Rhythmic sensory stimulation improves fitness by conditioning the autonomic nervous system

Endurance training is known to alter the functioning of the autonomic nervous system, a major goal when pursuing fitness. Here, we test the hypothesis that the training-associated rhythmic sensations alone, hence without the usual accompanying physical exercise, accomplish this effect.

We studied sixteen resting healthy male volunteers, age (mean±SD) 25.9±3.7 years. During one hour we applied, at marching pace (2 bursts per second), bipolar transcutaneous electrical sensory nerve stimulation to both feet. The stimulation intensity was controlled in such a way that discharges of sensory fibres in the tibial and fibular nerves were induced, while motor fibres were not excited. Heart rate, blood pressure, and baroreflex sensitivity were measured before and after stimulation.

Baseline baroreflex sensitivity and systolic blood pressure were 8.7±4.5 ms·mmHg-1 and 117.5±6.4 mmHg, respectively. Directly after rhythmic sensory stimulation baroreflex sensitivity had increased to 10.0±4.1 ms·mmHg-1 (p<0.05). One day later, systolic blood pressure had lowered to 111.7±5.5 mmHg (p<0.01).

Rhythmic sensory stimulation entails autonomic adaptations that are comparable with those of exercise. This demonstration of sensory-induced autonomic adaptations without any muscular involvement may help to design alternative, low-effort fitness programmes for specific categories of sedentary, diseased or disabled persons.