After doing workout classes for decades, I decided to switch to a strength-training program. Alexandra Frost Despite doing frequent workout classes for over 20 years, I felt weak at 37 years old. I started weightlifting at my local gym and gained strength surprisingly quickly. Eight months into my regimen, I feel better in my body and have a healthier perspective on fitness. For as long as I can remember, I've been a workout-class enthusiast. When I was 17, I followed my mom to Jazzercise c...