Hypoalgesic Effects of Exercise and Training of Different Modalities

Aim #1 follows a randomized and crossover design in which 16 young and healthy males are evaluated during thigh circulatory occlusion performed after a submaximal isometric plantar flexion contraction (PECO day). In the other session, participants are evaluated during free-flow conditions and without previous fatiguing contraction (no-PECO day). In PECO day, participants complete a 3-min contraction at 40% of maximal force. Then, for testing, blood flow from lower-leg is blocked during 4 min, by an inflatable cuff around the ipsilateral thigh before task termination, during which H- reflex is tested. At the end of recordings, the cuff is deflated. Participants ware allowed to rest for 5-10 min. Then, they are requested to perform a new 3 min contraction with the cuff being inflated before task termination. The cuff remains inflated for \~ 2 min during which V-wave recordings are obtained. In both days, leg pain intensity is reported by participants and brachial AP is measured.

Aim #2 follows a randomized and crossover-controlled design, consisting on two experimental sessions. 24 healthy male (all diferent from Experiment 1) are randomly allocated to one of the following exercising regimens: aerobic, anaerobic or dynamic resistance (8 participants for each exercise group). In one of the experimental days, participants are evaluated for pain sensitivity and neuromuscular responses both before and after a lower-limb acute exercise protocol (exercise day) and in the other day before and after 15 min of quiet rest (non-exercise day). In both sessions, participants are evaluated for rectus femoris, upper trapezius and biceps brachiis muscles pressure pain threshold, followed by the application of a cold pain tolerance test on the foot. The intensity of pain is reported by a 0-100mm VAS and AP and HRV continously measured. Then, participants are tested for H-reflex and V-wave excitability during PECO, with leg pain intensity (0-10) and brachial AP recorded.

Aim #3 follows a randomized-controlled design. 32 healthy male (all the 24 participants from Experimental 2 plus 8 new subjects) are randomly allocated to one of the following groups: aerobic, anaerobic, dynamic resistance training and no-training (control) (8 participants for each group). Each intervention group perform 6 weeks of exercise training (3x week). Participants allocated to each training group are evaluated before and after training (2 assessment days in each time-point). On one day participants are tested for pressure pain threshold and cold pain tolerance with concomitant measures of pain ratings (0-100mm VAS), AP and HRV. The influence of metaboreflex activation on H-reflex and V-wave is also measured (during PECO). In addition, during PECO ischemic pain rating and AP are obtained. On another day, participants are evaluated for motor performance (maximal oxygen uptake, maximal voluntary contraction and peak power) and neuromuscular adaptations (i.e. H-reflex and V-wave)