Contact or Collision Sport History, Repetitive Neurotrauma, and Patient-Reported Outcomes in Early to Midadulthood.

CONTEXT: Data on the early to midlife effects of repetitive neurotrauma on patient-reported outcomes have been delimited to homogeneous samples of male athletes without comparison groups or accounting for modifying factors such as physical activity. OBJECTIVE: To determine the effect of contact or collision sport participation and repetitive neurotrauma on patient-reported outcomes among early to middle-aged adults. DESIGN: Cross-sectional study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 113 adults (53 [46.9%] men, 60 [53.1%] women; age = 34.88 ± 11.80 years) in 4 groups: (1) physically inactive individuals with no repetitive head impact (RHI) exposure (NON); (2) noncontact sport athletes and nonathletes with no RHI exposure who were currently physically active (NCA); (3) former high-risk sport athletes with an RHI history who were physically active (HRS); and (4) former rugby players with prolonged RHI exposure who remained physically active. MAIN OUTCOME MEASURE(S): The 12-Item Short-Form Health Survey (SF-12), Apathy Evaluation Scale-self-rated version (AES-S), Satisfaction With Life Scale (SWLS), and Sport Concussion Assessment Tool-5th Edition (SCAT5) Symptom and Symptom Severity Checklist. RESULTS: The NON group had worse self-rated physical function than the NCA group as assessed by the SF-12 physical component summary (P = .03) and worse self-rated apathy (AES-S) and satisfaction with life (SWLS) than the NCA (P = .03 for both) and HRS groups (P = .03 and P = .040, respectively). We observed no group differences for self-rated mental health (SF-12 mental component summary; P = .26) or symptoms (SCAT5; P = .42). Career duration was not associated with any patient-reported outcomes. CONCLUSIONS: A history of contact or collision sport participation and career duration did not negatively affect patient-reported outcomes in physically active, early to middle-aged adults. However, physical inactivity status was negatively associated with patient-reported outcomes in these individuals in the absence of an RHI history.

Effects of contact/collision sport history on gait in early- to mid-adulthood.

BACKGROUND: To determine the effect of contact/collision sport participation on measures of single-task (ST) and dual-task (DT) gait among early- to middle-aged adults. METHODS: The study recruited 113 adults (34.88 ± 11.80 years, (mean ± SD); 53.0% female) representing 4 groups. Groups included (a) former non-contact/collision athletes and non-athletes who are not physically active (n = 28); (b) former non-contact/collision athletes who are physically active (n = 29); (c) former contact/collision sport athletes who participated in high-risk sports and are physically active (n = 29); and (d) former rugby players with prolonged repetitive head impact exposure history who are physically active (n = 27). Gait parameters were collected using inertial measurement units during ST and DT gait. DT cost was calculated for all gait parameters (double support, gait speed, and stride length). Groups were compared first using one-way analysis of covariance. Then a multiple regression was performed for participants in the high-risk sport athletes and repetitive head impact exposure athletes groups only to predict gait outcomes from contact/collision sport career duration. RESULTS: There were no significant differences between groups on any ST, DT, or DT cost outcomes (p > 0.05). Contact/collision sport duration did not predict any ST, DT, or DT cost gait outcomes. CONCLUSION: Years and history of contact/collision sport participation does not appear to negatively affect or predict neurobehavioral function in early- to mid-adulthood among physically active individuals.

Concussion Knowledge and Attitudes in Reserve Officers' Training Corps Cadets.

INTRODUCTION: Military members' knowledge of concussion signs and symptoms may be critical to appropriate concussion identification and health-seeking behavior, particularly for those in leadership roles. The current study aimed to characterize concussion knowledge and attitudes among future military officers undergoing U.S.-based Reserve Officers' Training Corps (ROTC) training. MATERIALS AND METHODS: Army and Air Force ROTC cadets at 2 large, public universities were utilized for a survey-based observational study. The study was approved by the institutional review board at both university research sites. Cadets completed a modified Rosenbaum Concussion Knowledge and Attitude Survey to obtain cadets' Concussion Knowledge Index and Concussion Attitude Index, where higher scores are preferable. Cadets' concussion knowledge and attitudes were characterized via descriptive statistics. RESULTS: Cadets (n = 110) had a mean Concussion Knowledge Index of 18.8 ± 3.2 (range = 9-23, out of 25). Potentially detrimental misconceptions included: belief that typically concussion symptoms no longer persist after 10 days (79.1%) and brain imaging shows visible physical damage following concussion (74.5%). Mean Concussion Attitude Index was 60.6 ± 7.4 (range = 46-75, out of 75). In general, cadets reported higher agreement with safe concussion behavior than what they believe peers would report. CONCLUSIONS: Cadets were found to have a high concussion knowledge, yet common misconceptions remained. Cadets consistently reported safe choices but were less sure that peers felt similarly; future investigations should evaluate ROTC concussion social norms and education should note peers' beliefs supporting safe concussion attitudes.

Age of First Exposure to Collision Sports Does Not Affect Patient Reported Outcomes in Women and Men Community Rugby Players.

PURPOSE: This study aimed to determine the relationship between age of first exposure (AFE) to repetitive head impacts through contact/collision sports and patient-reported outcomes in community rugby players. METHODS: We recruited community rugby players older than 18 yr with at least 1 yr of contact rugby participation to complete an online survey. Participants completed the Brief Symptom Inventory-18 (BSI-18), Short-Form Health Survey 12 (SF-12), and Satisfaction with Life Scale (SWLS) via Qualtrics. We used generalized linear models to examine the association between AFE (continuous) and patient-reported outcomes by sex, while controlling for cumulative years contact/collision sport history, age, and concussion history (yes/no). In addition, we used Mann-Whitney U tests to compare patient-reported outcomes between AFE <12 and AFE ≥12. RESULTS: A total of 1037 rugby players (31.6 ± 11.3 yr (range, 18-74 yr), 59.1% men) participated in this study. Whether analyzed continuously or dichotomously at age 12 yr, younger AFE was not associated with worse patient-reported outcomes for either men or women. Positive concussion history was a significant predictor of worse BSI-18 subscores, SF-12 subscores, and SWLS in women and worse BSI-18 subscores in men. Cumulative contact/collision sport history was a significant predictor of better BSI-18 Depression and SF-12 (Mental Component Summary) subscores in men only. In men and women, older age was a significant predictor of better BSI-18 Depression, Anxiety, and GSI subscores; better SWLS (in men only); and better SF-12 Mental Component Summary, but worse SF-12 (Physical Component Summary). CONCLUSIONS: Younger AFE to contact/collision sport is not associated with worse patient-reported outcomes in early adult rugby players. Concussion history was predictive of worse patient-reported outcomes.

Diagnosed concussion is associated with increased risk for lower extremity injury in community rugby players.

OBJECTIVES: To determine (1) the association between lifetime diagnosed concussion and lower extremity musculoskeletal injury (LE-MSI) among community rugby union players and (2) the sex specific risk of LE-MSI given concussion history among males and females. DESIGN: Retrospective survey. METHODS: 1037 (59.0% male, (612/1037), age: 31.6 ±â€¯11.3 years) rugby players (10.1 ±â€¯8.1 years played) completed an online survey to ascertain injury history. A chi-squared test of association was performed between concussion and LE-MSI; significant outcomes were followed-up with an odds ratio. A binary logistic regression with any LE-MSI (yes/no) as the outcome and concussion (yes/no) and sex (male/female) as predictors was performed to determine if there was a sex by concussion interaction. RESULTS: There was an overall significant association between concussion and any LE-MSI(χ(1) = 13.055, p < 0.001, OR = 2.30 [95%CI: 1.45, 3.65]). Both male (OR = 2.21) and females (OR = 2.49) had significant associations for concussion and LE-MSI, but there were no differences between sex for risk of LE-MSI (R2 = 0.024, p = 0.999). CONCLUSIONS: Community rugby players with a history of concussion are >2× more likely to also experience an LE-MSI than those without a history of concussion. There were no differences in the odds of LE-MSI between males and females with a history of diagnosed concussion. In line with current World Rugby injury prevention programs, future research should aim to reduce LE-MSI incidence to maximize player safety and wellness through targeted injury prevention and teams should utilize a conservative return to play protocols following concussion.

No Clinical Predictors of Postconcussion Musculoskeletal Injury in College Athletes.

PURPOSE: This study aimed to identify clinical predictors of postconcussion subsequent musculoskeletal (MSK) injuries. METHODS: We recruited 66 National Collegiate Athletic Association intercollegiate student-athletes with a diagnosed concussion as well as 36 National Collegiate Athletic Association student-athletes without a concussion. All participants completed a multifaceted concussion baseline consisting of 1) 22-item 0-6 self-reported symptom checklist with outcomes including both the number of symptoms endorsed (0-22) and 2) total symptom score (0-132), 3) Standard Assessment of Concussion, 4) Balance Error Scoring System, 5) Immediate Post-Concussion Assessment and Cognitive Testing, 6) clinical reaction time, and 7) the King-Devick as well as demographic and injury characteristics. The concussion participants completed the same examination acutely postconcussion, and binary logistic regression was used to identify predictors of subsequent MSK from the change scores (acute minus baseline). From the 66 concussed student-athletes, a subset 36, matched with the healthy athletes, compared the risk of subsequent MSK in the year before and year after their concussion. RESULTS: The concussion participants were 1.78 times (95% confidence interval, 1.12-2.84; P = 0.015) more likely to suffer a lower extremity MSK in the year after their concussion than the control participants. The participant demographics and injury characteristics (P = 0.318) and concussion clinical outcomes (P = 0.461) did not predict subsequent MSK. CONCLUSION: The concussion participants were 1.78 times more likely to sustain a subsequent MSK; however, no demographic, injury characteristic, or concussion assessments predicted the MSK. Thus, clinicians are not able to utilize common neurological measures or participant demographics to identify those at risk for subsequent lower extremity MSK. Injury prevention strategies should be considered for collegiate student-athletes upon premature return to participation after a concussion to reduce the subsequent MSK.

Reactive knee stiffening strategies between various conditioning histories.

Optimizing joint stiffness through appropriate muscular activation is crucial for maintaining stability and preventing injury. Conditioning techniques may affect joint stability by increasing joint stiffness and altering neuromuscular control; however no studies have assessed this in a controlled setting. Fifteen endurance athletes, 12 power athletes, and 15 control subjects sat on a stiffness device that generated a rapid knee flexion perturbation and were instructed to react to the perturbation. Main outcome measures included short-range (0-4°) and long range (0-40°) stiffness and muscle activation from quadriceps and hamstring muscles. Stiffness results revealed greater short-range stiffness in endurance athletes (0.057 ± 0.012 Nm/deg/kg) than controls (0.047 ± 0.008 Nm/deg/kg, p = 0.021); while passive long-range stiffness was greater in power (0.0020 ± 0.001 nm/deg/kg) than endurance athletes (0.0016 ± 0.001 nm/deg/kg, p = 0.016). Endurance athletes had greater reactive stiffness (0.051 ± 0.017 nm/deg/kg) than control (0.033 ± 0.011 nm/deg/kg, p = 0.001) and power (0.037 ± 0.015 nm/deg/kg, p = 0.044) groups. Endurance athletes also displayed greater quadriceps activity during passive and reactive conditions (p < 0.050) compared to power athletes and controls. These findings suggest that power-based training history may be associated with greater passive joint stiffness across the full range of motion, while endurance-based training could positively influence reactive muscular characteristics, as well as resting muscle tone. These unique variations in stiffness regulation could be beneficial to programmes for prevention and rehabilitation of joint injury.

The relationship between the sensory responses to ankle-joint loading and corticomotor excitability.

PURPOSE: Maintaining joint stability is dependent on the ability of the nervous system to sense and react to potentially injurious loads. In attempts to understand the neurophysiologic mechanisms underlying joint stability, this afferent and efferent activity has been quantified separately at the cortical, segmental and peripheral levels using various electrophysiologic techniques in vivo. However, no studies have attempted to quantify sensory and motor activation at multiple levels of the nervous system in a single subset, to understand potential adaptations for optimizing joint stability. MATERIALS AND METHODS: Muscle spindle afferent activity and sensory cortex event-related desynchronization were quantified during ankle-joint loading; and motor excitability was assessed through transcranial magnetic stimulation and the Hoffmann reflex in a subset of 42 able-bodied individuals. Microneurography and electroencephalography were used to collect the muscle spindle afferent and sensory cortex activation, respectively, as joint load was applied using an ankle arthrometer. Separately, motor-evoked potentials were obtained from the tibialis anterior (TA) and soleus (SOL) using transcranial magnetic stimulation over the motor cortex, and compared to the reflexive responses evoked via sciatic nerve electrical stimulation. RESULTS: Correlation coefficients revealed significant correlations between the motor threshold of the soleus and early muscle spindle afferent activity (r = -0.494) and early cortical event-related desynchronization (r = 0.470), as well as tibialis anterior motor-evoked potential size and late muscle spindle afferent activity (r = 0.499). CONCLUSIONS: The results of this study highlight the nervous system's capability to offset motor output based on the volume of sensory input at the segmental and cortical levels.

The Relationship Between Joint Stiffness and Muscle Activity in Unstable Ankles and Copers.

CONTEXT: Rolling sensations at the ankle are common after injury and represent failure in neural regulation of joint stiffness. However, deficits after ankle injury are variable and strategies for optimizing stiffness may differ across patients. OBJECTIVE: To determine if ankle stiffness and muscle activation differ between patients with varying history of ankle injury. PATIENTS: Fifty-nine individuals were stratified into healthy (CON, n = 20), functionally unstable (UNS, n = 19), and coper (COP, n = 20) groups. MAIN OUTCOME MEASURES: A 20° supination perturbation was applied to the ankle as position and torque were synchronized with activity of tibialis anterior, peroneus longus, and soleus. Subjects were tested with muscles relaxed, while maintaining 30% muscle activation, and while directed to react and resist the perturbation. RESULTS: No group differences existed for joint stiffness (F = 0.07, P = .993); however, the UNS group had higher soleus and less tibialis anterior activation than the CON group during passive trials (P < .05). In addition, greater early tibialis anterior activation generally predicted higher stiffness in the CON group (P ≤ .03), but greater soleus activity improved stiffness in the UNS group (P = .03). CONCLUSION: Although previous injury does not affect the ability to stiffen the joint under laboratory conditions, strategies appear to differ. Generally, the COP has decreased muscle activation, whereas the UNS uses greater plantar-flexor activity. The results of this study suggest that clinicians should emphasize correct preparatory muscle activation to improve joint stiffness in injury-rehabilitation efforts.

A sex comparison of reactive knee stiffness regulation strategies under cognitive loads.

BACKGROUND: Sex differences may exist in cognitive faculties and neuromuscular strategies for maintaining joint stability. The purpose of this study was to assess whether preparatory and reactive knee stiffening strategies are affected differently in males and females exposed to sex-biased cognitive loads. METHODS: 20 male and 20 female volunteers were tested for knee joint stiffness and quadriceps and hamstring muscle activation patterns throughout a rapid eccentric knee extension perturbation. Participants were tested under 3 cognitive loads (Benton's Judgment of Line Orientation; Symbol Digit modalities Test; and Serial 7's) and a control condition. Apparent knee joint stiffness and muscle activation amplitude and timing were quantified throughout the perturbation across the 4 conditions. FINDINGS: Reactive knee stiffness values were significantly less during the cognitive tasks compared to the control condition (Judgment of Line Orientation=0.034Nm/deg/kg, Symbol Digit Modalities Test=0.037Nm/deg/kg, Serial 7's=0.037Nm/deg/kg, control=0.048Nm/deg/kg). Females had greater normalized total apparent stiffness than males. The quadriceps muscles had faster and greater activation than the hamstring muscles; however, no group differences were observed. No overall differences in muscle activation (magnitude and timing) were found between the cognitive loading tasks. INTERPRETATION: Cognitive loading may decrease the ability of healthy individuals to reactively stiffen their knee joint and appears to interfere with the normal stiffness regulation strategies. This may elucidate an extrinsic risk factor for non-contact knee ligament injury.

Decoupling of laxity and cortical activation in functionally unstable ankles during joint loading.

PURPOSE: Recent studies have highlighted central nervous system alterations following ligamentous injury that may contribute to joint instability. However, research has not observed cortical responses to joint loading or sensory changes in the context of joint laxity following injury. METHODS: Forty-two subjects were stratified into healthy (CON), unstable (UNS), and coper (COP) groups using ankle injury and instability history. Event-related desynchronization (%) from electroencephalography quantified somatosensory cortex activity as the ankle was loaded using an arthrometer. RESULTS: Cortical activation increased as the ankle was loaded (F = 63.05, p < 0.001), but did not differ between groups (F = 1.387, p = 0.268), despite greater laxity in UNS (F = 3.58, p = 0.038). CONCLUSIONS: Increased somatosensory cortex activity was observed with joint loading; however, though UNS demonstrated a degree of mechanical instability, no differences in magnitude of cortical activation were observed. Continued research should explore how the relationship between cortical activation and joint stiffness is affected following ligamentous injury.

Brain regulation of muscle tone in healthy and functionally unstable ankles.

CONTEXT: Current research into the etiology of joint instability has yielded inconsistent results, limiting our understanding of how to prevent and treat ligamentous injury effectively. Recently, cortical reorganization was demonstrated in patients with ligamentous injury; however, these neural changes have not been assessed relative to joint laxity. OBJECTIVE: The purpose of the current study was to determine if changes in cortical excitability and inhibition occur in subjects with functional ankle instability, as well as to investigate the relationship between these measures and joint laxity. DESIGN: Posttest only with control group. SETTING: University laboratory. SUBJECTS: 12 subjects with no history of ankle sprain (CON) and 12 subjects with a history of unilateral functional ankle instability (UNS). INTERVENTIONS: Subjects were tested for joint laxity using an instrumented ankle arthrometer. Cortical excitability and inhibition were assessed using transcranial magnetic stimulation (TMS) to obtain motor-evoked potentials and the cortical silent period from the lower leg muscles. MAIN OUTCOME MEASURES: Joint laxity was quantified as peak anterior displacement and inversion rotation. Active motor threshold, slope, and intensity at 50% of peak slope of TMS-derived recruitment curves were used to quantify cortical excitability from lower leg muscles, while the cortical silent period from the peroneus longus was used to represent intracortical inhibition. RESULTS: No significant differences were observed between groups for laxity or cortical measures. CON demonstrated a significant relationship between laxity and tibialis anterior excitability, as well as laxity and silent period, while UNS ankles demonstrated significant relationships between peroneal and soleus excitability and laxity measures. CONCLUSION: Our results support relationships between laxity and measures of excitability and inhibition that differ between healthy and unstable subjects. Future research should further investigate the mechanisms behind these findings and consider cortical influences when investigating altered joint laxity.

Role of external prophylactic support in restricting accessory ankle motion after exercise.

BACKGROUND: To both prevent and accelerate recovery and return-to-play from ankle sprains, clinicians frequently employ the use of external prophylactic support (EPS), such as taping and bracing, to provide mechanical support to the ankle joint. While common practice clinically, research has been inconclusive in demonstrating the effectiveness of EPS in restricting accessory motion (laxity) throughout activity, as well as its efficacy in restricting laxity in patients with complaints of ankle instability, and patients with a history of ankle sprain. The purpose of this study was to investigate the effectiveness of EPS type (None, Tape, Brace) on ankle laxity before and after exercise in subjects with varying degrees of previous ankle injury. METHODS: Ankles from 24 participants (age, 20.6 ± 1.6 years; height, 173.6 ± 8.3 cm; mass, 72.8 ± 12.2 kg) were placed into one of three groups: healthy control (CON), potential coper (COP), and functionally unstable (UNS). Ankle laxity was assessed using an ankle arthrometer at 4 points in time; prior to EPS application, immediately following EPS application, following a 20-minute functional exercise protocol with EPS, and following removal of EPS. Peak ankle anterior displacement (ANT), inversion rotation (INV), and eversion rotation (EVR) were compared between groups and across conditions using a three-way ANOVA. RESULTS: Taping and bracing each decreased laxity from pre-application to pre-exercise and post-exercise. Tape provided greater restriction post-exercise in inversion and eversion rotation. Additionally, the UNS group demonstrated significantly greater anterior displacement post-exercise following removal of the brace compared to other groups. CONCLUSION: Compared to pre-application and post-removal, EPS significantly decreased ankle laxity before and after physical activity, with taping providing better restriction in inversion and eversion rotation throughout exercise. CLINICAL RELEVANCE: Following EPS removal, bracing revealed a greater increase in post-exercise laxity in subjects with ankle instability, suggesting tape may be more beneficial for controlling laxity in these patients.

The association between athleticism, prenatal testosterone, and finger length.

Research suggests that prenatal levels of testosterone are related to finger length development and traits beneficial to athletic skill, such as power, endurance, visual-spatial skills, or sensation seeking and dominance behavior. In men, the second digit to fourth digit ratio (2D:4D) has been shown to correlate with success in competitive levels of football (soccer), which suggests that the 2D:4D ratio is a possible marker for level of attainment in sport. The purpose of this study was to explore the 2D:4D relationships between sports and make comparisons with nonathletes. A multiple group posttest-only design was used. Participants included 138 male volunteers with 92 intercollegiate National Collegiate Athletic Association division I athletes and 46 nonathletes who were not varsity athletes. The independent variable was group (crew, football, gymnastics, soccer, nonathlete). The dependent variable was the 2D:4D ratio. No significant differences were noted between the athletes and nonathletes (p = 0.182). Significant differences were found among the different groups (p = 0.000), with significantly lower ratios between football and crew (p = 0.000), football and nonathletes (p = 0.030), and gymnastics and crew (p = 0.001). This research provides a stronger level of evidence that the 2D:4D ratio may help indicate potential athleticism or competition-level achievement, but the external validity may be limited to only specific sports.

Stiffness regulation and muscle-recruitment strategies of the shoulder in response to external rotation perturbations.

BACKGROUND: The complex interactions between capsuloligamentous structures and muscle-recruitment strategies that maintain glenohumeral stability remain unclear. The purposes of the present study were to determine whether stiffness regulation and muscle-activation strategies differed under varying joint positions and levels of contraction in the shoulder and to determine the relationship between generalized joint laxity, glenohumeral joint laxity, and joint stiffness. METHODS: Forty healthy, physically active subjects with a mean age (and standard deviation) of 25.2 +/- 4.6 years, a mean height of 174.7 +/- 6.7 cm, and a mean mass of 73.1 +/- 13.8 kg were tested. Shoulder stiffness and the activation of muscles (including the rotator cuff and the anterior deltoid) were measured at two levels of internal rotation torque (0% and 50% of maximum) and two joint positions (0 degrees and 90% of maximum external rotation) before and after a 5 degrees external rotation perturbation. Generalized laxity and glenohumeral joint laxity (in the anterior, posterior, and inferior directions) were also assessed. RESULTS: Stiffness was 77% greater at 50% of maximum internal rotation torque than at 0% of maximum internal rotation torque (p < 0.001) but was not significantly different between joint positions (p = 0.73). From 0% to 50% of maximum internal rotation torque, preparatory and reactive recruitment of the subscapularis increased significantly more (p < 0.05) than those of the other muscles. Also, subscapularis preparatory activity was 36% greater in 0 degrees of external rotation than in 90% of maximum external rotation (p < 0.01). Generalized joint laxity (as indicated by a score of >/=4) was present in 20% of the subjects. Glenohumeral joint laxity (as indicated by a grade of >/=2) was present in the anterior, posterior, and inferior directions in 13%, 15%, and 15% of the subjects, respectively. No correlation existed between passive stiffness and generalized or glenohumeral laxity (r = -0.12 to 0.29; p = 0.08 to 0.48). CONCLUSIONS: Moderate levels of muscle contraction can significantly increase glenohumeral joint stiffness and stability. Preactivation of the subscapularis appears to be the primary dynamic stabilizer with the arm in 0 degrees of external rotation. However, with the arm in 90% of maximum external rotation (the apprehension position), less subscapularis activity is observed and the maintenance of stability may shift toward other musculoskeletal structures because joint stiffness does not change. A relationship between generalized joint laxity, glenohumeral laxity, and stiffness was not observed in healthy subjects.

Compensatory mechanisms in basketball players with jumper's knee.

CONTEXT: Determining whether there are compensations in those with jumper's knee (JK) might further our understanding of the condition. OBJECTIVE: Comparing lower extremity kinematics and jump performance of basketball athletes with JK with those of healthy controls (C). DESIGN: Repeated-measures control-match design. SETTING: University laboratory. PARTICIPANTS: 24 male basketball players (12 JK, 12 C) matched by height, weight, position, experience, and frequency of play. INTERVENTIONS: Standing counter-movement and running layup jumps. MAIN OUTCOME MEASURES: Maximum vertical-jump height, footfall landing, and lower extremity sagittal-plane kinematics. RESULTS: There were no significant group differences (P > .05) in vertical-jump height (JK = 64.3 +/- 8.6 cm, C = 63.0 +/- 9.8 cm) or layup height (JK = 71.3 +/- 11.6 cm, C = 73.3 +/- 11.0 cm). JK subjects landed flat footed (50%) more than controls (8%). JK subjects showed significantly more hip flexion (JK = 105 degrees +/- 24.8 degrees, C = 89.8 degrees +/- 14.1 degrees; P = .039) with decreased hip acceleration during the countermovement (JK = -3039 +/- 1392 degrees /s2, C = -4229 +/- 1765 degrees /s2; P = .040). When landing from the countermovement jump, JK subjects had significantly less knee acceleration (JK = -4960 +/- 1512 degrees/s2, C = -6736 +/- 2009 degrees/s2, P = .023) and in the layup showed significantly less ankle dorsiflexion (JK = 106.5 degrees +/- 9.0 degrees, C = 112.5 degrees +/- 7.7 degrees; P = .048) and hip acceleration (JK = -2841 +/- 1094 degrees/s2, C = -3912 +/- 1575 degrees/s2; P = .033). CONCLUSION: Compensatory strategies observed in JK subjects might help maintain performance, because their jump height was similar to that of healthy controls.

Sex differences in neuropsychological function and post-concussion symptoms of concussed collegiate athletes.

OBJECTIVE: Our purpose was to determine whether sex differences exist with respect to post-concussion symptoms and neurocognitive function in concussed collegiate athletes. METHODS: A prospective dependent-sample cohort design was used to compare baseline and post-concussion neuropsychological test scores and endorsed symptoms as functions of serial post-concussion assessment with respect to time and sex. The Immediate Post-concussion Assessment and Cognitive Testing (ImPACT) battery was administered to a multicenter analysis group of 79 concussed athletes. This computerized neuropsychological test was given to the athletes during the preseason and, on average, 2 and 8 days postinjury. RESULTS: Multivariate analyses revealed no significant between-group differences on baseline test performance with respect to sex on any of the ImPACT composite scores or on the total symptom score. Multivariate analyses of post-concussion data revealed a significant main effect of time on ImPACT scores, but no main effect of sex was identified, and no time-by-sex interaction existed. Post hoc analysis revealed that concussed female athletes performed significantly worse than concussed male athletes on visual memory tasks (P = 0.001), and analysis of endorsed post-concussion symptoms revealed that concussed men were significantly more likely than concussed women to report post-concussion symptoms of vomiting (P = 0.001) and sadness (P = 0.017). Athletes' scores were examined individually using the reliable-change methodology. At 2 days post-injury, 58% of concussed athletes had one or more reliable incidents of performance decline or increases in symptom reporting. At 8 days post-concussion, 30% of concussed athletes were still showing one or more reliable change from preseason values. CONCLUSIONS: College athletes exhibit differences on visual memory composite scores and symptoms post-concussion as a function of sex. These data support the importance of evaluating neuropsychological status and post-concussion symptoms in concussed athletes. In addition, these data illustrate the importance of analyzing an individual athlete's recovery pattern, because individual differences in recovery trajectories may be overshadowed by global norm-group comparisons.

Anatomical evaluation of the tibial nerve within the popliteal fossa.

The purpose of this study was to evaluate the inter-hamstring position (medial to lateral intertendinous position) of the tibial nerve within the popliteal fossa. A descriptive cadaver model study was performed to permit controlled and direct measures of the tibial nerve. Fourteen embalmed lower extremities (8 left, 6 right) from nine cadavers (4 males, 5 females; 84.3 +/- 10.7 years of age) were examined. Nine anatomical variables were measured. All measurements, except the diameter of the tibial nerve at the apex of the popliteal fossa, were performed at the level of the femoral condyles, at their widest medial-to-lateral point. The tibial nerve's diameter increased as it descended from the apex (3.95 +/- 0.50 mm; CI = 2.94-4.96 mm) to the condyles (4.46 +/- 0.92 mm; CI = 2.62-6.31 mm). The distance between the semimembranosus tendon and the biceps femoris tendon in the popliteal fossa (the mid-intertendinous distance) was 48.50 +/- 11.50 mm. The location of the tibial nerve between these two tendons was highly variable: 21.45 +/- 8.40 mm lateral of the semimembranosus tendon and 22.60 +/- 4.90 mm medial of the biceps femoris tendon. Therefore, in 95% of the patients the tibial N could be located within 48.2% of midpoint of the inter-hamstring distance.

Transient electric changes immediately after surgical trauma.

CONTEXT: Electric stimulation is frequently used to promote soft tissue healing, although we do not have a complete understanding of the tissue's electromagnetic properties. OBJECTIVE: To measure the transient electric changes in skin and muscle tissue immediately after trauma. DESIGN: 1-group time series. SETTING: Climate-controlled operating room in a public urban hospital. PATIENTS OR OTHER PARTICIPANTS: Eleven participants (8 females, 3 males) with a mean age of 65.18 +/- 11.36 years undergoing total hip arthroplasty. INTERVENTION(S): An incision approximately 10 cm distal to the posterior superior iliac spine extended distally over the greater trochanter and along the lateral limb. The incision was completed in 2 cuts: (1) skin and subcutaneous fat and (2) muscle tissue. MAIN OUTCOME MEASURE(S): Three measurement sessions were performed with an electrometer before and after a skin incision and after a muscle incision. Potential differences and current intensity were measured immediately after acute trauma to determine the transient electric changes associated with soft tissue injury. RESULTS: The electric potentials were significantly more negative after the skin incision (P = .036) and skin plus muscle incision (P = .008; preincision = 0.001 +/- 0.015 V, skin incision = -0.127 +/- 0.134 V, skin plus muscle incision = -0.192 +/- 0.153 V). Current intensity changed significantly after the skin plus muscle incision (P = .008; preincision = 0.046 +/- 0.112 pA, skin incision = -0.803 +/- 0.904 pA, skin plus muscle incision = -1.708 +/- 1.302 pA). CONCLUSIONS: Soft tissue trauma generated negative transient electric changes.

Gender comparisons of dynamic restraint and motor skill in children.

OBJECTIVES: To assess differences in neuromuscular dynamic restraint between high-skilled and low-skilled prepubescent girls and boys. To determine the contribution of sport experience and physical characteristics to motor skill. SUBJECTS: Nineteen girls and 17 boys (8.89-9.40 y) participated. INTERVENTION: Isometric hamstring and quadriceps muscle strength was assessed. Subjects performed 3 landing trials for measurement of preparatory EMG and vertical leg stiffness. Motor skill was assessed through analysis of 12 fundamental tasks. Sport experience was reported as hours per week and total years in organized and nonorganized activity. OUTCOME MEASURES: Dynamic restraint variables of isometric strength, preparatory EMG activity, and vertical leg stiffness were measured between groups. The contributions of time in sport, type of sport, and physical characteristics on skill were analyzed. RESULTS: No significant gender or skill differences were found in quadriceps strength (P = 0.73), hamstring strength (P = 0.96), hamstring-to-quadriceps ratio (P = 0.71), or vertical leg stiffness (P = 0.38). Low-skilled children exhibited significantly greater (47.8%) preparatory hamstring-quadriceps coactivation than high-skilled subjects (P = 0.03). Participation in organized and nonorganized sport accounted for 29% of the variance in motor skill. CONCLUSIONS: Neuromuscular differences between genders were not observed, but dynamic restraint EMG measures differed between skill levels. The factors predisposing females to noncontact injuries may develop prepuberty to postpuberty from a combination of variables. Greater coactivation in the low-skilled group appears consistent with immature feedforward neuromuscular control strategies. These unrefined motor skills are less economical, may compromise dynamic restraint, and appear partially determined by sport experience.