Achilles tendon repair with following immobilisation causes atrophy of the calf musculature. The aim of this study was the long term evaluation of the strength and strength endurance deficit ten years after the injury. 63 patients (48 male, 15 female) were tested 10.8 years after achilles tendon rupture repair and subsequent 6-week immobilisation. The test was made in the eccentric (60
$^{\circ}$
/s), isometric and concentric(60
$^{\circ}$
/s, 180
$^{\circ}$
/s) mode for plantarflexion and dorsiflexion with a Lido Active dynamometer. The mean peak torque of the best 3 of 5 movements and the work over 1 minute(180
$^{\circ}$
/s) were evaluated for plantarflexion and dorsiflexion. The circumference of the calf musculature and the range of motion of the ankle (ROM) were measured. Differences to the non-operated side were assessed with the Wilcoxon matched pairs test and adjusted with the Bonferroni method. The mean peak torque in all modes showed no statistically significant difference between the operated and non-operated legs ten years after immobilisation. The work over 1 minute was markedly reduced for the operated leg in plantarflexion (516 J operated versus 634 J non-operated,
$p< 0.001$
). The circumference of the calf musculature(
$-1.1$
cm) and the ROM(
$-3.5$
$^{\circ}$
plantarflexion,
$-1.9$
$^{\circ}$
dorsiflexion) were also reduced (
$p< 0.001$
). It seems that a selective atrophy of the slow twitch fibers is relevant for the durable loss of musculature and the weakened calf musculature in the strength endurance test. Early remobilization should be chosen after reconstruction of the achilles tendon, and more strength endurance training must be done at the end of the rehabilitation.
