Clinical Burden of Injuries in Students at a Professional Circus College: A 7.5-Year Longitudinal Study.

OBJECTIVE: To characterize clinical burden of injuries incurred by circus students enrolled in a 3-year college training program. METHODS: Student (n=334) injury data derived from an in situ clinic was examined over a 7.5-year time frame from August 2009 to December 2016. Injury incidence rate (per 1,000 training hours) was calculated and clinical incidence (injuries/year) was examined in relation to year in program, sex, age, and circus discipline. Weekly and monthly injury incidence were plotted with respect to milestones in the scholastic training year. Clinical burden (injury incidence and duration) was examined according to anatomic location and circus discipline. RESULTS: The overall injury incidence rate was 1.89 injuries/1,000 training hours and 0.94 injuries/1,000 training hours for injuries with a duration longer than 4 weeks. Clinical incidence decreased with year in program (p<0.05) and there were no sex or age differences. Temporal analysis demonstrated elevated weekly injury incidence for the 3 weeks following return from both summer and winter vacation (p<0.01) and for the weeks leading up to technical exams (p<0.01). According to anatomical location, shoulder injuries accounted for the greatest clinic burden followed by ankles and according to discipline, ground acrobat flyers followed by ground acrobats with equipment accounted for the greatest clinic burden. CONCLUSION: Overall injury incidence rate in the circus training program was within the range reported by other circus training programs and similar artistic and athletic training programs. Resources should be designated for enhanced rehabilitation efficacy and prevention of shoulder and ankle injuries and for ground acrobats with equipment and flyers. Preventative strategies to improve safety upon return-to-training after vacations should be examined.

Comparison of Common Methodologies for the Determination of Knee Flexor Muscle Strength.

BACKGROUND: Knee flexion strength may hold important clinical implications for the determination of injury risk and readiness to return to sport following injury and orthopedic surgery. A wide array of testing methodologies and positioning options are available that require validation prior to clinical integration. The purpose of this study was to 1) investigate the validity and test-retest reliability of isometric knee flexion strength measured by a fixed handheld dynamometer (HHD) apparatus compared to a Biodex Dynamometer (BD), 2) determine the impact of body position (seated versus supine) and foot position (plantar- vs dorsiflexed) on knee flexion peak torque and 3) establish the validity and test-retest reliability of the NordBord Hamstring Dynamometer. STUDY DESIGN: Validity and reliability study, test-retest design. METHODS: Forty-four healthy participants (aged 27 ± 4.8 years) were assessed by two raters over two testing sessions separated by three to seven days. Maximal isometric knee flexion in the seated and supine position at 90o knee flexion was measured with both a BD and an externally fixed HHD with the foot held in maximal dorsiflexion or in plantar flexion. The validity and test-retest reliability of eccentric knee flexor strength on the NordBord hamstring dynamometer was assessed and compared with isometric strength on the BD. RESULTS: Level of agreement between HHD and BD torque demonstrated low bias (bias -0.33 Nm, SD of bias 13.5 Nm; 95% LOA 26.13 Nm, -26.79 Nm). Interrater reliability of the HHD was high, varying slightly with body position (ICC range 0.9-0.97, n=44). Isometric knee flexion torque was higher in the seated versus supine position and with the foot dorsiflexed versus plantarflexed. Eccentric knee flexion torque had a high degree of correlation with isometric knee flexion torque as measured via the BD (r=0.61-0.86). The NordBord had high test-retest reliability (0.993 (95%CI 0.983-0.997, n=19) for eccentric knee flexor strength, with an MDC95 of 26.88 N and 28.76 N for the left and right limbs respectively. CONCLUSION: Common measures of maximal isometric knee flexion display high levels of correlation and test-retest reliability. However, values obtained by an externally fixed HHD are not interchangeable with values obtained via the BD. Foot and body position should be considered and controlled during testing. LEVEL OF EVIDENCE: 2b.