How to use this running exposure change calculator
When a knee starts asking for attention, the first thing worth seeing is what changed since last week. Enter this week's and last week's mileage, the downhill share of each week, and your shoe mileage, and you get the change in weekly mileage with its rate, the downhill miles and how they moved, and the shoe total with this week added. Use 0 for a week off and 0 for the share if nothing was downhill.
Downhill miles are weekly mileage times the share, and the rate is this week divided by last week. With 0 miles last week there is nothing to divide by, so the change is shown and the rate is reported as unavailable. This page builds no risk score or probability: no authoritative threshold for when an increase raises injury risk is published (reviewed October 2026).
No shoe lifespan table is included and replacement timing is not judged; treat the shoe total as a record for comparison. This page is not a medical assessment and does not estimate recovery time or knee loading. If the front of your knee or the area around the kneecap hurts on every run, gets worse going downstairs or standing up after sitting, or changes how you walk, see a clinician as well as cutting mileage.
Frequently Asked Questions
This page gives no safe threshold. No authoritative figure for when an increase raises injury risk is published, so it only calculates the change and rate from your own numbers.
Dividing by zero is not possible, so the change is shown instead of a rate. A rate measured against a week off would not mean anything.
No. No shoe lifespan table is included and replacement timing is not judged; the running total is shown as a record only.