ABSTRACT
BACKGROUND:: Prior studies have examined muscle power via the countermovement jump (CMJ). Studies to date have examined neither the reliability nor the construct validity of the ballet first position CMJ (hips in lateral rotation, toes facing away from one another, legs straight) as a measure of power. HYPOTHESES:: There would be (1) good interrater reliability in the visual assessment of the best-quality first position CMJ (κ ≥ 0.60), (2) good test-retest reliability in the height of the first position CMJ of good quality (intraclass correlation coefficient [ICC] ≥ 0.80), and (3) a significant relationship between isokinetic torque of the quadriceps femoris and first position CMJ height ( r ≥ 0.40). STUDY DESIGN:: Correlational study. LEVEL OF EVIDENCE:: Level 3. METHODS:: A convenience sample of 39 healthy young adults who reported moderate activity levels participated in a warm-up and 2 sessions of 6 jumps. Quadriceps femoris isokinetic torque was measured in the first session. RESULTS:: Significant agreement was found within the same day for the best-quality first position CMJ (κ = 0.81), and in the highest, best-quality first position CMJ between days (ICC2,1 = 0.88). The highest, best-quality first position CMJ, when solving for a single trial, was comparable to the average of 2 trials (single trial: ICC2,1 = 0.96 vs average of 2 trials: ICC2,k = 0.98). There was a good relationship between quadriceps femoris isokinetic strength and first position CMJ height (Pearson r = 0.69 and P < 0.001 at 60 deg/s; r = 0.64 and P < 0.001 at 180 deg/s; r = 0.65 and P < 0.001 at 300 deg/s). CONCLUSION:: Visual video movement analysis has good to excellent interrater agreement and test-retest reliability. Selecting the single highest jump of good quality is acceptable. The first position CMJ is a measure of power. CLINICAL RELEVANCE:: Video analysis of the single highest first position CMJ of good quality is an acceptable method of assessing movement quality.
