as we get older it's better to alternate strength work and cardio days, so upper body and core one day, then walk/hike/jog/run/elliptical or bike the alternate days, to allow the muscles to recover (which they take longer to do).
Not that that applies for multi-day orienteering events, necessarily.
Thanks for the note, Janet. Most of the articles for "older" runners are for runners in their - gasp - 40's and 50's. I can't find much for the truly old runners; and I'll be 80 next year. I probably should stop the gym workouts with legs (presses and so forth), which account for 5 of the 13 machines I use. "Recovery" days are hard for me to justify, given the pace of workouts. I should fish and sail more, I suppose.