5 Exercises You Think You Need—but Don't

The current trend in fitness is to focus on "functional exercises" that mimic the movements we use in our daily lives. When's the last time you sat at your desk and tried to lift files with your ankles? That's one of the reasons "leg extensions have become a maligned exercise by many industry professionals," says Neal I. Pire, an exercise physiologist and fellow of the American College of Sports Medicine. The other reason is that this machine isolates the quadriceps. Pumping the quads while neglecting muscles like the hamstrings can lead to strain. Outside of the rehab clinic, "many people would say this exercise is a poor choice," says Pire.

Better: Lunges. "They require balance, which helps work muscles in the pelvis as well as the legs," says Pire.

How to Do Them

• Start by standing with your feet shoulder width apart, your hands behind your head, squeezing your shoulder blades back.
• Step forward and bend your knee until your thigh is parallel to the floor. Straighten the leg and return to the starting position.
• Repeat with the opposite leg.
• Do 12 lunges, six on each leg.
• Once you master the legs, try doing the lunges while holding a 5- or 7.5-pound dumbbell in each hand.