Muscle pain from different activities was tested with the muscle pain expected to vary in ways that may clarify mechanisms of activity-induced exacerbation of myofascial pain.
Participants [N=20; 45% women; 23 y old (SD=2.09)] consented to participate in a 6 session protocol. Bilateral muscle pain ratings and pressure pain thresholds (PPTs) were collected before and for 4 days after lengthening (ie, eccentric) muscle contractions were completed with the nondominant elbow flexors to induce delayed-onset muscle pain. The muscle pain ratings were collected with the arms in several conditions (eg, resting, moving, and contracting in a static position) and PPTs were collected with the arms.
In the ipsilateral arm, muscle pain ratings at rest and during activity significantly increased whereas PPTs significantly decreased after the eccentrics (η2s=0.17 to 0.54). The greatest increases in pain occurred during arm extension without applied load, in which there was more stretching but less force than isometrics. In the contralateral arm, neither muscle pain nor PPTs changed from baseline.
These results resemble earlier electrophysiology studies showing differential sensitization across stimuli and support that increased depth of information about aggravating activities from clinical patients is needed.