Background The link between the hypervascularisation and the pain symptoms in a tendinopathy is still obscure. It can be hypothesised that it is important to take the stage of the tendinopathy into account.

Objective The objective of this study was to evaluate the vascular response of the achilles tendon during a basic military training program of 6 weeks.

Design A prospective study.

Setting Officer cadets followed the same 6-week basic military training. This training mainly consists of running, roadwork, military tactical exercises, drills, shooting, marching with backpacks and some theoretical classes.

Patients 49 male military recruits (98 tendons) volunteered for this study. The mean age was 18.3 years. None of the persons had a history of achilles tendon problems.

Interventions Before and during the military training program, clinical symptoms, structural tendon changes and hypervascularisation were weekly screened.

Main outcome measurements The achilles tendons were screened by gray – scale ultrasonography and power Doppler US. Reactive tendinopathies were registered by means of a clinical examination, VAS – scores and VISA – A scores.

Results 13 of the 98 tendons developed a reactive tendinopathy. Three of these 13 symptomatic tendons showed intratendinous Doppler activity. In these tendons, pain was always present before the vascular response of the tendon. Both pain and hypervascularisation remained visible during till the end of the training program. In five asymptomatic tendons with no structural changes in the tendon, a vascular response was seen during one measurement.

Conclusion To our knowledge, this is the first prospective study that looked at the development of hypervascularisation in a specified subpopulation, that is, reactive tendinopathy. The results of this study show that there is no link between the vascular response of the tendon and the pain sensation of the patient in this early stage of tendinopathy. Other pain mechanism should be investigated.