Difference in perceived pain intensity depending on the order of submaximal isometric contractions performed at different intensities

Abstract

Purpose: Previous studies that examined pain after submaximal isometric contractions at different intensities are limited in that they used different intensities randomly. The present study aimed to examine the change in pain depending on the order of submaximal isometric contractions performed at two different intensities and inter-and intra-individual differences in pain responses. Methods: Twenty-nine volunteers participated (mean age=22.10±1.60 years) to the study. Hamstring flexibility was measured in the supine position. Maximal voluntary contraction (MVC) was measured during hip extension. Submaximal contractions were performed at two different target intensities: 25% and 75% of MVC. Visual Analogue Scale (VAS) was used to measure the pain after submaximal contractions. Group A (n=15) performed submaximal contraction in 25% to 75% of MVC in the 1st period and 75% to 25% of MVC in the 2nd period. In Group B (n=14), the submaximal contraction was performed in each period in the opposite order of Group A. Results: There was a significant decrease in pain in Group B during the 2nd period (p<0.05). The VAS at 75% of the MVC showed a significant decrease at 25% of the MVC (p=0.011). Correlations were observed between flexibility and 1st-period VAS score (p=0.048) and 2nd-period VAS score (p=0.036) and between the VAS scores in the 1st and 2nd periods (p<0.001). Conclusion: Pain intensity could be perceived differently depending on the order of sequential application, even when the intensities are identical, and might be more clinically useful in the analysis of intra-individual comparisons.