Increased knowledge is needed about new methods how to treat patients with Achilles tendon ruptures (ATR). A goal is to be able to individualize as well as improve treatment beyond the question about if surgery should be used or not. An overall aim of the project is to, in a randomized controlled trial (RCT), explore what impact a new treatment method with Neuromuscular Electrical Stimulation (NMES) - attached on the patients ́ calf muscles on the injured leg - in the early stages after an ATR, may have on tendon length, functional performance, biomechanical variables and patient reported outcome, both in the short and long term after the injury. 70 patients are planned to be included in this RCT and will be evaluated 3,6 and 12 months after their injury. Primary outcome will be heel-rise height. Secondary outcome will be tendon length, jumping ability, patient- reported outcome and biomechanical loading pattern. There is also a need to explore if the patients ́ loading patterns improve after treatment with NMES. Therefore, biomechanical variables in lower leg during walking and jumping will also be evaluated one year after their injury. The planned studies include completely new ways of exploring how to optimize the rehabilitation after an ATR. Since there might be an increased risk for overuse injuries in the healthy limb, there will also be focus on how the non- injured limb may be affected of an ATR. Taken together, this new knowledge can be helpful in the clinical setting to individualize and optimize patients' treatment and rehabilitation with the goal to guide the patient return to the same, or higher level of, physical activity as before the injury.