It's always good to mix things up -- especially when it comes to exercise. If you're a runner or walker, you can spice things up a bit by doing a hybrid walk/run workout.

"It's sort of like interval training," says Dr. John Swartzberg, who heads the editorial Board at the UC Berkeley Wellness Letter. "So you run some and then you walk some and then you run some and then you walk some.

"A you may not be as board and B you may be running and exercising for longer time, which will result in better conditioning."

Adding some walking to that run can reduce stress on your joints which will reduce the risk of injury.

Run a bit during that walk and you'll get a more intense workout - which enhances cardiovascular fitness. It also boosts your good cholesterol and burns more calories.

A word of caution for walkers.

"Start slowly," Swartzberg says. "Work up."

Dr. Swartzberg suggests this plan: Walk for about three or four minutes, then walk briskly or jog for a minute. Gradually increase your speed during the run portion and the amount of time you do it until you have a nice run/walk pattern in place.