Variability Among Individual Male Runners Influences Cumulative Loading More Than Foot Strike Type.

Abstract

Background: Foot strike type affects running mechanics and may influence overuse injury occurrence. Measuring the interaction between cumulative load and foot strike type may provide additional information that could increase understanding of injury mechanisms.

Hypothesis: There will be no differences in cumulative loading between runners using rearfoot strike (RFS) and nonrearfoot strike (NRFS) patterns. NRFS runners will have a greater stride rate. There will be differences in per stride metrics of select lower extremity mechanics.

Study design: Observational laboratory study.

Level of evidence: Level 3.

Methods: Thirty male participants (age, 22.7 ± 2.9 years; height, 1.79 ± 0.07 m; mass, 70.7 ± 7.86 kg; mean ± SD) ran on an instrumented treadmill for 5 km at 3.15 m/s with their preferred foot strike type (14 RFS, 16 NRFS). Stride rate, foot strike angle, loading rate (LR), per stride and per kilometer (cumulative) vertical ground-reaction force (VGRF) impulse, impact peak, absolute peak, knee negative work, and ankle negative work were calculated and compared across time and between groups.

Results: Per stride differences were seen for stance time, foot strike angle, and LR (greater for RFS runners, P = 0.003). Per stride and cumulative ankle and knee negative work showed significant differences (greater ankle negative work for NRFS runners, P < 0.001 [per stride and cumulative], greater knee negative work for RFS runners, P = 0.01 per stride, P = 0.008 cumulative).

Conclusion: Ankle and knee loading metrics showed differences in per stride and cumulative metrics between foot strike groups. Individual variability in VGRF loading patterns was more apparent than group distinctions. The common perception that NRFS runners have a higher stride rate was not supported.

Clinical relevance: Individual loading patterns, not just foot strike type, and training session characteristics related to cumulative load should be considered when assessing injury risk.