The effects of habitual foot strike patterns on Achilles tendon loading in female runners

Gait & Posture

Volume 66, October 2018, Pages 283-287

Thomas W.Kernozek

Highlights

This study compared habitual rearfoot and non-rearfoot strike runners.

Non-rearfoot strike runners demonstrated greater Achilles tendon stress.

Rearfoot and non-rearfoot runners had similar Achilles tendon cross-sectional area.

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Background

Female runners that habitually use a forefoot/midfoot strike pattern (non-rearfoot runners) may be at greater risk for Achilles tendinopathy compared to runners that habitually use a rearfoot strike pattern. Differences in Achilles tendon loading between non-rearfoot and rearfoot strike runners may be a contributing factor.

Research Question

Our purpose was to determine if there were differences in Achilles tendon loading and cross-sectional area between female habitual rearfoot and non-rearfoot strike runners.

Methods

Thirty-five female runners participated in this cross-sectional study (17 rearfoot strike runners, 18 non-rearfoot strike runners). Ultrasound images of the Achilles tendon were used to measure cross-sectional area. Kinematic and kinetic data were collected at a set running speed and used in a muscloskeletal model to calculate Achilles tendon force. Achilles tendon stress was determined from specific Achilles tendon cross-sectional area. Principal components (PC) analysis was performed to identify/characterize the primary sources of variability in the Achilles tendon stress time series. The PC scores and cross-sectional area where compared using independent t-tests.

Results

PC 1 reflected variability in the Achilles tendon stress magnitude from 25 to 100% of stance, PC 2 reflected timing variability, and PC 3 reflected variability in the magnitude during early stance (0–25%). The non-rearfoot strike runners demonstrated higher PC scores for PC 1 and PC 3 compared to the rearfoot strike runners. This reflected greater Achilles tendon stress during mid/late stance (PC 1) and early stance (PC 3) for the non-rearfoot strike runners. For PC 2, there was a trend toward higher PC scores in the non-rearfoot strike runners. Achilles tendon cross-sectional area for the rearfoot and non-rearfoot strike runners were not different.

Significance

Habitual non-rearfoot strike runners did not have greater cross-sectional area despite higher Achilles tendon loading, which may pose a higher risk for Achilles tendinopathy.

アキレス腱の横断面積は同じだが、フォアフットだとアキレス腱負荷が大きく、腱炎のリスクが高いという論文。欠点はアキレス腱の弾性を計測していない。アキレス腱ストレスを動作分析（地面反力と関節角度）から算出しているので、フォアフット接地の方が負荷が大きくなるのは当然の結果。実際にこの参加者の中でどのくらいがアキレス腱炎に悩まされているのか。幼少期からこうした走り方をしていれば特に障害にならない気もする。裸足ランナーのアンケートでもアキレス腱は少なかったはず。