{"id":11751,"date":"2025-10-06T06:00:01","date_gmt":"2025-10-06T05:00:01","guid":{"rendered":"https:\/\/blogs.bmj.com\/bjsm\/?p=11751"},"modified":"2025-10-05T09:08:06","modified_gmt":"2025-10-05T08:08:06","slug":"how-much-running-is-too-much-a-new-take-on-injury-risk-for-runners","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/bjsm\/2025\/10\/06\/how-much-running-is-too-much-a-new-take-on-injury-risk-for-runners\/","title":{"rendered":"How much running is too much? A new take on injury risk for runners"},"content":{"rendered":"

Key words: <\/b>Athletic Injuries; Running; Sporting injuries; Sports medicine<\/b><\/p>\n

This blog is based on a recently published BJSM <\/span>study<\/b><\/a> (1)<\/b>.<\/span><\/p>\n

Why is this study important?<\/b><\/p>\n

Running continues to grow in popularity worldwide\u2014celebrated for its health benefits and accessibility. Although it also comes with a downside: the risk of injuries. Up to half of all runners report an injury each year, many of them overuse-related. Traditionally, clinicians and coaches have focused on gradual increases in weekly mileage and workload ratios (like the acute:chronic workload ratio, or ACWR) to reduce injury risk.<\/span><\/p>\n

However, these traditional approaches are overlooking something crucial. Despite widespread use in science and wearable technology, these weekly-based calculations may not accurately reflect the moment-to-moment load decisions runners actually make. In practice, injuries may strike more \u201csuddenly\u201d for instance after a single ill-judged running session that is longer than usual. Equipped with this novel hypothesis, the present study offers a paradigm-shift by focusing on\u00a0<\/span>single-session spikes in running distance<\/b>, rather than week-to-week trends.<\/span><\/p>\n

How did the study go about this?<\/b><\/p>\n

This prospective cohort study included\u00a0<\/span>5,205 adult runners from 87 countries<\/b>, tracked over\u00a0<\/span>18 months<\/b>\u00a0using wearable GPS devices (Garmin). More than 35% of the runners sustained a self-reported running-related injury in the\u00a0<\/span>588,000 running sessions that<\/b>\u00a0were analyzed. Of these, a majority were classified as being based on overuse.\u00a0<\/span><\/p>\n

Researchers examined three ways of defining a \u201cspike\u201d in running distance:<\/span><\/p>\n

    \n
  1. Sudden Session-specific spikes<\/b>: Distance of a single run compared with the longest run in the past 30 days<\/span><\/li>\n
  2. Gradual spikes using ACWR<\/b>: One-week total compared with the average of the previous three weeks<\/span><\/li>\n
  3. Gradual spikes using week-to-week change<\/b>: Comparison of weekly totals between consecutive weeks<\/span><\/li>\n<\/ol>\n

    In all three approaches, spikes were categorized into one of the following categories after each running session: (1) <\/span>Regression\/small change<\/span><\/i>\u00a0(\u226410%) \u2013 reference group; (2)<\/span> Small spike<\/span><\/i>\u00a0(>10\u201330%); (3)<\/span> Moderate spike<\/span><\/i>\u00a0(>30\u2013100%); and (4)<\/span> Large spike<\/span><\/i>\u00a0(>100%)<\/span><\/p>\n

    What did the study find?<\/b><\/p>\n

    The key finding?\u00a0Injuries did not develop gradually over weeks of running as previously suggested but peaked when a runner ramped up the distance in a single session as <\/span>large jumps in distance during a single session significantly increased hazard rate (HRR)<\/b>.<\/span><\/p>\n