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 90 o 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 MDC 95 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

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.

Introduction Anterior dislocations, the most common type of shoulder dislocation, are often complicated by subsequent instability. With recurrent dislocations there often is attrition of the labrum and progressive loss of the anterior bony contour of the glenoid. Treatment options for this pathology involve either soft tissue repair or bony augmentation procedure. The optimal management remains unknown and current clinical practice is highly varied. Methods and analysis The Shoulder instability Trial comparing Arthroscopic stabilization Benefits compared with Latarjet procedure Evaluation (STABLE) is an ongoing multi-centre, pilot randomized controlled trial of 82 patients who have been diagnosed with recurrent anterior shoulder instability and subcritical glenoid bone loss. Patients are randomized to either soft tissue repair (Bankart + Remplissage) or bony augmentation (Latarjet procedure). The primary outcome for this pilot is to assess trial feasibility and secondary outcomes include recurrent instability as well as functional outcomes up to two years post-operatively. Conclusions This trial will help to identify the optimal treatment for patients with recurrent shoulder instability with a focus on determining which treatment option results in reduced risk of recurrent dislocation and improved patient outcomes. Findings from this trial will guide clinical practice and improve care for patients with shoulder instability. Trial registration This study has been registered on http://www.ClinicalTrials.gov with the following identifier: ClinicalTrials.gov Identifier: NCT03585491, registered 13 July 2018, https://www.clinicaltrials.gov/ct2/show/NCT03585491?term=NCT03585491&draw=2&rank=1. Ethics and dissemination This study has ethics approval from the McMaster University/Hamilton Health Sciences Research Ethics Board (REB) (approval #4942). Successful completion will significantly impact the global management of patients with recurrent instability. This trial will develop a network of collaboration for future high-quality trials in shoulder instability.

Many types of muscular exercise promote the production of reactive oxygen species and result in oxidative stress, as evidenced by increased levels of lipid peroxidation products in both blood plasma and saliva. PURPOSE: To assess the agreement between quantitative measurements of lipid peroxidation products in plasma and saliva of athletes at rest and following the Åstrand-Rhyming test. METHODS: 20 elite athletes, aged 18-22 years, participated in the study. Athletes underwent the Åstrand-Rhyming cycle ergometer test. Blood and saliva samples were collected before (preexercise) and immediately after the exercise (postexercise). Diene conjugates (DC), triene conjugates (TC) and Schiff bases (SB) were photometrically determined. Optical densities were measured at 220 nm (absorption of isolated double bonds), 232 nm (absorption of DC), 278 nm (absorption of TC), and 400 nm (absorption of SB). Assumption of normality was verified using the Shapiro-Wilk test. Since all data were normally distributed, comparisons were made using paired Student's t-test. Bland-Altman (B&A) analysis was applied. RESULTS: DC levels were elevated in plasma (0.17+0.02 vs. 0.19+0.02 a.u., p<0.001) and saliva (0.17+0.02 vs. 0.19+0.02 a.u., p<0.01) in response to exercise, as were the plasmatic (0.12+0.04 vs. 0.14+0.04 a.u., p<0.05) and salivary (0.11+0.03 vs. 0.14+0.03 a.u., p<0.05) TC concentrations. SB levels were also significantly higher at postexercise compared to pre-exercise in both plasma (21.46+4.63 vs. 31.14+6.25 a.u., p<0.001) and saliva (20.83+4.06 vs. 30.19+6.45 a.u., p<0.001). The bias calculated for DC (0.005, pre-exercise; 0.004, postexercise), TC (0.002, pre-exercise; 0.004, postexercise) and SB (0.64, pre-exercise; 0.95, postexercise) using the B&A statistics was not significant both at pre-exercise and at postexercise because the line of equality was within the confidence interval of the mean difference. All of the data points lay within the respective agreement limits. CONCLUSIONS: High agreement between quantitative measurements of plasmatic and salivary DC, TC and SB was detected both at rest and following the Åstrand-Rhyming test. Saliva may be considered as an attractive option for identifying exercise-induced oxidative stress in athletes.