Isometric exercises reduce temporal summation of pressure pain in humans

BACKGROUND: Aerobic and isometric exercises are known to decrease pain sensitivity. The effect of different types of exercise on central mechanisms such as temporal summation of pain (TSP) is less clear. This study hypothesized that both aerobic and isometric exercises would increase pressure pain tolerance (PTT) and reduce TSP with greater effects after higher-intensity exercises. METHODS: One hundred thirty-six healthy subjects (18-65 years; 68 women) participated in two randomized crossover experiments with trials on two different days. PTT and TSP were assessed before and after bicycling and a non-exercise condition (experiment 1), and after low- and high-intensity bicycling and low- and high-intensity isometric arm and leg exercises with the dominant arm/leg (experiment 2). PTT and TSP were assessed before and after each exercise condition on the non-dominant arm and leg by computer-controlled cuff algometry. TSP was assessed by visual analogue scale (VAS) scores of the pain intensity during sequential cuff-pressure stimulation at the pain tolerance intensity related to that specific time point. RESULTS: In experiment 1, bicycling, but not the non-exercise condition, slightly increased PTT when assessed at the leg (p < 0.05). In experiment 2, isometric arm and leg exercises increased PTT and reduced VAS scores to sequential stimulation at the arm and leg (p < 0.05). No systematic difference was found between low- and high-intensity exercises. CONCLUSIONS: Different manifestations of hypoalgesia between aerobic and isometric exercises were found. Isometric exercises reduced temporal summation illustrating the potential for exercise as a rehabilitation procedure also targeting the central mechanisms.