Alteration in tendinous and peritendinous blood flow during and after exercise is suggested to contribute to the development of Achilles tendon injury and inflammation. In the present study a method for evaluating the influence of standardized workload on peritendinous flow is presented. The radioactive isotope xenon-133 was injected just ventrally to the Achilles tendon 5 cm proximal to the tendon's insertion on the calcaneous. The disappearance of 133Xe was used to determine blood flow during intermittent static exercise of the calf muscle (1.5 s exercise/1.5 s rest) for 30 min at a workload equivalent to individual body weight (1 BW) in six healthy volunteers around both Achilles tendons (n = 12). During intermittent static exercise, blood flow was increased from 1.8 +/- 0.3 ml 100 g tissue-1 min-1 (mean value and SEM) (rest) to 6.1 +/- 1.3 ml 100 g tissue-1 min-1 (exercise) (P <0.05). The exercise induced an average increase in blood flow (3.4-fold) equivalent to results previously obtained during regular dynamic heel raises (P > 0.05). It is concluded that the method is well suited to study the influence of standardized workload on the physiology and pathophysiology of the tissue around the Achilles tendon in humans.