Potential mechanisms underpinning aerobic exercise-induced analgesia in primary dysmenorrhea: a controlled non-randomized pilot trial

Abstract

BackgroundAerobic exercise has been shown to alleviate the pain of primary dysmenorrhea in several studies however, no study has yet identified the physiological mechanisms underlying the beneficial effects of aerobic exercise-induced pain relief in primary dysmenorrhea. The objectives of the study are: (1) To evaluate the feasibility of the protocol for a randomized controlled trial to investigate the physiological mechanisms underlying the beneficial effects of aerobic exercise on the pain associated with primary dysmenorrhea and (2) to obtain preliminary results (effect size) to estimate the sample size for the future randomized controlled trial.MethodsTwenty women aged 18–29 years were divided into two groups (high-intensity aerobic-exercise group and no-exercise control group) in a 1:1 ratio. Women assigned to the exercise group performed high-intensity treadmill-based aerobic exercise for three days a week, at 70–85% of maximum heart rate for 30 minutes for 4 weeks. The control group did not receive trial intervention but provided blood for estimation of plasma variables. Blood plasma levels of progesterone, metabolites of prostaglandin (PG) F2-alpha (13,14-dihydro-15-keto-prostaglandin F2 alpha [KDPGF2α]) and PGE2 (13,14-dihydro-15-keto-prostaglandin E2 [KDPGE2]), and tumor necrosis factor-alpha (TNF-α) were measured at 4-weeks post-intervention.ResultsWith respect to feasibility outcomes, 90% of the required number of participants were recruited in 3-4 weeks. Adherence to the intervention was 97% and the retention rate was 90%. There was an increase in progesterone levels (d = 0.36) and decreases in KDPGF2α (d = 0.35), KDPGE2 (d = 0.47), and TNF-α (d = 0.33) from baseline to week 4 in the exercise group compared with the control group.ConclusionThe study methodology appears to be feasible for conducting a full-scale randomized controlled trial. The findings indicated a trend towards an increase in progesterone levels and decreases in inflammatory pain mediators, including KDPGF2α, KDPGE2, and TNF-α, in the exercise group compared with the control group, suggesting the possibility that aerobic exercise may be effective for primary dysmenorrhea via its influence on progesterone and inflammatory pain mediators. Trial Registration Our trial is registered in the Australian New Zealand Clinical Trials Registry (ACTRN12618000784213). The date of registration is 09 May 2018. Trial registration was completed prior to enrollment of the first participant.