Mechanical loading is a regulator of tissue metabolism in tendon, which may lead to alterations in structural and mechanical properties via mechanotransduction processes. The present study investigated specified responses of tenocyte metabolism in isolated tendon fascicles subjected to four loading regimes. Cyclic tensile strain of 3% amplitude superimposed on a 2% static strain was applied to the fascicles for 10 min, 1, 6 or 24 h of a 24-h incubation period. Collagen synthesis, assessed by [H-3]-proline incorporation, was upregulated by the 24 h straining regime, but was inhibited by the 10-min regime. Cyclic strain enhanced the retention of newly synthesised collagen within the matrix. More than 90% of the newly synthesised collagen was retained in all cases, but the long-term application of cyclic strain had less pronounced effects on the retention. These results indicate that collagen synthesis by tenocytes is controlled by a complex mechanosensitive process with a temporal component. (c) 2007 Elsevier Inc. All rights reserved.