Increasing ground contact time reduces Achilles tendon forces during rearfoot strike running outdoors.

OBJECTIVES

Strategies to reduce Achilles tendon forces during running may be beneficial for injury prevention. Increasing ground contact time could reduce Achilles tendon forces during running but may also elicit changes in cadence that could offset these reductions. The purpose of this study was to determine if changing ground contact time altered Achilles tendon forces during running, with both a fixed and a free cadence.

DESIGN

This was a cross-sectional study of healthy rearfoot strike runners.

METHODS

Thirty rearfoot strike runners ran on a concrete sidewalk at 3.0 m/s with preferred, low, and high ground contact times, with both a fixed and a free cadence. Achilles tendon forces were estimated using data collected from Loadsol insoles.

RESULTS

Peak Achilles tendon force, cumulative Achilles tendon fatigue load, and Achilles tendon impulse were compared among ground contact time and cadence conditions. Peak Achilles tendon force and cumulative Achilles tendon fatigue load decreased as ground contact time increased. These changes occurred with both a fixed and a free cadence.

CONCLUSIONS

Increasing ground contact time may be a viable intervention for decreasing peak Achilles tendon force and cumulative Achilles tendon fatigue load in runners, without the need for additional instructions to control cadence.