Sex Differences and Reductions in Pressure-Induced Pain Following Submaximl Isometric Contractions

Abstract

PUROSE: To investigate the reliability of pain measurement and perception using a pressure-induced pain device, and to examine the effects of submaximal isometric contractions on pressure pain perception in men and women. METHODS: Pain perception was assessed using a pressure stimulus consisting of a 1 kg weight mounted on a plastic edge and placed on the forefinger for two minutes. Subjects pressed a timing device when they first felt pain (pain threshold) and pain ratings were reported every 20 seconds using a 0–10 scale. At the first session, reliability of pain measurement using the pressure-induced pain device was assessed by measuring pain perception before and after a 30-minute rest period. At the last two sessions, pain perception was measured before and after the performance of a submaximal isometric contraction of the elbow flexor muscles 25 minutes after the first pain assessment. These last two sessions were randomized with subjects performing an isometric contraction at 25% of their maximal voluntary contraction force until task failure or for two minutes. RESULTS: Pain thresholds and pain ratings were similar before and after 30 minutes of rest for men and women (p > 0.05). However, women had lower pain thresholds (p = 0.019) and higher pain ratings (p = 0.04) than men before and after the 30-minute rest. Pain ratings decreased for both men and women following the submaximal fatiguing contraction at task failure (p = 0.001) but not after the 2-minute contraction. Pain threshold increased for both men and women following the submaximal fatiguing contraction at task failure (p = 0.021) and after 2 minutes (p = 0.039). CONCLUSION:1) Pain thresholds and pain ratings were repeatable with the pressure-induced pain device after 30 minutes, 2) Pain perception is more likely to decrease following a low intensity submaximal contraction held to task failure than after 2 minutes, and 3) Women have higher pain ratings and lower pain thresholds than men at rest and after the performance of submaximal voluntary contractions.