People who lift weights for muscular gain tend to limit their range of motion (the ability of a joint to articulate through an unhampered area of movement) when they perform an exercise. This practice can lead to improper muscular development, lack of tendon strength and limited joint mobility. There is nothing wrong with this form of training on an occasional basis, but when you regularly shorten range of movement in favor of heavier weights, you are training your body to only work that way.
First, muscles trained in a shortened state tend to form scar tissue or adhesions in the muscle, which greatly compromises range of motion. These adhesions are a normal part of muscle development and are created when the muscle is traumatized. They allow the muscle to heal and form strong bonds in the muscle to facilitate muscle function. But in the case of shortened RoM lifting, they actually limit range of motion and muscle function.
Second, tendons that connect muscle to bone are not trained to handle heavy loads through a large range of motion. This often results in torn tendons, tendonitis or, in some cases, a torn muscle. This can be very detrimental, especially when we look at athletic performance. If someone who trains in a shortened range of motion attempts to perform their sport in a full range of motion, the tendons have not been trained to handle those strains and injuries are likely.
Third, by affecting the above factors, joints cease moving in their optimal movement pattern and can create improper joint movement. This can be very harmful and lead to improper wear patterns which affect cartilage. Joints have optimal movement patterns, and once that pattern is changed, the joint suffers.
In conclusion, training with lighter weight through a full range of motion on a regular lifting program can be more beneficial that continually lifting heavier through a short range of motion.