When it comes to exercise, most people start a program -- or are at least think of starting a program -- because they want to lose weight. Like I said, this is most people. But, it's not everyone.

Hardgainers -- that is, people who have difficulty putting on weight of any kind -- usually turn to weight training as a means of bulking up. These folks are usually classified as ectomorphs; the skinniest of the three somatypes, they are characterized by long arms and legs and a short upper body and in most cases have long, thin muscles. While the concept of somatypes is a bit outdated these days, labeling hard gainers as such serves the general purpose for the sake of this discussion.

However, try as some hardgainers might to pack on a bit of muscle, many find this task to be quite difficult. While this may be due to any of a host of reasons, there's a strong possibility that it may be related to the amount of cardio being performed. Because of the metabolism-boosting effect cardiovascular exercise has on the body, a hardgainer may have trouble holding onto enough calories to build and retain new muscle. Again, I'm speaking in very broad and general terms here, but this is pretty much the gist of it. So, if you happen to be someone who can't seem to put any meat on your bones, you may want to cut back on the time you spend on the treadmill and instead focus on mass-building, compound lifting moves.