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 history is associated with increased lower-extremity injury incidence in Reserve Officers' Training Corps cadets

INTRODUCTION

Concussions have been associated with an increased risk of lower-extremity musculoskeletal injury (LE-MSI) in athletes and US Army soldiers, creating an added economic, physical and social burden. Yet, there is a paucity of evidence on this relationship among Reserve Officers' Training Corps (ROTC) cadets, a group which engages in activities with high-injury risk and will subsequently commission as active duty officers. This study aimed to examine the association between concussions and LE-MSI in ROTC cadets.

METHODS

125 (83 were male) Army and Air Force ROTC cadets (19.8±2.0 years) from two large state universities' Army and Air Force ROTC programmes participated in this study. Cadets completed a reliable injury history questionnaire to ascertain the following variables of interest: (1) any concussion history, (2) reported concussions, (3) undiagnosed concussions, and (4) potentially unrecognised concussion history and LE-MSI history (eg, ankle sprain, knee sprain or muscle strain). Data were analysed using a χ² test for association and binary logistic regression to determine ORs.

RESULTS

Cadets with any concussion history (n=42) had a significantly (p=0.035) higher association with LE-MSI (OR 2.47, 95% CI 1.05 to 5.83) than those without. Cadets who had a reported concussion (n=33) had a significantly (p=0.026) higher association with LE-MSI (OR 2.95, 95% CI 1.11 to 7.84) compared to cadets without.

CONCLUSIONS

ROTC cadets with a history of diagnosed concussion were more likely to have suffered an LE-MSI than cadets without a concussion history. ROTC cadre should be aware of this relationship and incorporate injury prevention protocols.

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.

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.

Preliminary Concussion and Lower Extremity Injury Risk Among R.O.T.C. Cadets

Objective

To examine the association between concussions and lower extremity musculoskeletal injury (LE-MSI) rates in Reserve Officer Training Corps (ROTC) cadets.

Background

Concussions have been associated with an increased risk for LE-MSI among high school, collegiate, and professional athletes as well as U.S. Army Soldiers. However, there is a paucity evidence on this relationship among U.S. Army ROTC cadets, future U.S. Army Officers, and a group similar to student-athletes in regards to physical activity levels.

Design/Methods

A modified reliable injury questionnaire (ICC = 0.92) was used to identify the total number of reported concussions, intentionally unreported concussions, and potentially unrecognized concussions (e.g., memory loss not diagnosed as a concussion) as well as LE-MSI (e.g., muscle strains, ACL rupture) a cadet had suffered. A chi-square analysis was performed to identify the association between concussion and LE-MSI and any concussive injury and LE-MSI.

Results

47 cadets (19.9 ± 1.3 years) were recruited from one Army ROTC program. There was not a significant association between reported concussions and LE-MSI (Χ(1) = 3.122, p = 0.077). There was not a significant association between any concussive injury (reported, unreported, or potentially unrecognized) and LE-MSI (Χ(1) = 3.590, p = 0.058). The reported concussion history was 38.3% (18/47), any concussive history was 46.8% (22/47), and 68.1% (32/47) reported history of LE-MSI.

Conclusions

Preliminary results showed that there was no statistically significant association between concussion and LE-MSI among ROTC cadets at this university. Future research is warranted on a larger cohort of cadets to determine if this relationship exists since cadets will soon commission, potentially risking injury while serving on active duty, causing limited duty days, reduced Department of Defense readiness, and increased healthcare costs. Cadets showed a high incidence of concussion and LE-MSK injury, and future research should target reducing these injuries among ROTC cadets prior to commissioning.

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.

An acoustic startle alters knee joint stiffness and neuromuscular control

Growing evidence suggests that the nervous system contributes to non-contact knee ligament injury, but limited evidence has measured the effect of extrinsic events on joint stability. Following unanticipated events, the startle reflex leads to universal stiffening of the limbs, but no studies have investigated how an acoustic startle influences knee stiffness and muscle activation during a dynamic knee perturbation. Thirty-six individuals were tested for knee stiffness and muscle activation of the quadriceps and hamstrings. Subjects were seated and instructed to resist a 40-degree knee flexion perturbation from a relaxed state. During some trials, an acoustic startle (50 ms, 1000 Hz, 100 dB) was applied 100 ms prior to the perturbation. Knee stiffness, muscle amplitude, and timing were quantified across time, muscle, and startle conditions. The acoustic startle increased short-range (no startle: 0.044 ± 0.011 N·m/deg/kg; average startle: 0.047 ± 0.01 N·m/deg/kg) and total knee stiffness (no startle: 0.036 ± 0.01 N·m/deg/kg; first startle 0.027 ± 0.02 N·m/deg/kg). Additionally, the startle contributed to decreased [vastus medialis (VM): 13.76 ± 33.6%; vastus lateralis (VL): 6.72 ± 37.4%] but earlier (VM: 0.133 ± 0.17 s; VL: 0.124 ± 0.17 s) activation of the quadriceps muscles. The results of this study indicate that the startle response can significantly disrupt knee stiffness regulation required to maintain joint stability. Further studies should explore the role of unanticipated events on unintentional injury.

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.

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.

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.

Sex differences in baseline neuropsychological function and concussion symptoms of collegiate athletes

OBJECTIVE

To investigate sex differences in baseline neuropsychological function and concussion symptoms between male and female collegiate athletes.

METHODS

A post-test only design was used to examine baseline neuropsychological test scores and concussion symptoms. A total of 1209 NCAA Division I collegiate athletes from five northeastern universities in the USA completed a baseline ImPACT test. ImPACT, a computerised neuropsychological test battery, was administered during an athlete's pre-season.

RESULTS

Female athletes performed significantly better than male athletes on baseline verbal memory scores (p = 0.001), while male athletes performed significantly better than female athletes on baseline visual memory scores (p = 0.001). Female athletes endorsed a significant number of mild baseline symptoms as compared to male athletes.

CONCLUSIONS

Male and female athletes exhibit differences on baseline neuropsychological test performance and concussion symptoms.

Gender differences in head-neck segment dynamic stabilization during head acceleration

PURPOSE

Recent epidemiological research has revealed that gender differences exist in concussion incidence but no study has investigated why females may be at greater risk of concussion. Our purpose was to determine whether gender differences existed in head-neck segment kinematic and neuromuscular control variables responses to an external force application with and without neck muscle preactivation.

METHODS

Forty (20 females and 20 males) physically active volunteers participated in the study. The independent variables were gender, force application (known vs unknown), and force direction (forced flexion vs forced extension). The dependent variables were kinematic and EMG variables, head-neck segment stiffness, and head-neck segment flexor and extensor isometric strength. Statistical analyses consisted of multiple multivariate and univariate analyses of variance, follow-up univariate analyses of variance, and t-tests (P < or = 0.05).

RESULTS

Gender differences existed in head-neck segment dynamic stabilization during head angular acceleration. Females exhibited significantly greater head-neck segment peak angular acceleration (50%) and displacement (39%) than males despite initiating muscle activity significantly earlier (SCM only) and using a greater percentage of their maximum head-neck segment muscle activity (79% peak activity and 117% muscle activity area). The head-neck segment angular acceleration differences may be because females exhibited significantly less isometric strength (49%), neck girth (30%), and head mass (43%), resulting in lower levels of head-neck segment stiffness (29%).

CONCLUSION

For our subject demographic, the results revealed gender differences in head-neck segment dynamic stabilization during head acceleration in response to an external force application. Females exhibited significantly greater head-neck segment peak angular acceleration and displacement than males despite initiating muscle activity earlier (SCM only) and using a greater percentage of their maximum head-neck segment muscle activity.

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.

Joint stiffness and pain in individuals with patellofemoral syndrome

STUDY DESIGN

Pretest-posttest matched control group design.

OBJECTIVES

To measure passive knee joint stiffness and pain in participants with and without patellofemoral pain syndrome (PFPS) and to determine the relationship between mechanical knee joint stiffness, self-reported stiffness, and pain.

BACKGROUND

Patients with PFPS complain of knee joint stiffness and pain, but no research has quantified both of these characteristics in this population.

METHODS AND MEASURES

Twenty-eight individuals (14 with PFPS [mean age +/- SD, 25.5 +/- 4.8 years] and 14 healthy controls [mean age +/- SD, 22.8 +/- 5.4 years]) volunteered for this study. Mechanical passive knee joint stiffness was calculated using the damped natural frequency of oscillation of the lower leg while sitting. Mechanical stiffness was compared to self-reports of knee stiffness and pain. All measurements were recorded presitting and after 20 minutes of sitting.

RESULTS

Sitting for 20 minutes did not induce significant changes in mechanical knee joint stiffness. However, participants with PFPS reported significantly greater (P<.01) knee stiffness after sitting for 20 minutes. A significant correlation (r = 0.70, P<.01) was found between self-reported stiffness and pain in participants with PFPS; however, no significant relationship was observed between mechanical and self-reported knee joint stiffness.

CONCLUSIONS

Despite frequent complaints of joint stiffness, the knees of individuals with PFPS do not appear physiologically stiffer than those of control subjects. Individuals with PFPS perceive increased knee stiffness after sitting, but may misinterpret the sensation of pain as joint stiffness.

Effects of sport massage on limb girth and discomfort associated with eccentric exercise

CONTEXT

Sport massage is often used to help prepare for exercise, expedite recovery from muscle soreness, and enhance athletic performance. However, the effect of sport massage on recovery from delayed-onset muscle soreness is unknown.

OBJECTIVE

To determine the effect of a short sport massage treatment on intramuscular swelling and pain in response to eccentric exercise.

DESIGN

We used a 2 x 8 (treatment x time) repeated-measures design to compare triceps surae muscle girth and pain ratings over the 72 hours after eccentric exercise.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Nineteen healthy, college-aged subjects.

INTERVENTION(S)

Delayed-onset muscle soreness was induced with several sets of eccentric triceps surae contractions at 90% of the estimated concentric, 1-repetition maximum weight. Subjects returned on 3 consecutive days after eccentric exercise with a cycle ergometer for active rest treatments. In addition, 1 leg received the sport massage.

MAIN OUTCOME MEASURE(S)

Girth measurements were taken at 5.08 cm (2 in), 10.16 cm (4 in), 15.24 cm (6 in), and 20.32 cm (8 in) below the knee joint line, and pain was assessed with a visual analog scale before and after all 4 sessions.

RESULTS

No interaction was noted between treatment and time for any girth or pain measurements, and no main effect was seen for treatment.

CONCLUSIONS

Sport massage did not reduce girth or pain in the lower leg after eccentric exercise within 72 hours.

Effects of Plyometric Training on Muscle-Activation Strategies and Performance in Female Athletes

OBJECTIVE: To evaluate the effects of plyometric training on muscle-activation strategies and performance of the lower extremity during jumping exercises. SUBJECTS: Twenty healthy National Collegiate Athletic Association Division I female athletes. DESIGN AND SETTING: A pretest and posttest control group design was used. Experimental subjects performed plyometric exercises 2 times per week for 6 weeks. MEASUREMENTS: We used surface electromyography to assess preparatory and reactive activity of the vastus medialis and vastus lateralis, medial and lateral hamstrings, and hip abductors and adductors. Vertical jump height and sprint speed were assessed with the VERTEC and infrared timing devices, respectively. RESULTS: Multivariate analyses of variance revealed significant (P <.05) increases in firing of adductor muscles during the preparatory phase, with significant interactions for area, mean, and peak. A Tukey honestly significant difference post hoc analysis revealed significant increases in preparatory adductor area, mean, and peak for experimental group. A significant (P =.037) increase in preparatory adductor-to-abductor muscle coactivation in the experimental group was identified, as well as a trend (P =.053) toward reactive quadriceps-to- hamstring muscle coactivation in the experimental group. Pearson correlation coefficients revealed significant between-groups adaptations in muscle activity patterns pretest to posttest. Although not significant, experimental and control subjects had average increases of 5.8% and 2.0% in vertical jump height, respectively. CONCLUSIONS: The increased preparatory adductor activity and abductor-to-adductor coactivation represent preprogrammed motor strategies learned during the plyometric training. These data strongly support the role of hip-musculature activation strategies for dynamic restraint and control of lower extremity alignment at ground contact. Plyometric exercises should be incorporated into the training regimens of female athletes and may reduce the risk of injury by enhancing functional joint stability in the lower extremity.

Proprioception, kinesthesia, and balance after total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses

BACKGROUND

The effect of total knee arthroplasty on proprioception, kinesthesia, and postural control remains controversial. It is argued that retaining the posterior cruciate ligament may help to preserve these sensorimotor functions and improve the longevity of the prosthesis and the functional outcome. We performed a prospective, randomized study to assess proprioception, kinesthesia, and balance following total knee arthroplasty with cruciate-retaining and posterior stabilized prostheses.

METHODS

Twenty patients scheduled to undergo total knee arthroplasty were randomly assigned to receive either a cruciate-retaining or a posterior stabilized prosthesis. Joint-position sense, the threshold to detect joint motion, and the subject's ability to balance on an unstable platform were assessed prior to and at least six months after the operation. Paired two-tailed t tests (with a level of significance of p < 0.05) were used to assess the effect of the arthroplasty on the preoperative measures for all subjects. Analysis of covariance was performed to identify the effects of prosthetic design.

RESULTS

Following total knee arthroplasty, patients detected motion significantly faster and reproduced joint position with less error. The balance index also improved significantly from the preoperative to the postoperative evaluation. The group treated with the posterior stabilized prosthesis more accurately reproduced joint position when the knee was extended from a flexed position.

CONCLUSIONS

Total knee arthroplasty results in mild improvements in proprioception, kinesthesia, and balance. These changes may result from the retensioned capsuloligamentous structures and reduced pain and inflammation. Retention of the posterior cruciate ligament does not appear to significantly improve proprioception and balance compared with those functions in patients with a posterior stabilized total knee design.

Effects of Football Collars on Cervical Hyperextension and Lateral Flexion

OBJECTIVES: To evaluate the effectiveness of 3 football collars in reducing cervical range of motion. DESIGN AND SETTING: A repeated-measures design in a controlled laboratory setting. SUBJECTS: Fifteen male National Collegiate Athletic Association Division I varsity football athletes. MEASUREMENTS: Cervical hyperextension and lateral flexion were measured with video analysis. Subjects underwent 5 testing conditions: standard football helmet, standard helmet and shoulder pads, and standard pads with the addition of the Cowboy Collar, A-Force Neck Collar, or a foam neck roll. Subjects performed motions both actively and passively. RESULTS: All 3 collars reduced hyperextension when compared with the helmet and shoulder pads alone (P <.05); in addition, the Cowboy Collar was superior to the foam neck roll (P <.05) in reducing hyperextension. No collar reduced passive lateral flexion when compared with the helmet and shoulder pads, but the foam neck roll permitted significantly less active lateral flexion (P <.01) than the other 3 brace conditions. CONCLUSIONS: In a laboratory setting, cervical hyperextension can be controlled through the use of various cervical collars. Cervical lateral flexion (a more common cause of burners in a scholastic population) cannot be controlled with any of the cervical collars tested. Moreover, foam collars may impede active lateral flexion while not providing additional protection when loaded. These results are limited in that they were produced in a controlled situation as opposed to active football play.

Sex Differences and the Incidence of Concussions Among Collegiate Athletes

OBJECTIVE: To compare sex differences regarding the incidence of concussions among collegiate athletes during the 1997-1998, 1998-1999, and 1999-2000 seasons. DESIGN AND SETTING: A cohort study of collegiate athletes using the National Collegiate Athletic Association (NCAA) Injury Surveillance System; certified athletic trainers recorded data during the 1997-2000 academic years. SUBJECTS: Collegiate athletes participating in men's and women's soccer, lacrosse, basketball, softball, baseball, and gymnastics. MEASUREMENTS: Certified athletic trainers from participating NCAA institutions recorded weekly injury and athlete-exposure data from the first day of preseason practice to the final postseason game. Injury rates and incidence density ratios were computed. Incidence density ratio is an estimate of the relative risk based on injury rates per 1000 athlete-exposures. RESULTS: Of 14 591 reported injuries, 5.9% were classified as concussions. During the 3-year study, female athletes sustained 167 (3.6%) concussions during practices and 304 (9.5%) concussions during games, compared with male athletes, who sustained 148 (5.2%) concussions during practices and 254 (6.4%) concussions during games. Chi-square analysis revealed significant differences between male and female soccer players (chi(2)(1) = 12.99, P =.05) and basketball players (chi(2)(1) = 5.14, P =.05). CONCLUSIONS: Female athletes sustained a higher percentage of concussions during games than male athletes. Of all the sports, women's soccer and men's lacrosse were found to have the highest injury rate of concussions. Incidence density ratio was greatest for male and female soccer players.

Epidemiological considerations of concussions among intercollegiate athletes

The purpose of this study was to examine epidemiological trends of concussions among 15 different intercollegiate sports during the 1997-1998, 1998-1999, and 1999-2000 seasons. Data were collected using the National Collegiate Athletic Association (NCAA) Injury Surveillance System (ISS). For the 15 sports studied during the 3 academic years, the NCAA ISS documented 3,535 team-seasons, 40,547 reportable injuries, 5,566,924 practice athlete exposures (AEs), and 1,090,298 game AEs. Concussions accounted for 6.2% of all reported injuries during this 3-year study. Of all the reported injuries, women lacrosse players (13.9%) reported the highest percentage of suffering a concussion during a game followed by women's soccer (11.4%), men's ice hockey (10.3%), men's lacrosse (10.1%), football (8.8%), women's basketball, (8.5%), field hockey (7.2%), men's soccer (7.0%), wrestling (6.6%), men's basketball (5.0%), baseball (4.2%), and women's volleyball (4.1%). Female athletes from all 7 sports were found to be at a lower risk for suffering concussions during practice sessions than the 8 male sports. However, female athletes were found to be at a greater risk for suffering concussions during games compared to male athletes. Injury trends over the 3- year period indicate concussions continue to be on the rise for athletes participating in collegiate football, men's soccer, and women's and men's basketball.

The effects of shoulder plyometric training on proprioception and selected muscle performance characteristics

The purpose of this study was to determine the effect of plyometric training of the shoulder internal rotators on proprioception, kinesthesia, and selected muscle performance characteristics in female swimmers. Twenty-four female division I swimmers were evaluated before and after a 6-week plyometric training program. Proprioception and kinesthesia were assessed for internal and external rotation at 0 degrees, 75 degrees, and 90% of the subject's maximum external rotation. The Biodex II was used to assess strength characteristics at 60 degrees /s, 240 degrees /s, and 450 degrees /s. Plyometric training sessions (2 times/week) involved 3 sets of 15 repetitions with a trampoline, weighted balls, and elastic tubing. A 2-way analysis of variance revealed significant improvement (P <.05) in proprioception at 0 degrees moving into external rotation, as well as 75 degrees and 90% moving into both internal and external rotation. Kinesthesia demonstrated significant improvement for all test conditions after plyometric training. Significant gains in selected muscle performance characteristics included time to peak torque (60 degrees /s and 240 degrees /s), amortization time (450 degrees /s), and torque decrement (240 degrees /s). This study suggests that plyometric activities may facilitate neural adaptations that enhance proprioception, kinesthesia, and muscle performance characteristics. Significant neuromuscular benefits may be attained if they are implemented earlier into shoulder rehabilitation programs.

Reactive muscle firing of anterior cruciate ligament-injured females during functional activities

OBJECTIVE

The high incidence of noncontact anterior cruciate ligament (ACL) injuries in females has attracted research to investigate the capacity of muscles to reflexively protect the knee joint from capsuloligamentous injury. Numerous reflex pathways link mechanoreceptors in the ACL with contractile fibers in the quadriceps and hamstring muscles. Loads placed on the ACL modify reactive muscle activity through the feed-back process of neuromuscular control and are critical for dynamic muscular stabilization. Noncontact ACL injuries may be the result of aberrations in reactive muscle firing patterns. Therefore, compensatory muscle activation strategies must be employed if functional stability is to be restored after injury or surgical reconstruction. The purpose of our study was to compare the amplitude of reactive muscle activity in females with ACL-deficient (ACLD), ACL-reconstructed (ACLR), and control knees during functional activities.

DESIGN AND SETTING

Female volunteer subjects were stratified into groups based on the status of their ACLs. Each subject performed 4 functional activities, bilaterally, during a single test session.

SUBJECTS

Twenty-four female subjects participated in this study (ACLD = 6, ACLR = 12, control = 6).

MEASUREMENTS

Integrated electromyographic (IEMG) data were collected with surface electrodes from the vastus medialis, vastus lateralis, medial hamstring, and lateral hamstring during downhill walking (15 degrees , 0.92 m/s), level running (2.08 m/s), and hopping and landing from a jump (20.3 cm). IEMG was normalized to the mean amplitude of 3 to 6 consecutive test repetitions. The mean area and peak IEMG of a 250-millisecond period after ground contact was used to represent reactive muscle activity. Side-to-side differences were determined using dependent t tests, and group differences were determined using a one-way analysis of variance.

RESULTS

During running, the ACLD group demonstrated significantly greater area and peak IEMG activity in the medial hamstring in comparison with the ACLR group and greater peak activity in the lateral hamstring when compared with the control group. The ACLD group also demonstrated greater peak activity in the vastus medialis and a smaller area of IEMG activity in the lateral hamstring than the control group during running. During landing, the ACLD group demonstrated significantly less area of IEMG activity in the vastus lateralis when compared with the control group. No significant differences were identified between the ACLR and control groups, nor were side-to side differences revealed.

CONCLUSIONS

Our results suggest that adaptations occur in the reactive muscle activity of ACLD females during functional activities. Strategies to minimize the anterior tibial translation in response to joint loading included increased hamstring activity and quadriceps inhibition. The reactive muscle activity exhibited in ACLD subjects is presumably an attempt to regain functional stability through the dynamic restraint mechanism. The absence of side-to-side differences suggests that these adaptations occur bilaterally after ACL injury.

Muscle preactivity of anterior cruciate ligament-deficient and -reconstructed females during functional activities

OBJECTIVE

Underlying the ability of the hamstrings to decrease tibial anterior shear is the time of firing in comparison with the quadriceps. This timing may be aided by neural programming during a planned or expected activity. It is theorized that individuals who have better programming ability will suffer fewer anterior cruciate ligament (ACL) injuries due to joint protection through muscular stabilization. A component of this dynamic restraint is the development of muscular tension before the knee is loaded. The objective of our study was to compare the muscular activity before footstrike in ACL-deficient (ACL-D), ACL-reconstructed (ACL-R), and control (C) females during functional activities.

DESIGN AND SETTING

Active females were divided into groups based on their ACL status. The study was conducted in a neuromuscular research laboratory.

SUBJECTS

Twenty-four female subjects (ACL-D = 6, ACL-R = 12, C = 6).

MEASUREMENTS

Integrated electromyographic (IEMG) activity from the thigh (vastus medialis obliquus [VMO], vastus lateralis [VL], medial hamstring, and lateral hamstring) and leg (medial gastrocnemius and lateral gastrocnemius [LG]) and footswitch signals were recorded during downhill walking (15 degrees at 0.92 m/s), running (2.08 m/s), hopping, and landing from a step (20.3 cm). IEMG activity was normalized to the mean amplitude of the sample and analyzed for area and mean amplitude for 150 milliseconds before heelstrike. Side-to-side differences were determined by t tests, and separate one-way analyses of variance (ANOVA) were used to detect differences among the 3 groups for each muscle of each activity.

RESULTS

IEMG area side-to-side differences for the ACL-D group appeared in the LG (involved [I] = 36.4 +/- 19.7, uninvolved [U] = 60.1 +/- 23.6) during landing, in the VMO (I = 11.4 +/- 3.8, U = 7.2 +/- 3.1) and VL (I = 13.3 +/- 2.7, U = 8.9 +/- 1.9) during running, and in the VMO (I = 9.2 +/- 4.2, U = 19.5 +/- 7.3) during downhill walking. IEMG mean amplitude side-to-side differences for the ACL-D group appeared in the LG (I = 79.7 +/- 30.3, U = 122.3 +/- 34.9) during downhill walking and in the VMO (I = 78.6 +/- 23.2, U = 45.8 +/- 18.9) during the run; IEMG mean amplitude side-to-side differences for the ACL-R group appeared in the LG (I = 74.7 +/- 40.0, U = 52.8 +/- 14.3) during the hop. The ACL-D group had higher IEMG means than control in the VL (ACL-D = 12.9 +/- 5.8, C = 7.1 +/- 3.9), but lower in the VMO (ACL-D = 9.2 +/- 4.2, C = 15.7 +/- 3.6).

CONCLUSIONS

The side-to-side differences of the ACL-D and ACL-R groups, as well as the group differences between ACL-D and control, suggest that different muscle activation strategies are used by females when performing different dynamic activities. Therefore, muscle unit differentiation may be the cause of our results. These changes appear to be reversed through surgery or the associated postoperative rehabilitation.

Chronic brachial plexopathies and upper extremity proprioception and strength

Brachial plexopathies, where traction or compressive forces disrupt motor and sensory nerve conduction, are the most common nerve injuries in collision sports. Athletes frequently do not report these episodes, however, predisposing the brachial plexus to recurrent trauma. The purpose of this study was to identify how multiple injuries to the brachial plexus affects shoulder strength and proprioception. Ten male intercollegiate football players with at least three unilateral episodes of brachial plexopathies were tested an average of 10 weeks after the most recent episode. The uninvolved shoulder was used as the control. Isometric peak torque was assessed for shoulder abduction, external rotation, and elbow flexion. Proprioception was measured under two conditions: threshold to detection of passive motion and reproduction of passive positioning. Dependent t tests revealed significant mean differences (p < .05) between the involved and uninvolved extremity for abduction peak torque, overall mean peak torque, and one out of four conditions of threshold to detection of passive motion conditions. This was in the neutral position moving into external rotation. In addition, subjects with greater numbers of episodes exhibited larger strength deficits. The results of this study emphasize the need for timely re-evaluation of athletes with chronic brachial plexopathies.