Bought a rower over the summer to use for cross training. I had to use on day one of marathon training due to lightning. I was curious what people used for distance equivalencies. I'm sure some of it depends on what you want in the workout. It looked like CrossFit uses 500 meters of rowing to 400 meters of running.

I'm thinking the best way to do it would be to check heart rate ranges during various running efforts. Then match the heart rate on the rower while matching the typical length of time the run I am replacing would take.

Just my opinion but I wouldn't sub a running day for a rower day. I would just say it was a cross train day and still run the prescribed amount this week.

Depends on the rowing intensity. A 500 meter sprint row may be like running a competitive 800m or it could be like me checking the mail. Watch the heart.

Rowing has been shown to produce a lower heart rate than running at the same blood lactate concentration and at max efforts.

I'd suggest using 5-10 bpm less for a comparative heart rate while rowing if that's the route you plan on taking.

Like anything else, attempting to create an equivalency for two disparate exercises is very difficult. However, rowing 500m should be more difficult than running 400m. A 400m 'sprint' should take you right around 1:00. A 500m sprint should take, at least, 1:25...and that's only for those that are very strong rowers.

500 m row takes me 2:00 at moderate effort.

400 m run takes me 2:00 at moderate effort.