top of page
Search

How Much Running Is Too Much? What Runners (and Clinicians) Should Know

If you’ve ever pushed through one “just one more mile” run and ended up sidelined by nagging pain, you’re not alone. A new large-scale cohort study challenges some of our long-standing beliefs about how running injuries develop—and has practical lessons for runners and physical therapists alike. (PubMed)

ree

The Study in a Nutshell

  • Researchers followed 5,205 adult runners (average age ~46, about 22% female) over 18 months. (PubMed)

  • They collected data via Garmin devices—tracking distance and training history. (Luxembourg Institute of Health)

  • They examined three types of “spikes” or sudden increases in training load:

    1. Single-session spike: how a run’s distance compares to the longest run in the preceding 30 days

    2. Acute:Chronic Workload Ratio (ACWR): weekly distance vs. preceding 3 weeks

    3. Week-to-week ratio: change from one week to the next (Luxembourg Institute of Health)

  • The main outcome was self-reported overuse running injuries (pain, discomfort, inability to train) (PubMed)

Key Findings: It’s the Big Spike in One Run That Seems Most Risky

  1. Single-session spikes matter a lot. Compared to sessions with up to a 10% increase over the 30-day max (the “reference” group), the risk of injury increased as the spike got larger:

    • Small spikes (10–30% greater): hazard ratio ~1.64

    • Moderate spikes (30–100% greater): HR ~1.52

    • Large spikes (>100%): HR ~2.28 (PubMed)

  2. In plain language: if in one session you run more than ~10% extra beyond what your previous maximum was, your risk of injury jumps significantly.

  3. The ACWR relationship was negative (inverse).Rather than a clear “20% safe increase” threshold, the data showed a negative dose-response—meaning that as ACWR went higher, the relative risk decreased in some ranges. This suggests the classic ACWR formula (so popular in training apps and sports watches) may not predict injury risk in runners the way we thought. (Luxembourg Institute of Health)

  4. Week-to-week changes were not strongly tied to injury.The study found no consistent association between injury and simply comparing one week’s total distance to the next week’s. (Luxembourg Institute of Health)

Why These Results Matter

Traditionally, many coaches, apps, and physical therapists have leaned heavily on the “don’t increase your training load by more than 10% per week” rule, or used ACWR as a safety metric. But this study suggests:

  • Injuries may often happen suddenly during one decently large run, rather than creeping up gradually over weeks.

  • The specific “spike” in a single session may have more predictive power than weekly formulas like ACWR.

  • We may need to rethink how we monitor and prescribe risk thresholds in runner training.

Practical Tips for Runners & Clinicians at Hubert PT

Here are a few take-aways you might use (or share with your patients) to reduce the risk of overuse injury:

  1. Don't suddenly “step up” one run too much. Even if you feel good, avoid doing a run that is significantly farther than your recent longest run (past 30 days). Long runs are fine—but build them gradually.

  2. Track your past longest runs. Keep a rolling “longest 30-day run” record. Use that as your reference when planning your next runs.

  3. Be cautious with abrupt increases—even if weekly totals seem okay. Weekly progression matters, but one isolated overreach may be surprisingly dangerous.

  4. Use ACWR (or similar metrics) carefully. They can help, but they are not foolproof for runners—and, per this study, may mislead if used as a strict “injury threshold.”

  5. Listen to your body. A run that feels tougher than it should, or unusual soreness during or after a session—don’t just brush it off. Early detection and correction matters.

  6. When in doubt, ease off and cross-train. If you feel risk accumulating, swap a long run for a low-impact session (bike, swim, elliptical), and resume progression slowly.

What This Means for Our Practice

At Hubert PT, we always emphasize smart, evidence-based training and injury prevention. This new study reinforces our philosophy: training is not just about “more” — it's about smart.

When rehabbing runners or designing return-to-running plans, we’ll keep an eye on:

  • the recent longest runs as a benchmark

  • avoiding large single-session “jumps”

  • early signs of overload (e.g. tissue tenderness, fatigue)

  • combining quantitative data (GPS, wearable metrics) with subjective feedback (how the runner feels)

If you or a patient ever wants help interpreting their training load, or making a safe progression plan, we’d be happy to consult or integrate this kind of data into your rehab or training strategy!

—

References & Further Reading Frandsen JSB et al. “How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study.” Br J Sports Med 2025. (PubMed)


 
 
 

Comments

bottom of page