Stretching
Current research suggests that static stretching -- that is, stretching exercises where a stretch is attained and held for a period of time -- should be done after your workout, not before. (G. Reynolds, "Stretching: The Truth," New York Times, Oct. 31, 2008.) To warm yourself up, do a bit of dynamic stretching by extending your arms to your sides and moving them clockwise and counter-clockwise in small circles. Then continue your warm-up with cardiovascular exercise on a treadmill or elliptical machine, or by walking. Try to maintain a level where you're working at 40-60% of your maximum exertion. 