The first time I tried step aerobics my hair was in a side ponytail and Ace of Base was on the playlist. In A Christmas Carol, Ebenezer Scrooge is haunted one evening by the ghost of Christmas past.

I approach treadmills with trepidation. I hate running and associate treadmills with the feeling of wanting to die — but I loved this interval workout. Photo credit: HIKEology I don’t run. My two ...