Background: Achilles' tendon ruptures result in impaired plantar flexion strength and endurance. It is interesting to know the plantar flexion strength, the number of heel-rise repetitions, and the maximal calf circumference following Achilles' tendon ruptures repair. Methods: Both the injured and non-injured legs of thirty male patients with Achilles' tendon ruptures treated with the percutaneous Dresden technique were compared with the ankle function of 30 healthy participants. Rehabilitation involved partial weight-bearing for three weeks and then increased to full weight-bearing and ankle exercises. Results: The injured legs had weaker plantar flexion strength (1.64 +/- 0.17 Nm/kg) compared with the non-injured legs (1.91 +/- 0.24 Nm/kg; p = 0.002) and the healthy participants' legs (1.93 +/- 0.32 Nm/kg; p < 0.001). The non-injured leg had greater ability in doing heel-rise repetitions (39.4 +/- 6.1 rep.) compared with the injured legs (37.2 +/- 5.7 rep.; p < 0.023) and the healthy participants' legs (31.0 +/- 13.0 rep.; p < 0.001). Conclusions: The injured leg had not recovered full isometric strength but had improved heel-rise repetition. (c) 2021 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.