It is hypothesized that physiotherapy including a change in running landing pattern and surgical fasciotomy are equally good as treatment options for chronic exertional compartment syndrome (CECS) of the anterior compartment of the lower leg. The endpoints/outcomes are: Change from week 0 (start of study) to week 12 (completion of intervention) in: patient reported outcome measure (PROM) (Exercise induced leg pain Questionnaire (EILP)). Secondary outcomes are: Visual Analogue Scale (VAS) score after an exercise provocation test: Change in intracompartmental pressure (ICP)Change in muscle compartment compliance. Change in Global Rating of Change Score/Scale (GRC). Change in Single Assessment Numeric Evaluation (SANE) The study is important because: 1. Results from recent studies suggest that physiotherapy represents a valid alternative to surgery for the treatment of CECS. Surgery is currently standard treatment and a change towards physiotherapy as primary treatment could potentially reduce both complication rates and costs. 2. Intracompartmental pressure (ICP) is gold standard for diagnosing CECS. However, the association between ICP and symptoms of CECS, both before and after physiotherapeutic and surgical treatment, muscle compartment compliance and intracompartmental perfusion, has not been thoroughly investigated.