3. Long-Term High-Heel (HH) Use Shortens gastrocnemius muscle fascicles Increases Achilles Tendon Stiffness What are the functional consequences of these changes during HH and barefoot walking? – Muscle activity – Muscle strain

4. Methods: Subjects 2 groups – HH group: 9 young women who have worn heels for at least 40 hr/wk for last two years (2 inch heels) – Control group: 10 women who habitually wore heels for less than 10 hr/week.

5. Methods: Protocol Walk over a level 8m walkway 10 times: – Barefoot/HH Data Collection – EMG: Soleus, Gastrocnemius, Tibialis Anterior Muscles – Ultrasound gastrocnemius

6. Results: Muscle Activity Percent Contact Time Greater muscle activity in habitual high-heel walkers Even when barefoot!

7. Results: Muscle Fascicle Strain Percent Contact Time Shorter fascicle lengths in habitual high-heel walkers Greater fascicle strains in habitual high-heel walkers Even when barefoot!

8. Putting it all together In habitual high-heel walkers: – Stiffer tendon – Shorter fascicle lengths – Greater muscle activity – Greater fascicle strains – Even when barefoot! Length change is being redistributed from the tendon to the muscle!  BAD Muscle-Tendon units operate the best when the length change is taken up by the tendon, with minimal length change in the muscle.