Isometric exercises do not provide immediate pain relief in Achilles tendinopathy: A quasi-randomized clinical trial

Background Isometric exercises may provide an immediate analgesic effect in patients with lower-limb tendinopathy and have been proposed as initial treatment and for immediate pain relief. Current evidence is conflicting, and previous studies were small. Objective To study whether isometric exercises result in an immediate analgesic effect in patients with chronic midportion Achilles tendinopathy. Methods Patients with clinically diagnosed chronic midportion Achilles tendinopathy were quasi-randomized to one of four arms: isometric calf-muscle exercises (tiptoes), isometric calf-muscle exercises (dorsiflexed ankle position), isotonic calf-muscle exercises, or rest. The primary outcome was pain measured on a visual analogue scale (VAS) score (0-100) during a functional task (10 unilateral hops) both before and after the intervention. Between-group differences were analyzed using a generalized estimation equations model. Results We included 91 patients. There was no significant reduction in pain on the 10 hop test after performing any of the four interventions: isometric (tiptoes) group 0.2, 95%CI -11.2 to 11.5; isometric (dorsiflexed) group -1.9, 95%CI -13.6 to 9.7; isotonic group 1.4, 95%CI -8.3 to 11.1; and rest group 7.2, 95%CI -2.4 to 16.7. There were also no between-group differences after the interventions. Conclusion The isometric exercises investigated in this study did not result in immediate analgesic benefit in patients with chronic midportion Achilles tendinopathy. We do not recommend isometric exercises if the aim is providing immediate pain relief. Future research should focus on the use of isometric or isotonic exercise therapy as initial treatment as all exercise protocols used in this study were well-tolerated.