Can geometric indices of heart rate variability predict improvement in autonomic modulation after resistance training in chronic obstructive pulmonary disease?

Chronic obstructive pulmonary disease (COPD) is associated with autonomic dysfunctions that can be evaluated through heart rate variability (HRV). Resistance training promotes improvement in autonomic modulation; however, studies that evaluate this scenario using geometric indices, which include nonlinear evaluation, thus providing more accurate information for physiological interpretation of HRV, are unknown. This study aimed to investigate the influence of resistance training on autonomic modulation, using geometric indices of HRV, and peripheral muscle strength in individuals with COPD. Fourteen volunteers with COPD were submitted to resistance training consisting of 24 sessions lasting 60 min each, with a frequency of three times a week. The intensity was determined as 60% of one maximum repetition and was progressively increased until 80% for the upper and lower limbs. The HRV and dynamometry were performed at two moments, the beginning and the end of the experimental protocol. Significant increases were observed in the RRtri (4·81 ± 1·60 versus 6·55 ± 2·69, P = 0·033), TINN (65·36 ± 35·49 versus 101·07 ± 63·34, P = 0·028), SD1 (7·48 ± 3·17 versus 11·04 ± 6·45, P = 0·038) and SD2 (22·30 ± 8·56 versus 32·92 ± 18·78, P = 0·022) indices after the resistance training. Visual analysis of the Poincare plot demonstrated greater dispersion beat-to-beat and in the long-term interval between consecutive heart beats. Regarding muscle strength, there was a significant increase in the shoulder abduction and knee flexion. In conclusion, geometric indices of HRV can predict improvement in autonomic modulation after resistance training in individuals with COPD; improvement in peripheral muscle strength in patients with COPD was also observed.

Influence of Smoking Consumption and Nicotine Dependence Degree in Cardiac Autonomic Modulation / Influência do Consumo Tabagístico e Grau de Dependência Nicotínica na Modulação Autonômica Cardíaca

Abstract Background: Smoking consumption alters cardiac autonomic function. Objective: Assess the influence of the intensity of smoking and the nicotine dependence degree in cardiac autonomic modulation evaluated through index of heart rate variability (HRV). Methods: 83 smokers, of both genders, between 50 and 70 years of age and with normal lung function were divided according to the intensity of smoking consumption (moderate and severe) and the nicotine dependency degree (mild, moderate and severe). The indexes of HRV were analyzed in rest condition, in linear methods in the time domain (TD), the frequency domain (FD) and through the Poincaré plot. For the comparison of smoking consumption, unpaired t test or Mann-Whitney was employed. For the analysis between the nicotine dependency degrees, we used the One-way ANOVA test, followed by Tukey's post test or Kruskal-Wallis followed by Dunn's test. The significance level was p < 0,05. Results: Differences were only found when compared to the different intensities of smoking consumption in the indexes in the FD. LFun (62.89 ± 15.24 vs 75.45 ± 10.28), which corresponds to low frequency spectrum component in normalized units; HFun (37.11 ± 15.24 vs 24.55 ± 10.28), which corresponds to high frequency spectrum component in normalized units and in the LF/HF ratio (2.21 ± 1.47 vs 4.07 ± 2.94). However, in the evaluation of nicotine dependency, significant differences were not observed (p > 0.05). Conclusion: Only the intensity of smoking consumption had an influence over the cardiac autonomic modulation of the assessed tobacco smokers. Tobacco smokers with severe intensity of smoking consumption presented a lower autonomic modulation than those with moderate intensity.

Resumo Fundamento: O tabagismo altera a função autonômica cardíaca. Objetivo: Avaliar a influência da intensidade do consumo tabagístico e do grau de dependência nicotínica na modulação autonômica cardíaca avaliada por meio de índices de variabilidade da frequência cardíaca (VFC). Métodos: 83 tabagistas, de ambos os sexos, faixa etária entre 50 e 70 anos de idade e com função pulmonar normal foram divididos de acordo com a intensidade do consumo tabagístico (moderado e grave) e o grau de dependência nicotínica (leve, moderado e grave). Os índices de VFC foram analisados em condição de repouso, em métodos lineares no domínio do tempo (DT), domínio da frequência (DF) e pelo plot de Poincaré. Para comparação do consumo tabagístico, foi utilizado teste t não pareado ou Mann-Whitney. Para análise entre os graus de dependência nicotínica, foi utilizado teste One-way ANOVA seguido de pós-teste de Tukey ou Kruskal-Wallis seguido pelo teste de Dunn. O nível de significância foi de p < 0,05. Resultados: Diferenças só foram encontradas quando comparadas às diferentes intensidades do consumo tabagístico nos índices no DF: LFun (62,89 ± 15,24 vs 75,45 ± 10,28), que corresponde ao componente espectral de baixa frequência em unidades normalizadas; HFun (37,11 ± 15,24 vs 24,55 ± 10,28), que corresponde ao componente espectral de alta frequência em unidades normalizadas e na relação LF/HF (2,21 ± 1,47 vs 4,07 ± 2,94). No entanto, na avaliação da dependência nicotínica não foram observadas diferenças significativas (p > 0,05). Conclusão: Apenas a intensidade do consumo tabagístico promoveu influências sobre a modulação autonômica cardíaca dos tabagistas avaliados. Tabagistas com intensidade de consumo tabagístico grave apresentaram menor modulação autonômica do que tabagistas moderados.

Influence of Smoking Consumption and Nicotine Dependence Degree in Cardiac Autonomic Modulation.

BACKGROUND: Smoking consumption alters cardiac autonomic function. OBJECTIVE: Assess the influence of the intensity of smoking and the nicotine dependence degree in cardiac autonomic modulation evaluated through index of heart rate variability (HRV). METHODS: 83 smokers, of both genders, between 50 and 70 years of age and with normal lung function were divided according to the intensity of smoking consumption (moderate and severe) and the nicotine dependency degree (mild, moderate and severe). The indexes of HRV were analyzed in rest condition, in linear methods in the time domain (TD), the frequency domain (FD) and through the Poincaré plot. For the comparison of smoking consumption, unpaired t test or Mann-Whitney was employed. For the analysis between the nicotine dependency degrees, we used the One-way ANOVA test, followed by Tukey's post test or Kruskal-Wallis followed by Dunn's test. The significance level was p < 0,05. RESULTS: Differences were only found when compared to the different intensities of smoking consumption in the indexes in the FD. LFun (62.89 ± 15.24 vs 75.45 ± 10.28), which corresponds to low frequency spectrum component in normalized units; HFun (37.11 ± 15.24 vs 24.55 ± 10.28), which corresponds to high frequency spectrum component in normalized units and in the LF/HF ratio (2.21 ± 1.47 vs 4.07 ± 2.94). However, in the evaluation of nicotine dependency, significant differences were not observed (p > 0.05). CONCLUSION: Only the intensity of smoking consumption had an influence over the cardiac autonomic modulation of the assessed tobacco smokers. Tobacco smokers with severe intensity of smoking consumption presented a lower autonomic modulation than those with moderate intensity.