Immediate Effects of Neuromuscular Electrical Stimulation on Pain and Function in Achilles Tendon Disorders

Immediate Effects of Neuromuscular Electrical Stimulation on Pain and Functional Performance in Individuals With Achilles Tendinopathy and Tendon Rupture: A Randomized Crossover Clinical Trial

The Achilles tendon exhibits high tensile strength and can withstand extremely high loads. However, it is susceptible to injuries such as tendinopathies and ruptures, which are associated with structural alterations and loss of function. Strategies have been investigated to enhance clinical rehabilitation. Nevertheless, the effects of neuromuscular electrical stimulation on pain and functional improvement, as well as the optimal dosing parameters for the rehabilitation of Achilles tendon injuries, remain inconclusive. The aim of this study is to compare the immediate effects of two electrical stimulation protocols on pain, functional performance, peripheral oxygen extraction, and maximal tendon displacement during a single leg heel rise functional task in patients with Achilles tendinopathy and/or a history of Achilles tendon rupture. In addition, this study aims to characterize Achilles tendon structural properties and ankle plantarflexor muscle strength in this population.

All groups will be composed of participants with a primary complaint of pain and/or a history of previous Achilles tendon rupture. Participants will perform the interventions in two blocks separated by a seven-day interval (wash-out). Block A: (1) control without active intervention and (2) electrical stimulation applied at the maximum tolerated intensity. Block B: (3) control with sham stimulation and (4) sensory-level electrical stimulation. Block A will always be performed first, followed by Block B. Interventions within each block will be conducted in three sets of 10 repetitions, totaling six sets per day.

Inclusion Criteria:

• Primary complaint of pain localized in the midportion (2-6 cm proximal to the calcaneus) or insertion of the Achilles tendon, and/or a history of Achilles tendon rupture occurring at least 3 months prior to assessment.
• Pain on palpation of the Achilles tendon.
• Pain during load-bearing activities

Exclusion Criteria:

• Exclusive diagnosis of bursitis confirmed by ultrasonographic assessment
• Any other lower limb injury
• History of lower limb surgery within the past year
• Previous Achilles tendon tenoplasty performed less than 3 months prior to assessment