Q: If a person improved their body composition and at the same time gained a lot of weight would this cause them to be slower when performing in a fast paced sport?

A: This is not a common occurence, but yes it is possible to actually hurt your athletic performance by packing on too much muscle. For example, consider a soccer player who bulks up his upper body. His extra back or chest or shoulder strength will give him very little or no competitive edge, but will slow him down due to the extra weight he is now carrying.

If you are concerned about athletic performance in a fast-paced sport, you should structure your weight-training program to emphasize muscle groups that are relevant to that sport. For a soccer player that would mean working legs heavily, but upper body only a little or even not at all. You should also introduce plyometric training into sport-specific programs. Plyometrics is designed specifically to improve explosive strength needed in most sports.

In general, the best time to train for a sport is in the off-season since you can afford to be tired and sore after training sessions. You would most likely want to incorporate the traditional weightlifting exercises that target sport-specific muscle groups, as well as power exercises (cleans, jerks, snatches) and plyometrics into your off-season training program.