What is the appropriate unit to measure the distance ran over a one week period?

As there are the 100m, 200m, 400m, 1500m 10,000m races, I think metres is a good measurement to use.

Track races are normally run round a 400m track, so the longer races are measured using a count of 400m laps, for example 1500m is 3 3/4 laps of a 400m track.

The one exception could possibly be the marathon which is not run around a track and which at 26 miles 385 yards is about 42195m = 42.195km and kilometres would be a better measurement.