Why Stress Fractures Are So Common in Marathon Training (And How to Avoid Them)

There's something special about marathon training. Those steady miles that help you switch off. The growing confidence as your long runs stretch out. The structure it brings to busy weeks. The sense of purpose when your training plan tells you exactly what to do that day. But whilst the routine feels good, the repetitive load can quietly overwhelm the body if the right foundations aren't in place.

Every marathon season, I see the same pattern: an influx of runners dealing with early bone stress, stress reactions, or full stress fractures.

This article explores why stress fractures are so common right now, what causes them, and how you can reduce your risk whilst still enjoying your training.

Why Stress Fractures Happen in Marathon Training

Running is brilliant for bone health - when the load is right. When it isn't, problems build slowly and quietly. Bones respond to impact by remodelling and getting stronger. But this process takes time. If training increases too quickly, or the body doesn't have the ingredients it needs to rebuild tissue properly, bone fatigue sets in.

Common contributing factors include:

• A sudden jump in weekly mileage

• Intense blocks of speed work

• Back-to-back hard sessions with limited recovery

• Running plans not adjusted to your personal fitness or life stress

• Old shoes with worn-out cushioning

• Muscle fatigue altering your running mechanics

• Under-fuelling or inconsistent eating patterns

• Low Vitamin D levels affecting bone remodelling

Almost every stress fracture I see is caused by a combination of these rather than one single mistake.

The Rise of Influencer Training Plans

This year, more runners are copying influencer workouts, building their own hybrid plans, or trying to keep up with people who have very different training histories. The result? Loads increase faster than bones can cope.

Training plans like Runna can be fantastic tools—as long as they're personalised and adjusted when life gets busy. The problems start when runners try to "cling" to the plan even when fatigued, under-fuelled, or playing catch-up after missed sessions. A good training plan should guide you, not pressure you.

The Most Common Stress Fractures I'm Seeing

Tibial Stress Injuries (Shin)

Deep, pinpoint pain on the shin often mistaken for medial tibial stress syndrome (shin splints) - but bone pain gets sharper, more localised, and worsens with impact.

Metatarsal Stress Fractures (Foot)

These flare up during long runs or speed work, especially when footwear is worn out or the forefoot is doing more work than usual.

Femoral Neck Stress Injury (Hip/Groin)

A more serious but increasingly common injury in high-volume runners or those with low energy availability or low Vitamin D.

Vitamin D: The Underrated Factor

Vitamin D is essential for bone health, tissue repair, and calcium absorption. But in the UK, levels are frequently low - especially in runners training through winter.

Low Vitamin D is one of the most consistent findings in runners who present with stress fractures.

If you're training seriously for a marathon, it's worth:

• Getting your Vitamin D levels checked

• Supplementing during winter or year-round if you're deficient

• Combining it with adequate calcium intake
  
  

Practical Ways to Reduce Your Stress Fracture Risk

A few smart adjustments can dramatically reduce your risk:

• Adapt your training plan to your life, not the other way around. Plans like Runna should be guides, not rules. Missed sessions don't need to be "made up." Coopah is a great running app that allows you to work with running professionals to help guide you through and adjust your training plan.

• Replace your running shoes regularly. Worn-out cushioning is a huge factor in metatarsal and tibial stress injuries.

• Increase mileage gradually. Small, steady increases help bones adapt.

• Strength train twice per week. Especially calves, quads, glutes, and hamstrings ideally in single leg exercises.

• Fuel before and after runs. Under-fuelling is one of the biggest contributors to bone stress.

• Check your Vitamin D levels. Deficiency is incredibly common and very treatable.

• Don't ignore early warning signs. Localised, impact-related pain is never something to "push through."

How Physiotherapy Helps Prevent Stress Fractures

Preventing bone-stress injuries isn't as simple as "strengthen your legs" or "run less."

At Stride Sports Physiotherapy, a marathon-prep assessment looks at:

• Muscle strength in key running muscles

• Your running gait and impact patterns

• Footwear and shoe lifespan

• Training structure (e.g., Runna plan fit, long-run progressions)

• Recovery habits, sleep, and nutrition

• Red flags for low energy availability or Vitamin D deficiency

From there, we build a tailored strategy to help your body tolerate the mileage you want to run. Strength training is a key part of this.

If you'd like help staying injury-free this season, or want expert support returning from a stress fracture, you're very welcome to get in touch via the contact section.