Why You Should Chill at Least One Day a Week

Why should you take at least one day of rest from exercise a week?  Let the L.A. Times count the ways.  Because, the paper reminds us, exercise causes micro-trauma to muscles, which get stronger when they repair themselves during rest. And without proper recovery time, areas of wear and tear become weak links
and are more prone to injury and, importantly, less likely to show
strength gains.  So while you might burn a few extra calories by not taking
a day off, your body will be less efficient in capitalizing on the work
you do.
Next question: What, exactly, is a day of rest? For someone who jogs regularly, the Times suggests, rest could mean a light swim. For a
devoted weight lifter, it could be a casual bike ride or noncompetitive
tennis game. The story’s experts, Dr. William Roberts, an associate professor in the Division of Sports Medicine at the University of Minnesota, and Conrad Earnest, chief exercise physiologist at the Cooper Institute in Dallas, agree that a rest day is not
needed for low-intensity exercisers, such as people who walk a couple
miles a day simply to clear their head and get a little blood flowing.  But, they advise,
for those who train hard, go for "periodization" — variation in
the amount and intensity of exercise — and some volume of rest,
regardless of your training cycles. For those devoted to what is called
the "macro-cycle" of year-round sports training, Roberts recommends
taking a month of rest per year. For people in a "meso-cycle" of three
to six months of training, he recommends one week off. Read the whole story in the L.A. Times.