The purpose of this dissertation was to explore the potential use of net impulse and its characteristics in vertical jumping to monitor athletes' performance status and responses/adaptations to interventions. Five variables were proposed as net impulse characteristics: net impulse height and width, rate of force development, shape factor, and net impulse proportion. The following were then examined: 1) test-retest reliability of a new approach to identify net impulse in a force-time curve and of net impulse characteristics and criterion validity of the new approach; 2) effective measures of net impulse characteristics; 3) relationships between training-induced changes in its characteristics and force production ability. The following are major findings of the dissertation. Rate of force development particularly for the countermovement jump require a large magnitude of change to overcome the variable's inherent variability. Shape factor and net impulse proportion for the static jump should be used with caution and requires further investigations. Alternative net impulse can be used interchangeably to criterion net impulse. Of the proposed net impulse characteristics, net impulse height and width and shape factor were found to contribute to countermovement jump height, whereas all the net impulse characteristics were found to contribute to static jump height. Of the characteristics found to contribute, relative net impulse height (net impulse height divided by system mass) appears to be an important characteristic to achieve a high jump height for the countermovement and static jumps and net impulse proportion for the static jump. A mechanism behind increased countermovement jump height may be an increased countermovement displacement as a result of increased force production ability. A mechanism behind increased static jump height is the increased proportion of the entire positive impulse occupied by net impulse (i.e. increased net impulse proportion). The findings of this dissertation show the possibility of the use of the net impulse characteristics to monitor athletes' performance status and responses/adaptations to interventions. However, because this dissertation was the first to explore the potential use of the net impulse characteristics for athletes' performance monitoring, the existing knowledge is still preliminary and further research is required before practical recommendations are made.

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The purpose of this study was to observe physiological metrics relative to training-induced adaptations in conjunction with laboratory- and competition-based performances in a super-heavyweight weightlifter recovering from a meniscus injury. A retrospective analysis was conducted on a collegiate level male weightlifter (23.2 yrs; 131.9 kg; 187.3 cm) over the course of 21-weeks post-meniscus surgery. Body mass, body fat percentage, hydration status, vastus lateralis muscle cross-sectional area, jump performance, and isometric midthigh pull were regularly assessed as part of an ongoing athlete monitoring program. Pre-injury baseline (T0) measurements were collected relative to a major national competition (COMP1). Post-injury measurements took place at the end of sequential training blocks: strength-endurance training block 1 (T1), basic strength block 2 (T2), and transmutation block 3 (T3). The final measurement session (T4) was conducted three-days post-local competition (COMP2). Only statistically significant increases were observed from T0-T4 for muscle CSA (p=0.0367), isometric peak force (pp=0.0367), and rate of force development at 250ms (p=.0367). While non-significant changes were observed for jumping performance, jump height and net impulse did, however, return to baseline. Competition based performances also showed marked improvements from pre-to-post injury via an increase in weightlifting total (3.2%∆, +9kg) and Sinclair score (1.8%∆, +5.3au). Thus, based on these findings, implementing an evidence-based training program along with a sound athlete monitoring protocol can aid with reducing an athlete’s return-to-train timeline while improving physiological, laboratory- and competition-based performance outcomes.