Slowing in peak-alpha frequency recorded after experimentally-induced muscle pain is not significantly different between high and low pain-sensitive subjects

Peak alpha frequency (PAF) reduces during cutaneous pain, but no studies have investigated PAF during movement-related muscle pain. Whether high-pain sensitive (HPS) individuals exhibit a more pronounced PAF response to pain than low-pain sensitive (LPS) individuals is unclear. As a pain model, twenty-four participants received nerve growth factor injections into a wrist extensor muscle at Day0, Day2, and Day4. At Day4, a subgroup of twelve participants also undertook eccentric wrist exercise to induce additional pain. Pain numerical rating scale (NRS) scores and electroencephalography were recorded at Day0 (before injection), Day4, and Day6 for 3 minutes (eyes closed) with wrist at rest (Resting-state) and extension (Contraction-state). The average pain NRS scores in contraction-state across Days were used to divide participants into HPS (NRS-scores≥2) and LPS groups. PAF was calculated by frequency decomposition of electroencephalographic recordings. Compared with Day0, contraction NRS-scores only increased in HPS-group at Day4 and Day6 (P<0.001). PAF in Contraction-state decreased in both groups at Day6 compared with Day0 (P=0.011). Across days, HPS-group showed faster PAF than LPS-group during Resting-state and Contraction-state (P<0.04). Average pain NRS-scores across days during Contraction-states correlated with PAF at Day0 (P=0.012). Pain NRS-scores were associated with PAF during Contraction-state at Day4 and Day6 (P<0.05). Perspective: PAF was slowed during long-lasting movement-related pain in both groups, suggesting a widespread change in cortical excitability independent of the pain sensitivity. Moreover, HPS individuals showed faster PAF than LPS individuals during muscle pain, which may reflect a different cognitive, emotional, or attentional response to muscle pain among individuals.