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Context: Different resistance exercise determinants modulate the musculotendinous adaptations following eccentric hamstring training. The Nordic Hamstring Exercise (NHE) can be performed 2-fold: the movement velocity irreversibly increases toward the end of the range of motion or it is kept constant. Design: This cross-sectional study aimed to investigate if the downward acceleration angle (DWA_angle) can be used as a classification parameter to distinguish between increasing and constant velocity NHE execution. Furthermore, the kinetic and kinematic differences of these 2 NHE execution conditions were examined by analyzing the DWA_angle in relation to the angle of peak moment. Methods: A total of 613 unassisted NHE repetitions of 12 trained male sprinters (22 y, 181 cm, 76 kg) were analyzed. Results: The majority of analyzed parameters demonstrated large effects. NHEs with constant velocity  (n = 285) revealed significantly higher impulses (P < .001; d = 2.34; + 61%) and fractional time under tension (P < .001; d = 1.29; +143%). Although the generated peak moments were significantly higher for constant velocity (P = .003; d = 0.29; +4%), they emerged at similar knee flexion angles (P = .167; d = 0.28) and revealed on average just low relationships to the DWA_angle ( $R_{\mathrm{mean}}^2=22.4\%$ ). DWA_angle highly correlated with the impulse ( $R_{\mathrm{mean}}^2=60.8\%$ ) and δ (DWA_angle–angle of peak moment; $R_{\mathrm{mean}}^2=83.6\%$ ). Conclusions: Relating DWA_angle to angle of peak moment assists to distinguish between significantly different NHE execution, which will potentially elicit different musculotendinous adaptations. These insights are essential for coaches and athletes to understand how to manipulate eccentric hamstring training to change its purpose.

Context: Current lower-extremity return to sport testing primarily considers the physical status of an athlete; however, sport participation requires continuous cognitive dual-task engagement. Therefore, the purpose was to develop and evaluate the reliability of a visual-cognitive reactive (VCR) triple hop test that simulates the typical sport demand of combined online visual-cognitive processing and neuromuscular control to improve return to sport testing after lower-extremity injury. Design: Test–retest reliability. Methods: Twenty-one healthy college students (11 females, 23.5 [3.7] y, 1.73 [0.12] m, 73.0 [16.8] kg, Tegner Activity Scale 5.5 [1.1] points) participated. Participants performed a single-leg triple hop with and without a VCR dual task. The VCR task incorporated the FitLight system to challenge peripheral response inhibition and central working memory. Maximum hop distance, reaction time, cognitive errors, and physical errors were measured. Two identical testing visits were separated by 12 to 17 days (14 [1] d). Results: Traditional triple hop (intraclass correlation coefficients: ICC_(3,1) = .96 [.91–.99]; standard error of the measurement = 16.99 cm) and the VCR triple hop (intraclass correlation coefficients_(3,1) = .92 [.82–.97]; standard error of the measurement = 24.10 cm) both demonstrated excellent reliability for the maximum hop distance, and moderate reliability for the VCR triple hop reaction time (intraclass correlation coefficients_(3,1) = .62 [.09–.84]; standard error of the measurement = 0.09 s). On average, the VCR triple hop resulted in a hop distance deficit of 8.17% (36.4 [5.1] cm; P < .05, d = 0.55) relative to the traditional triple hop. Conclusions: Hop distance on the VCR triple hop had excellent test–retest reliability and induced a significant physical performance deficit when compared with the traditional triple hop assessment. The VCR triple hop reaction time also demonstrated moderate reliability.

Context: The assessment of strength is one of the most usual practices among professionals involved in health care or sport. Quadriceps and hamstrings are the most commonly assessed muscle groups. Generally, the methods used to assess muscle strength are active and, therefore, alternative passive methods could be useful. Myoton provides measures on 3 mechanical properties of the muscle: tone, elasticity, and stiffness. Objective: This study aimed to analyze the association of Myoton, an easy-to-use tool not requiring voluntary stimulus from the subject, with strength values in quadriceps and hamstrings. Study Design: Experimental. Setting: University kinesiology laboratory. Participants: Thirty-eight recreational athletes were evaluated. Main Outcome Measures: Anthropometric and demographic data, Myoton-based measures of vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and semitendinosus, and the maximum voluntary isometric contraction of quadriceps and hamstrings. Procedures: The association was examined using multiple regression models to estimate strength through Myoton-based parameters and different patient characteristics. The models encompassed either 2 or 3 independent variables. Results: The adjusted R ² values for predicting quadriceps strength were .666 for rectus femoris, .726 for vastus lateralis, and .667 for vastus medialis, while in regard to hamstrings, they were .617 for biceps femoris and .604 for semitendinosus. Conclusions: The main finding was that acceptable relationships were found between muscle strength and Myoton-based parameters when variables such as gender and/or age are considered. Our study reveals a new tool for estimating strength with outstanding advantages: it is easy, time-efficient, adaptable, and highly manageable through the feasible equations provided.

Clinical Scenario: Sport-related injuries are a common occurrence within the athletic population and every athlete responds differently. The cognitive, emotional, and behavioral responses associated with injuries ultimately impact the injury rehabilitation process and return to play. Specifically, self-efficacy significantly impacts the rehabilitation process and psychological techniques to improve self-efficacy are crucial in the recovery process. Imagery is one of these beneficial techniques. Clinical Question: Does the use of imagery during injury rehabilitation improve self-efficacy of rehabilitation capabilities compared with rehabilitation alone in athletes with a sport-related injury? Summary of Key Findings: The current literature was searched to identify the effects of imagery use to improve self-efficacy of rehabilitation capabilities, and 2 studies were selected: a mixed methods ecologically valid design and randomized controlled trial. Both studies investigated the relationship between imagery and self-efficacy and found positive results for imagery use in rehabilitation. Additionally, one of the studies specifically assessed rehabilitation satisfaction and found positive results. Clinical Bottom Line: The use of imagery should be considered as a clinical option for increasing self-efficacy during injury rehabilitation. Strength of Recommendation: Based on the Oxford Centre for Evidence-Based Medicine strength of recommendation, there is a grade B of recommendation to support the use of imagery to improve self-efficacy of rehabilitation capabilities during an injury rehabilitation program.

Context: Early physical activity (PA) after concussion may promote symptom resolution. Prior studies have investigated exercise frequency/duration, yet precise PA intensity or volume required for optimal recovery requires further investigation. moderate to vigorous physical activity (MVPA) is beneficial for physical health. We investigated whether sedentary time, light activity time, MVPA time, or activity frequency in the weeks following concussion are associated with time to symptom resolution among adolescents. Design: Prospective cohort study. Methods: Adolescents 10–18 years of age were tested ≤14 days of concussion and followed until symptom resolution. At the initial visit, participants rated symptom severity and were provided wrist-worn activity trackers to monitor PA for the following week. PA behavior was categorized each day based on heart rate: sedentary (resting), light PA (50%–69% age-predicted max heart rate), and MVPA (70%–100% age-predicted max heart rate). Symptom resolution was defined as the date when participants reported cessation of concussion-like symptoms. Patients were not given specific PA instructions, though some may have received instructions from their physician. Results: Fifty-four participants were included in the study (54% female; mean age = 15.0 [1.8] y; initially assessed 7.5 [3.2] d after concussion). Female athletes recorded more sedentary time (900 [46] vs 738 [185] min/d; P = .01; Cohen d = 0.72), and less time in light PA (194.7 [64.5] vs 224 [55] min/d; P = .08; Cohen d = 0.48) and MVPA (23 [17] vs 38 [31] min/d; P = .04; Cohen d = 0.58) than male athletes. After adjusting for sedentary time, hours per day with >250 steps, sex, and initial symptom severity, more MVPA time was associated with faster symptom resolution time (hazard ratio = 1.016; 95% confidence interval, 1.001–1.032; P = .04). Conclusion: Our findings offer preliminary insight into how varying PA intensities affect concussion recovery, as MVPA may be a higher intensity than what is typically prescribed in concussion care.

Context: Early identification of incoming military personnel at elevated odds for bone stress injury (BSI) is important for the health and readiness of the US military. Design: Prospective cohort study. Methods: Knee kinematic data of the incoming US Military Academy cadets were collected while performing a jump-landing task (The Landing Error Scoring System) using a markerless motion capture system and depth camera. Data on incidence of lower-extremity injury, including BSI, were collected throughout the study period. Results: A total of 1905 participants (452 females, 23.7%) were examined for knee valgus and BSI status. A total of 50 BSI occurred during the study period (incidence proportion = 2.6%). The unadjusted odds ratio for BSI at initial contact was 1.03 (95% confidence interval [CI], 0.94–1.14; P = .49). Adjusted for sex, the odds ratio for BSI at initial contact was 0.97 (95% CI, 0.87–1.06; P = .47). At the instant of maximum knee-flexion angle, the unadjusted odds ratio was 1.06 (95% CI, 1.02–1.10; P = .01), and the odds ratio was 1.02 (95% CI, 0.98–1.07; P = .29) after adjusting for sex. This suggests that there was not a significant enough association for an increase in the odds of BSI based on either degree of knee valgus. Conclusions: Our results did not demonstrate an association between knee valgus angle data during a jump-landing task and future increased odds of BSI in a military training population. Further analysis is warranted, but the results suggests the association between kinematics and BSI cannot be effectively screened by knee valgus angle data in isolation.

Context: Exertional heat stroke (EHS) is the most deadly form the exertional heat illness with a higher incidence among active duty US military members than in the general population. Current guidelines on EHS recovery timelines and return to duty vary among the military branches. In some cases, individuals experience prolonged heat and exercise intolerance with repeat exertional heat illness events, which can complicate the recovery process. Management and rehabilitation of such individuals is unclear. Case Presentation: This manuscript addresses the case and management of a US Air Force Special Warfare trainee who experienced 2 episodes of EHS, despite early recognition, gold standard treatment, and undergoing 4 weeks of a stepwise recovery after an initial EHS. Management and Outcomes: After the second episode, a 3-step process was utilized, consisting of a prolonged and personalized recovery period, heat tolerance testing using Israeli Defense Force advanced modeling, and stepwise reacclimatization. This process allowed the trainee to successfully recover from repeat EHS and return to duty, and set a framework for future repeat EHS treatment guidelines. Conclusions: In individuals with repeat EHS, a prolonged recovery period followed by heat tolerance testing can be used to demonstrate appropriate thermotolerance and safely clear an individual to begin stepwise reacclimatization. Overall, patient care and military readiness may be improved by unified Department of Defense guidelines for return to duty after EHS.

Context: Long-lever shoulder strength tests may aid clinical decision-making regarding return to sport after a shoulder injury. The Athletic Shoulder Test (AST) was developed to measure force production in 3 positions of shoulder abduction (90°, 135°, and 180°) using force plates. However, handheld dynamometers (HHDs) are more portable, affordable, and may provide valid and reliable results which would increase the clinical utility of long-lever tests. HHDs vary in shape, design, and their capacity to report parameters such as rate of force production and require further investigation. The aim of this study was to examine the intrarater reliability of the Kinvent HHD and assess its validity against Kinvent force plates in the AST. Peak force (in kilograms), torque (in Newton meters), and normalized torque (in Newton meters per kilogram) were reported. Design: Validity and reliability study. Methods: Twenty-seven participants with no history of upper limb injury performed the test in a randomized order using the Kinvent HHD and force plates. Each condition was assessed 3 times, and peak force was recorded. Arm length was measured to calculate peak torque. Normalized peak torque was calculated by dividing torque by bodyweight (in kilograms). Results: The Kinvent HHD is reliable when measuring force (intraclass correlation coefficient [ICC] ≥ .80), torque (ICC ≥ .84), and normalized torque (ICC ≥ .64) during the AST. The Kinvent HHD is also valid when compared with the Kinvent force plates for force (ICC ≥ .79; r ≥ .82), torque (ICC ≥ .82; r ≥ .76), and normalized torque (ICC ≥ .71; r ≥ .61). There were no statistically significant differences across the 3 trials on analyses of variance (P > .05). Conclusions: The Kinvent HHD is a reliable tool when used to measure force, torque, and normalized torque in the AST. Furthermore, given the lack of significant difference between trials, clinicians can use one test to accurately report relative peak force/torque/normalized torque rather than average 3 separate trials. Finally, the Kinvent HHD is valid when compared with Kinvent force plates.

Context: The influence of several psychological characteristics on the willingness of athletes to report concussion behaviors has not been well explored. Therefore, the purpose of this study was to understand how athletic identity and sport passion predicted participants’ willingness to report symptoms above what was explained by athlete demographics, concussion knowledge, and perceived seriousness of concussions. Design: The study was cross-sectional. Methods: Three-hundred and twenty-two male and female high school and club sport athletes completed survey measures of concussion knowledge, athletic identity, harmonious and obsessive passion, and degree to which athletes indicated they would report concussions and concussion symptoms. Results: Athletes scored moderately high on their knowledge of symptoms and other concussion information (mean = 16.21; ± = 2.88) and above the midpoint on their attitudes and behaviors toward reporting concussion symptoms (mean = 3.64; ± = 0.70). There were no differences between gender, t(299) = −.78, P = .44, and previous concussion education, t(296) = 1.93, P = .06, related to concussion knowledge. Results of a hierarchical regression indicated that after entering athlete demographics, concussion knowledge, and perceived seriousness of concussions, of the 3 psychological variables in the final stage of the model, only obsessive passion was a significant predictor of athlete’s attitudes to report a concussion. Conclusions: Perceived seriousness of concussion, perceived threat to long-term health, and obsessive passion were the strongest predictors of athlete’s willingness to report concussions. Athletes who did not believe concussions posed a threat to their current or future health, and those that held an obsessive passion for sport were most at risk for not reporting concussions. Future research should continue to investigate the relationship between reporting behaviors and psychological factors.