Article

Dose-response relationship of endurance training for autonomic circulatory control in healthy seniors

University of Texas at Dallas, Richardson, Texas, United States
Journal of Applied Physiology (Impact Factor: 3.43). 10/2005; 99(3):1041-9. DOI: 10.1152/japplphysiol.00085.2005
Source: PubMed

ABSTRACT Aging results in marked abnormalities of cardiovascular regulation. Regular exercise can improve many of these age-related abnormalities. However, it remains unclear how much exercise is optimal to achieve this improvement or whether the elderly can ever improve autonomic control by exercise training to a degree similar to that observed in healthy young individuals. Ten healthy sedentary seniors [71 +/- 3 (SD) yr] trained for 12 mo; training involved progressive increases in volume and intensity. Static hemodynamics were measured, and R-wave-R-wave interval (RRI), beat-to-beat blood pressure (BP) variability, and transfer function gain between systolic BP and RRI were calculated at baseline and every 3 mo during training. Data were compared with those obtained in 12 Masters athletes (68 +/- 3 yr) and 11 healthy sedentary young individuals (29 +/- 6 yr) at baseline. Additionally, the adaptation of these variables after completion of identical training loads was compared between the seniors and the young. Indexes of RRI variability and baroreflex gain were decreased in the sedentary seniors but preserved in the Masters athletes compared with the young at baseline. With training in the seniors, baroreflex gain and resting BP showed a peak adaptation after moderate doses of training following 3-6 mo. Indexes of RRI variability continued to improve with increasing doses of training and increased to the same magnitude as the young at baseline after heavy doses of training for 12 mo; however, baroreflex gain never achieved values equivalent to the young at baseline, even after a year of training. The magnitude of the adaptation of these variables to identical training loads was similar (no interaction effects of age x training) between the seniors and the young. Thus RRI variability in seniors improves with increasing "dose" of exercise over 1 yr of training. In contrast, more moderate doses of training for 3-6 mo may optimally improve baroreflex sensitivity, associated with a modest hypotensive effect; however, higher doses of training do not lead to greater enhancement of these changes. Seniors retain a similar degree of "trainability" as young subjects for cardiac autonomic function to dynamic exercise.

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    • "Alternatively, Goldstein and colleagues (Goldstein et al. 2011; Rahman et al. 2011) suggest LF power reflects baroreflex function and cardiac autonomic modulation by these sensory neurones (Rahman et al. 2011). Young apparently healthy (Iwasaki et al. 2003; Komine et al. 2009) and older participants (Monahan et al. 2001; Okazaki et al. 2005) display improved baroreflex function with training and our observation of increased absolute LF power complements this work. Whether a greater dose of interval exercise that induces high metabolic stress eventually causes an unfavourable regulation of HRV and baroreflex as noted in athletes (Iellamo et al. 2002) requires detailed study. "
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    • "Heart rate variability measures showed no dose– response between the more fit groups in our study and other cross-sectional data show a negative dose– response (Buchheit et al., 2005, 2006). Longitudinal studies have shown that 3 months of moderate exercise is sufficient to increase heart rate variability indices and that longer-term, more intense training results in no further gains (Iwasaki, Zhang, Zuckerman , & Levine, 2003; Okazaki et al., 2005). The lack of a dose–response between exercise levels and heart rate variability indices appears to be a reproducible physiological phenomenon. "
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