Abstract
PurposeThe purpose of this study was to explore the immediate effects of heavy isometric plantar flexor exercise on sensory output (pain during a functional task and mechanical pain sensitivity) and motor output (plantar flexor torque) in individuals with Achilles tendinopathy.MethodsSixteen subjects with Achilles tendinopathy participated in the study, mean (SD) age 48.6 (8.9) years and Victorian institute assessment-Achilles (VISA-A) score 61.3 (23.0). Sensory testing assessing pain during a functional task, mechanical pain sensitivity and motor output, and plantar flexor peak torque was completed prior to the intervention. All subjects completed a 45-s heavy isometric plantar flexor contraction and were then re-tested using the same sensory and motor tests. Motor output was assessed using isokinetic dynamometry at speeds previously identified as of interest in subjects with Achilles tendinopathy.ResultsOnly 9 of the 16 subjects experienced pain during a functional task, self-reported pain was 4.2 (1.9) numerical rating scale (NRS) pre-intervention and 4.9 (3.2) NRS postintervention (n.s.). Mechanical pressure sensitivity was 446.5 (± 248.5) g/mm2 pre-intervention and 411.8 (± 211.8) g/mm2 post-intervention (n.s.). Mean concentric plantar flexor torque at 90 and 225°/s was 47.1 (14.5) and 33.6 (11.6) Nm, respectively, pre-intervention and 53.0 (18.5) and 33.4 (6.6) Nm post-intervention (p = 0.039 and n.s.). Eccentric torque at 90°/s was 98.5 (34.2) Nm preintervention versus 106.0 (41.4) Nm post-intervention (n.s.).ConclusionIn this exploratory study, patients with Achilles tendinopathy had a varied sensory and motor output response to heavy isometric contractions. Using the recommended approach of heavy 45-s isometric contractions did not offer a meaningful acute benefit for sensory or motor output for subjects with Achilles tendinopathy. Based on this study, heavy 45-s isometric contractions cannot be recommended for immediate pain relief or improved motor output for patients with Achilles tendinopathy.Level of evidenceIV, prospective cohort study.
Highlights
Successful treatment of Achilles and patella tendinopathy has for the last three decades focussed on eccentric resistance training [1, 3, 15, 44]
From 2015 to 2016, preliminary evidence from studies on patellar tendinopathy suggests an immediate improvement in pain after heavy isometric contractions and an improvement in motor output [40, 41]
All subjects were examined; two subjects were excluded as they did not have a diagnosis of Achilles tendinopathy
Summary
Successful treatment of Achilles and patella tendinopathy has for the last three decades focussed on eccentric resistance training [1, 3, 15, 44]. From 2015 to 2016, preliminary evidence from studies on patellar tendinopathy suggests an immediate improvement in pain after heavy isometric contractions and an improvement in motor output [40, 41]. Rio et al used heavy isometric holds at 70% of maximal voluntary contraction (MVC) in athletes with patellar tendinopathy and reported an immediate reduction in pain during a single-leg decline squat. Subject’s pain reduced from 7/10 to 0/10 on a numerical rating scale (NRS) and this pain reduction lasted for at least 45 min. Pain reductions of this magnitude and longevity have obvious benefits in clinical practice where individuals may be able to participate in activities previously limited due to pain. The reported increases in motor output may expedite a return to normal activities, the mechanism by which this may occur is thought to be a reduction in cortical inhibition [40]
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