Stress Fracture
Stress Fracture · Causes

What Causes Stress Fracture — The Real Reasons

The root causes of stress fracture in runners: training, biomechanics, footwear, recovery, and fueling factors.

The Core Mechanism

Bone breakdown outpacing remodeling from mileage spikes, low energy availability, or low bone density.

The Real-World Triggers

Stress Fracture rarely has a single cause. In runners, these are the consistent contributors:

  • Mileage spike beyond bone adaptation capacity
  • Low energy availability / under-fueling (RED-S)
  • Menstrual cycle disruption (in female athletes)
  • Low vitamin D or calcium intake
  • Switch to harder surfaces or stiffer shoes
  • History of prior stress injury

Why Runners in Particular

Running concentrates repeated impact and load through the same tissues thousands of times per session. Stress Fracture develops when that load exceeds the tissue's adaptation rate — usually because training spiked, recovery dropped, or strength didn't keep up.

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