Getting stuck in a rut
When it comes to exercise, variety is the spice of life. "When you do, say, a shoulder exercise, you're training many of the fibers of the shoulder muscles, but not all of them," Schoenfeld says. "To work out all of the fibers in a muscle, you need to use different movements-using different angles or even just changing your grip on the weights."
This goes for cardio as well as weight training. "When you use the same exercise over and over, it's a repetitive motion task, just like typing at your keyboard, which can produce carpal tunnel syndrome," Schoenfeld says. So falling into a cardio rut ups your chances for injury.
Mixing up your workout also combats boredom-always a handy excuse for skipping the gym.