Effects of Musical Auditory Stimulation on Autonomic Cardiac Response and Cardiorespiratory Parameters During and After Long-term Submaximal Aerobic Exercise

To implement the experimental protocol, all volunteers were informed to not ingest alcoholic or caffeine-based drinks for 12 hours before the experimental procedure; consuming light meal only two hours before and avoid any vigorous physical exertion 24 hours before the testing.

The experimental procedures were divided into three segments, all performed on a treadmill, with a minimum interval of 48 hours between them in order to allow the volunteers to recover. The protocols running time was always set between 5:30 PM and 9:30 PM, to avoid circadian influences. In addition to these, temperature was fixed between 23 ° C and 24 ° C and humidity between 60% and 70%.

Before the first phase of the experimental protocol the volunteers were approved and the investigators obtained body mass by means of a digital scale (Plenna, TIN 00139 Maxima, Brazil) then height, by means of a stadiometer (ES 2020 - Sanny, Brazil). The comparable stages of the experimental protocol were undertaken:

I) Maximal exercise test: the investigators undertook this to record the maximum velocity (Vmax) reached by the volunteer. This was then applied to indirectly determine the anaerobic threshold via the Conconi threshold. Intensity of 60% of the Vmax obtained in the test was lesser than that found in the anaerobic threshold, and this intensity was enforced to perform subsequent steps;

II) Control Protocol (CP): In this period the volunteers were at rest, in the supine position for 15 minutes, followed by 30 minutes of aerobic exercise on a treadmill (five minutes at a speed of 6.0 km / h followed by 25 minutes with 60% of Vmax + 1% grade) and then a recovery period lasting 60 minutes (three minutes standing on the treadmill followed by 57 minutes in the supine position). The volunteers were instructed to remain awake during all the protocol and this was verified and monitored by one of the researchers.