Lifelong endurance training and dynamic cerebral autoregulation

It is well known that aerobic exercise training enhances cardiac baroreflex function and lowers arterial blood pressure. As discussed in previous posts, the impact of exercise training on cerebral hemodynamics remains ambiguous. I once wrote a post over at Scientopia describing a study that reported a less effective dynamic cerebral autoregulation (measured by the thigh cuff method) in rather fit subjects. Interestingly, evidence suggests that cardiac baroreflex function is inversely related to dynamic cerebral autoregulation. Could exercise training lead to a deterioration of dynamic cerebral autoregulation notwithstanding the known benefit for cardiac baroreflex function ?

A new and very interesting study by Aengevaeren et al. investigated the influence of lifelong exercise (comparing 11 Masters athletes (73±6 yrs, aerobic training >15 yrs) and 12 healthy sedentary elderly (71±6 yrs)) on cardiac baroreflex function and dynamic cerebral autoregulation.

Baroreflex function and dynamic cerebral autoregulation were assessed using transfer function analysis of spontaneous changes in systolic blood pressure and R-R interval in the low frequency range (0.05-0.15 Hz) and during sit-stand induced changes in mean blood pressure and cerebral blood flow velocity at 0.05 Hz (10s sit, 10s stand), respectively.

The Masters athletes had a better cardiac baroreflex function but dynamic cerebral autoregulation was similar compared to sedentary elderly. In addition, there were no correlations between cardiac baroreflex function and dynamic cerebral autoregulation.

These results are in contrast with findings from that study suggesting a less effective dynamic cerebral autoregulation in fit volunteers.

However, as discussed by the authors:

Confounding factors, such as the limitations of cross-sectional study, differences in the study population as well as the uncertainty about a potential dose response relationship of exercise training and CBF regulation all may have contributed to these inconsistent findings. However, the present study provides evidence that dCA was not compromised in the Masters athletes who had participated in lifelong endurance exercise training.

I am wondering if similar results would have been reported if the authors used the thigh cuff method in order to induce an important reduction in mean arterial pressure…We now need a well-designed intervention study to elucidate the impact of aerobic exercise training on dynamic cerebral autoregulation in athletes !

Reference

Aengevaeren VL, Claassen JA, Levine BD, Zhang R.  Cardiac baroreflex function and dynamic cerebral autoregulation in elderly masters athletes J Appl Physiol 2012. Epub ahead of print.

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