Procedures
All subjects agreed not to change or increase their current exercise habits during the course of the study. The plyometric training group participated in a 6-week training program performing a variety of plyometric exercises designed for the lower extremity (Table 2), while the control group did not participate in any plyometric exercises. All subjects were instructed not to start any lower extremity strengthening programs during the 6-week period and to only perform activities of normal daily living. Prior to the study, procedures and guidelines were presented orally and in written form. Subjects agreeing to participate signed an institutionally approved consent form.