Plantarflexor neuromuscular performance in Insertional Achilles tendinopathy

Abstract

BACKGROUND: Insertional Achilles tendinopathy (IAT) is a common and painful musculoskeletal condition. The management of IAT commonly involves strengthening of the plantarflexors, although there is currently a paucity of research investigating plantarflexor neuromuscular performance specific to people with IAT.

OBJECTIVES: To compare plantarflexor neuromuscular performance between men with IAT and controls, and to investigate the relationship between plantarflexor neuromuscular performance and patient reported outcome measures for men with IAT.

DESIGN: Case control.

METHOD: 34 men with IAT (age 43.7 years [SD 10.02], weight 89.6 kg [16.3]) were matched with 34 healthy men (age 42.8 years [SD 8.9], weight 87.2 kg [9.7]). Participants underwent a plantarflexion maximal voluntary isometric contraction (MVIC) task, and a target force matching task. Neuromuscular variables from these tasks include; MVIC, rate of torque development (RTD), electromechanical delay (EMD), and muscle force steadiness. Participants also completed questionnaires regarding; pain and function, and psychological factors.

RESULTS: The IAT group had reduced MVIC (p < 0.01) and RTD, (p < 0.01) compared to controls, however no significant difference in plantarflexor force steadiness (p = 0.08), or EMD (p = 0.71) was observed. Low strength correlations were detected between the VISA-A and RTD (r = 0.37, p = 0.04), kinesiophobia and EMD (r = 0.45, p = 0.03).

CONCLUSIONS: This study established impairments in plantarflexor strength and RTD among people with IAT. Plantarflexor force steadiness and EMD is not altered in IAT, which is in contrast to evidence from mid-portion Achilles tendinopathy. Plantarflexor RTD was the only neuromuscular outcome measure linked to symptom severity, which may indicate it is an important rehabilitation finding.