Bone Stress Injuries: The Risk Hiding in a Summer Mileage Jump

Winnipeg summers are short and glorious, and it is tempting to make up for a long winter in a few enthusiastic weeks. The trails open, the daylight stretches past nine o'clock, and mileage that crawled through the cold suddenly doubles. That surge of motivation is a good thing — but it is also the exact scenario in which one of the more preventable running injuries develops: the bone stress injury.

How bone responds to load

Bone is living, adaptive tissue. When you load it through running or jumping, it responds by remodelling — old bone is resorbed and new, stronger bone is laid down along the lines of stress. This is a feature, not a flaw: appropriate loading makes bones denser and more resilient over time.¹ The catch is timing. Remodelling has two phases, and the resorption phase comes first. For a window of weeks, the bone is temporarily weaker before it becomes stronger.¹

If loading keeps climbing during that vulnerable window — before the rebuilding phase catches up — microdamage accumulates faster than the body can repair it. This continuum runs from a stress reaction (bone that is irritated and remodelling under strain) to a frank stress fracture (an actual crack in the bone).^1,2 It is the same principle behind sensible training load management: bone, like tendon and muscle, adapts beautifully to gradual load and poorly to sudden spikes.

Why the summer ramp is the classic trigger

Bone stress injuries are strongly associated with rapid increases in training load, changes in surface or footwear, and a sharp jump in volume or intensity.² A runner going from 15 kilometres a week in May to 45 in July has tripled the demand on tissue that needs months, not days, to adapt. The old ten-percent guideline is a rough tool, but the principle behind it is sound: give bone time to complete its remodelling before you ask more of it.

Energy availability and RED-S

Load is only half the equation. Bone remodelling is an expensive metabolic process, and it depends on the body having enough energy to fund it. When energy intake does not match the demands of training — a state called low energy availability — hormonal changes reduce bone formation and raise the risk of bone stress injury, independent of training load.³ This is the core of Relative Energy Deficiency in Sport (RED-S), which affects both female and male athletes and links inadequate fuelling to impaired bone health, hormonal disruption, and more.^3,4 A runner who under-eats through a heavy training block is loading a bank account and withdrawing from it at the same time.

Reading the warning signs

Bone stress injuries usually announce themselves differently from ordinary muscle soreness. Learning the difference matters, because caught early, most are managed conservatively; caught late, some require extended time off. Features that point toward bone rather than muscle:

• Localized, pinpoint pain. You can often cover the sore spot with a fingertip, frequently over a bony surface — the shin, the top of the foot, the hip, the heel.
• Pain that worsens with impact and progresses. It tends to come on earlier in each run as the injury advances, and it can start to ache at rest or at night.
• Tenderness directly on the bone, sometimes with local swelling.
• Pain that does not warm up and go away, unlike diffuse muscle soreness that eases once you get moving.

Muscle soreness, by contrast, is diffuse, spread across a muscle belly, symmetrical, and settles within a couple of days. Certain sites — the front of the shin, the femoral neck at the hip, the navicular in the foot, and the fifth metatarsal — are considered higher-risk locations and deserve prompt assessment rather than a wait-and-see approach.² Persistent, localized bony pain that keeps getting worse is worth having looked at.

Building bone the smart way

The good news is that the same tissue that is vulnerable to spikes is remarkably responsive to graded loading. A few principles keep bone on the building side of the ledger:

• Progress gradually. Increase volume in modest, stepwise increments and include lighter weeks so remodelling can catch up.
• Fuel the work. Match intake to training demand, with adequate overall energy, protein, calcium, and vitamin D — the latter genuinely relevant through a long Manitoba winter.³
• Vary the stimulus. Mixing surfaces and cross-training spreads load rather than hammering the same structures every session.
• Include strength work. Resistance and impact training build the muscular and bony capacity that tolerates running.

Bone injuries also rarely happen in isolation from the rest of the body. Hip and calf strength, foot mechanics, and running form all feed into how load is distributed down the chain — the kind of whole-system view the Boreal team takes when a runner's summer suddenly gets busy. Build the base first, and the mileage takes care of itself.

References

1. Warden SJ, Davis IS, Fredericson M. Management and prevention of bone stress injuries in long-distance runners. J Orthop Sports Phys Ther. 2014;44(10):749-765.
2. Kiel J, Kaiser K. Stress reaction and fractures. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2023.
3. Mountjoy M, Sundgot-Borgen J, Burke L, et al. IOC consensus statement on relative energy deficiency in sport (RED-S): 2018 update. Br J Sports Med. 2018;52(11):687-697.
4. Nattiv A, Loucks AB, Manore MM, et al. American College of Sports Medicine position stand: the female athlete triad. Med Sci Sports Exerc. 2007;39(10):1867-1882.