I used to get painful twinges after doing step-ups because my quad and calve muscles were so tight--but after I started using a foam roller, all that changed. These inexpensive long log-like rolls (which are often found in physical therapists' offices as well as in gyms; see pic) can help loosen up the tightness in the tissue--called fascia--surrounding the muscles. You can develop this after working out. This stretching is called myofascial release and gives you more range of motion, not to mention preventing all-too-common injuries like strains. I keep one at home and roll out each of my legs after every home (or gym) workout--or if I just feel my muscles getting tight. My executive beauty director also loves lying on one at night (just place it vertically beneath your spine) while watching TV because it feels like a mini massage. There are plenty of uses!
One daily change: Try the foam roller at the gym--or buy one so you can 'roll' in your living room. I got mine from performbetter.com for about $20; this website also tells you how to use one (and shows you an instructional video).