RESUMO
ABSTRACT: Fleitas-Paniagua, PR, de Almeida Azevedo, R, Trpcic, M, Murias, JM, and Rogers, B. Combining near-infrared spectroscopy and heart rate variability derived thresholds to estimate the critical intensity of exercise. J Strength Cond Res 38(1): e16-e24, 2024-Critical intensity determination often requires costly tools and several testing sessions. Alternative approaches display relatively large individual variation. Therefore, simpler estimations with improved precision are needed. This study evaluated whether averaging the heart rate (HR) and oxygen uptake (VÌO 2 ) responses associated with the muscle deoxyhemoglobin concentration breakpoint ([HHb] BP ) and the heart rate variability (HRV) given by the detrended fluctuation analysis second threshold (HRVT2) during ramp incremental (RI) test improved the accuracy of identifying the HR and VÌO 2 at the respiratory compensation point (RCP). Ten female and 11 male recreationally trained subjects performed a 15 W·minute -1 RI test. Gas exchange, near-infrared spectroscopy (NIRS), and RR interval were recorded to assess the RCP, [HHb] BP , and HRVT2. Heart rate (mean ± SD : 158 ± 14, 156 ± 13, 160 ± 14 and, 158 ± 12 bpm) and VÌO 2 (3.08 ± 0.69, 2.98 ± 0.58, 3.06 ± 0.65, and 3.02 ± 0.60 L·minute -1 ) at the RCP, [HHb] BP , HRVT2, and HRVT2&[HHb] BP average (H&H Av ), respectively, were not significantly different ( p > 0.05). The linear relationship between H&H Av and RCP was higher compared with the relationship between [HHb] BP vs RCP and HRVT2 vs RCP for both HR ( r = 0.85; r = 0.73; r = 0.79, p > 0.05) and VÌO 2 ( r = 0.94; r = 0.93; r = 0.91, p > 0.05). Intraclass correlation between RCP, [HHb] BP , HRVT2, and H&H AV was 0.93 for VÌO 2 and 0.79 for HR. The [HHb] BP and the HRVT2 independently provided VÌO 2 and HR responses that strongly agreed with those at the RCP. Combining [HHb] BP and the HRVT2 resulted in estimations of the VÌO 2 and HR at the RCP that displayed smaller variability compared with each modality alone.
Assuntos
Consumo de Oxigênio , Espectroscopia de Luz Próxima ao Infravermelho , Humanos , Masculino , Feminino , Frequência Cardíaca , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Consumo de Oxigênio/fisiologia , Exercício Físico/fisiologia , Teste de Esforço , OxigênioRESUMO
PURPOSE: To determine in trained females and males i) the agreement between the gas exchange threshold (GET), lactate threshold 1 (LT1), and heart rate variability threshold 1 (HRVT1), as well as between the respiratory compensation point (RCP), lactate threshold 2 (LT2), and heart rate variability threshold 2 (HRVT2), and ii) the reproducibility of HRVT1 and HRVT2 during 2-min incremental step protocols. METHODS: Fifty-seven trained participants (24 females) completed a 2-min step incremental test to task failure. Nineteen participants (eight females) completed a second test to evaluate reproducibility. Gas exchange and ventilatory responses, blood lactate concentration, and RR time series were recorded to assess the oxygen consumption (VÌO 2 ) and heart rate (HR) associated with the GET, RCP, LT1, LT2, HRVT1, and HRVT2. RESULTS: VÌO 2 -GET versus VÌO 2 -HRVT1 and HR-GET versus HR-HRVT1 were statistically different for females (29.5 ± 4.0 vs 34.6 ± 6.1 mL·kg -1 ·min -1 ; 154 ± 11 vs 166 ± 12 bpm) and for males (33.9 ± 4.2 vs 42.7 ± 4.6 mL·kg -1 ·min -1 ; 145 ± 11 vs 165 ± 9 bpm; P < 0.001). VÌO 2 and HR at HRVT1 were greater than at LT1 ( P < 0.05). VÌO 2 -RCP versus VÌO 2 -HRVT2 and HR-RCP versus HR-HRVT2 were not statistically different for females (40.1 ± 4.7 vs 39.5 ± 6.7 mL·kg -1 ·min -1 ; 177 ± 9 vs 176 ± 9 bpm) and males (48.4 ± 5.4 vs 47.8 ± 4.8 mL·kg -1 ·min -1 ; 176 ± 8 vs 175 ± 9 bpm; P > 0.05). VÌO 2 and HR responses at LT2 were similar to HRVT2 ( P > 0.05). Intraclass correlation coefficient for VÌO 2 -HRVT1, HR-HRVT1, VÌO 2 -HRVT2, and HR-HRVT2 indicated good reproducibility when comparing the two different time points to standard methods. CONCLUSIONS: Whereas HRVT2 is a valid and reproducible estimate of the RCP/LT2, current approaches for HRVT1 estimation did not show good agreement with outcomes at GET and LT1.
Assuntos
Teste de Esforço , Frequência Cardíaca , Ácido Láctico , Consumo de Oxigênio , Troca Gasosa Pulmonar , Humanos , Frequência Cardíaca/fisiologia , Feminino , Masculino , Consumo de Oxigênio/fisiologia , Reprodutibilidade dos Testes , Ácido Láctico/sangue , Adulto Jovem , Adulto , Teste de Esforço/métodos , Troca Gasosa Pulmonar/fisiologia , Limiar Anaeróbio/fisiologia , Fatores SexuaisRESUMO
An index of heart rate variability (HRV), detrended fluctuation analysis (DFA a1) has gathered interest as a surrogate marker of exercise intensity boundaries. The aim of this report was to examine heart rate variability threshold (HRVT) behavior across different ramp incremental (RI) slopes. Seventeen participants completed a series of three RI (15, 30, and 45 W · min-1 slopes) with monitoring of gas exchange parameters, heart rate (HR) and HRV. HRVT1 was defined as the VÌO2 or HR at which DFA a1 reached 0.75 and the HRVT2 at which these values reached 0.5. HRVTs were compared by Pearson's r, Bland-Altman analysis, ICC3,1 , ANOVA, and paired t-testing. An excellent degree of reliability was seen across all three ramps, with an ICC3,1 of 0.93 and 0.88 for the HRVT1 VÌO2 and HR, respectively, and 0.90 and 0.92 for the HRVT2 VÌO2 and HR, respectively. Correlations between HRVT1/2 of the individual ramps were high with r values 0.84-0.95 for both HR and VÌO2 . Bland-Altman differences ranged between -1.4 and 1.2 mL · kg-1 · min-1 and -2 and +2 bpm. Paired t-testing showed no mean differences between any HRVT1/2 ramp comparisons. Cycling ramp slope does not appear to affect either HRVT1 or HRVT2 in terms of HR or VÌO2 .
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Teste de Esforço , Consumo de Oxigênio , Humanos , Consumo de Oxigênio/fisiologia , Frequência Cardíaca/fisiologia , Reprodutibilidade dos Testes , Ciclismo/fisiologiaRESUMO
The aim of this article is to investigate the effects of different ramp-incremental (RI) slopes on fatigability and its recovery in females and males. Ten females and 11 males performed RI tests with distinct slopes, in separated and randomized sessions, 15 (RI15), 30 (RI30), and 45 (RI45) W·min-1. Performance fatigability was assessed by femoral nerve electrical stimuli evoked during and after isometric maximal voluntary contraction (IMVC) of knee extensors at baseline and after task failure at min 0.5, 1.5, 2.5, 5, and 10. Maximal oxygen uptake (VÌo2max) and peak power output (POpeak) were also measured. There were significant and similar declines from pre- to post-RI test in RI15, RI30, and RI45 for IMVC (-23%; -25%; -25%, respectively; P < 0.05) and potentiated single twitch (-46%; -47%; -49%; P < 0.05), whereas voluntary activation did not change (-1%; -1%; 0%; P > 0.05). There were no RI condition effects, nor time × condition interaction for IMVC, potentiated single twitch and voluntary activation (all P > 0.05). VÌo2max was not different among RI15, RI30, and RI45 conditions (3.30, 3.29, and 3.26 L·min-1, respectively; P = 0.717), but POpeak was (272, 304, and 337 W, respectively; P < 0.001). Overall, performance fatigability profiles were similar between sexes after the RI tests and during recovery. In addition, during recovery, high-frequency doublets and single twitch recovered faster after RI30 and RI45 compared with RI15, regardless of sex (all P > 0.05 for sex differences). In conclusion, RI tests of different slopes that elicited similar VÌo2max but different POpeak did not affect the profile of performance fatigability at task failure in females and males.NEW & NOTEWORTHY It was unknown whether performance fatigability and its recovery are affected by different slopes in a ramp incremental (RI) test. It was also uncertain if females and males would respond differently. Performance fatigability was the same regardless of the RI slope adopted and the sex of the population, which was accompanied by similar maximal oxygen uptake but different power output achieved. The recovery of contractile function was similar between sexes but delayed after slower RI slopes.
Assuntos
Fadiga Muscular , Músculo Esquelético , Humanos , Masculino , Feminino , Fadiga Muscular/fisiologia , Músculo Esquelético/fisiologia , Contração Muscular/fisiologia , Joelho/fisiologia , Contração Isométrica/fisiologia , Oxigênio , EletromiografiaRESUMO
Muscle fatigue is a common symptom induced by exercise. A reversible loss of muscle force is observed with variable rates of recovery depending on the causes or underlying mechanisms. It can not only affect locomotion muscles, but can also affect the heart, in particular after intense prolonged exercise such as marathons and ultra-triathlons. The goal of our study was to explore the effect of four different natural extracts with recognized antioxidant properties on the contractile function of skeletal (locomotion) and cardiac muscles after a prolonged exhausting exercise. Male Wistar rats performed a bout of exhausting exercise on a treadmill for about 2.5 h and were compared to sedentary animals. Some rats received oral treatment of a natural extract (rosemary, buckwheat, Powergrape®, or rapeseed) or the placebo 24 h and 1 h before exercise. Experiments were performed 30 min after the race and after 7 days of recovery. All natural extracts had protective effects both in cardiac and skeletal muscles. The extent of protection was different depending on muscle type and the duration post-exercise (just after and after one-week recovery), including antiarrhythmic effect and anti-diastolic dysfunction for the heart, and faster recovery of contractility for the skeletal muscles. Moreover, the muscular protective effect varied between natural extracts. Our study shows that an acute antioxidant supplementation can protect against acute abnormal endogenous ROS toxicity, induced here by prolonged exhausting exercise.