SUMMARY
Wearing high heels (HH) places the calf muscle–tendon unit (MTU) in a shortened position. As muscles and tendons are highly malleable tissues, chronic use of HH might induce structural and functional changes in the calf MTU. To test this hypothesis, 11 women regularly wearing HH and a control group of 9 women were recruited. Gastrocnemius medialis (GM) fascicle length, pennation angle and physiological cross-sectional area (PCSA), the Achilles' tendon (AT) length, cross-sectional area (CSA) and mechanical properties, and the plantarflexion torque–angle and torque–velocity relationships were assessed in both groups. Shorter GM fascicle lengths were observed in the HH group (49.6±5.7 mm vs 56.0±7.7 mm), resulting in greater tendon-to-fascicle length ratios. Also, because of greater AT CSA, AT stiffness was higher in the HH group (136.2±26.5 N mm–1 vs 111.3±20.2 N mm–1). However, no differences in the GM PCSA to AT CSA ratio, torque–angle and torque–velocity relationships were found. We conclude that long-term use of high-heeled shoes induces shortening of the GM muscle fascicles and increases AT stiffness, reducing the ankle's active range of motion. Functionally, these two phenomena seem to counteract each other since no significant differences in static or dynamic torques were observed.
LIST OF SYMBOLS AND ABBREVIATIONS
- AT
- Achilles' tendon
- CSA
- cross-sectional area
- CTRL
- control
- E
- Young's modulus
- GL
- gastrocnemius lateralis muscle
- GM
- gastrocnemius medialis muscle
- HH
- high heels
- K
- tendon stiffness
- Lf
- fascicle length
- Ltend
- tendon length
- MA
- moment arm
- MRI
- magnetic resonance imaging
- MTU
- muscle–tendon unit
- MVC
- maximum voluntary contraction
- PCSA
- physiological cross-sectional area
- SOL
- soleus muscle
- TA
- tibialis anterior muscle
- vmax
- maximum contraction velocity
- vopt
- optimal contraction velocity
- θ
- pennation angle
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