TY - JOUR
T1 - Hypoalgesia after exercises with painful vs. non-painful muscles in healthy subjects - a randomized cross-over study
AU - Hansen, Simon
AU - Petersen, Kristian Kjær
AU - Sloth, Emilie
AU - Manum, Line Appelon
AU - McDonald, Anita Kjær
AU - Andersen, Per Grünwald
AU - Vaegter, Henrik Bjarke
N1 - © 2021 Walter de Gruyter GmbH, Berlin/Boston.
PY - 2022/7/26
Y1 - 2022/7/26
N2 - Objectives: Exercise-induced hypoalgesia (EIH) is a decrease in the pain sensitivity after exercise. Individuals with chronic pain show less EIH after one exercise session compared with pain-free individuals possibly due to pain in exercising muscles. The primary aim of this randomized controlled cross-over study was to compare the EIH response at the exercising thigh muscle following exercises performed with painful vs. non-painful muscles. Secondary aims were to explore if a reduced EIH response was confined to the painful muscle, and whether the muscle pain intensity and the EIH responses were negatively associated. Methods: In two sessions, 34 pain-free participants received a painful (hypertonic saline, 5.8%) injection and a control (isotonic saline, 0.9%) injection in the right thigh muscle before performing a 3 min isometric wall squat exercise. Pressure pain thresholds (PPTs) were assessed at both thighs and the left neck/shoulder at baseline, after injections and after exercise. Pain intensities in the thighs were rated on numerical rating scales (NRS: 0-10). Results: Hypertonic saline induced moderate thigh pain at rest (NRS: 4.6 ± 2.1) compared to the control injection (NRS: 0.3 ± 0.4; p<0.001). EIH at the thighs and neck/shoulder were not different between sessions (Injected thigh: 0 kPa; 95% CI: -51 to 52; Contralateral thigh: -6 kPa; 95% CI: -42 to 30; neck/shoulder: 19 kPa; 95% CI: -6 to 44). No significant associations between pain intensity ratings immediately after the Painful injection and EIH responses at any assessment sites were found (right thigh: β=0.08, 95% CI: -12.95 to 20.64, p=0.64, left thigh: β=-0.33, 95% CI: -27.86 to 0.44, p=0.06; neck/shoulder: β=-0.18, 95% CI: -15.11 to 4.96, p=0.31). Conclusions: Pain in the area of an exercising muscle did not reduce local or systemic EIH responses. Trial registration number: NCT04354948.
AB - Objectives: Exercise-induced hypoalgesia (EIH) is a decrease in the pain sensitivity after exercise. Individuals with chronic pain show less EIH after one exercise session compared with pain-free individuals possibly due to pain in exercising muscles. The primary aim of this randomized controlled cross-over study was to compare the EIH response at the exercising thigh muscle following exercises performed with painful vs. non-painful muscles. Secondary aims were to explore if a reduced EIH response was confined to the painful muscle, and whether the muscle pain intensity and the EIH responses were negatively associated. Methods: In two sessions, 34 pain-free participants received a painful (hypertonic saline, 5.8%) injection and a control (isotonic saline, 0.9%) injection in the right thigh muscle before performing a 3 min isometric wall squat exercise. Pressure pain thresholds (PPTs) were assessed at both thighs and the left neck/shoulder at baseline, after injections and after exercise. Pain intensities in the thighs were rated on numerical rating scales (NRS: 0-10). Results: Hypertonic saline induced moderate thigh pain at rest (NRS: 4.6 ± 2.1) compared to the control injection (NRS: 0.3 ± 0.4; p<0.001). EIH at the thighs and neck/shoulder were not different between sessions (Injected thigh: 0 kPa; 95% CI: -51 to 52; Contralateral thigh: -6 kPa; 95% CI: -42 to 30; neck/shoulder: 19 kPa; 95% CI: -6 to 44). No significant associations between pain intensity ratings immediately after the Painful injection and EIH responses at any assessment sites were found (right thigh: β=0.08, 95% CI: -12.95 to 20.64, p=0.64, left thigh: β=-0.33, 95% CI: -27.86 to 0.44, p=0.06; neck/shoulder: β=-0.18, 95% CI: -15.11 to 4.96, p=0.31). Conclusions: Pain in the area of an exercising muscle did not reduce local or systemic EIH responses. Trial registration number: NCT04354948.
KW - exercise
KW - exercise-induced hypoalgesia
KW - experimental pain
KW - isometric exercise
KW - pain modulation
KW - saline injection
UR - http://www.scopus.com/inward/record.url?scp=85122004457&partnerID=8YFLogxK
U2 - 10.1515/sjpain-2021-0161
DO - 10.1515/sjpain-2021-0161
M3 - Journal article
C2 - 34958721
SN - 1877-8860
VL - 22
SP - 614
EP - 621
JO - Scandinavian Journal of Pain
JF - Scandinavian Journal of Pain
IS - 3
ER -