I can only run 3 days a week.
I have access to a elliptical and a exercise bike. I figure I can use them to keep in reasonably decent shape. But I don't know how hard or really how to train on them to keep fit.
Both have a heart rate montitor on them. I don't even know what heart rate range I should shoot for. I thought I read before I should keep the revolutions on the bike at around 90.
Any advice if I am training for a half or to finish a marathon without too much pain?