Why Do I Always Get Injured When I Increase My Running? The Load Management Explanation

You're running consistently, feeling good, and decide to push harder — then within a few weeks you're injured. This pattern is so common it's called the injury trap. Here's exactly why it happens.

The Training Load Concept

Your body has a capacity — the amount of load it can safely handle. Your training creates a demand. When demand exceeds capacity, tissue fails. The tricky part: capacity changes slowly (weeks to months) while demand can increase rapidly (day to day).

Why Increasing Running Volume Triggers Injury

When you increase running volume, the most vulnerable tissues are the ones with the slowest adaptation rate. Cardiovascular fitness adapts within days. Muscles adapt in 1–2 weeks. Tendons adapt in 6–12 weeks. Bone adapts in 12–24 weeks. You can feel cardiovascularly ready to run more long before your tendons and bone can actually handle it. The feeling of fitness is a leading indicator; structural readiness is a lagging indicator.

The Acute:Chronic Workload Ratio

Research by Tim Gabbett introduced the acute:chronic workload ratio (ACWR). Your acute workload is the load of the last week; your chronic workload is the average of the last 4 weeks. Ratios between 0.8 and 1.3 are associated with low injury risk. Ratios above 1.5 are associated with substantially elevated injury risk.

Practical Rules

• Increase weekly mileage by no more than 10% per week
• After every 3 weeks of building, take a down week at 70% of the previous week's load
• Don't simultaneously increase mileage, intensity and frequency — change one variable at a time
• Persistent soreness beyond 48 hours or sharp pain are signals to reduce load, not push through

Load management is central to injury prevention — our exercise physiology team designs progressive running programmes that build capacity safely. For a broader understanding of why injuries recur, see our article on why your injury keeps coming back. Our sports chiropractic team can also assess biomechanical factors contributing to load-related running injuries across the Hills District and Earlwood.

The 10% Rule — Useful But Imperfect

The commonly cited "10% rule" — never increase weekly mileage by more than 10% — provides a reasonable starting point for runners new to structured training. However, it has important limitations. The rule is based on relative percentage, which means a runner at 10 km/week should only add 1 km, while a runner at 80 km/week can add 8 km — a much greater absolute load increase. The rule also takes no account of training intensity, surface changes, footwear changes or the runner's history of injury and training resilience.

More sophisticated frameworks — particularly the acute:chronic workload ratio — account for relative load changes across a rolling window of time, which better captures the cumulative stress on tissues. But even these are tools, not rules: individual variation in load tolerance is significant, and the same percentage increase will be well-tolerated by one runner and injurious for another.

Practical Load Management for Runners

A few principles that consistently reduce injury risk when increasing running volume:

• Increase one variable at a time. Don't add mileage, intensity and a new surface simultaneously. Change one variable, observe your response for 2–3 weeks, then adjust another.
• Monitor response, not just load. Your perceived effort, soreness the day after and energy levels across the week are all useful signals. If they trend negatively as volume increases, pull back before injury develops.
• Build a base before building volume. Runners who try to jump from low mileage to high mileage quickly are consistently at higher risk. Spending 3–4 months at a stable, manageable volume before increasing builds the connective tissue capacity that reduces injury risk with subsequent increases.
• Include rest days. Adaptation happens during recovery, not during training. Two to three consecutive days of running without a rest day increases cumulative load and reduces the recovery window for tissue repair.

If you are regularly getting injured when you increase your running, a single assessment with our sports chiropractic or exercise physiology team can identify whether the issue is load management, biomechanics, strength deficits or a combination — and provide a structured plan for building volume safely.

Frequently Asked Questions

What is a safe amount to increase running per week?

The commonly cited 10% weekly mileage increase rule provides a useful starting point, though evidence suggests that absolute load — not just percentage change — and recovery capacity also matter. Newer frameworks such as the acute:chronic workload ratio suggest keeping weekly load within approximately 0.8–1.3 times the four-week rolling average as a safer guide.

What causes shin splints when increasing running?

Medial tibial stress syndrome (shin splints) is typically caused by a rapid increase in bone loading through impact. The bone's remodelling capacity is exceeded by the rate of loading — particularly when weekly distance or session frequency increases too quickly. Footwear, surface changes and running biomechanics are secondary contributing factors.

How do I increase running without getting injured?

Build load gradually, prioritise recovery between sessions, and monitor your response using a simple system — rate of perceived exertion, soreness the day after, and whether each session feels harder than the last. If any of these signal fatigue accumulation, reduce load before the next increase.

References

1. Gabbett TJ. (2016). The training-injury prevention paradox. British Journal of Sports Medicine, 50(5), 273–280.
2. Nielsen RO, et al. (2014). Training load and injury incidence in competitive marathon runners. International Journal of Sports Physiology and Performance, 9(2), 269–277.
3. Drew MK & Finch CF. (2016). The relationship between training load and injury, illness and soreness. Sports Medicine, 46(6), 861–883.