Single-group, repeated measures. To investigate the relationship between tubing length and tubing tension for 6 colors of Thera-Band tubing (each color representing a different level of resistance) and to estimate the resistive shoulder torque provided during shoulder abduction exercise. Thera-Band tubing is popular for providing resistance in rehabilitation strengthening programs. Unfortunately, it is difficult to compare use of elastic tubing with other resistance training methods because no published data exist on how much resistance is being provided during exercise. Nine male and 6 female subjects (age, 25.9 +/- 3.6 years; height, 173 +/- 10 cm) performed shoulder abduction, using 6 colors of tubing. A strain gauge attached at the fixed end of the tubing directly measured the tension generated during stretch. For each color of tubing, each subject momentarily held a position at 30 degrees, 60 degrees, 90 degrees, 120 degrees, and 150 degrees of abduction. Shoulder joint abduction, limb segment position, and tubing length were analyzed by means of the Peak Motion Measurement System. Simple linear regression equations predicted tubing tension from percent change in tubing length at the joint angle positions. A 2-way (5 x 6) repeated-measures ANOVA determined the mean differences in tubing tension across tubing colors at the shoulder abduction positions. Strong linear relationships were found for each tubing tension when referenced according to changes in tubing length. Significant differences in tension were found for the various colors of tubing. The resistive torque curves for each color tubing were similar to isotonic exercise. Thera-Band tubing provides linear resistance during shoulder abduction, but the resistive torque provided by the tubing mimics isotonic exercise.