Moral Identity Predicts Adherence to COVID-19 Mitigation Procedures Depending on Political Ideology: A Comparison Between the USA and New Zealand.

Reducing the spread of infectious viruses (e.g., COVID-19) can depend on societal compliance with effective mitigations. Identifying factors that influence adherence can inform public policy. In many cases, public health messaging has become highly moralized, focusing on the need to act for the greater good. In such contexts, a person's moral identity may influence behavior and serve to increase compliance through different mechanisms: if a person sees compliance as the right thing to do (internalization) and/or if a person perceives compliance as something others will notice as the right thing to do (symbolization). We argue that in societies that are more politically polarized, people's political ideology may interact with their moral identity to predict compliance. We hypothesized that where polarization is high (e.g., USA), moral identity should positively predict compliance for liberals to a greater extent than for conservatives. However, this effect would not occur where polarization is low (e.g., New Zealand). Moral identity, political ideology, and support for three different COVID-19 mitigation measures were assessed in both nations (N = 1,980). Results show that while moral identity can influence compliance, the political context of the nation must also be taken into account.

Diagnosis, Management, and Return to Sport of a 16-Year-Old Patient With a Chiari I Malformation: A Case Report and Literature Review.

This case report discusses a 16-year-old female volleyball, basketball, and track and field athlete who was diagnosed with a Chiari I malformation after a concussion. Surgical decompression was recommended and performed 3 months after her initial diagnosis. This patient presented unique challenges due to her age, desire to return to sport, and lack of access to medical care due to living in a rural area. Few evidence-based best-practice recommendations are available for the management and return to sport of patients with Chiari I malformation, particularly for those who have undergone surgical decompression. In this case study, we address the treatment and return-to-sport process for the patient and provide a comprehensive review of the published literature on patients attempting to return to sport after a diagnosis of Chiari I malformation. In addition, we explore the value of an athletic trainer in reconciling various barriers in management and return to sport evident in this case and the reviewed literature.

Males with chronic ankle instability demonstrate deficits in neurocognitive function compared to control and copers.

The purpose of this study was to determine if there were neurocognitive deficits among controls, copers and those with chronic ankle instability (CAI). Participants included those without history of ankle injury (n = 14), ankle sprain copers (n = 13) and patients with self-reported CAI (n = 14). They completed a battery of valid and reliable computer-based neurocognitive tests. The differences between neurocognitive domain scores were compared across the Control, Coper and CAI groups. Patients with CAI had lower composite memory, visual memory and simple attention compared to controls. In males with CAI, large differences in memory and attention were found relative to control participants. These differences may contribute to uncontrolled episodes of giving way through deficits in spatial awareness and/or an inability to identify environmental obstacles. Clinicians should explore ways to provide additional stimuli through innovative rehabilitation protocols aimed at maximizing neurocognitive abilities in patients with CAI.

Development and validation of the Harm Concept Breadth Scale: Assessing individual differences in harm inflation.

Three studies (Ns = 350, 301 & 341) examined the reliability, validity, and correlates of a new measure of harm inflation, the individual differences counterpart of 'concept creep'. The Harm Concept Breadth Scale (HCBS) assesses variability in the expansiveness of concepts of harm (i.e., bullying, mental disorder, prejudice, trauma), such that these concepts refer to a wider range of phenomena among people scoring high on the scale. Study 1 developed 66 vignettes representing potential instances of the four concepts, selected optimal subsets of 10 vignettes for each concept, and demonstrated satisfactory internal consistency of the subscales. Study 2 demonstrated that the HCBS had excellent internal consistency, and established construct validity through associations with measures of moral foundations, justice sensitivity, general category inclusiveness, and political orientation. Study 3 employed participants from a different national background and further clarified the correlates of the HCBS via measures of empathy, moral expansiveness, and the Big Five personality traits. The findings indicate that concept breadth is a reliably measurable individual difference variable with weak to moderate associations with harm-based morality, prosocial concern, political liberalism, female gender, and negative emotionality. The HCBS is a valid psychometric instrument for examining the causes and implications of harm inflation.

Dimensions over categories: a meta-analysis of taxometric research.

Taxometric procedures have been used extensively to investigate whether individual differences in personality and psychopathology are latently dimensional or categorical ('taxonic'). We report the first meta-analysis of taxometric research, examining 317 findings drawn from 183 articles that employed an index of the comparative fit of observed data to dimensional and taxonic data simulations. Findings supporting dimensional models outnumbered those supporting taxonic models five to one. There were systematic differences among 17 construct domains in support for the two models, but psychopathology was no more likely to generate taxonic findings than normal variation (i.e. individual differences in personality, response styles, gender, and sexuality). No content domain showed aggregate support for the taxonic model. Six variables - alcohol use disorder, intermittent explosive disorder, problem gambling, autism, suicide risk, and pedophilia - emerged as the most plausible taxon candidates based on a preponderance of independently replicated findings. We also compared the 317 meta-analyzed findings to 185 additional taxometric findings from 96 articles that did not employ the comparative fit index. Studies that used the index were 4.88 times more likely to generate dimensional findings than those that did not after controlling for construct domain, implying that many taxonic findings obtained before the popularization of simulation-based techniques are spurious. The meta-analytic findings support the conclusion that the great majority of psychological differences between people are latently continuous, and that psychopathology is no exception.

Reliability of a Novel Semiautomated Ultrasound Segmentation Technique for Assessing Average Regional Femoral Articular Cartilage Thickness.

CONTEXT: Ultrasound imaging is a clinically feasible tool to assess femoral articular cartilage and may have utility in tracking early knee osteoarthritis development. Traditional assessment techniques focus on measurements at a single location, which can be challenging to adopt for novice raters. OBJECTIVE: To introduce a novel semiautomated ultrasound segmentation technique and determine the intrarater and interrater reliability of average regional femoral articular cartilage thickness and echo intensity of a novice and expert rater. DESIGN: Descriptive observational study. SETTING: Orthopedic clinic. PATIENTS OR OTHER PARTICIPANTS: Fifteen participants (mean [SD]; age 23.5 [4.6] y, height = 172.6 [9.3] cm, mass = 79.8 [15.7] kg) with a unilateral history of anterior cruciate ligament reconstruction participated. INTERVENTION: None. MAIN OUTCOME MEASURES: One rater captured anterior femoral cartilage images of the participants' contralateral knees using a transverse suprapatellar ultrasound assessment. The total femoral cartilage cross-sectional area of each image was segmented by a novice and expert rater. A novel custom program automatically separated the cartilage segmentations into medial, lateral, and intercondylar regions to determine the cross-sectional area and cartilage length. The average cartilage thickness in each region was calculated by dividing the cross-sectional area by the cartilage length. Echo intensity was calculated as the average gray-scale pixel value of each region. Two-way random effect intraclass correlations coefficient (ICC) for absolute agreement were used to determine the interrater reliability between a novice and expert rater, as well as the intrarater reliability of the novice rater. RESULTS: The novice rater demonstrated excellent intrarater (ICC [2,k] range = .993-.997) and interrater (ICC [2,k] range = .944-.991) reliability with the expert rater of all femoral articular cartilage average thickness and echo intensity regions. CONCLUSIONS: The novel semiautomated average cartilage thickness and echo-intensity assessment is efficient, systematic, and reliable between an expert and novice rater with minimal training.

Cognitive Loading Produces Similar Change in Postural Stability in Patients With Chronic Ankle Instability and Controls.

Purpose: While postural stability is compromised in individuals with chronic ankle instability (CAI), few studies have attempted to examine how performing simultaneous cognitive and balancing tasks may alter the complexity of the center of pressure. The purpose of this study was to compare postural stability in patients with CAI to controls during a dual-task condition via sample entropy. Methods: Thirty participants (15 CAI, 15 healthy control) performed 3-trials of single-leg stance for 60-seconds each under two different conditions: single-task and dual-task (serial subtraction). Sample entropy (SampEn), a measure of pattern regularity, was calculated from the center of pressure excursion in the anterio-posterior (AP) and medio-lateral (ML) directions. 2x2 mixed-model ANOVAs determined any differences by task or group (p≤0.05). Results: SampEn-AP decreased in the dual-task condition compared to single-task, single-leg balance across groups (F1,28=8.23, p=0.008, d=0.53). A significant interaction for group by task was found for SampEn-ML (F1,28=4.18, p=0.05), but post hoc testing failed to reveal significant differences. Serial subtraction was completed with significantly fewer errors during dual-task compared to single-task (F1,27=12.75, p=0.001, d=0.66). Conclusions: Patients with CAI do not display differences in regularity of postural stability, even when attention is divided. However, the addition of serial subtraction increased the regularity of AP center-of-pressure motion. Increased regularity may suggest a change in motor control strategy, reducing natural fluctuations and flexibility within movement patterns during more challenging tasks. Clinicians could utilize dual-task situations during rehabilitation of patients with CAI, in order to adequately restore stability and function when attention is divided.

Alterations in Cortical Activation Among Individuals With Chronic Ankle Instability During Single-Limb Postural Control.

CONTEXT: Chronic ankle instability (CAI) is characterized by repetitive ankle sprains and perceived instability. Whereas the underlying cause of CAI is disputed, alterations in cortical motor functioning may contribute to the perceived dysfunction. OBJECTIVE: To assess differences in cortical activity during single-limb stance among control, coper, and CAI groups. DESIGN: Cross-sectional study. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 31 individuals (10 men, 21 women; age = 22.3 ± 2.4 years, height = 169.6 ± 9.7 cm, mass = 70.6 ± 11.6 kg), who were classified into control (n = 13), coper (n = 7), and CAI (n = 11) groups participated in this study. INTERVENTION(S): Participants performed single-limb stance on a force platform for 60 seconds while wearing a 24-channel functional near-infrared spectroscopy system. Oxyhemoglobin (HbO2) changes in the supplementary motor area (SMA), precentral gyrus, postcentral gyrus, and superior parietal lobe were measured. MAIN OUTCOME MEASURE(S): Differences in averages and standard deviations of HbO2 were assessed across groups. In the CAI group, correlations were analyzed between measures of cortical activation and Cumberland Ankle Instability Tool (CAIT) scores. RESULTS: No differences in average HbO2 were present for any cortical areas. We observed differences in the standard deviation for the SMA across groups; specifically, the CAI group demonstrated greater variability than the control (r = 0.395, P = .02; 95% confidence interval = 0.34, 0.67) and coper (r = 0.38, P = .04; 95% confidence interval = -0.05, 0.69) groups. We demonstrated a strong correlation that was significant in the CAI group between the CAIT score and the average HbO2 of the precentral gyrus (ρ = 0.64, P = .02) and a strong correlation that was not significant between the CAIT score and the average HbO2 of the SMA (ρ = 0.52, P = .06). CONCLUSIONS: The CAI group displayed large differences in SMA cortical-activation variability. Greater variations in cortical activation may be necessary for similar static postural-control outcomes among individuals with CAI. Consequently, variations in cortical activation for these areas provide evidence for an altered neural mechanism of postural control among populations with CAI.

Twentieth century morality: The rise and fall of moral concepts from 1900 to 2007.

Trends in the cultural salience of morality across the 20th century in the Anglophone world, as reflected in changing use of moral language, were explored using the Google Books (English language) database. Relative frequencies of 304 moral terms, organized into six validated sets corresponding to general morality and the five moral domains proposed by moral foundations theory, were charted for the years 1900 to 2007. Each moral language set displayed unique, often nonlinear historical trajectories. Words conveying general morality (e.g., good, bad, moral, evil), and those representing Purity-based morality, implicating sanctity and contagion, declined steeply in frequency from 1900 to around 1980, when they rebounded sharply. Ingroup-based morality, emphasizing group loyalty, rose steadily over the 20th century. Harm-based morality, focused on suffering and care, rose sharply after 1980. Authority-based morality, which emphasizes respect for hierarchy and tradition, rose to a peak around the social convulsions of the late 1960s. There were no consistent tendencies for moral language to become more individualist or less grounded in concern for social order and cohesion. These differing time series suggest that the changing moral landscape of the 20th century can be divided into five distinct periods and illuminate the re-moralization and moral polarization of the last three decades.

Clinical Measures and Their Contribution to Dysfunction in Individuals With Patellar Tendinopathy.

CONTEXT: Patellar tendinopathy (PT) is prevalent in physically active populations, and it affects their quality of living, performance of activity, and may contribute to the early cessation of their athletic careers. A number of previous studies have identified contributing factors for PT; however, their contributions to self-reported dysfunction remain unclear. OBJECTIVE: The purpose of this investigation was to determine if strength, flexibility, and various lower-extremity static alignments contributed to self-reported function and influence the severity of PT. DESIGN: Cross-sectional research design. SETTING: University laboratory. PARTICIPANTS: A total of 30 participants with PT volunteered for this study (age: 23.4 [3.6] y, height: 1.8 [0.1] m, mass: 80.0 [20.3] kg, body mass index: 25.7 [4.3]). MAIN OUTCOME MEASURES: Participants completed 7 different patient-reported outcomes. Isometric knee extension and flexion strength, hamstring flexibility and alignment measures of rearfoot angle, navicular drop, tibial torsion, q-angle, genu recurvatum, pelvic tilt, and leg length differences were assessed. Pearson's correlation coefficients were assessed to determine significantly correlated outcome variables with each of the patient-reported outcomes. The factors with the highest correlations were used to identify factors that contribute the most to pain and dysfunction using backward selection, linear regression models. RESULTS: Correlation analysis found significant relationships between questionnaires and body mass index (r = -.35-.46), normalized knee extension (r = .38-.50) and flexion strength (r = -.34-.50), flexibility (r = .32-.38, q-angle (r = .38-.56), and pelvic tilt (r = -.40). Regression models (R2 = .22-.54) identified thigh musculature strength and supine q-angle to have greatest predictability for severity in patient-reported outcomes. CONCLUSIONS: These findings put an emphasis of bodyweight management, improving knee extensor and flexor strength, and posterior flexibility in PT patients.

Attention is associated with postural control in those with chronic ankle instability.

Chronic ankle instability (CAI) is often debilitating and may be affected by a number of intrinsic and environmental factors. Alterations in neurocognitive function and attention may contribute to repetitive injury in those with CAI and influence postural control strategies. Thus, the purpose of this study was to determine if there was a difference in attentional functioning and static postural control among groups of Comparison, Coper and CAI participants and assess the relationship between them within each of the groups. Recruited participants performed single-limb balance trials and completed the CNS Vital Signs (CNSVS) computer-based assessment to assess their attentional function. Center of pressure (COP) velocity (COPv) and maximum range (COPr), in both the anteroposterior (AP) and mediolateral (ML) directions were calculated from force plate data. Simple attention (SA), which measures self-regulation and attention control was extracted from the CNSVS. Data from 45 participants (15 in each group, 27=female, 18=male) was analyzed for this study. No significant differences were observed between attention or COP variables among each of the groups. However, significant relationships were present between attention and COP variables within the CAI group. CAI participants displayed significant moderate to large correlations between SA and AP COPr (r=-0.59, p=0.010), AP COPv (r=-0.48, p=0.038) and ML COPr (r=-0.47, p=0.034). The results suggest a linear relationship of stability and attention in the CAI group. Attentional self-regulation may moderate how those with CAI control postural stability. Incorporating neurocognitive training focused on attentional control may improve outcomes in those with CAI.

Developing a concussion assessment mHealth app for certified Athletic Trainers.

Annually, 1.6-3.8 million concussions occur from sports in the United States, which account for 5-9% of all sports injuries. The dangers of concussions include prolonged post-concussive symptoms, increased risk of subsequent concussions, seizures, mental health issues, and in cases of second-impact syndrome (SIS), possible death. Certified Athletic Trainers (ATC) continue to serve an important role in providing assessment and treatments for athletes with sports-related injuries. They provide a critical safety net due to limited knowledge and misconceptions of concussion held by some youth sports coaches and athletes. However, availability of services from ATCs in rural areas is a challenge. In order to help extend coverage to more rural student athletes, we propose designing a telemedicine app following the mHealth development roadmap from the Center for eHealth Research (CeHRes). In this paper we will document contextual inquiry, user requirements capture, design phases, and app evaluation from the targeted user base.

Oxygen cost and physiological responses of recreational badminton match play.

BACKGROUND: Badminton, as an Olympic sport, is popular worldwide. However, the benefits of recreational badminton match play are not well known. The purpose of the study was to determine the oxygen cost of recreational badminton match play. Heart rate (HR), blood lactate (BL), rating of perceived exertion (RPE), step count and energy expenditure were also assessed. METHODS: Fourteen male recreational badminton players aged 35.9±6.62 years participated in test sessions to assess oxygen uptake (VO2) and the related physiological responses of match play. During the match play sessions, participants played singles badminton matches for 30 min while wearing a portable metabolic system. VO2 and HR were continuously recorded while blood lactate and RPE were determined following warm-up, at 15 minutes and 30 minutes of match play. Step count was recorded at 15 minutes and 30 minutes of play. RESULTS: VO2 over 30 minutes was 34.4±5.8 mL/kg/min which was 76.1% of maximal oxygen uptake. Across three 10-minute periods of play, VO2 was not significantly different while HR was higher in the third 10-minute period than the first and second 10-minute periods (P=0.001). Mean HR over 30 minutes was 167.9±9.4 bpm. BL was significantly higher at 15 and 30 minutes than following warm-up while RPE of 17.57±1.91 after 30 minutes was significantly higher (P=0.009) than RPE of 15.79±1.63 at 15 minutes. Step count did not vary between the two 15-minute periods of play with a total of 2404±360 steps while energy expenditure over 30 minutes of play was 391.7±66 kcal. CONCLUSIONS: Recreational badminton match play can be categorized as vigorous intensity suggesting that it can be a viable means of achieving recommended physical activity and improving aerobic fitness.

Ankle Dorsiflexion Displacement During Landing is Associated With Initial Contact Kinematics but not Joint Displacement.

The ankle, knee, and hip joints work together in the sagittal plane to absorb landing forces. Reduced sagittal plane motion at the ankle may alter landing strategies at the knee and hip, potentially increasing injury risk; however, no studies have examined the kinematic relationships between the joints during jump landings. Healthy adults (N = 30; 15 male, 15 female) performed jump landings onto a force plate while three-dimensional kinematic data were collected. Joint displacement values were calculated during the loading phase as the difference between peak and initial contact angles. No relationship existed between ankle dorsiflexion displacement during landing and three-dimensional knee and hip displacements. However, less ankle dorsiflexion displacement was associated with landing at initial ground contact with larger hip flexion, hip internal rotation, knee flexion, knee varus, and smaller plantar flexion angles. Findings of the current study suggest that restrictions in ankle motion during landing may contribute to contacting the ground in a more flexed position but continuing through little additional motion to absorb the landing. Transverse plane hip and frontal plane knee positioning may also occur, which are known to increase the risk of lower extremity injury.

The effects of three jump landing tasks on kinetic and kinematic measures: implications for ACL injury research.

This study compared the biomechanics of jump landing tasks used in ACL research. Twenty-seven female subjects performed a drop landing (DL), a drop landing with a vertical jump (DVJ), and a forward jump landing with a vertical jump (FVJ). We hypothesized that as one progressed from the drop landing through the forward-vertical jump that the kinematic and kinetic demands would increase, with progressively increasing knee and hip forces, moments, and angles on landing. Separate repeated-measures ANOVAs were performed. The FVJ had the highest peak anterior tibial shear force (p < 0.001), hip flexion angle (p < 0.001), knee flexion moment (p < 0.001), and knee valgus moment (p < 0.001). The DL had the smallest knee flexion angle (p = 0.001) and hip flexion angle (p < 0.001), while the DVJ had the lowest knee valgus moment (p < 0.001). These results indicate that seemingly minor variations between jump landing tasks may influence landing biomechanics. Caution should be used when comparing studies using different tasks.

Scapular bracing and alteration of posture and muscle activity in overhead athletes with poor posture.

CONTEXT: Overhead athletes commonly have poor posture. Commercial braces are used to improve posture and function, but few researchers have examined the effects of shoulder or scapular bracing on posture and scapular muscle activity. OBJECTIVE: To examine whether a scapular stabilization brace acutely alters posture and scapular muscle activity in healthy overhead athletes with forward-head, rounded-shoulder posture (FHRSP). DESIGN: Randomized controlled clinical trial. SETTING: Applied biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-eight healthy overhead athletes with FHRSP. INTERVENTION(S): Participants were assigned randomly to 2 groups: compression shirt with no strap tension (S) and compression shirt with the straps fully tensioned (S + T). Posture was measured using lateral-view photography with retroreflective markers. Electromyography (EMG) of the upper trapezius (UT), middle trapezius (MT), lower trapezius (LT), and serratus anterior (SA) in the dominant upper extremity was measured during 4 exercises (scapular punches, W's, Y's, T's) and 2 glenohumeral motions (forward flexion, shoulder extension). Posture and exercise EMG measurements were taken with and without the brace applied. MAIN OUTCOME MEASURE(S): Head and shoulder angles were measured from lateral-view digital photographs. Normalized surface EMG was used to assess mean muscle activation of the UT, MT, LT, and SA. RESULTS: Application of the brace decreased forward shoulder angle in the S + T condition. Brace application also caused a small increase in LT EMG during forward flexion and Y's and a small decrease in UT and MT EMG during shoulder extension. Brace application in the S + T group decreased UT EMG during W's, whereas UT EMG increased during W's in the S group. CONCLUSIONS: Application of the scapular brace improved shoulder posture and scapular muscle activity, but EMG changes were highly variable. Use of a scapular brace might improve shoulder posture and muscle activity in overhead athletes with poor posture.

Lower extremity muscle activation and knee flexion during a jump-landing task.

CONTEXT: Decreased sagittal-plane motion at the knee during dynamic tasks has been reported to increase impact forces during landing, potentially leading to knee injuries such as anterior cruciate ligament rupture. OBJECTIVE: To describe the relationship between lower extremity muscle activity and knee-flexion angle during a jump-landing task. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty recreationally active volunteers (15 men, 15 women: age = 21.63 ± 2.01 years, height = 173.95 ± 11.88 cm, mass = 72.57 ± 14.25 kg). INTERVENTION(S): Knee-flexion angle and lower extremity muscle activity were collected during 10 trials of a jump-landing task. MAIN OUTCOME MEASURE(S): Simple correlation analyses were performed to determine the relationship between each knee-flexion variable (initial contact, peak, and displacement) and electromyographic amplitude of the gluteus maximus (GMAX), quadriceps (VMO and VL), hamstrings, gastrocnemius, and quadriceps : hamstring (Q : H) ratio. Separate forward stepwise multiple regressions were conducted to determine which combination of muscle activity variables predicted each knee-flexion variable. RESULTS: During preactivation, VMO and GMAX activity and the Q : H ratio were negatively correlated with knee-flexion angle at initial contact (VMO: r = 0.382, P = .045; GMAX: r = 0.385, P = .043; Q : H ratio: r = 0.442, P = .018). The VMO, VL, and GMAX deceleration values were negatively correlated with peak knee-flexion angle (VMO: r = 0.687, P = .001; VL: r = 0.467, P = .011; GMAX: r = 0.386, P = .043). The VMO and VL deceleration values were negatively correlated with knee-flexion displacement (VMO: r = 0.631, P = .001; VL: r = 0.453, P = .014). The Q : H ratio and GM activity predicted 34.7% of the variance in knee-flexion angle at initial contact (P = .006). The VMO activity predicted 47.1% of the variance in peak knee-flexion angle (P = .001). The VMO and VL activity predicted 49.5% of the variance in knee-flexion displacement (P = .001). CONCLUSIONS: Greater quadriceps and GMAX activation and less hamstrings and gastrocnemius activation were correlated with smaller knee-flexion angles. This landing strategy may predispose an individual to increased impact forces due to the negative influence on knee-flexion position.

Ankle-dorsiflexion range of motion and landing biomechanics.

CONTEXT: A smaller amount of ankle-dorsiflexion displacement during landing is associated with less knee-flexion displacement and greater ground reaction forces, and greater ground reaction forces are associated with greater knee-valgus displacement. Additionally, restricted dorsiflexion range of motion (ROM) is associated with greater knee-valgus displacement during landing and squatting tasks. Because large ground reaction forces and valgus displacement and limited knee-flexion displacement during landing are anterior cruciate ligament (ACL) injury risk factors, dorsiflexion ROM restrictions may be associated with a greater risk of ACL injury. However, it is unclear whether clinical measures of dorsiflexion ROM are associated with landing biomechanics. OBJECTIVE: To evaluate relationships between dorsiflexion ROM and landing biomechanics. DESIGN: Descriptive laboratory study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-five healthy, physically active volunteers. INTERVENTION(S): Passive dorsiflexion ROM was assessed under extended-knee and flexed-knee conditions. Landing biomechanics were assessed via an optical motion-capture system interfaced with a force plate. MAIN OUTCOME MEASURE(S): Dorsiflexion ROM was measured in degrees using goniometry. Knee-flexion and knee-valgus displacements and vertical and posterior ground reaction forces were calculated during the landing task. Simple correlations were used to evaluate relationships between dorsiflexion ROM and each biomechanical variable. RESULTS: Significant correlations were noted between extended-knee dorsiflexion ROM and knee-flexion displacement (r  =  0.464, P  =  .029) and vertical (r  =  -0.411, P  =  .014) and posterior (r  =  -0.412, P  =  .014) ground reaction forces. All correlations for flexed-knee dorsiflexion ROM and knee-valgus displacement were nonsignificant. CONCLUSIONS: Greater dorsiflexion ROM was associated with greater knee-flexion displacement and smaller ground reaction forces during landing, thus inducing a landing posture consistent with reduced ACL injury risk and limiting the forces the lower extremity must absorb. These findings suggest that clinical techniques to increase plantar-flexor extensibility and dorsiflexion ROM may be important additions to ACL injury-prevention programs.

The relationship between blood potassium, blood lactate, and electromyography signals related to fatigue in a progressive cycling exercise test.

Local muscle fatigue may be related to potassium efflux from the muscle cell and/or lactate accumulation within the muscle. Local fatigue causes a decrease in median frequency (MPF) of the electromyogram's power spectrum during isometric contractions but its relationship to changes in potassium and lactate during dynamic exercise is equivocal. Thus, this investigation evaluated relationships between changes in the MPF from the vastus lateralis and blood levels of lactate and potassium during an incremental cycling test and recovery. Trained cyclists (n=8) completed a discontinuous, graded cycle test to exhaustion under normal and glycogen-reduced conditions. The glycogen reduced condition promoted an environment of lower lactate production while permitting a consistent potassium response. Blood samples and maximal isometric EMG data were collected at the end of each stage and during recovery. Maximal lactate levels were ∼ 60% lower in the glycogen reduced condition; potassium was similar between trials. MPF did not change significantly at volitional fatigue. Further, MPF was not significantly related to lactate (p>0.27) or potassium (p>0.16) in either condition. Though both lactate and potassium have been implicated as factors relating to local muscle fatigue, neither is significantly related to changes in MPF during or after progressive exercise on a cycle ergometer.

The relationship between anterior tibial shear force during a jump landing task and quadriceps and hamstring strength.

BACKGROUND: Eccentric quadriceps contraction during landing and the resulting anterior tibial shear force are anterior cruciate ligament injury risk factors, while hamstring contraction limits anterior cruciate ligament loading. Anterior tibial shear force is derived from quadriceps and hamstring co-contraction, and a greater quadriceps/hamstring strength ratio has been associated with heightened lower extremity injury risk. The purpose of this investigation was to evaluate relationships between anterior tibial shear force during landing and quadriceps and hamstring strength. METHODS: Anterior tibial shear force was calculated during a jump landing task in 26 healthy females. Isokinetic eccentric quadriceps strength and concentric hamstrings strength were assessed at 60 degrees /s, 180 degrees /s, and 300 degrees /s. Correlational analyses were conducted to evaluate relationships between lower extremity strength and anterior tibial shear force. FINDINGS: Quadriceps (r=0.126 to 0.302, P>0.05) and hamstrings strength (r=-0.019 to 0.058, P>0.05) and the quadriceps/hamstring ratio (r=0.036 to 0.127, P>0.05) were not significant predictors of anterior tibial shear force. INTERPRETATION: Quadriceps and hamstring strength are not indicative of sagittal-plane knee loading during landing. Contractile force resulting from maximal strength testing may not represent that produced during landing, as it is unlikely that landing requires maximal effort. Additionally, peak anterior tibial shear force, quadriceps torque, and hamstrings torque are generated at different points in the knee flexion/extension range of motion. Therefore, peak anterior tibial shear force is a function of the available strength at a given point in the range of motion rather than of peak strength. These findings illustrate the limitations of peak strength values in predicting dynamic loading during landing.