Experimental Group

Control Group

In both experimental and control groups participants walked on a treadmill at 5.5 km/h with 5º inclination for 6 minutes. The experimental group (EG) added throughout the 6 minutes intervention the following breathing pattern cyclically: 5 seconds breathing normally followed by 10 seconds of low volume apnoea, performing a total of 24 cycles of normal breathing continued by apnoea.

PPT refers to the minimal amount of pressure needed to cause the first sensation of pain. The mechanical pressure algometer (PAIN TEST™ FPX 25, Wagner Instruments, Greenwich, CT, USA) counted with a round rubber disc of 1 cm2, displaying values in Kg, hence, data was expressed in Kg/cm2. Two locations, in upper and lower limbs, were examined to examine systemic hypoalgesia effects. The dorsal distal-phalange base of the thumb and tibialis anterior muscle belly, both in the dominant limb, were tested. These regions were marked with a pen before assessments, to repeat the trials in the same place. Three trials were tested in each location, with 30 seconds rest between trials. Pressure speed was paced with a metronome applying a constant force of 0.5 Kg/cm2/s ± 0.1 Kg/cm2/s.

Conditioning stimulus was applied on the contralateral limb to test stimulus, since its arrangement does not influence CPM response. Only controversial CPM response have appeared when tests and conditioned stimuli were applied on the same body region. Ischemic pain was applied as conditioning stimulus and PPT as test stimulus. Ischemic pain was provoked inflating a sphygmomanometer at the proximal region of the non-dominant arm. When inflated up to 180-200 mmHg patients were asked to actively move fingers and wrist. They were asketd to report when a 7/10 pain in Numerical Pain Rating Scale (NPRS) scale was reached. In that moment, three trials of test stimuli were applied on the dorsal distal-phalange base of the thumb in the dominant arm, while maintaining the ischemic pain perception.