Background Orthotic heel lifts are thought to lower tension in the Achilles tendon, but the evidence supporting this is equivocal.
Objective To investigate the effect of a 12 mm in-shoe orthotic heel lift on Achilles tendon loading using transmission mode ultrasonography.
Design Controlled study.
Patients (or Participants) 12 active males.
Interventions (or Assessment of Risk Factors) The propagation speed of ultrasound, which is governed by the elastic modulus and density of tendon and proportional to the tensile load to which it is exposed, was measured in 12 recreationally active men, during shod treadmill walking at matched speeds (3.4 +/− 0.7 km/h), with and without the addition of a heel lift. Vertical ground reaction forces and spatiotemporal gait parameters were simultaneously recorded. Data were acquired at 100 Hz during 10 seconds of steady state walking.
Main Outcome Measurements Ultrasound transmission speed maxima (P1, P2) and minima (M1,M2) in the Achilles tendon, vertical ground reaction force peaks, step length, and cadence.
Results Ultrasound transmission speed in the Achilles tendon was characterised by 2 maxima (P1,P2) and minima (M1,M2) during walking. Addition of a heel lift to footwear resulted in a 2% increase and a 2% decrease in the first vertical ground reaction force peak and the local minimum respectively (P< 0.05). Ultrasonic velocity in the Achilles tendon (P1, P2, M2) was significantly lower with the addition of an orthotic heel lift (P<0.5).
Conclusions Peak ultrasound transmission speed in the Achilles tendon was lower with the addition of a 12 mm orthotic heel lift, indicating that the heel lift reduced tensile load in the Achilles tendon, thereby counteracting the effect of footwear observed in previous studies. These findings support the addition of orthotic heel lifts to footwear in the rehabilitation of Achilles tendon disorders where management aims to lower tension within the tendon.
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