Experimental pain dulled after aerobic, resistance exercises

Aerobic and dynamic resistance exercises could exert a slight hypoalgesic effect on experimental pain, reports a new meta-analysis. The literature around this subject, however, is sparse, and further studies are needed, particularly those looking at patients with chronic musculoskeletal pain.

The researchers retrieved 13 randomized controlled trials from six online databases: Medline, SPORTDiscus, CINAHL, PsycINFO, Embase, and Scopus. All trials implemented a single bout of exercise and enrolled a healthy sample free from current pain or chronic disease. The primary outcome was the change in quantitative experimental pain following exercise.

Ten studies looked at healthy individuals. Pooled analysis of seven (n=236) showed that aerobic exercise triggered a large exercise-induced hypoalgesia (EIH) effect (g, –0.85, 95 percent confidence interval [CI], –1.58 to –0.13), though heterogeneity of evidence was high.

Two studies, on the other hand, found that dynamic resistance exercises had a small but significant EIH effect (g, –0.45, 95 percent CI, –0.69 to –0.22) with low heterogeneity. Isometric exercises had no significant impact on postexercise pain (g, –0.16, 95 percent CI, –0.36 to 0.05).

The remaining three trials enrolled patients with chronic musculoskeletal pain. In pooled analyses, isometric exercises did not yield a significant EIH effect (g, –0.41, 95 percent CI, –1.08 to 0.25), while the impacts of aerobic and dynamic exercise could not be ascertained due to lack of studies.

However, the researchers noted that “overall quality of the evidence according to the Grades of Recommendation Assessment, Development, and Evaluation was rated as very low due to issues with inconsistency, imprecision, publication bias, and risk of bias.”

“Although we judged some categories to be at low risk of bias, most categories were generally considered unclear, which casts doubt about the strength of evidentiary support for the findings in this review,” they added.