I am an endurance athlete, and I’m concerned about my bone health. What is happening here and what do I need to change?

Endurance athletes are often very fit.

But being fit is not the same as being robust.

This is an important distinction.

You can have a big engine, strong cardiovascular fitness, excellent discipline, and still have poor bone health or repeated bone stress injuries.

That can feel confusing, especially for runners.

Running is weight-bearing. Surely that should be good for bone?

The answer is: sometimes, but not always enough.

Why running alone may not be enough

Running does load the skeleton, but it is also repetitive.

The body adapts to repeated loading patterns. Over time, the same stimulus may become less effective for bone. Running also tends to load the body in a fairly narrow way: same direction, same rhythm, same stride pattern, same tissues.

Bone tends to respond well to loading that is high enough, novel enough, multidirectional enough, and supported by good recovery.

So an endurance athlete may be doing a lot of loading, but not necessarily the right kind of loading for bone adaptation.

That is one part of the puzzle.

The second part is energy availability.

The RED-S connection

Relative Energy Deficiency in Sport, or RED-S, occurs when the body does not have enough available energy to support both training and normal physiological function. The International Olympic Committee defines RED-S as impaired physiological and/or psychological functioning caused by problematic low energy availability.

For bone, this matters enormously.

Bone is living tissue. It needs energy, hormones, protein, calcium, vitamin D and recovery to remodel properly.

If you are training hard but under-fuelling, the body may downregulate systems that are not immediately essential for survival. Hormones can change. Recovery can suffer. Bone turnover can be affected. Injury risk can rise.

In endurance athletes, low energy availability and low BMD are not rare concerns. A 2025 study in endurance athletes reported a high prevalence of low BMD and risk of low energy availability, reinforcing the need for targeted nutrition and bone-health strategies in this population.

That does not mean every endurance athlete has RED-S.

But if you have recurrent bone stress injuries, fatigue, poor recovery, menstrual disturbance, low libido, persistent niggles, or performance decline despite training hard, it should be considered.

The chassis and engine problem

I often think of endurance athletes as having a strong engine.

But the chassis may be underbuilt.

The cardiovascular system can be excellent, while the musculoskeletal system is not strong enough to tolerate the training load.

That is not a criticism. It is just a programming gap.

Many endurance athletes spend hours developing aerobic fitness but very little time developing:

Maximal strength.
Hip strength.
Calf strength.
Trunk strength.
Tendon capacity.
Landing control.
Power.
Bone-specific loading.

Then they wonder why the body starts protesting.

The answer is not always to train less.

Sometimes the answer is to train differently.

What needs to change?

The first change is to stop assuming that more running, cycling or swimming will solve every problem.

For bone health, most endurance athletes need some form of progressive resistance training.

That may include:

Squats or squat variations.
Deadlift or hip hinge variations.
Calf strengthening.
Step-ups.
Loaded carries.
Hip and trunk strengthening.
Single-leg control.
Plyometric progressions where appropriate.

The goal is not to become a bodybuilder.

The goal is to build a stronger frame for the sport you love.

Strength training should be specific, not random

Endurance athletes often make one of two mistakes.

They either avoid strength training completely, or they do random gym work that does not progress.

A few clams, planks and light band exercises may be useful at the right time, but they are not a complete strength programme.

Bone and tendon need meaningful load.

That does not mean every session needs to be maximal. But it does mean the programme should have structure, progression and intent.

For runners with bone stress injury risk, I want to see capacity built around the foot, ankle, calf, hip, trunk and posterior chain. For cyclists, I want to consider hip, spine, pelvis and lower-limb loading because cycling is not impact-based and may not provide enough osteogenic stimulus by itself.

Nutrition has to be part of the plan

If low energy availability is part of the problem, strength training alone will not fix it.

You cannot out-train under-fuelling.

A dietitian consult can be central here, especially for athletes who are trying to balance performance, body composition, training load and health.

The questions are practical:

Are you eating enough?
Are you eating enough carbohydrate to support training?
Are you getting enough protein?
Are you getting calcium and vitamin D?
Are you recovering properly between sessions?
Are you trying to stay too lean for too long?
Are you scared to increase intake?

These are not soft questions.

They are performance questions.

What about impact training?

For some endurance athletes, impact training or plyometric work may be useful.

But it needs to be earned.

If an athlete has a current bone stress injury, poor strength, poor landing control, or suspected RED-S, then jumping straight into plyometrics may be the wrong move.

The order usually looks like this:

Restore energy availability.
Address medical concerns.
Build strength.
Improve movement control.
Progress impact gradually.
Return to sport-specific loading.

That is the safer pathway.

The bottom line

If you are an endurance athlete concerned about bone health, the answer is not to panic.

But it is worth paying attention.

Running alone may not be enough. Cycling and swimming alone are usually not enough. Fitness alone is not enough.

You need:

Enough energy.
Enough protein.
Enough calcium and vitamin D.
Enough recovery.
Progressive resistance training.
Appropriate impact loading.
A sensible training plan.
A willingness to look beyond mileage.

The goal is not to take you away from endurance sport.

The goal is to help your body keep up with your engine.

That is how you stay in the sport longer.

References

Mountjoy M et al. 2023 International Olympic Committee’s consensus statement on Relative Energy Deficiency in Sport — REDs. British Journal of Sports Medicine, 2023.

Gowers CR et al. Assessing the risk of low energy availability, bone mineral density and associated factors in endurance athletes. 2025.

Hutson MJ et al. Effects of Low Energy Availability on Bone Health in Endurance Athletes and High-Impact Exercise as a Potential Countermeasure. 2021.

Herbert AJ et al. Bone mineral density in high-level endurance runners. 2021.