Clinical tools to quantify torso flexion endurance: normative data from student and firefighter populations.

Given that torso muscle endurance is one of the few metrics that has been shown to be linked to having a history of back disorders together with predicting future back disorders, endurance tests for workers have been developed. While some data exists on the V-sit exercise for flexor endurance, some have specifically adopted the plank test. The primary objective of this study was to assess links between the two tests. Two data sets were collected. The first set was obtained from a convenience group of fire fighters where the plank endurance test scores, together with the Biering Sorensen test for extension endurance, were obtained over three years. The second data set was obtained from a tightly controlled cross-sectional study of university students that included scores for both flexor and extensor endurance. 620 fire fighters for the first data set and 181 university students for the second. While flexor endurance in the firefighters peaked when aged in their 40's, extensor endurance peaked in their 20's. In the study of university students, the plank scores were relatively higher than the V-sit scores in males but relatively lower than the V-sit in the females. A pearson correlation test between the paired plank and V-sit scores of each subject rendered a coefficient of r = 0.34. This means that the performance on one flexor test only predicted 11% of the score in the other. ANOVA comparison of scores based on their history of having had shoulder or back troubles showed no significant link between V-sit or plank scores. The plank scores are not well correlated with the V-sit scores suggesting that the two measure different variables. Since more data exists for the V-sit, measurement of flexor endurance in occupational settings using this test probably forms a stronger link to back injury.