I am text block. Click edit button to change this text. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut elit tellus, luctus nec ullamcorper mattis, pulvinar dapibus leo.

Abstract
Muscle strain injuries disrupt the muscle-tendon unit, early rehabilitation is associated with
a faster return to sports (RTS), but the time course of tissue healing remains sparsely
described. The purpose was to examine tissue regeneration and the effectiveness of early
versus delayed rehabilitation onset on functional and structural recovery after strain
injuries. 50 recreational athletes with a severe acute strain injury in their thigh or calf
muscles were randomized to early or delayed rehabilitation onset. Magnetic resonance
imaging (MRI) was obtained initially, 3 and 6 months post injury and dynamic contrastenhanced
MRI (DCE-MRI) estimated tissue inflammation initially and after 6 months. Muscle
strength was determined 5 weeks, 3 and 6 months post injury and a questionnaire
determined soreness, pain and confidence. DCE-MRI microvascular perfusion was higher in
the injured compared to an uninjured muscle acutely (p< 0.01) and after 6 months (p< 0.01),
for both groups (p> 0.05) and unrelated to RTS (p> 0.05). Total volume of the injured muscle
decreased from the acute to the 3 months scan, and to the 6 months scan (p< 0.01) in both
groups. Muscle strength was similar in both groups at any time. There was a non-significant
trend (p≤ 0.1) towards less pain and higher confidence with early rehabilitation. One reinjury
was recorded. In conclusion, our data showed prolonged tissue repair with the initial
response linked to muscle atrophy but did not explain why early rehabilitation onset
accelerated recovery considering that structural and functional recovery was similar with
early and delayed rehabilitation.