It is often difficult to optimize strength qualities in-season due to the conflicting influences of extensive skill practices combined with frequent game play of the competition schedule. The purpose of this study was to investigate the effects of two interventions on strength qualities and CMJ performance. Thirteen women volleyball players competing in NCAA Division I were tested before and after four weeks of an inseason strength training program with emphasis on heavy squatting (6-IORM), and then before and after three weeks of unloaded jump training. Dynamic squat strength, isometric squat strength, optimal power, CMJ, SJ and approach jump and reach were all tested before and after both cycles. There was a significant increase in both average 1RM squat strength (5%) and vertical jump (1%) following the strength cycle. Following the unloaded training, there was a significant increase in both peak power output (18%) and peak velocity (14%) in the CMJ. SJ performance significantly increased in both peak force (6%) and maximum height (10%). Throughout training, there were no decreases in maximal strength levels or post-test Vertec jump and reach. This study indicates that heavy squatting can improve vertical jump as well as 1RM squat despite a high volume in-season practice and competition schedule. Furthermore, unloaded training can improve the explosive qualities of athletes when used as a peaking cycle late in-season. Athletes maintained dynamic strength and jumping ability from pre-testing scores, while significantly increasing both peak velocity and power in the CMJ. / School of Physical Education