Strengthening your muscles improves your posture, making you look taller and slimmer—a great confidence booster. It also releases feel-good endorphins, putting you on the road to physical and emotional wellness. Twisting WalKing Lunge. This multi-muscle exercise from Kent Burden, owner of the Ventura, Calif., personal training group My Life Fitness and author of "Is Your Chair Killing You?" (MLF Press), utilizes not only the upper and lower body, but also the abdominals, making it a fast way to shape up all over. Adding the balance challenge forces your muscles to work harder to stay upright and stable. 1. Warm up by walking on a treadmill or outside for 5 minutes, pumping your arms as you go. 2. Stand with your feet about hip-width apart, holding a ball in front of your chest. Keep your elbows bent and close to your ribs, and your abs pulled in. (If you’re new to strength training, use a volleyball or other lightweight ball until you are comfortable with your balance and stability. those who are more advanced can use a 3- to 5-pound medicine ball; find one at spriproducts.com.) 3. Take a step forward with your left leg, bending both knees to 90 degrees. Your front knee should stay over your ankle as your back knee approaches the floor. When you are in a full lunge, rotate your torso and shoulders to the left, taking the ball to your left hip as you draw your abs in tight. 4. Rotate back to center, then push off the back foot and lift your right knee to hip height as you raise the ball above your head. Keeping the right knee lifted, toss the ball up in the air and catch it. 5. Take a step forward with your right leg to repeat the sequence on the opposite side. 6. Continue lunging forward, alternating sides. Start with 1 to 2 sets of 10 to 12 repetitions, building up to 15 reps; add another set when you’re ready.