Early neuromechanical outcomes of the triceps surae muscle-tendon after an Achilles' tendon repair

Abstract

Objectives: To compare the neuromechanical and functional characteristics of the legs of athletes who underwent unilateral Achilles' tendon repair and their controls, and to determine any correlation between the characteristics.

Design: A case-control and cross-sectional study.

Setting: A university institute.

Participants: Male athletes (N=33) were recruited; 23 in the ≥3- and <12-month postsurgical group (median age, 29.8y; age range, 21.9-40.0y) and 10 in the control group (median age, 30.0y; age range, 21.1-39.5y) who had not undergone any surgery.

Intervention: Surgical Achilles' tendon repair in the study group.

Main outcome measures: Bilateral measurements of activation strategy involving the triceps surae and tibialis anterior muscles, mechanical properties of the Achilles' tendon, and explosive performance tests were conducted.

Results: Compared with the noninjured legs and the control legs, the repaired legs showed lower normalized rates of electromyographic rise (RER) in the soleus, gastrocnemius medialis, and gastrocnemius lateralis (P ranged between .006 and .001); and less tendon stiffness, greater hysteresis, and less rates of force development (RFD) (P ranged between .006 and <.001). Repaired legs had less ankle dorsiflexion, a shorter 1-leg hopping distance, and lower balance scores (P≤.001). The noninjured legs of the athletes who underwent surgical Achilles' tendon repair had a lower normalized RER (0-50 ms) in the soleus and lateral gastrocnemius when compared with the legs of the healthy controls (P=.011). The neuromechanical outcomes and explosive performances showed correlations with RFD, 1-leg hopping distance, and balance score.

Conclusions: The athletes who underwent unilateral Achilles' tendon repair demonstrated bilateral neuromechanical deficits within the 1-year postsurgical period.

Keywords: M(max); M(sup); MVIC; Mechanical phenomena; Nervous system; Postural balance; RER; RFD; RMS; Rehabilitation; SEBT; Star Excursion Balance Test; Tendons; VISA-A; Victorian Institute of Sports Assessment–Achilles questionnaire; maximal M wave; maximal voluntary isometric contraction; rate of electromyographic rise; rate of force development; root mean square; supramaximal M wave.