BACKGROUND & OBJECTIVE
This study investigated if the biomechanical parameters suspected to be involved in running-related tibial stress fracture (TSF) could be altered via acute conversion to forefoot strike (FFS) or increased cadence. Runners with a history of TSF have been found in some areas of the biomechanical literature to exhibit:
- Higher peak & average loading rates
- Higher peak tibial acceleration
- Higher peak hip adduction angles
- Higher peak absolute free moments
Subjects: 17 habitual rear foot striking (RFS) experienced long distance runners (F=11, M=6; av. age 32.1; av. height 168cm; av. mass 64.9kg) who ran a minimum of 10 km/week (33.5 ± 17.5km/week) were recruited.
Pressure sensitive innersoles were fitted into standardized neutral shoes and linked to provide computerized visual feedback as to foot strike pattern during FFS habituating treadmill runs. A full body marker set and an antero-medial tibial accelerometer were attached. A 16.5m force plate embedded track collected ground reaction force data during overground testing runs. Cadence was increased by 10% over steady-state via metronome auditory feedback on treadmill habituating and overground runs.
Kinematic and kinetic variables for each subject over 3 running conditions were calculated:
- RFS at preferred cadence
- FFS at free cadence
- Increased cadence with free foot strike type
Repeated measures ANOVA and paired t-tests with Bonferroni corrections were used to compare differences in parameters over the 3 running conditions.
Forefoot Strike (FFS) conversion reduced 2 suspected risk factors for TSF – average and peak loading rates: