Despite the positive effects of low-level laser therapy (LLLT) on muscle fatigue before exercises using a single muscle group, the acute effects of LLLT on performance in cardiopulmonary exercise testing (CPET) are poorly understood. We aimed to assess the acute effects of LLLT on physiologic and electromyographic responses to the CPET in healthy adults. A randomized, double-blind, placebo-controlled crossover trial was performed with 18 untrained participants (nine males, 22 ± 2 years). We applied LLLT or placebo on quadriceps and gastrocnemius 10 min before two rapidly incremental CPETs randomly performed in alternate days on a cycle ergometer. Participants received LLLT using a multidiode cluster, 20 s/site (850 nm, 100 mW/diode, 14 J/site). Physiological responses to the CPET were continuously monitored using a gas analyzer. The electromyographic fatigue threshold (EMGth) was assessed through surface electrodes on vastus lateralis. The root mean square (RMS) was plotted every 5 s against the exercise intensity, and its breakpoint values throughout the CPET was identified as EMGth. Compared to placebo, the LLLT significantly increased peak O2 uptake (V'O2 33 ± 10 vs. 31 ± 9 mL/min/kg). We observed a shallower slope of the Δheart rate/ΔV'O2 during the CPET after LLLT compared to placebo, i.e., increased cardiovascular efficiency (56 ± 24 vs. 66 ± 30 bpm/L/min). There were no LLLT-related changes in EMGth. The LLLT acutely increases exercise performance in healthy untrained adults probably due to increased O2 extraction by peripheral muscles without causing a significant impact on muscle fatigue.
We evaluated age- and sex-dependent differences in heart rate variability (HRV) during the 6-min walk test (6MWT) in healthy adults. We also evaluated the intensity of the 6MWT based on HRV. 78 participants aged 40-49, 50-59, 60-69, and ≥ 70 years (42 females; 36 men) performed the 6MWT. Heart rate and HRV were monitored 1 min at rest and during the last 2-min of the test. The root mean square (RMSSD), instantaneous beat-to-beat variability (SD1), and long-term standard deviation (SD2) of RR intervals were calculated. The SD1 <3 ms at the end of the 6MWT was defined as high-intensity exercise. Despite the significantly higher peak values of heart rate observed for women, we did not find sex- and age-related differences in HRV during the 6MWT. The ROC curve identified percentage of maximum heart rate >67% as the best cut-point for prediction of high-intensity exercise with 94% of sensitivity and 65% of specificity (area under the curve=0.804). We may conclude that autonomic modulation of heart rate during exercise was not dependent of age and sex. The HRV assessment during walking enables a valid estimation of exercise intensity in adults. We may therefore suggest the use of 6MWT for assessing exercise capacity and for prescribing exercises in adults aged 40 yrs and older.
O objetivo deste estudo foi avaliar as correlações existentes entre o Nível de Atividade Física Habitual (NAFH) mensurado por acelerometria, a distância percorrida no Teste de Caminhada de Seis Minutos (DTC6) e o escore obtido por meio de um questionário de NAFH. Trinta e três adultos (23 mulheres; 64±7 anos) foram avaliados. Os participantes responderam ao Questionário Internacional de Atividade Física (IPAQ) e foram submetidos a dois Testes de Caminhada de Seis Minutos (TC6). A média do número de passos diários (NPM) de cinco dias foi analisada por um acelerômetro uniaxial. As correlações entre as variáveis estudadas foram avaliadas e dois modelos de regressão múltipla foram desenvolvidos para comparar a influência das variáveis estudadas no NPM. No primeiro modelo, foram considerados a DTC6 e o escore total do IPAQ como variáveis independentes. No segundo modelo, a DTC6 e variáveis demográficas e antropométricas foram incluídas (por exemplo, idade, estatura, peso e gênero). O NPM correlacionou-se significativamente (p<0,05) com a DTC6 (r=0,51) e com o escore total do IPAQ (r=0,47). Após análise de regressão, apenas a DTC6 foi selecionada como determinante de 26,5% da variabilidade total do NPM. Podemos concluir que o TC6 correlacionou-se apenas moderadamente com o NAFH. Entretanto, associado ao sexo, a DTC6 foi capaz de explicar 36,6% da variabilidade total do NPM.
Fisioter Mov. 2012 out/dez;25(4):839-47 Bueno FR, Corrêa FR, Alves MAS, Bardin MG, Modesto JA, Dourado VZ. 840 apresentaram complicações pós-operatórias (grupo C) e dez evoluíram bem (grupo SC). O grupo C apresentou idade mais avançada (57 ± 6 vs. 71 ± 7 anos; p < 0,05), FPM inferior (33 ± 6 vs. 41 ± 9 kgf) e ISWT inferior (208 ± 81 vs. 311 ± 66 m). Não houve diferenças significativas para o TC6. A regressão logística selecionou o ISWT como determinante do prognóstico dos pacientes (p = 0,04). Conclusão: Os pacientes à espera de CRM eletiva apresentam significativa redução da capacidade de exercício e o ISWT apresentou valor prognóstico significativo discriminando os pacientes com complicações pós-operatórias.[P]Palavras-chave: Doença arterial coronariana. Capacidade de exercício. ISWT. TC6.[ [K]
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