Because of their unrealistic goals, he says, people risk injury or burnout and sometimes abandon their workout program entirely. The ACE, the largest nonprofit fitness certifying organization in the world, asked more than 3,000 ACE-certified fitness professionals across the country in 1998 to give their take on the worst mistakes they see people making in the gym. Alan says the survey could have just as well been done today, because the same mistakes get repeated over and over. The best time to stretch is immediately before and after aerobic activity. Before stretching, take a few minutes to warm up as stretching cold muscles can cause injury.
Flexible muscles are far less likely to be strained or pulled than tight ones.
Lifting too much weight. The best way to guarantee yourself an injury is to try to lift more weight than your muscles can handle. If you want to go fast, do that on cardiovascular work. But when it comes to strength, in general, the slower you go, the more benefit you get. Not warming up prior to aerobic activity.