THE RELATIONSHIP BETWEEN MUSCULOSKELETAL STRENGTH, PHYSIOLOGICAL CHARACTERISTICS, AND KNEE KINESTHESIA FOLLOWING FATIGUING EXERCISE

Fatiguing exercise may result in impaired functional joint stability and increased risk of unintentional injury. While there are several musculoskeletal and physiological characteristics related to fatigue onset, their relationship with proprioceptive changes following fatigue has not been examined. The purpose of this study was to establish the relationship between musculoskeletal and physiological characteristics and changes in proprioception, measured by threshold to detect passive motion (TTDPM), following fatiguing exercise. Twenty, physically active females participated (age: 28.65 ± 5.6 years, height: 165.6 ± 4.3 cm, weight: 61.8 ± 8.0 kg, BMI: 22.5± 2.3 kg/m2, BF: 23.3 ± 5.4%). During Visit 1, subjects completed an exercise history and 24-hour dietary questionnaire, and body composition, TTDPM familiarization, isokinetic knee strength, and maximal oxygen uptake/lactate threshold assessments. During Visit 2, subjects completed TTDPM and isometric knee strength testing prior to and following a fatiguing exercise protocol. Wilcoxon signed rank tests determined TTDPM and isometric knee strength changes from pre- to post- fatigue. Spearman’s rho correlation coefficients determined the relationship between strength and physiological variables with pre- to post-fatigue changes in TTDPM and with pre-fatigue and post-fatigue TTDPM in extension and flexion (α=0.05). No significant differences were demonstrated from pre-fatigue to post-fatigue TTDPM despite a significant decrease in isometric knee flexion strength (P<0.01) and flexion/extension ratio (P<0.05) following fatigue. No significant correlations were observed between strength or physiological variables and changes in TTDPM from pre- to post-fatigue in extension or flexion. Flexion/extension ratio was significantly correlated with pre-fatigue TTDPM in extension (r=-0.231, P<0.05). Peak oxygen uptake was significantly correlated with pre-fatigue (r=-0.500, P<0.01) and post-fatigue (r=-0.520, P<0.05) TTDPM in extension. No significant relationships were demonstrated between musculoskeletal and physiological characteristics and changes in TTDPM following fatigue. The results suggest that highly trained individuals may have better proprioception, and that the high fitness level of subjects in this investigation may have contributed to absence of TTDPM deficits following fatigue despite reaching a high level of perceptual and physiological fatigue. Future studies should consider various subject populations, other musculoskeletal strength characteristics, and different modalities of proprioception to determine the most important contributions to proprioceptive changes following fatigue

What is the true evidence for gender-related differences during plant and cut maneuvers? A systematic review

Purpose Female athletes have a significantly higher risk of sustaining an anterior cruciate ligament (ACL) injury than male athletes. Biomechanical and neuromuscular factors have been reported as the main cause. The purpose of this review was to critically review results of the published literature on gender differences regarding biomechanical and neuromuscular movement patterns during plant and cutting maneuvers. Methods MEDLINE (1966 to December 2008), EMBASE (1947 to December 2008) and CINAHL (1981 to December 2008) searches were performed. The seven studies meeting the inclusion criteria were analyzed. Results Biomechanical gender differences were of questionable clinical relevance. Quadriceps dominance was not found in women. Conclusion The question raises whether ACL injuries during plant and cutting maneuvers are purely gender related and whether women do have to move like men in order to reduce injury risk? Caution is warranted in making inferences as studies were heterogeneous in terms of subject and study characteristics and had low statistical power as a result of insufficient number of subjects. It is advised that future research moves beyond the isolated gender comparison and that larger sample sizes will be included. This review may aid in improving experiments to draw valid conclusions, in order to direct future ACL injury prevention programs, which might need to be more individualized

Accuracy of Recall of Musculoskeletal Injuries in Elite Military Personnel: A Cross-Sectional Study

Background Self-reported data are often used in research studies among military populations. Objective The accuracy of self-reported musculoskeletal injury data among elite military personnel was assessed for issues with recall. Design Cross-sectional study. Setting Applied research laboratory at a military installation. Participants A total of 101 subjects participated (age 28.5±5.6 years). Study participants were active duty military personnel, with no conditions that precluded them from full duty. Primary and secondary outcome measures Self-reported and medical record reviewed injuries that occurred during a 1-year period were matched by anatomic location, injury side (for extremity injuries), and injury year and type. The accuracy of recall was estimated as the per cent of medical record reviewed injuries correctly recalled in the self-report. The effect of injury anatomic location, injury type and severity and time since injury, on recall, was also assessed. Injuries were classified as recent (≤4 years since injury) or old injuries (\u3e4 years since injury). Recall proportions were compared using Fisher\u27s exact tests. ResultsA total of 374 injuries were extracted from the subjects\u27 medical records. Recall was generally low (12.0%) and was not different between recent and old injuries (P=0.206). Injury location did not affect recall (P=0.418). Recall was higher for traumatic fractures as compared with less severe non-fracture injuries (P values 0.001 to \u3c0.001). Recall for non-fracture injuries was higher for recent as compared with old injuries (P=0.033). This effect of time since injury on recall was not observed for fractures (P=0.522). Conclusions The results of this study highlight the importance of weighing the advantages and disadvantages of self-reported injury data before their use in research studies in military populations and the need for future research to identify modifiable factors that influence recall

A Comparison of Cervical and Trunk Musculoskeletal Characteristics between Female and Male Army Helicopter Pilots

Introduction: Neck pain (NP) and low back pain (LBP) are prevalent among military helicopter pilots. Although there have been few studies on sex differences in the NP/LBP prevalence in this population, females are shown to be at a greater risk of NP/LBP in civilian studies. This disparity may be due to musculoskeletal characteristics differences that predispose females for NP/LBP. The purpose of this study was to compare cervical and trunk musculoskeletal characteristics between male and female pilots. Methods: A total of 8 female pilots (Age: 27.6 ± 4.2yrs, HT: 166.1 ± 7.7cm, WT: 67.9 ± 10.6kg) were tested, and they were matched (1:1 matching ratio) with male pilots (Age: 27.8 ± 4.2yrs, HT: 175.0 ± 6.8cm, WT: 79.5 ± 5.8kg), based on age (± three years) and flight experience (± two years). Cervical/trunk strength and flexibility were tested using the hand-held/isokinetic dynamometer and inclinometers, respectively. Strength values were normalized to body weight for analyses. Paired t-tests or Wilcoxon Signed Rank tests were used to examine sex differences across all variables (p \u3c 0.05). Results: Female pilots had significantly lower cervical flexion strength, trunk flexion strength, and trunk rotation strength (p \u3c 0.05). For flexibility measures, female pilots had significantly greater cervical rotation flexibility (p \u3c 0.05). No significant differences were observed in the lumbar spine flexibility. Discussion/Conclusion: The current preliminary study found sex differences in cervical and trunk musculoskeletal characteristics in Army helicopter pilots. Continued efforts are warranted to explore sex-specific intervention strategy and its effectiveness in reducing the NP/LBP prevalence among military helicopter pilots

Normative Data for the NeuroCom Sensory Organization Test in US Military Special Operations Forces.

CONTEXT: Postural stability is the ability to control the center of mass in relation to a person\u27s base of support and can be affected by both musculoskeletal injury and traumatic brain injury. The NeuroCom Sensory Organization Test (SOT) can be used to objectively quantify impairments to postural stability. The ability of postural stability to predict injury and be used as an acute injury-evaluation tool makes it essential to the screening and rehabilitation process. To our knowledge, no published normative data for the SOT from a healthy, highly active population are available for use as a reference for clinical decision making. OBJECTIVE: To present a normative database of SOT scores from a US Military Special Operations population that can be used for future comparison. DESIGN: Cross-sectional study. SETTING: Human performance research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 542 active military operators from Naval Special Warfare Combatant-Craft Crewmen (n = 149), Naval Special Warfare Command, Sea, Air, and Land (n = 101), US Army Special Operations Command (n = 171), and Air Force Special Operations Command (n = 121). MAIN OUTCOME MEASURE(S): Participants performed each of the 6 SOT conditions 3 times. Scores for each condition, total equilibrium composite score, and ratio scores for the somatosensory, visual, and vestibular systems were recorded. RESULTS: Differences were present across all groups for SOT conditions 1 (P \u3c .001), 2 (P = .001), 4 (P \u3e .001), 5 (P \u3e .001), and 6 (P = .001) and total equilibrium composite (P = .000), visual (P \u3e .001), vestibular (P = .002), and preference (P \u3e .001) NeuroCom scores. CONCLUSIONS: Statistical differences were evident in the distribution of postural stability across US Special Operations Forces personnel. This normative database for postural stability, as assessed by the NeuroCom SOT, can provide context when clinicians assess a Special Operations Forces population or any other groups that maintain a high level of conditioning and training

The Relationship Between Hip Strength and Postural Stability in Collegiate Athletes Who Participate in Lower Extremity Dominant Sports

# Background Lower extremity (LE) injuries are common across many sports. Both core strength (including hip strength) deficits and poor postural stability have been linked to lower extremity (LE) injury. The relationship between these two characteristics is unknown. # Purpose To explore the relationships between hip strength, static postural stability, and dynamic postural stability. # Study Design Descriptive Cross-Sectional Study # Methods 162 Division I student-athletes (111 males and 51 females) participated in this study. Isometric hip strength was measured using a hand-held dynamometer and both single-leg static (eyes open EO and eyes closed EC) and dynamic postural stability were assessed with a force plate. Pairwise correlations were calculated to examine the relationship between the hip strength variables and the postural stability scores for all subjects and separately for males and females. # Results There were no significant correlations between hip strength and dynamic postural stability for any of the pairwise correlations. Significant, albeit minimal, correlations between EO and EC static postural stability and each of the hip strength variables for all subjects and male subjects (correlation coefficients ranged from -0.19 to -0.34). However, there were only two significant correlations between hip strength and EC static postural stability (hip internal/external rotation) and one for hip strength and EO postural stability (hip internal rotation) found for female subjects (correlation coefficients ranged from -0.28 to -0.31). # Conclusion There was no relationship between isometric hip strength and dynamic postural stability; whereas, there were some relationships between the strength measures and static postural stability. These significant, but minimal correlations were observed in more of the comparisons within the male cohort potentially demonstrating a sex difference. # Level of Evidence 3

Genetic mechanisms of critical illness in COVID-19.

Host-mediated lung inflammation is present1, and drives mortality2, in the critical illness caused by coronavirus disease 2019 (COVID-19). Host genetic variants associated with critical illness may identify mechanistic targets for therapeutic development3. Here we report the results of the GenOMICC (Genetics Of Mortality In Critical Care) genome-wide association study in 2,244 critically ill patients with COVID-19 from 208 UK intensive care units. We have identified and replicated the following new genome-wide significant associations: on chromosome 12q24.13 (rs10735079, P = 1.65 × 10-8) in a gene cluster that encodes antiviral restriction enzyme activators (OAS1, OAS2 and OAS3); on chromosome 19p13.2 (rs74956615, P = 2.3 × 10-8) near the gene that encodes tyrosine kinase 2 (TYK2); on chromosome 19p13.3 (rs2109069, P = 3.98 ×  10-12) within the gene that encodes dipeptidyl peptidase 9 (DPP9); and on chromosome 21q22.1 (rs2236757, P = 4.99 × 10-8) in the interferon receptor gene IFNAR2. We identified potential targets for repurposing of licensed medications: using Mendelian randomization, we found evidence that low expression of IFNAR2, or high expression of TYK2, are associated with life-threatening disease; and transcriptome-wide association in lung tissue revealed that high expression of the monocyte-macrophage chemotactic receptor CCR2 is associated with severe COVID-19. Our results identify robust genetic signals relating to key host antiviral defence mechanisms and mediators of inflammatory organ damage in COVID-19. Both mechanisms may be amenable to targeted treatment with existing drugs. However, large-scale randomized clinical trials will be essential before any change to clinical practice

Specificity of isokinetic assessment in noncontact knee injury prevention screening: A novel assessment procedure with relationships between variables in amateur adult agility-sport athletes

Objectives To present a new knee isokinetic assessment procedure linked to noncontact knee injury mechanisms and examine correlations between variables relevant to noncontact knee injury prevention screening (peak torque [PT, Nm], time-to-peak torque [TTPT, ms], angle-of-peak torque [APT, °], mean PT [MPT, Nm]). Design Cross-sectional. Setting Sports medicine laboratory. Participants Thirty-four agility-sport athletes (male/female n=18/16, age 24.1±3.5yr, height 171.8±9.6cm, mass 70.6±12 kg). Main outcome measures Pearson's/Spearman's correlation (r/rs), coefficient of determination (r2/rs2). Results Most correlations were statistically non-significant or statistically-significant with only weak-to-moderate coefficients. For both knee extension and flexion, PT and MPT were significantly and strongly correlated (r=0.99, r2=0.98, p=0.001). Graphical analyses revealed two datapoint clusters for knee flexion TTPT and APT. One cluster indicated some participants could generate knee flexor PT rapidly (200ms, >50°). Conclusions In this study, most isokinetic variables represented distinct knee neuromuscular characteristics. For both knee extension and flexion, only PT or MPT need be used to represent isokinetic maximal strength. Knee flexion TTPT and APT may have utility in noncontact knee injury prevention screening with amateur adult agility-sport athletes

Force Sense of the Knee Not Affected by Fatiguing the Knee Extensors and Flexors

Context: Knee injuries commonly occur in later stages of competition, indicating that fatigue may influence dynamic knee stability. Force sense (FS) is a submodality of proprioception influenced by muscle mechanoreceptors, which, if negatively affected by fatigue, may result in less-effective neuromuscular control. Objectives: To determine the effects of peripheral fatigue on FS of the quadriceps and hamstrings. Design: Quasi-experimental study design. Participants: 20 healthy and physically active women and men (age 23.4 +/- 2.7 y, mass 69.5 +/- 10.9 kg, height 169.7 +/- 9.4 cm). Interventions: Fatigue was induced during a protocol with 2 sets of 40 repetitions, and the last set was truncated at 90 repetitions or stopped if torque production dropped below 25% of peak torque. Main Outcome Measures: FS of the hamstrings and quadriceps was tested on separate days before and after 3 sets of isokinetic knee flexion and extension to fatigue by examining the ability to produce a target isometric torque (15% MVIC) with and without visual feedback (FS error). Electromyographic data of the tested musculature were collected to calculate and determine median frequency shift. T tests and Wilcoxon signed-rank tests were conducted to examine prefatigue and postfatigue FS error for flexion and extension. Results: Despite verification of fatigue via torque-production decrement and shift in median frequency, no significant differences were observed in FS error for either knee flexion (pre 0.54 +/- 2.28 N.m, post 0.47 +/- 1.62 N.m) or extension (pre -0.28 +/- 2.69 N.m, post -0.21 +/- 1.78 N.m) prefatigue compared with the postfatigue condition. Conclusions: Although previous research has demonstrated that peripheral fatigue negatively affects threshold to detect passive motion (TTDPM), it did not affect FS as measured in this study. The peripheral-fatigue protocol may have a greater effect on the mechanoreceptors responsible for TTDPM than those responsible for FS. Further investigation into the effects of fatigue across various modes of proprioception is warranted