Running shoes increase achilles tendon load in walking: an acoustic propagation study.
BACKGROUND
Footwear remains a prime candidate for the prevention and rehabilitation of Achilles tendinopathy because it is thought to decrease tension in the tendon through elevation of the heel. However, evidence for this effect is equivocal.


OBJECTIVE
This study used an acoustic transmission technique to investigate the effect of running shoes on Achilles tendon loading during barefoot and shod walking.


METHODS
Acoustic velocity was measured in the Achilles tendon of 12 recreationally active males (age, 31 ± 9 yr; height, 1.78 ± 0.06 m; weight, 81.0 ± 16.9 kg) during barefoot and shod walking at matched self-selected speed (3.4 ± 0.7 km·h). Standard running shoes incorporating a 10-mm heel offset were used. Vertical ground reaction force and spatiotemporal parameters were determined with an instrumented treadmill. Axial acoustic velocity in the Achilles tendon was measured using a custom-built ultrasonic device. All data were acquired at a rate of 100 Hz during 10 s of steady-state walking. Statistical comparisons between barefoot and shod conditions were made using paired t-tests and repeated-measure ANOVA.


RESULTS
Acoustic velocity in the Achilles tendon was highly reproducible and was typified by two maxima (P1, P2) and minima (M1, M2) during walking. Footwear resulted in a significant increase in step length, stance duration, and peak vertical ground reaction force compared with barefoot walking. Peak acoustic velocity in the Achilles tendon (P1, P2) was significantly higher with running shoes.


CONCLUSIONS
Peak acoustic velocity in the Achilles tendon was higher with footwear, suggesting that standard running shoes with a 10-mm heel offset increase tensile load in the Achilles tendon. Although further research is required, these findings question the therapeutic role of standard running shoes in Achilles tendinopathy.
1Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, AUSTRALIA; 2Centre of Excellence for Applied Sport Science Research, Queensland Academy of Sport, Brisbane, AUSTRALIA; 3School of Health Sciences, University of Melbourne, Melbourne, AUSTRALIA; and 4Faculty of Sports and Health Sciences, Technische Universität München, Munich, GERMANY.
Scott C
SC
Wearing
Lloyd
L
Reed
Sue L
SL
Hooper
Simon
S
Bartold
James E
JE
Smeathers
Torsten
T
Brauner
D000125:Achilles Tendon / Q000502:physiology*; D000162:Acoustics; D000328:Adult; D000842:Ankle / Q000502:physiology; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D012775:Shoes; D052256:Tendinopathy / Q000517:prevention & control; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing; D055815:Young Adult