This thesis aimed to: (a) design a factorially valid survey to assess sub-themes relating to ‘involvement opportunities’ (IOs), which are an antecedent variable in the sport commitment model (Wilson et al., 2004); (b) examine the placement of enjoyment alongside IOs in the sport commitment model; (c) determine the pathways (i.e., direct and/or indirect) by which specific IOs sub-themes affect functional and obligatory commitment and if they differ in number, strength and direction of association (Choosakul et al., 2009); and (d) examine differences between recent initiates compared to those who have been more continuously involved (Chu & Wang, 2012) in Masters swimming. Based on exploratory and confirmatory factor analyses of survey data from 725 swimmers (260 males, 465 females, M age = 50.5, range = 25-92), results confirmed a 10 factor solution of IOs sub-themes. Structural equation modeling demonstrated that the number, direction, and strength of associations between specific IOs sub-themes and commitment vary depending on commitment type, as do the nature of direct and indirect pathways affecting commitment. Invariance testing showed recent initiates and continuously-involved swimmers to be invariant across measurement and structural models. Overall, results support the need to measure and assess IOs at the level of the sub-theme and to consider a bi-dimensional (Santi et al., 2014; Wilson et al., 2004) sport commitment model.