Relationships Among Baseline Concussion Balance Test and Gaze Stability Test Scores in Division-I Collegiate Athletes.

CONTEXT: Sports-related concussions are commonly occurring injuries as a result of sports and recreation that may cause alterations in brain functioning. It is important to be able to evaluate the impact of these injuries on function to manage the injury recovery and ensure recovery. Recent literature suggests the use of objective evaluation strategies in a multifaceted approach to evaluate and manage these injuries. It is important to understand the relationships between the assessments and how best to utilize each assessment. The purpose of this study was to investigate if relationships exist between measures of vestibular function at baseline in assessments that may be used following sports-related concussions. Additionally, a secondary purpose was to determine if self-reported symptoms were related to performance on the assessments. This study aimed to identify if these assessments measured independent functions of the vestibulo-ocular reflex or if some redundancy existed among the assessment strategies. DESIGN: A cross-sectional study design was used in a cohort of collegiate athletes ages 18-24. METHODS: Participants completed demographics questionnaires, the Post-Concussion Symptom Scale, Gaze Stabilization Test, and Concussion Balance Test. Spearman rho correlations were used to examine the relationships between the measures. RESULTS: One hundred and thirty-five collegiate athletes (82 males and 53 females) were included, representative of 3 sports (cheerleading, soccer, and football) with a mean age of 19.77 (1.42) years old. There were weak to moderate, significant relationships between measures of Gaze Stabilization Test and Concussion Balance Test errors (r = .20-.31, P = .001-.03). CONCLUSIONS: The direction of these relationships indicated that greater Concussion Balance Test errors were associated with greater Gaze Stabilization Test performance. These relationships may be attributed to the difficulty created by the foam conditions and the integration of more complex sensory tasks required to maintain balance during the more difficult conditions.

The Acute Effect of High-Intensity Resistance Training on Subsequent Firefighter Performance.

ABSTRACT: Mason, MR, Heebner, NR, Abt, JP, Bergstrom, HC, Shapiro, R, Langford, EL, and Abel, MG. The acute effect of high-intensity resistance training on subsequent firefighter performance. J Strength Cond Res 37(7): 1507-1514, 2023-High-intensity resistance training (HIRT) is commonly performed by structural firefighters on duty to enhance occupational readiness. However, exercise-induced fatigue may negatively impact subsequent occupational performance. Therefore, the purpose of this study was to assess the acute effect of HIRT on subsequent occupational physical ability in structural firefighters and to determine the time course of recovery. Seven resistance-trained male firefighters performed a timed maximal effort simulated fireground test (SFGT) in 3 randomized conditions: baseline (SFGT baseline ), 10 minutes post HIRT (SFGT 10min ), and 60 minutes post HIRT (SFGT 60min ). Work efficiency and air depletion were assessed during the SFGT. The timed HIRT session consisted of a standardized set of exercises using absolute training loads. Repeated measures analysis of variance and minimal difference (MD) analysis assessed group and individual effects between the conditions, respectively. The level of significance was set at p < 0.05. SFGT 10min completion time was greater than SFGT baseline (430 ± 137 vs. 297 ± 69 seconds, p < 0.01), with no difference between SFGT baseline and SFGT 60min (297 ± 69 vs. 326 ± 89 seconds, p = 0.08). The MD analysis indicated that all firefighters' SFGT 10min times exceeded the MD (±26.4 seconds) compared with SFGT baseline . However, 43% of firefighters still exceeded the MD at SFGT 60min . Air depletion during SFGT 10min was greater than that during SFGT baseline (2,786 ± 488 vs. 2,186 ± 276 lb·in -2 , p = 0.02), with no difference between SFGT baseline and SFGT 60min ( p = 0.25). Work efficiency during SFGT 10min was 40% lower than that during SFGT baseline ( p < 0.01), with no difference between SFGT baseline and SFGT 60min ( p = 0.25). These findings indicate that an acute bout of HIRT decreases multiple descriptors of firefighters' occupational performance 10 minutes post exercise with varied responses at 60 minutes post exercise.

Computerized Cognitive Function Does Not Correlate With Choice Reaction Time During a Hopping Task.

CONTEXT: Cognitive performance has been shown to be associated with musculoskeletal injury risk. Cognitive assessments are often administered in controlled environments despite sport settings challenging cognition in uncontrolled, less predictable environments. Cognitive assessments should be representative of sport demands; thus, integrating motor with cognitive assessments may be more clinically relevant. Accordingly, the purpose of this research was to investigate the relationship between tablet-based cognitive tests and choice reaction time during a hopping task. DESIGN: Cross-sectional. METHODS: A total of 20 healthy participants volunteered to participate. Participants completed 3 tablet-based cognitive assessments. Average raw response time and fully corrected scores were used for analysis. In addition, participants completed a choice reaction hopping task to capture neuromuscular-cognitive reaction time. Participants completed a forward hop over a hurdle, landing on a single limb. Light sensors were utilized for the choice reaction component to capture reaction time in seconds, cue them when to hop, and indicate the landing limb. The relationship between the tablet-based cognitive assessments and reaction time during a hopping task was examined with Pearson correlations (α = .05). RESULTS: The choice reaction time from the hop task had a negligible correlation (r = -.20-.07) to the fully corrected tablet-based cognitive tests. The choice reaction time from the hop task had a negligible correlation (r = .02) to the average response time of the Pattern Comparison Processing Speed Test and a low correlation (r = .34-.36) to the Dimensional Change Card Sort Test and Flanker Inhibitory Control and Attention Test. CONCLUSIONS: This study determined that tablet-based cognitive assessments had trivial relationships to choice reaction time during a hopping task. This research has implications as clinicians aim to evaluate and analyze cognitive performance. Although reaction time was a critical component of all the assessments in this study, an individual's performance on a tablet-based assessment does not indicate performance during a functional reaction time assessment.

Slower visuomotor reaction time in division-I collegiate athletes with a history of ankle sprain.

The purpose of this study was to compare visuomotor reaction time (VMRT) in collegiate athletes based on ankle sprain history. Participants included athletes with ankle sprain history (n = 18) and athletes with no ankle sprain history (n = 33). Participants completed an upper-extremity VMRT task which was comprised of eight wireless light-emitting diode sensors. The difference between reaction time (sec) and the number of "Hits" and "Misses" were compared between groups. The ankle sprain history group had significantly slower VMRT compared to the no ankle sprain history group with moderate effect sizes. However, there was no difference in the number of "Hits" or "Misses" between groups, despite observing moderate effect sizes. This result suggests that VMRT may be a potential target for prevention and rehabilitation strategies in individuals with ankle sprains. However, further research is needed to better understand the role of VMRT on the risk of ankle sprains.

Resting state functional connectivity responses post-mild traumatic brain injury: a systematic review.

Mild traumatic brain injuries (mTBI) are associated with functional network connectivity alterations throughout recovery. Yet, little is known about the adaptive or maladaptive nature of post-mTBI connectivity and which networks are predisposed to altered function and adaptation. The objective of this review was to determine functional connectivity changes post-mTBI and to determine the adaptive or maladaptive nature of connectivity through direct comparisons of connectivity and behavioral data. Literature was systematically searched and appraised for methodological quality. A total of 16 articles were included for review. There was conflicting evidence of post-mTBI connectivity responses as decreased connectivity was noted in 4 articles, 6 articles reported increased connectivity, 5 reported a mixture of increased and decreased connectivity, while 1 found no differences in connectivity. Supporting evidence for adaptive post-mTBI increases in connectivity were found, particularly in the frontoparietal, cerebellar, and default mode networks. Although initial results are promising, continued longitudinal research that systematically controls for confounding variables and that standardizes methodologies is warranted to adequately understand the neurophysiological recovery trajectory of mTBI.

Altered Physical Performance Following Advanced Special Operations Tactical Training.

ABSTRACT: Winters, JD, Heebner, NR, Johnson, AK, Poploski, KM, Royer, SD, Nagai, T, Randall, CA, Abt, JP, and Lephart, SM. Altered physical performance following advanced special operations tactical training. J Strength Cond Res 35(7): 1809-1816, 2021-The purpose of this study was to determine how the unique challenges of specific military tactical training phases influence overall physical performance characteristics. Broad jump, 5-10-5, 300-yd shuttle, percent body fat (%BF), anaerobic power (AP) and anaerobic capacity (AC), maximal oxygen uptake (V̇o2max), isokinetic knee extension/flexion strength, shoulder internal/external rotation strength, and trunk extension/flexion strength were collected on 73 United States Marine Corps Forces Special Operations Command (MARSOC) students (age: 27.4 ± 3.8 years, height: 178.7 ± 6.6 cm, and body mass: 85.8 ± 9.4 kg) at the beginning of (P1), in between (P2), and at the completion of 2 distinct tactical training phases (P3). Linear mixed models were used to analyze within-subject performance changes over the 3 time points, and post hoc Bonferroni pairwise comparisons analyzed performance changes between each testing time point. There were significant changes in broad jump (p < 0.0001), 5-10-5 agility time (p < 0.001), %BF (p = 0.011), AP (p < 0.0001), V̇o2max (p = 0.001), and both right and left shoulder internal rotation strength (p = 0.004 and p = 0.015, respectively) between P1 and P2. There were also significant changes in 300-yd shuttle run time (p = 0.001), AP (p < 0.0001), AC (p < 0.0001), left knee extension strength (p = 0.006), trunk flexion strength (p < 0.0001), and left shoulder external rotation strength (0.027) between P2 and P3. Identifying the effect that specific tactical training phases may have on physical performance will allow for the development of effective phase-specific evidence-based human performance programs, reducing performance deficits and thereby reducing the risk of injury.

Effect of Dry Needling on Spinal Reflex Excitability and Postural Control in Individuals With Chronic Ankle Instability.

OBJECTIVE: The purpose of this study was to compare postural control and neurophysiologic components of balance after dry needling of the fibularis longus between individuals with chronic ankle instability (CAI) and a healthy control group. METHODS: This quasi-experimental university-laboratory study included 50 adult volunteers-25 with CAI (16 female, 9 male; age: 26 ± 9.42 years; height: 173.12 ± 9.85 cm; weight: 79.27 ± 18 kg) and 25 healthy controls (15 female, 10 male; age: 25.8 ± 5.45 years; height: 169.47 ± 9.43 cm; weight: 68.47 ± 13 kg). Participants completed the Star Excursion Balance Test (SEBT), single-leg balance, and assessment of spinal reflex excitability before and after a single treatment of dry needling to the fibularis longus. The anterior, posterolateral, and posteromedial directions of the SEBT were randomized, and reach distances were normalized to a percentage of leg length. A composite SEBT score was calculated by averaging the normalized scores. Postural control was assessed in single-limb stance on a force plate through time-to-boundary measurements in eyes-open and eyes-closed conditions. Fibularis longus and soleus spinal reflexes were obtained by providing electrical stimulation to the common fibular and tibial nerves with participants lying prone. A Group × Time analysis examined changes in performance, and effect sizes were calculated to assess significance. RESULTS: Significant group × time interactions were identified for composite (P = .006) and posteromedial (P = .017) SEBT scores. Significant time effects for all directions of the SEBT, time to boundary with eyes open, and the mediolateral direction with eyes closed indicate improved postural control following treatment (P < .008). Within-group effect sizes for significant time effects ranged from small to large, indicating potential clinical utility. CONCLUSION: Dry needling demonstrated immediate short-term improvement in measures of static and postural control in individuals with CAI as well as healthy controls.

The Effect of Attending Physical Rehabilitation After the First Acute Lateral Ankle Sprain on Static Postural Control in Patients With Chronic Ankle Instability.

CONTEXT: Static postural control deficits are commonly documented among individuals with chronic ankle instability (CAI). Evidence suggests individuals with CAI who seek medical attention after an ankle sprain report fewer subjective symptoms. It is unknown if seeking medical attention and receiving supervised physical rehabilitation has a similar effect on objective outcomes, such as static postural control. OBJECTIVE: To compare measures of single-limb postural control and center of pressure (COP) location between participants with CAI who did or did not self-report attending supervised rehabilitation at the time of their first lateral ankle sprain. DESIGN: Retrospective cohort. SETTING: Laboratory. Patients (or Other Participants): Twenty-nine participants with CAI who did (n = 14) or did not (n = 15) self-report attending supervised rehabilitation. INTERVENTION(S): Self-reported attendance or not of supervised rehabilitation at the time of initial injury. MAIN OUTCOME MEASURES: Participants performed three 20-second trials of single-limb stance on a force plate with eyes open. Main outcome measures included the COP velocities, time-to-boundary (TTB) absolute minima, mean of TTB minima, and SD of TTB minima in the anteroposterior and mediolateral directions. The spatial distribution of the COP data points under the foot was quantified within 4 equally proportional sections labeled anteromedial, anterolateral, posteromedial, and posterolateral. RESULTS: Participants who reported attending supervised rehabilitation after their initial ankle sprain had a lower COP velocity in the anterior-posterior direction (P = .030), and higher TTB anterior-posterior absolute minimum (P = .033) and mean minima (P = .050) compared with those who did not attend supervised rehabilitation. CONCLUSIONS: Among individuals with CAI, not attending supervised rehabilitation at the time of initial injury may lead to worse static postural control outcomes. Clinicians should continue advocating for patients recovering from an acute ankle sprain to seek medical attention and provide continued care in the form of physical rehabilitation.

Relationship of performance on the sensory organization test to landing characteristics.

Jump landing tasks have been used to assess landing characteristics and require significant sensorimotor feedback to maintain functional joint stability (FJS) throughout the task. Postural stability (PS) also requires significant sensorimotor feedback and control and would seemingly involve similar sensory feedback pathways. However, previous literature clarifying the relationship between these two processes, maintaining FJS and PS, is limited. 80 Special Tactics Operators. PS was assessed using the Sensory Organization Test (SOT). SOT variables included: Composite, Somatosensory, Visual, Vestibular, and Preference scores. Landing characteristics were assessed using motion analysis during a double-legged (DLSJ) and single-legged (SLSJ) stop jump task. Pearson's correlation coefficients were calculated to assess the relationship between SOT scores and landing characteristics (α < .05). For the DLSJ, significant correlations were found between: Composite and peak posterior ground reaction forces (-.257), Vestibular and peak knee abduction moment (-.237), and Preference and initial contact hip flexion (-.297), peak hip flexion (-.249). For the SLSJ, significant correlations were found between: Somatosensory and peak vertical ground reaction forces (-.246); Preference and initial contact hip flexion (-.295), peak hip flexion (-.262). The results indicate that the SOT may not be a sensitive enough tool to assess sensorimotor control in a healthy, athletic population.

Reliability of 5 Novel Reaction Time and Cognitive Load Protocols.

CONTEXT: Reaction time (RT) is crucial to athletic performance. Therefore, when returning athletes to play following injury, it is important to evaluate RT characteristics ensuring a safe return. The Dynavision D2® system may be utilized as an assessment and rehabilitation aid in the determination of RT under various levels of cognitive load. Previous research has demonstrated good reliability of simple protocols when assessed following a 24- to 48-hour test-retest window. Expanding reliable test-retest intervals may further refine novel RT protocols for use as a diagnostic and rehabilitation tool. OBJECTIVE: To investigate the test-retest reliability of a battery of 5 novel RT protocols at different time intervals. DESIGN: Repeated measures/reliability. SETTING: Interdisciplinary sports medicine research laboratory. PARTICIPANTS: Thirty healthy individuals. METHODS: Participants completed a battery of protocols increasing in difficulty in terms of reaction speed requirement and cognitive load. Prior to testing, participants were provided 3 familiarization trials. All protocols required participants to hit as many lights as quickly as possible in 60 seconds. After completing the initial testing session (session 1), participants waited 1 hour before completing the second session (session 2). Approximately 2 weeks later (average 14 [4] d), the participants completed the same battery of tasks for the third session (session 3). MAIN OUTCOME MEASURES: The intraclass correlation coefficient, standard error of measurement, minimal detectable change, and repeated-measures analysis of variance were calculated for RT. RESULTS: The intraclass correlation coefficient values for each of the 5 protocols illustrated good to excellent reliability between sessions 1, 2, and 3 (.75-.90). There were no significant differences across time points (F < 0.105, P > .05). CONCLUSIONS: The 1-hour and 14-day test-retest intervals are reliable for clinical assessment, expanding the time frames previously reported in the literature of when assessments can be completed reliably. This study provides novel protocols that challenge cognition in unique ways.

The Effect of Target Position on the Accuracy of Cervical-Spine-Rotation Active Joint-Position Sense.

CONTEXT: The cervical spine can be divided into upper and lower units, each making a different contribution to the magnitude of rotation and proprioception. However, few studies have examined the effect of the cervical-rotation positions on proprioception. OBJECTIVE: To compare cervical-spine rotation active joint-position sense (AJPS) near midrange of motion (mid-ROM; 30°) and near end-ROM (60°). DESIGN: Cross-sectional study. SETTING: Human performance research laboratory. PARTICIPANTS: 53 military helicopter pilots (age 28.4 ± 6.2 y, height 175.3 ± 9.3 cm, weight 80.1 ± 11.8 kg). MAIN OUTCOME MEASURES: A motion-analysis system was used to record cervical-rotation kinematics. Subjects sat in a chair wearing a headband and blindfold. First, they actively rotated the head right or left to a target position (30°/60°), with real-time verbal cues provided by the tester. Subjects held the target position for 5 s and then returned to the start position. After this, they replicated the target position as closely as possible. Five trials were performed in both directions to both target positions (R30/R60/L30/L60). Order of direction/position was randomized. The difference between target and replicated positions was calculated and defined as absolute error (AE), and the mean of 5 trials was used for analyses. Wilcoxon signed-ranks tests were used to compare AJPS at the different target positions (P < .0125 with Bonferroni adjustments). RESULTS: End-ROM AEs were significantly more accurate than mid-ROM AEs (P = .001). CONCLUSION: Cervical-spine-rotation AJPS is more accurate near end-ROM than mid-ROM. Both target positions should be used to examine cervical-spine-rotation AJPS of both the upper and lower units.

Reliability and validity of instrumented soccer equipment.

Ankle ligament sprains are the most common injury in soccer. The high rate of these injuries demonstrates a need for novel data collection methodologies. Therefore, soccer shoes and shin guards were instrumented with inertial sensors to measure ankle joint kinematics in the field. The purpose of this study was to assess test-retest reliability and concurrent criterion validity of a kinematic assessment using the instrumented soccer equipment. Twelve soccer athletes performed athletic maneuvers in the laboratory and field during 2 sessions. In the laboratory, ankle joint kinematics were simultaneously measured with the instrumented equipment and a conventional motion analysis system. Reliability was assessed using ICC and validity was assessed using correlation coefficients and RMSE. While our design criteria of good test-retest reliability was not supported (ICC > .80), sagittal plane ICCs were mostly fair to good and similar to motion analysis results; and sagittal plane data were valid (r = .90-98; RMSE < 5°). Frontal and transverse plane data were not valid (r < .562; RMSE > 3°). Our results indicate that the instrumented soccer equipment can be used to measure sagittal plane ankle joint kinematics. Biomechanical studies support the utility of sagittal plane measures for lower extremity injury prevention.

The Influence of Emergency Call Volume on Occupational Workload and Sleep Quality in Urban Firefighters.

OBJECTIVE: The aim of the study is to determine the impact of emergency call volume on exertion, autonomic activity, and sleep among urban structural firefighters. METHODS: Thirty-four firefighters wore a wrist-based monitor to track sleep and autonomic parameters and rated their level of perceived exertion (Borg Rating of Perceived Exertion) and subjective sleepiness after a 24-hour shift. Predictive variables included total run time and total run time after 11:59 PM. RESULTS: Total run time and sleep duration accounted for Borg Rating of Perceived Exertion and subjective sleepiness, while total run time and total run time after 11:59 PM accounted for sleep durations on-duty. CONCLUSIONS: The current results suggest that emergency call volume is associated with indicators of exertion and sleep. As such, call volume tracking is an important consideration for departments to ensure personnel readiness and wellness and provide a method of tracking the occupational demands experienced by firefighters on-duty.

Protocol for a feasibility randomized controlled trial of gentle yoga in older patients discharged from phase II cardiac rehabilitation.

Background: Physical activity (PA) is essential following an acute cardiac event. Cardiac rehabilitation (CR) is commonly prescribed, and PA after CR is recommended. Because of age-related changes in functional ability and multi-comorbidity, many older cardiac patients struggle to continue performing PA at home after CR. Depressive symptoms and anxiety are prevalent in cardiac patients and associated with poor self-care, including lack of daily PA. Yoga has been demonstrated to improve psychological and physical health outcomes in cardiac patients, but it is unknown whether yoga, modified for older CR patients - Gentle Yoga - is beneficial in managing psychological distress and maintaining PA following phase II CR. Our specific aims are to:1) determine the feasibility and acceptability of a modified gentle yoga intervention delivered via video conferencing for older cardiac patients; 2) compare, at 3-month follow-up, the effects and determine effect sizes of a gentle yoga intervention versus control on psychological health and physical health. Methods: We are conducting a 2-group (intervention versus control) randomized controlled pilot study. The intervention is a 12-week gentle yoga program delivered via video conference. Short-term effects will be evaluated at 3-month. Conclusion: This study is designed to be suited for older cardiac patients who would not have access to supervised PA opportunities after facility-based CR to enhance PA. This study will provide data about the feasibility and acceptability of the protocol for older cardiac patients and will offer effect sizes to determine sample size for a fully powered randomized controlled trial.

Restoration of sagittal and transverse plane proprioception following anatomic double-bundle ACL reconstruction.

PURPOSE: To investigate the restoration of knee proprioception after anatomic double-bundle ACL reconstruction. METHODS: Eleven subjects who underwent anatomic double-bundle ACL reconstruction (12.5-15 months following surgery) and eleven healthy control subjects participated in the study. Sagittal and transverse plane threshold to detect passive motion (TTDPM) were assessed utilizing a customized isokinetic dynamometer by passively rotating the tibia about a fixed femur in both the sagittal plane and transverse plane at 0.25°/s until the subject signalled recognition of movement and movement direction. Based on the normality assumption, either dependent t test or Wilcoxon test was utilized to determine whether significant differences were present between the ACL-reconstructed and the uninjured contralateral limbs. Independent t test or Mann-Whitney test was utilized to compare between the ACL-reconstructed/uninjured contralateral and the external control limbs. RESULTS: There were no significant differences in TTDPM measurement in eleven out of twelve comparisons between the ACL-reconstructed and the uninjured contralateral/external control limbs. The only statistical significant difference was found on TTDPM towards internal rotation direction from the externally rotated-test position between the ACL-reconstructed and the uninjured contralateral limbs (p = 0.01). CONCLUSIONS: Based on a small sample of eleven subjects, the current results indicate a restoration of both sagittal and transverse plane TTDPM following the anatomic double-bundle ACL reconstruction. LEVEL OF EVIDENCE: III.

No pain, no gain: The military overtraining hypothesis of musculoskeletal stress and injury.

The purpose of this manuscript is to present a model of military overtraining and subsequent injury, discharge, and disability. Military training and combat operations are physically and physiologically demanding, placing great strain on the musculoskeletal system of warfighters. Non-battle musculoskeletal injuries (MSKI) are common and present a serious threat to operational readiness in today's military. MSKI risk stratification and prevention are an active area of research and is steeped in the background of sports science. Here, a model is proposed that incorporates the theory of General Adaptation Syndrome to describe how military training stressors may exceed that of training in traditional athletics and may induce sub-optimal training stressors. Positive feedback loops are discussed to explain how military overtraining (MOT) creates a system of ever-increasing stressors that can only be fully understood in the greater context of all environmental factors leading to overtraining. The Military Overtraining Hypothesis (MOTH) is proposed as a model that encapsulates the elevated MSKI risk in combat arms and other operational military personnel as an effort to broaden understanding of multifactorial military MSKI etiologies and as a tool for researchers and commanders to contextualize MSKI research and risk mitigation interventions.

The effect of extended shift work on autonomic function in occupational settings: A systematic review and meta-analysis.

OBJECTIVE: To examine the effect of 24-h shift work on autonomic nervous system function via heart rate variability (HRV) methodologies. METHODS: Electronic databases (indexed in either PubMed, MEDLINE, CINAHL, SPORTDiscus, or OpenDissertations) were searched from January 1964 to March 2023. A modified Downs and Black checklist was used for assessing methodological quality and the Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) approach was used to evaluate the quality of evidence. Study design, study population, study sample, shift work description, and assessment of HRV metrics and methods were extracted from each study. FINDINGS: A total of 58 478 study articles were identified, of which 12 articles met inclusion criteria. Sample sizes varied from eight to 60 participants, with the ratio of low- to high-frequency HRV (LF/HF) as the most common frequency-domain variable reported. Of the nine included studies that observed LF/HF, three (33.3%) demonstrated a significant increase after 24-h shift work. Moreover, of the five studies that reported HF, two (40%) noted a significant decrease after 24-h shift work. When observing risk of bias, two (16.6%) studies were low quality, five (41.7%) were moderate quality, and five (41.7%) were high quality. INTERPRETATION: There were inconsistent findings demonstrating an effect of 24-h shift work on autonomic function, with a suggested shift away from parasympathetic dominance. Discrepancies in HRV methodologies, such as the duration of recordings and hardware used for measurement, may have contributed to the disparity in findings. In addition, differences in roles and responsibilities across occupations may explain the incongruence in findings across studies.

Comparisons and Intercorrelations of Physical Performance Variables of Operational Preparedness in Special Operations Forces.

INTRODUCTION: Marine Forces Special Operations Command (MARSOC) deploys teams of operators (OP) and enablers (EN) to accomplish special operations missions. OP and EN are required to train and deploy together to accomplish these missions; however, they have different training and selection pipelines. Advanced strength and conditioning training strategies are applied to both OP and EN to enhance physical preparedness; however, it is unclear how the selection pipeline of these two personnel types affects overall physical preparedness and the relationships between performance variables. The purpose of this study is to gain a greater understanding of the relationships of a wide array of physical preparedness variables in OP and EN in an effort to streamline testing and training strategies. MATERIALS AND METHODS: For this study, 155 male (82 OP, 73 EN) MARSOC personnel (age: 29.5 ± 4.9 years, mass: 87.9 ± 11.1 kg, height: 1.79 ± 0.07 m) completed a physical preparedness assessment that included a DEXA assessment of body composition (BF%), 27.4 m sprint (30 yd), countermovement jump (VJ), 5-10-5 pro-agility (Agility), medicine ball toss (UBP), isometric mid-thigh pull (IMTP), and a 30 second (AnC) and 5 minute (AC) non-motorized treadmill run. Independent samples t tests, Mann-Whitney U tests, and Spearman's Rank correlations were used to compare variables between OP and EN. RESULTS: OP demonstrated greater VJ, UBP, IMTP, AnC, and AC (P < 0.05); and significantly lower BF% and agility time (P < 0.05). Measurements of mass, height, body mass index, and 30 yd were not significantly different (P > 0.05). Weak to moderate correlations were seen between anthropometric and performance variables. OP and EN demonstrated similar correlations for most performance and anthropometric variables. CONCLUSIONS: These results suggest that MARSOC OP demonstrate better physical preparedness over EN, while similar trends are observed between performance variables. Tests with moderate to high correlations may be removed from the protocol to account for testing time constraints. Height, weight, and BF% variables are poorly correlated with performance, particularly in OP, questioning their value in physical performance assessments in this population.

Pain Early After Anterior Cruciate Ligament Reconstruction is Associated With 6-Month Loading Mechanics During Running.

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) results in persistent altered knee biomechanics, but contributing factors such as pain or patient function, leading to the altered loading, are unknown. HYPOTHESIS: Individuals with worse self-reported pain after ACLR would have poorer biomechanics during running, and poor loading mechanics would be present in the ACLR limb compared with contralateral and control limbs. STUDY DESIGN: Cohort pilot study. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 20 patients after ACLR (age, 18.4 ± 2.7 years; height, 1.7 ± 0.1 m; mass, 84.2 ± 19.4 kg) completed visual analog scale and Knee Injury and Osteoarthritis Outcomes Score (KOOS) at 1 and 6 months postsurgery. At 6 months postsurgery, patients underwent biomechanical testing during running. A total of 20 control individuals also completed running biomechanical analyses. Associations between patient outcomes and biomechanics were conducted, and differences in running biomechanics between groups were analyzed. RESULTS: KOOS pain score 1 month after surgery was associated with peak ACLR knee abduction moment (R2 = 0.35;P = 0.01). At 6-months, KOOS sport score was related to peak abduction moment in the ACLR limb (R2 = 0.23; P = 0.05). For change scores, the improvement in pain scores related to ACLR limb peak knee abduction moment (R2 = 0.55; P = 0.001). The ACLR limb had lower knee excursion, extension moments, and ground-reaction forces compared with the uninvolved and control limb. The uninvolved limb also had higher ground-reaction forces compared with the ACLR limb and control limb. CONCLUSION: These results suggest that patient-reported outcomes 1 and 6 months after surgery are associated with running mechanics 6 months after ACLR. Further, the underloading present in the ACLR limb and overloading in the uninvolved limb indicates greater need for running rehabilitation after ACLR. CLINICAL RELEVANCE: Understanding pain and how it may be linked to movement dysfunction is important for improving long-term outcomes.

Etiology of Exercise Injuries in Firefighters: A Healthcare Practitioners' Perspective.

The purpose of this study was to query healthcare practitioners (HCPs) who treat firefighter injuries to identify risk factors and mechanisms associated with musculoskeletal injuries during exercise. A phenomenological design was utilized to understand the experiences of HCPs while treating firefighters' musculoskeletal injuries due to exercise. Semi-structured interviews were conducted with 14 HCPs. Two interviews were pilot-tested with HCPs to ensure reliability and validity. Interviews were transcribed and uploaded to a qualitative analysis software program. Although the study inquired about injuries incurred by any exercise modality (e.g., endurance and resistance training), injuries induced during resistance training were prominent among HCPs as resistance training emerged as a primary exercise injury mechanism. HCPs indicated that the back and shoulder were prevalent anatomical exercise injury locations. Risk factors for exercise injuries included age, immobility, movement proficiency, and factors associated with fatigue. Exercise injury mechanisms included poor resistance training technique and overexertion. These findings could guide exercise program design, use of movement assessments, and the identification of other countermeasures to decrease the risk of resistance training exercise injuries among firefighters.