Muscle fiber conduction velocity and muscle strength impairments 12 months after repaired Achilles tendon rupture: a cross-sectional study
BACKGROUND: Clinically, muscle strength and neuromuscular function are expected to return toward normal levels within 12 months after surgical repair of Achilles tendon rupture (rATR). However, the recovery of muscle fiber conduc-tion velocity (MFCV) as a muscle fiber property remains unclear. Thus, we aimed to determine whether MFCV and maximal voluntary isometric contraction (MVIC) of the plantar-flexors are restored 12 months after rATR compared with healthy individuals. AIM: Thus, we aimed to determine whether MFCV and MVIC of the plantar-flexors are restored 12 months after rATR compared with healthy individuals. METHODS: A total of 20 participants (10 men with rATR and 10 healthy controls) were included in this cross-sectional study. Medial gastrocnemius MFCV at 40% and 60% of MVIC was measured using a 16-channel linear electro-myography array to be compared between groups using mixed-model repeated-measures ANOVA. Plantar-flexion MVIC was compared using a one-tailed Mann-Whitney U test. Alpha error was set to 0.05. RESULTS: The Achilles group showed higher MFCV at 60% compared to 40% of MVIC (4.7±1.2 vs 4.2±1.1 ms-1; p=0.020), whereas the control group did not (4.0±0.3 vs 3.6±0.7 ms-1; p=0.120). The Achilles group exhibited higher MFCV than controls at both 40% (4.2±1.1 vs 3.6±0.7 ms-1; p=0.040) and 60% MVIC (4.7±1.2 vs 4.0±0.3 ms-1; p=0.010). The Achilles group exhibited lower MVIC than controls (1.5±0.6 vs 2.1±0.5 Nmkg-1; p=0.033). INTERPRETATION: Neuromuscular function and strength are not normalized one-year after rATR. Patients generate plantar-flexion strength with higher MFCV than healthy individuals.