Effects of age and physical activity on the autonomic control of heart rate in healthy men

The effects of the aging process and an active life-style on the autonomic control of heart rate (HR) were investigated in nine young sedentary (YS, 23 ± 2.4 years), 16 young active (YA, 22 ± 2.1 years), 8 older sedentary (OS, 63 ± 2.4 years) and 8 older active (OA, 61 ± 1.1 years) healthy men. Electrocardiogram was continuously recorded for 15 min at rest and for 4 min in the deep breathing test, with a breath rate of 5 to 6 cycles/min in the supine position. Resting HR and RR intervals were analyzed by time (RMSSD index) and frequency domain methods. The power spectral components are reported in normalized units (nu) at low (LF) and high (HF) frequency, and as the LF/HF ratio. The deep breathing test was analyzed by the respiratory sinus arrhythmia indices: expiration/inspiration ratio (E/I) and inspiration-expiration difference (deltaIE). The active groups had lower HR and higher RMSSD index than the sedentary groups (life-style condition: sedentary vs active, P < 0.05). The older groups showed lower HFnu, higher LFnu and higher LF/HF ratio than the young groups (aging effect: young vs older, P < 0.05). The OS group had a lower E/I ratio (1.16) and deltaIE (9.7 bpm) than the other groups studied (YS: 1.38, 22.4 bpm; YA: 1.40, 21.3 bpm; OA: 1.38, 18.5 bpm). The interaction between aging and life-style effects had a P < 0.05. These results suggest that aging reduces HR variability. However, regular physical activity positively affects vagal activity on the heart and consequently attenuates the effects of aging in the autonomic control of HR.

Modulacao do sistema nervoso autonomico na resposta da frequencia cardiaca em repouso e a manobra de valsalva com o incremento da idade / Modulation of autonomic nervous system in the heart rate responseto rest and the valsalva maneuver with increasing age

A Manobra de Valsalva (MV) provoca sobrecarga no sistema cardiovascular, ativando barorreceptores arteriais, quimiorreceptores e receptores cardiopulmonares. Ha interacao entre os receptores e o sistema nervoso central, desencadeando respostas autonomicas que modulam a resposta da frequencia cardiaca (FC). O objetivodo presente estudo foi verificar o controle autonomico do coracao nas seguintes condicoes: a)durante a MV; b)em repouso, nas condicoes supina e sentada; c)antes e apos a MV, na posicao supina em homens jovens de meia idade. Dezesseis voluntarios jovens (mediana=22,5 anos) e 11 de meia idade (mediana=43 anos) foram submetidos a uma avaliacao clinica e cardiovascular. A FC foi captada batimento a batimento em tempo real: a) durante 900s em repouso, na posicao supina sentada; b) durante 60sem repouso, com respiracao espontanea, e 20s em MV, mantendo pressao oral de 40mmHg e apos, por 280s, com respiracao espontanea. Os dados foram analisados por meio do indicede Valsava, da variacao dos intervalos RR e da variabilidade da FC (VFC) por meio do indice RMSSD dos intervalos RR em milissegundos. Os resultados mostram que a VFC, o indice de Valsavae a variacao dos intervalos RR foram menores nos voluntarios de meia idade comparativamente aos jovens (p<0,05). Tais resultados sugerem diminuicao da atividade parassimpatica atuante sobre o nodulo sinoatrial com o incremento de idade