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Magnusson, S P.1; Aagaard, P1; Hansen, J1; Kirkeby, K1; Andersen, R1; Hansen, P1; Bojsen-Møller, J1

Medicine & Science in Sports & Exercise: May 2003 - Volume 35 - Issue 5 - p S81
B-13L Free Communication/Poster Bone and Connective Tissue

1Team Danmark/Sports Medicine Research Unit, Bispebjerg Hospital, Copenhagen, Denmark. E-mail:

So-called pre-conditioning of isolated tendon prior to mechanical testing is the procedure of loading and unloading to achieve more repeatable results. However, it remains unknown whether the load-deformation curve of human tendon, in vivo, is altered by such pre-conditioning procedures.

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To examine the deformation of the human triceps surae tendon-aponeurosis complex in healthy subjects with repeated plantarflexion contractions.

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Synchronous real-time ultrasonography for displacement of the tendon-aponeurosis complex of the medial gastrocnemius muscle, electromyography of the gastrocnemius, soleus, and dorsiflexor muscles, and joint angular rotation were obtained during maximal 10-s ramp isometric plantarflexion contractions in 5 healthy male subjects. Displacement obtained during passive range of motion served to correct for displacement attributed to small joint rotation, while EMG and moment data obtained during maximal dorsiflexion efforts served to account for coactivation on tendon force. Five consecutive contractions with ∼30 s rest were performed, and 2 additional contractions were performed after 5 and 10 min. Displacement was analyzed to the least common force for all contractions for each subject.

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(mean ± sem) There was a significant effect of repeated contractions on displacement, P < 0.01. Displacement increased from contraction 1 (5.3 ± 0.9 mm) to contraction 5 (7.2 ± 1.2 mm), P < 0.05. However, displacement 5 min (5.2 ± 1.0 mm) and 10 min (5.2 ± 0.9 mm) after the 5 repeated contractions was similar to that of contraction 1.

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These data demonstrate that human tendon-aponeurosis deformation, in vivo, was markedly increased (∼40%) with slow isometric contractions. However, the change in viscoelastic properties of the tendon-aponeurosis was abolished within 5 min.

©2003The American College of Sports Medicine