Pre: 501.4 ± 77.9; Post: 523.1 ± 84.6 s; p <0.01) and 1600m running test (Pre: 371.6 ± 42.3 s; Post: 393.9 ± 42.7 s; p <0.01), without association between the pre-season performance time and the swimming (r = 0.441, p = 0.115) or running (r= -0.179, p = 0.541) impairment magnitudes. It was concluded that running and swimming performance are impaired at the end of the summer season on civilian lifeguards, which could cause a loss of performance in routine activities. Thus, become important strategies, such as systematic training, to minimize this fall in the performance of civilian lifeguards, avoiding the risk to themselves and potential victims. (AU)

Time Spent Near V˙O2max During Different Cycling Self-Paced Interval Training Protocols.

PURPOSE: Cyclists may increase exercise intensity by prolonging exercise duration and/or shortening the recovery period during self-paced interval training, which could impact the time spent near V˙O2max. Thus, the main objective of this study was to compare the time spent near V˙O2max during 4 different self-paced interval training sessions. METHODS: After an incremental test, 11 cyclists (mean [SD]: age = 34.4 [6.2] y; V˙O2max=55.7 [7.4] mL·kg-1·min-1) performed in a randomized order 4 self-paced interval training sessions characterized by a work-recovery ratio of 4:1 or 2:1. Sessions comprised 4 repetitions of 4 minutes of cycling with 1 minute (4/1) or 2 minutes (4/2) of active recovery or 8 minutes of cycling with 2 minutes (8/2) or 4 minutes (8/4) of active recovery. Time spent at 90% to 94% (t90V˙O2max), ≥95% (t95V˙O2max), and 90% to 100% V˙O2max (tV˙O2max) was analyzed in absolute terms and relative to the total work duration. Power output, heart rate, blood lactate, and rating of perceived exertion were compared. RESULTS: The 8/4 session provided higher absolute tV˙O2max and t95V˙O2max than 8/2 (P = .015 and .029) and 4/1 (P = .002 and .047). The 4/2 protocol elicited higher relative tV˙O2max (47.7% [26.9%]) and t95V˙O2max (23.5% [22.7%]) than 4/1 (P = .015 and .028) and 8/2 (P < .01). Session 4/2 (275 [23] W) elicited greater mean power output (P < .01) than 4/1 (261 [27] W), 8/4 (250 [25] W), and 8/2 (234 [23] W). CONCLUSIONS: Self-paced interval training composed of 4-minute and 8-minute work periods efficiently elicit tV˙O2max, but protocols with a work-recovery ratio of 2:1 (ie, 4/2 and 8/4) could be prioritized to maximize tV˙O2max.

Comparative effects of two heat acclimation protocols consisting of high-intensity interval training in the heat on aerobic performance and thermoregulatory responses in exercising rats.

Acclimation resulting from low- to moderate-intensity physical exertion in the heat induces several thermoregulatory adaptations, including slower exercise-induced increases in core body temperature. However, few studies have investigated the thermoregulatory adaptations induced by high-intensity interval training (HIIT) protocols. Thus, the present study aimed to compare the adaptations in rats' thermoregulatory parameters and aerobic performance observed after two different heat acclimation regimens consisting of HIIT protocols performed in a hot environment. Twenty-three adult male Wistar rats were initially subjected to an incremental-speed exercise at 32°C until they were fatigued and then randomly assigned to one of the following three heat acclimation strategies: passive heat exposure without any exercise (untrained controls-UN; n = 7), HIIT performed at the maximal aerobic speed (HIIT100%; n = 8) and HIIT performed at a high but submaximal speed (HIIT85%; n = 8). Following the two weeks of interventions, the rats were again subjected to a fatiguing incremental exercise at 32°C, while their colonic temperature (TCOL) was recorded. The workload performed by the rats and their thermoregulatory efficiency were calculated. After the intervention period, rats subjected to both HIIT protocols attained greater workloads (HIIT100%: 313.7 ± 21.9 J vs. HIIT85%: 318.1 ± 32.6 J vs. UN: 250.8 ± 32.4 J; p < 0.01) and presented a lower ratio between the change in TCOL and the distance travelled (HIIT100%: 4.95 ± 0.42°C/km vs. HIIT85%: 4.33 ± 0.59°C/km vs. UN: 6.14 ± 1.03°C/km; p < 0.001) when compared to UN rats. The latter finding indicates better thermoregulatory efficiency in trained animals. No differences were observed between rats subjected to the two HIIT regimens. In conclusion, the two HIIT protocols induce greater thermoregulatory adaptations and performance improvements than passive heat exposure. These adaptations do not differ between the two training protocols investigated in the present study.

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.

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.

Comparison of linear periodized and non-periodized combined training in health markers and physical fitness of adults with obesity: Clinical trial protocol.

The literature discusses that combined training, aerobic more resistance exercises in the same session, is a suitable strategy for people with obesity and that exercise periodization leads to positive health outcomes; however, the implication of different periodizations of combined training for health outcomes in obese adults requires further investigation. The aim of the study will be to describe the methodology used to compare the effect of linear periodized and non-periodized combined training on health markers and health-related physical fitness in adults with obesity. This is a blinded randomized controlled clinical trial investigating adults with obesity in the age group 20-50 years. The sample will be non-probabilistic, and participants will be allocated randomly into one of three groups: control group (CG), non-periodized group (NG), and periodized group (PG). The intervention will occur in 60-min sessions, 3 days a week for 16 weeks, with 1 week dedicated to familiarization with the training and 15 weeks of combined training (aerobic followed by resistance in the same session). The PG group will perform three mesocycles of 5 weeks each, progressing in intensity throughout the intervention [aerobic: from 40-49% to 60-69% of heart rate reserve (HRR); strength: from 12 to 14 maximum repetitions (MR) to 8 to 10MR]; the NG group will maintain the same relative intensity throughout the study (aerobic: 50-59% of HRR; strength: 2 sets of 10-12 MR). Participants in the CG group will maintain their usual activities without the proposed intervention. Pre- and post-intervention assessments will be performed for biochemical markers, body composition, cardiovascular parameters, cardiorespiratory fitness, maximum upper and lower limb strength, flexibility, and subjective health-related parameters. This project was approved by the Committee of Ethics and Research with Human Beings of the institution of origin (protocol 2,448,674) and registered in the Brazilian Registry of Clinical Trials (RBR-3c7rt3).

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.

Association Between Deoxygenated Hemoglobin Breaking Point, Anaerobic Threshold, and Rowing Performance.

PURPOSE: To compare the intensity and physiological responses of deoxygenated hemoglobin breaking point ([HHb]BP) and anaerobic threshold (AnT) during an incremental test and to verify their association with 2000-m rowing-ergometer performance in well-trained rowers. METHODS: A total of 13 male rowers (mean [SD] age = 24 [11] y and V˙O2peak = 63.7 [6.1] mL·kg-1·min-1) performed a step incremental test. Gas exchange, vastus lateralis [HHb], and blood lactate concentration were measured. Power output, V˙O2, and heart rate of [HHb]BP and AnT were determined and compared with each other. A 2000-m test was performed in another visit. RESULTS: No differences were found between [HHb]BP and AnT in the power output (236 [31] vs 234 [31] W; Δ = 0.7%), 95% confidence interval [CI] 6.7%), V˙O2 (4.2 [0.5] vs 4.3 [0.4] L·min-1; Δ = -0.8%, 95% CI 4.0%), or heart rate (180 [16] vs 182 [12] beats·min-1; Δ = -1.6%, 95% CI 2.1%); however, there was high typical error of estimate (TEE) and wide 95% limits of agreement (LoA) for power output (TEE 10.7%, LoA 54.1-50.6 W), V˙O2 (TEE 5.9%, LoA -0.57 to 0.63 L·min-1), and heart rate (TEE 2.4%, LoA -9.6 to 14.7 beats·min-1). Significant correlations were observed between [HHb]BP (r = .70) and AnT (r = .89) with 2000-m mean power. CONCLUSIONS: These results demonstrate a breaking point in [HHb] of the vastus lateralis muscle during the incremental test that is capable of distinguishing rowers with different performance levels. However, the high random error would compromise the use of [HHb]BP for training and testing in rowing.