Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Kinesiology and Health Science

Committee Chair(s)

Eadric Bressel


Eadric Bressel


Timothy A. Slocum


Dennis Dolny


Guifang Fu


Brennan Thompson


Breanna Studenka


The reactive strength index (RSI) is the current “gold standard” assessment of reactive strength. Traditional measures of reactive strength, including the RSI, are not strength-based and are founded using untested theoretical assumptions. The purpose of this study was to develop two versions of a kinetic-based paradigm of reactive strength (New and AdjNew) and compare them against the Coefficient of Reactivity (CoR) and the RSI. Twenty one NCAA Division I basketball players and 59 young adults from the general population performed two reactive strength protocols: Progressive drop jumping and repetitive countermovement jumping. For every jump, the CoR, RSI, New, and AdjNew were computed. Measure agreeability was assessed using the Bland-Altman approach and linear regressions. Analyses of variance (ANOVA) assessed the effect of sport participation, age, and sex on the four measures of reactive strength. Lastly, effects of self-reported physical activity levels were assessed using stepwise linear regressions. The strongest association was observed between AdjNew and the RSI (R2= 0.636). All NCAA > young adults). The RSI, New, and AdjNew were sensitive to effects of sex and sport participation in repetitive countermovement jumping (males > females; NCAA > young adults). There are theoretical issues with the computation and implementation of the CoR and RSI. For example, the CoR and RSI are non-strength based measures that attempt to measure a strength construct. Further, the CoR, RSI, and New make the theoretical assumption that no biological variability exists in human movement. The AdjNew paradigm addresses and solves the theoretical issues with the CoR, RSI, and New. Therefore it may be argued that the AdjNew paradigm improves the theoretical validity of reactive strength assessment and is preferred over the RSI. The AdjNew is kinetic based, comprised of only measured component variables, and is not founded in assumptions of theory. This dissertation provides objective theoretical evidence to suggest that the AdjNew paradigm is an improvement over the RSI as a model of reactive strength.