Objective: The purpose of this study is to determine the inter-rater reliability of commonly used musculoskeletal screening components in a population of contemporary professional dancers. Participants: Study participants were 30 women from six contemporary dance companies between the ages of 18 and 32, with a mean age of 24, and Body Mass Index of 22.4.
This randomized controlled trial examined the immediate effect of whole body vibration (WBV) on first position sauté height, and on static and dynamic bal-
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 (ICC
2,1
= 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: ICC
2,1
= 0.96 vs average of 2 trials: ICC
2,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.
Whole Body Vibration (WBV) is a new exercise trend in fitness and performance enhancement. WBV platforms oscillate over a range of frequencies and amplitudes; however no study to date has examined the experience of perceived exertion with differences in vibration frequency and static or dynamic body position, nor examined the difference between sexes based on position and frequency during WBV. The purpose of this study was to assess the effects of position and frequency on perceived exertion during WBV in healthy, active adults. A convenience sample of 39 healthy young adults who participated in moderated exercise was blinded and randomly allocated to six WBV conditions composed of different frequency and position combinations. The participants received instruction, provided informed consent, participated in a warm-up session, and then reported rating of perceived exertion for each WBV condition. A 2×3 within-subjects multivariate approach ANOVA was conducted against an alpha of 0.05. A statistically significant main effect of position (p = 0.004) and significant main effect of frequency (p = 0.025) were found. Significant marginal means were found between the frequencies of 0 Hz and 50 Hz (p = 0.007). Statistically significant differences were found between sexes for all combinations.
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