Evaluation of the 60-second bent knee sit-up and curl-up as measures of abdominal strength and fatigue
The purpose of this study was to evaluate the relationship between criterion measures of strength and fatigue of abdominal musculature and the number of sit-ups or modified curl-ups an individual can perform in 60 seconds. Criterion measures of strength were obtained using an isokinetic dynamometer that measured peak torque of the musculature when the feet were anchored, and when the feet were unanchored. The criterion measure for fatigue was determined by isokinetic torque and was expressed as the decline in performance as a percent of initial force values. Reliability values for the strength test and fatigue test were R= .69 and R=.70, respectively. Nonsignificant Pearson correlation coefficients were found for the following relationships: sit-up scores and abdominal strength with the feet anchored (r=.13); modified curl-up scores and abdominal strength with the feet unanchored (r=.07); fatigue index and sit-up scores (r=.19); and fatigue index and modified curl-up scores (r=.10). Significant correlation coefficients (pc.Ol) were found between the following variables: modified curl-up scores and sit-up scores (r= .62); strength with the feet anchored and strength with the feet unanchored (r =.77); weight and abdominal strength with the feet anchored (r=.75); and weight and abdominal strength with the feet unanchored (r=.64). The results of multiple-regression analysis revealed that when height and weight are included as independent variables in addition to sit-up scores or modified curl-up scores, the relationship to strength becomes significant (R=.82 and R=.68; pc.Ol). Multiple regression investigating fatigue using height, weight and modified curl-up scores demonstrated a relationship of R=.26. Based on the results of this study the following conclusions are warranted: (a) neither sit-ups nor modified curl-ups appear to highly related to measures of abdominal muscular strength; (b) neither sit-ups nor modified curl-ups appear to be highly related to measures of abdominal muscular fatigue; (c) there is a strong relationship between the weight of the subjects in this study, and their demonstrated abdominal muscular strength; and (d) there is, at best, a moderate correlation between sit-up scores and modified curl-up scores, and these tests are not interchangeable.