Concussion Symptoms and Neurocognitive Performance of Children and Adolescents on Antidepressants

INTRODUCTION/PURPOSE

There is a well-established association between preexisting depression/anxiety and greater postconcussion symptom burden, but the potential impact of antidepressant medications has not been fully explored. The primary objective of this study was to compare preinjury/baseline and postinjury concussion symptom scores and neurocognitive performance of athletes on antidepressant medications, both with healthy controls and with those with depression/anxiety not on antidepressants.

METHODS

This is a cross-sectional study using data collected from 49,270 junior and high school athletes from computerized neurocognitive assessments (Immediate Post-Concussion Assessment and Cognitive Test [ImPACT]) administered between 2009 and 2018 held by the Massachusetts Concussion Management Coalition. The main outcome measures were symptom scores and neurocognitive performance measures, all of which were assessed both at baseline and postinjury. Statistical analysis included analysis of variance and Tukey pairwise comparisons for continuous variables and Fisher's exact test for categorical variables. Multivariate regression models were used to adjust for potential confounding variables.

RESULTS

Both at baseline and postinjury, athletes with depression/anxiety had mean total symptom scores that were more than double that of healthy controls regardless of antidepressant use. Although there were no significant differences in neurocognitive performance at baseline, depression/anxiety was associated with small but significant decreases in postinjury visual memory and visual motor scores.

CONCLUSIONS

Both at baseline and after sustaining a concussion, young athletes with depression/anxiety experience significantly greater symptom burden compared with healthy controls regardless of antidepressant use.

Influence of sleep symptoms on recovery from concussion in collegiate athletes: a LIMBIC MATARS consortium investigation

OBJECTIVE

Changes in sleep quality and quantity are commonly endorsed by individuals following a concussion. Limited data exists examining the role of sleep disturbances within 72 hours, and throughout recovery, from concussion. The objective of this study was to determine if the number of days to symptom resolution varied between collegiate athletes with or without sleep-related symptoms following a concussion.

DESIGN

Retrospective chart review.

METHODS

Collegiate athletes (n = 539) who were diagnosed with a concussion between the 2015-2020 sport seasons participated in this retrospective chart review. Participants were divided into groups based on the presence or absence of sleep symptoms within 72 hours of a diagnosed concussion. A Mann-Whitney U test was used to compare days to symptom resolution between groups with α = 0.05.

RESULTS

Of the 539 participants, 250 (46.3%) reported sleep-related symptoms. Participants with sleep-related symptoms took significantly longer (U = 30656, p = 0.002) to report symptom resolution at rest (median [full range] = 8.00[0-423]) as compared to participants who did not report sleep-related symptoms (6.00[0-243] days).

CONCLUSION

Collegiate athletes that report sleep-related symptoms immediately following concussion (<72 hours) were observed to take, on median, two days longer to achieve symptom resolution at rest when compared to athletes who did not endorse the same symptoms.

Physical activity and recovery following concussion in collegiate athletes: a LIMBIC MATARS Consortium Investigation

OBJECTIVE

To investigate whether routine daily activities (RDA), non-prescribed exercise (Non-ERx), or prescribed exercise (ERx) were associated with recovery from sport-related concussion (SRC) in collegiate athletes.

MATERIALS AND METHODS

Data for this cross-sectional, retrospective chart review of collegiate athletes diagnosed with SRC (n = 285[39.6% female], age = 19.5 ± 1.4 years) were collected during the 2015-16 to 2019-20 athletic seasons. The independent variable was group (RDA, Non-ERx, ERx). Dependent variables included days from date of diagnosis to symptom resolution (Dx-SR) and SR to return to sport (SR-RTS).

RESULTS

Those in the Non-ERx group took nearly 1.3 times longer to achieve SR (IRR = 1.28, 95% CI: 1.11, 1.46) and, 1.8 times longer for RTS (IRR = 1.82, 95% CI: 1.11, 2.71) when compared to those in the RDA group. No other comparisons were significant.

CONCLUSION

Collegiate athletes in the Non-ERx group took approximately 1 week longer to achieve SR as compared to the RDA and ERx groups. Our findings suggest that if exercise is recommended following SRC, it must be clearly and specifically prescribed. If exercise parameters cannot be prescribed, or monitored, RDA appear to be similarly beneficial during recovery for collegiate athletes with concussion.

Access to athletic trainers and sex as modifiers of time to reach clinical milestones after sport-related concussion in collegiate athletes

OBJECTIVE

Investigate whether an athlete's biological sex and exposure to a dedicated athletic trainer (AT) were related to clinical milestones after a sports-related concussion (SRC).

DESIGN

Retrospective chart review.

METHODS

Medical charts of collegiate athletes (n = 196 [70.9% female]) diagnosed with SRC were reviewed to extract: biological sex, dedicated AT exposure for their sport (yes/no), and time (days) to reaching clinical milestones (diagnosis, symptom resolution, unrestricted return to sport [RTS]). Mann-Whitney U tests were used to determine whether time to clinical milestones differed by sex, AT exposure, or their interaction. Proportions of same-day diagnoses and times to diagnosis, symptom resolution, and unrestricted RTS were evaluated with chi-squared and spearman's rank correlations, respectively.

RESULTS

There were no significant differences in times to reaching any clinical milestone by sex, AT exposure, or their interaction (ps > 0.05). Forty-three percent of participants were diagnosed on the day of their SRC. This did not differ by sex or AT exposure (ps > 0.29). Longer times to SRC diagnosis were associated with more days to symptom resolution (ρ = 0.236, p = 0.001) and unrestricted RTS (ρ = 0.223, p < 0.001).

CONCLUSIONS

Athlete sex and AT exposure were not associated with times to reach any clinical milestone; however, delayed diagnosis was associated with longer times to reach clinical recovery.

Sport Type and Risk of Subsequent Injury in Collegiate Athletes Following Concussion: a LIMBIC MATARS Consortium Investigation

OBJECTIVE

To investigate the association between sport type (collision, contact, non-contact) and subsequent injury risk following concussion in collegiate athletes.

MATERIALS AND METHODS

This retrospective chart review of 248 collegiate athletes with diagnosed concussions (age: 20.0 ± 1.4 years; height: 179.6 ± 10.9 cm; mass: 79.0 ± 13.6 kg, 63% male) from NCAA athletic programs (n = 11) occurred between the 2015-2020 athletic seasons. Acute injuries that occurred within six months following concussion were evaluated. Subsequent injuries were grouped by lower extremity, upper extremity, trunk, or concussion. The independent variable was sport type: collision, contact, non-contact. A Cox proportional hazard model was used to assess the risk of subsequent injury between sport types.

RESULTS

Approximately 28% (70/248) of athletes sustained a subsequent acute injury within six months post-concussion. Collision sport athletes had a significantly higher risk of sustaining any injury (HR: 0.41, p < 0.001, 95% CI: 0.28, 0.62), lower extremity (HR: 0.55, p = 0.04, 95% CI: 0.32, 0.97), and upper extremity (HR: 0.41, p = 0.01, 95% CI: 0.20, 0.81) injuries following concussion. No differences between sport types were observed for other injuries.

CONCLUSION

Collision sport athletes had a higher rate of any subsequent injury, lower, and upper extremity injuries following concussion. Future research should focus on sport-specific secondary injury prevention efforts.

Clinical Mental Health Measures and Prediction of Postconcussion Musculoskeletal Injury

CONTEXT

The rate of lower extremity musculoskeletal injury (LE MSK) is elevated after concussion; however, the underlying mechanism has not been elucidated. Physical characteristics have been investigated despite poorer mental health being a common postconcussion complaint and linked to MSKs.

OBJECTIVE

To evaluate the role of mental health as a predictor of postconcussion LE MSK.

DESIGN

Case-control study.

SETTING

Intercollegiate athletic training facility.

PATIENTS OR OTHER PARTICIPANTS

A total of 67 National Collegiate Athletic Association Division I student-athletes (n = 39 females) who had been diagnosed with a sport-related concussion.

MAIN OUTCOME MEASURE(S)

The Brief Symptom Inventory-18, Hospital Anxiety and Depression Scale, and Satisfaction With Life Scale (SWLS) measures were completed at baseline (preseason) and on the day participants were cleared for unrestricted return to play (RTP) after a concussion. Two binary logistic regressions were used to predict postconcussion LE MSK within a year, one for the baseline time point and the second for the RTP time point. A 2 (group: LE MSK, no LE MSK)-by-2 (time: baseline, RTP) repeated-measures analysis of variance compared performance between baseline and RTP.

RESULTS

Subsequent LE MSKs were sustained by 44 participants (65.7%). The only significant predictor of postconcussion LE MSK was the SWLS score at RTP, with Exp(B) = 0.64, indicating that an increased (improved) SWLS score was associated with a lower LE MSK rate. No significant interactions were present between mental health measures and subsequent MSK (P values = .105-.885).

CONCLUSIONS

Limited associations were evident between postconcussion LE MSK and scores on commonly used measures of anxiety, depression, and satisfaction with life. Reported increased satisfaction with life was associated with a decreased injury risk, which warrants further attention. Our results suggest that these measures of anxiety, depression, and satisfaction with life have limited value in assisting sports medicine clinicians with determining which student-athletes are at elevated risk of postconcussion LE MSK.

Influential Factors and Preliminary Reference Data for a Clinically Feasible, Functional Reaction Time Assessment: The Standardized Assessment of Reaction Time

CONTEXT

Clinical reaction-time (RT) measures are frequently used when examining patients with concussion but do not correlate with functional movement RT. We developed the Standardized Assessment of RT (StART) to emulate the rapid cognitive demands and whole-body movement needed in sport.

OBJECTIVE

To assess StART differences across 6 cognitive-motor combinations, examine potential demographic and health history confounders, and provide preliminary reference data for healthy collegiate student-athletes.

DESIGN

Prospective, cross-sectional study.

SETTING

Clinical medicine facilities.

PATIENTS OR OTHER PARTICIPANTS

A total of 89 student-athletes (56 [62.9%] men, 33 [37.1%] women; age = 19.5 ± 0.9 years, height = 178.2 ± 21.7 cm, mass = 80.4 ± 24 kg; no concussion history = 64 [71.9%]).

MAIN OUTCOME MEASURE(S)

Student-athletes completed health history questionnaires and StART during preseason testing. The StART consisted of 3 movements (standing, single-legged balance, and cutting) under 2 cognitive states (single task and dual task [subtracting by 6's or 7's]) for 3 trials under each condition. The StART trials were calculated as milliseconds between penlight illumination and initial movement. We used a 3 × 2 repeated-measures analysis of variance with post hoc t tests and 95% CIs to assess StART cognitive and movement differences, conducted univariable linear regressions to examine StART performance associations, and reported StART performance as percentiles.

RESULTS

All StART conditions differed (P ≤ .03), except single-task standing versus single-task single-legged balance (P = .36). Every 1-year age increase was associated with an 18-millisecond (95% CI = 8, 27 milliseconds) slower single-task cutting RT (P < .001). Female athletes had slower single-task (15 milliseconds; 95% CI = 2, 28 milliseconds; P = .02) and dual-task (28 milliseconds; 95% CI = 2, 55 milliseconds; P = .03) standing RT than male athletes. No other demographic or health history factors were associated with any StART condition (P ≥ .056).

CONCLUSIONS

The StART outcomes were unique across each cognitive-motor combination, suggesting minimal subtest redundancy. Only age and sex were associated with select outcomes. The StART composite scores may minimize confounding factors, but future researchers should consider age and sex when providing normative data.

Postconcussion Exercise Volume Associations With Depression, Anxiety, and Dizziness Symptoms, and Postural Stability: Preliminary Findings

OBJECTIVE

To examine the association between postconcussion exercise volume and changes in depression, anxiety, dizziness, and postural stability.

DESIGN

Secondary analysis of a single-site prospective clinical trial.

SETTING

Cerebrovascular research laboratory.

PARTICIPANTS

Participants completed questionnaires and underwent tests of gait and balance within 2 weeks of a concussion (mean = 11 ± 3 days postconcussion) and approximately 1 month later (mean = 41 ± 7 days postconcussion). Exercise volume was tracked by weekly exercise logs.

INTERVENTIONS

On the basis of a previous work classifying exercise volume following concussion, we grouped participants according to self-reported exercise volume between visits as high exercise volume (≥150 min/wk) or low exercise volume (<150 min/wk).

MAIN OUTCOME MEASURES

Participants completed assessments evaluating anxiety and depression (Hospital Anxiety and Depression Scale), dizziness (Dizziness Handicap Inventory), and postural stability (tandem gait and modified Balance Error Scoring System).

RESULTS

Thirty-eight participants completed the study, of which 22 were in the high exercise volume group (mean = 71 ± 40 min/wk; 16.8 ± 2.1 years; 59% female) and 16 were in the low exercise volume group (mean = 379 ± 187 min/wk; 17.5 ± 2.1 years; 31% female). Although depression symptoms were not significantly different initially (mean difference = 1.5; 95% CI, -0.68 to 3.68; P = .24), the high exercise volume group had significantly lower depression symptom scores at follow-up (mean difference = 3.0; 95% CI, 1.40 to 4.47; P < .001). Anxiety symptoms (mean difference = 2.8; 95% CI, 0.3 to 5.4; P = 0.03), dizziness symptoms (mean difference = 10.9; 95% CI, 0.2 to 21.5; P = .047), single-task tandem gait (mean difference = 3.1 seconds; 95% CI, 0.2 to 6.0; P = .04), and dual-task tandem gait (mean difference = 4.2 seconds; 95% CI, 0.2 to 8.2; P = .04) were significantly better among the high exercise volume group.

CONCLUSION

Greater exercise volumes were associated with lower depression, anxiety, and dizziness symptoms, and faster tandem gait performance. These preliminary findings suggest a potentially beneficial role for exercise within several different domains commonly affected by concussion.

Association Between Collision Sport Career Duration and Gait Performance in Male Collegiate Student-Athletes

BACKGROUND

Investigations of estimated age of first exposure to repetitive head impacts from collision and contact sports have shown no associations with neurocognitive or neurobehavioral function at the collegiate level, but the effect of career duration may be a more comprehensive factor. Understanding whether longer career duration influences gait performance would provide insights into potential neurological impairment.

PURPOSE

To examine the relationship between career duration of collision sports and single/dual-task gait performance in collegiate student-athletes.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We recruited 168 male student-athletes from collision sports: football, lacrosse, ice hockey, and wrestling (mean ± SD age, 19.2 ± 1.3 years; height, 184.5 ± 7.2 cm; mass, 94.3 ± 15.9 kg; estimated age of first exposure, 8.6 ± 3.1 years; career duration, 10.6 ± 3.0 years). All participants completed a baseline single- and dual-task gait assessment before the start of their athletic season. Inertial measurement units were used to measure gait speed and stride length. During the dual task, participants were asked to perform working memory cognitive tasks while walking. The dependent variables were single/dual-task gait speed and stride length, cognitive accuracy, and dual-task cost. The relationship between career duration, analyzed as a continuous variable, and the dependent variables was analyzed using a linear regression.

RESULTS

There were no significant associations between career duration and single-task gait speed (1.16 ± 0.16 m/s; β = -0.004; P = .35; 95% CI = -0.012 to 0.004; η² = 0.005) or dual-task gait speed (1.02 ± 0.17 m/s; β = -0.003; P = .57; 95% CI = -0.011 to 0.006; η² = 0.002). There were also no significant associations between career duration and single/dual-task stride length, cognitive accuracy, or dual-task cost.

CONCLUSION

Career duration among collegiate collision sport athletes was not associated with single- or dual-task gait performance, suggesting that a greater exposure to repetitive head impacts is not detrimental to dynamic postural control at the college level. However, the effects of diminished gait performance over the lifetime remain to be elucidated.

Neurocognitive functioning and symptoms across levels of collision and contact in male high school athletes

OBJECTIVE

We sought to determine whether male collision sport athletes perform worse on computerised neurocognitive assessments and report higher symptom burdens than athletes in contact (but not collision) sports and athletes in non-contact sports.

METHODS

This cross-sectional study used data collected by the Massachusetts Concussion Management Coalition on high school boys who underwent computerised neurocognitive testing between 2009 and 2018. We divided sports participation in three different sport types: (1) collision, (2) contact, non-collision and (3) non-contact. Our outcomes included the four computerised neurocognitive composite scores (verbal memory, visual memory, visual motor speed and reaction time) and the total symptom score. The independent variable was sport type (collision, contact, non-contact), adjusted for age, concussion history and comorbidities.

RESULTS

Of the 92 979 athletes (age: 15.59±2.08 years) included in our study, collision sport athletes performed minimally but significantly worse than other athletes on neurocognitive composite scores (verbal memory: β=-1.64, 95% CI -1.85 to -1.44; visual memory: β=-1.87, 95% CI -2.14 to -1.60; visual motor speed: β=-2.12, 95% CI -2.26 to -1.97; reaction time: β=0.02, 95% CI 0.02 to 0.02). Collision and contact sport athletes also had slightly but significantly lower total symptom scores (collision: 3.99±7.17; contact: 3.78±6.81; non-contact: 4.32±7.51, p<0.001, η2=0.001) than non-contact sport athletes.

CONCLUSION

There are minimal observed differences in performance on neurocognitive assessments between collision sport, contact sport and non-contact sport athletes. The repetitive subconcussive head impacts associated with collision sport participation do not appear to negatively affect self-reported symptoms or neurocognitive functioning in current youth athletes.

Single-Task and Dual-Task Tandem Gait Performance Across Clinical Concussion Milestones in Collegiate Student-Athletes

OBJECTIVE

To determine the length of time after concussion that impaired tandem gait performance is observed.

DESIGN

Clinical measurement, prospective longitudinal.

SETTING

NCAA collegiate athletic facility.

PARTICIPANTS

Eighty-eight concussed NCAA Division I student-athletes and 30 healthy controls.

INDEPENDENT VARIABLES

Group (concussion/control) and time (Baseline, Acute, Asymptomatic, and RTP).

MAIN OUTCOME MEASURES

Participants completed 4 single-task and dual-task tandem gait trials. The concussion group completed tests at the following time points: preseason (Baseline), within 48 hours after concussion (Acute), on the day symptoms were no longer reported (Asymptomatic), and when cleared to return to sports (RTP). Controls completed the same protocol at similar intervals. The dual-task trials involved minimental style cognitive questions answered simultaneously during tandem gait. We analyzed the best time of the 4 trials, comparing groups with a linear mixed model.

RESULTS

Acutely after concussion, the concussion group performed single-task tandem gait slower (worse) than controls (concussion: 11.36 ± 2.43 seconds, controls: 9.07 ± 1.78 seconds, P < 0.001). The concussion group remained significantly slower than controls (9.95 ± 2.21 vs 8.89 ± 1.65 seconds, P = 0.03) at Asymptomatic day but not RTP. There were significant group (P < 0.001) and time (P < 0.001) effects for dual-task tandem gait. The groups were not significantly different at baseline for single-task (P = 0.95) or dual-task (P = 0.22) tandem gait.

CONCLUSIONS

Our results indicate that tandem gait performance is significantly impaired acutely after concussion, compared with both preseason measures and controls. Postural control impairments were not present when the student-athletes were cleared for RTP. This information can assist clinicians when assessing postural control and determining recovery after a concussive injury.

The Association between Baseline Eye Tracking Performance and Concussion Assessments in High School Football Players

SIGNIFICANCE

Concussions are complex injuries that require a multifaceted testing battery. Vision impairments are common after concussion, but it is unknown exactly how eye tracking may be affected after injury and how it is associated with other clinical concussion assessments.

PURPOSE

This study aimed to (1) examine the relationship between eye tracking performance (BOX score) and other common concussion evaluations, (2) identify if eye tracking adds novel information that augments baseline concussion evaluations, and (3) examine the effect of age, concussion history, and attention-deficit/hyperactivity disorder on eye tracking and other ophthalmological measures.

METHODS

A total of 102 male high school football athletes (age, 16.0 years; 95% confidence interval, 15.8 to 16.2 years) completed a series of visual and neurocognitive tests during their pre-season baseline assessment. The main outcome measures were BOX score, near point of convergence (NPC) distance, binocular accommodative amplitude (BAA) distance, Standardized Assessment of Concussion score, and Immediate Post-Concussion Assessment and Cognitive Testing composite scores.

RESULTS

BOX score was not significantly associated with symptoms, Standardized Assessment of Concussion score, NPC distance, BAA distance, or any Immediate Post-Concussion Assessment and Cognitive Testing composite scores. Age, concussion history, attention-deficit/hyperactivity disorder, and number of prior years playing football were not significantly associated with BOX score or NPC distance, but there was a significant association between concussion history and greater BAA distance (β = 1.60; 95% confidence interval = 0.19 to 3.01; P < .03). The BOX score cutoff of 10 resulted in a 12% false-positive rate.

CONCLUSIONS

Eye tracking was not significantly associated with the commonly used clinical concussion assessments. These results suggest that an objective eye tracking variable may be a valuable addition to the current concussion battery.

Gait Performance Is Associated with Subsequent Lower Extremity Injury following Concussion

PURPOSE

The purpose was to examine gait characteristics between collegiate athletes who did and did not sustain a lower-extremity musculoskeletal (LEMSK) injury in the year after concussion.

METHODS

Thirty-four NCAA collegiate athletes with diagnosed concussions were divided into two groups based on if they did (n = 16) or did not (n = 18) sustain a LEMSK in the year after concussion. Participants completed baseline testing before the start of the season and again at return to play postconcussion. Injuries were tracked using an electronic medical database. Participants were instrumented with three APDM Opal triaxial accelerometers and performed five single-task (ST) and five dual-task (DT) gait trials. Participants traversed a 10-meter walkway, turned around a specified endpoint, and returned to the original line. During DT, participants simultaneously walked and answered mini-mental style questions. A linear mixed-effects model assessed interactions and/or main effects between groups for gait speed, double support time, cadence, stride length, and cognitive accuracy.

RESULTS

The LEMSK group walked slower (ST, 1.15 ± 0.10 m·s; DT, 1.01 ± 0.10 m·s) than the uninjured group (ST, 1.23 ± 0.11 m·s; DT, 1.10 ± 0.11 m·s) during both ST (P = 0.04) and DT (P = 0.03). The injury group spent longer in double support (ST, 20.19% ± 2.34%; DT, 21.92% ± 2.13%) than the uninjured group (ST, 18.16% ± 2.60%; DT, 20.00% ± 2.32%) during both ST (P = 0.02) and DT (P = 0.02). The injury group had a significantly lower cognitive accuracy (89.56% ± 6.48%) than the uninjured group (95.40% ± 7.08%) across time points (P = 0.02).

CONCLUSIONS

There were significant differences in gait characteristics and cognitive accuracy between those who did and did not sustain a LEMSK injury after concussion. The LEMSK group demonstrated a conservative gait strategy both before and after their concussive injury.

Impaired eye tracking is associated with symptom severity but not dynamic postural control in adolescents following concussion

PURPOSE

The purpose of the study was to (1) examine the relationship between self-reported symptoms and concussion-related eye tracking impairments, and (2) compare gait performance between (a) adolescents with a concussion who have normal eye tracking, (b) adolescents with a concussion who have abnormal eye tracking, and (c) healthy controls.

METHODS

A total of 30 concussed participants (age: 14.4 ± 2.2 years, mean ± SD, 50% female) and 30 controls (age: 14.2 ± 2.2 years, 47% female) completed eye tracking and gait assessments. The BOX score is a metric of pupillary disconjugacy, with scores <10 classified as normal and ≥10 abnormal. Symptoms were collected using the Post-Concussion Symptom Scale (PCSS), and gait speed was measured with triaxial inertial measurement units. We conducted a linear regression to examine the relationship between PCSS and BOX scores and a two-way mixed effects analysis of variance to examine the effect of group (abnormal BOX, normal BOX, and healthy control) on single- and dual-task gait speed.

RESULTS

There was a significant association between total PCSS score and BOX score in the concussion group (β = 0.16, p = 0.004, 95% confidence interval (95%CI): 0.06‒0.27), but not in the control group (β = 0.21, p = 0.08, 95%CI: -0.03 to 0.45). There were no significant associations between PCSS symptom profiles and BOX scores in the concussion or control groups. There were also no significant differences in single-task (Abnormal: 1.00 ± 0.14 m/s; Normal: 1.11 ± 0.21 m/s; Healthy: 1.14 ± 0.18 m/s; p = 0.08) or dual-task (Abnormal: 0.77 ± 0.15 m/s; Normal: 0.84 ± 0.21 m/s; Healthy: 0.90 ± 0.18 m/s; p = 0.16) gait speed.

CONCLUSION

The concussed group with impaired eye tracking reported higher total symptom severity, as well as worse symptom severity across the 5 PCSS symptom domain profiles. However, eye tracking deficits did not appear to be driven by any particular symptom domain. While not statistically significant, the slower gait speeds in those with abnormal BOX scores may still be clinically relevant since gait-related impairments may persist beyond clinical recovery.

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.

Estimated age of first exposure to American football and outcome from concussion

OBJECTIVE

To examine the association between estimated age at first exposure (eAFE) to American football and clinical measures throughout recovery following concussion.

METHODS

Participants were recruited across 30 colleges and universities as part of the National Collegiate Athletic Association (NCAA)-Department of Defense Concussion Assessment, Research and Education Consortium. There were 294 NCAA American football players (age 19 ± 1 years) evaluated 24-48 hours following concussion with valid baseline data and 327 (age 19 ± 1 years) evaluated at the time they were asymptomatic with valid baseline data. Participants sustained a medically diagnosed concussion between baseline testing and postconcussion assessments. Outcome measures included the number of days until asymptomatic, Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) composite scores, Balance Error Scoring System (BESS) total score, and Brief Symptom Inventory 18 (BSI-18) subscores. The eAFE was defined as participant's age at the time of assessment minus self-reported number of years playing football.

RESULTS

In unadjusted regression models, younger eAFE was associated with lower (worse) ImPACT Visual Motor Speed (R ² = 0.031, p = 0.012) at 24-48 hours following injury and lower (better) BSI-18 Somatization subscores (R ² = 0.014, p = 0.038) when the athletes were asymptomatic. The effect sizes were very small. The eAFE was not associated with the number of days until asymptomatic, other ImPACT composite scores, BESS total score, or other BSI-18 subscores.

CONCLUSION

Earlier eAFE to American football was not associated with longer symptom recovery, worse balance, worse cognitive performance, or greater psychological distress following concussion. In these NCAA football players, longer duration of exposure to football during childhood and adolescence appears to be unrelated to clinical recovery following concussion.

Impairments in Dynamic Postural Control across Concussion Clinical Milestones

The aim of this study was to assess gait initiation (GI) performance longitudinally across clinical concussion recovery milestones through return to participation (RTP). We recruited 54 collegiate student-athletes, 27 with concussions and 27 matched controls (15 female and 12 male per group). Participants performed five trials of GI at baseline and again at five post-concussion clinical milestones: 1) Acute, the day clinical tests achieved baseline values on the 2) Balance Error Scoring System (BESS), 3) Immediate Post-Concussion Assessment and Cognitive Test ImPACT, 4) Asymptomatic, and 5) RTP Day. GI performance on six outcome measures (anterior/posterior and medial/lateral center of pressure displacements and velocities during the anticipatory postural adjustment [APA] phase and initial step length and velocity) with repeated-measures mixed model and pair-wise post hoc. A reliable change index (RCI) was calculated, and post-concussion participant's performance was compared to the RCI at milestones. There were significant interactions for APA posterior and lateral displacement, APA posterior velocity, step length, and step velocity. The post-hoc tests identified significant deficits across clinical milestones and at RTP for APA posterior and lateral displacement, step length, and step velocity. There were no post-hoc differences for any outcome measure in the control group. At RTP, 85.2-88.9% of concussion participants had at least one outcome measure which exceeded the 80% or 95% RCI. The primary finding of this study was persistent impairments in dynamic postural control, suggesting ongoing neurophysiological impairment despite clinical recovery. These results suggest that collegiate student-athletes may be RTP before neurophysiological recovery and potentially exposing themselves to elevated risk of recurrent concussion or subsequent musculoskeletal injury.

Differential Effects of Acute and Multiple Concussions on Gait Initiation Performance

OBJECTIVE

To identify the effect of acute and multiple concussions on gait initiation performance.

DESIGN

Cohort study.

SETTING

University research center.

PARTICIPANTS

A population-based sample of participants (N=45) divided into 3 groups: No Prior Concussion, ≥3 Prior Concussions, and Acute Concussion. The Acute Concussion participants were assessed within 24 hours of their concussion. Participants were matched based on (1) sport, (2) position, and (3) anthropometric measures.

INTERVENTIONS

Participants were tested on a single occasion and performed 5 trials of gait initiation on 4 force plates. The No Prior Concussion and ≥3 Prior Concussions groups were tested out of their primary athletic season.

MAIN OUTCOME MEASURES

The dependent variables were the posterior and lateral displacement and velocity of the center of pressure (COP) during the anticipatory postural adjustment phase and initial step kinematics (step length and step velocity). Comparisons between groups used a 1-way analysis of variance with Tukey post hoc when significant effects were identified and effect sizes were calculated.

RESULTS

There were significant effects for group for all 6 outcome measures with large effect sizes. Post hoc tests identified differences between Acute Concussion and No Prior Concussion groups for all measures. The ≥3 Prior Concussions group and No Prior Concussion group were different for COP posterior displacement (4.91±1.09 and 4.91±1.09cm, respectively, P=.032, d=0.91) and velocity (0.18±0.06 and 0.27±0.08m/s, respectively, P=.002, d=1.27).

CONCLUSION

There was continuum of performance identified whereby the Acute Concussion participants performed worse and the No Prior Concussion participants performed the best. The ≥3 Prior Concussions generally fell between these 2 groups, but only statistical significance on COP posterior displacement and velocity. These results suggest there may be subtle neurophysiological deficits present in collegiate student-athletes with ≥3 Prior Concussions group, and further investigation over the lifespan is warranted.

No differences in tandem gait performance between male and female athletes acutely post-concussion

OBJECTIVES

To test whether 1) concussed athletes demonstrate slower tandem gait times compared to controls and 2) concussed female athletes display greater post-injury deficits than males.

DESIGN

Prospective longitudinal METHOD: Fifty concussed collegiate student-athletes (32% female, age=20.18±1.27 years) completed tandem gait tests during pre-season (Time 1) and acutely (<72hours) post-concussion (Time 2), and twenty-five controls (52% female, age=21.08±2.22 years) completed tandem gait at two time points, 1.96±0.46 days apart. Participants completed four single-task (ST) and dual-task (DT) trials. During DT trials, they simultaneously completed a cognitive assessment. The best ST and DT times were recorded, along with cognitive accuracy, and the change score between the two assessments was calculated. A positive change in tandem gait time was indicative of worsening performance. A 2×2 (group*sex) ANOVA was used to examine change between pre-injury and post-injury tests for ST/DT tandem gait time and DT cognitive accuracy.

RESULTS

The change in tandem gait time from Time 1 to Time 2 was significantly higher for the concussion group relative to controls during both ST (Concussion: 1.36±2.6 seconds, Controls: -1.16±0.8 seconds, p<0.001) and DT (Concussion: 1.70±3.8 seconds, Controls: -0.94±1.7 seconds, p=0.002) tandem gait. There were no interactions or main effects of sex for tandem gait time or cognitive accuracy.

CONCLUSIONS

There were no sex-specific differences in the change in tandem gait performance among concussed collegiate athletes or controls. However, all concussed participants, regardless of sex, performed significantly worse on tandem gait than male and female controls, who both improved between testing time points.

Exercise in the first week following concussion among collegiate athletes: Preliminary findings

OBJECTIVES

Our purpose was to examine the association between exercise after concussion with symptom severity, postural control, and time to symptom-resolution.

DESIGN

Longitudinal cohort.

METHODS

Collegiate athletes (n = 72; age = 20.2 ± 1.3 years; 46% female) with concussion completed a symptom questionnaire at initial (0.6 ± 0.8 days post-injury) and follow-up (2.9 ± 1.4 days post-injury) evaluations, and a postural control assessment at follow-up. Participants were grouped into those who exercised in between the time of injury and the follow-up evaluation and those who did not. Decisions regarding post-concussion exercise were made by a sports medicine team consisting of a single team physician and athletic trainers.

RESULTS

Thirteen athletes were not included in the current study, resulting in an 85% response rate. Thirteen of the athletes who completed the study exercised between evaluations (18%). There was no symptom resolution time difference between groups (median = 13 [IQR = 7-18] days vs. 13 [7-23] days; p = 0.83). Symptom ratings were similar between groups at the acute post-injury assessment (median PCSS = 18.5 [7.5-26] vs. 17 [14-40]; p = 0.21), but a main effect of group after adjusting for time from injury to assessment indicated the exercise group reported lower symptom severity than the no exercise group across both assessments (p = 0.044). The dual-task gait speed of the exercise group was higher than the no exercise group (0.90 ± 0.15 vs. 0.78 ± 0.16 m/s; p = 0.02).

CONCLUSIONS

Athletes who were recommended aerobic exercise after concussion did not have worse outcomes than those who were not. Exercise within the first week after concussion does not appear to be associated with detrimental clinical outcomes.

Repetitive Head Impacts in Football Do Not Impair Dynamic Postural Control

PURPOSE

The purpose of this study was to assess the effect of repetitive head impacts experienced by football players compared to noncontact athletes on dynamic postural control during both single-task (ST) and dual-task (DT) conditions.

METHODS

Thirty-four football players wearing accelerometer instrumented helmets and 13 cheerleaders performed a dynamic postural control battery, consisting of ST and DT gait initiation, gait, and gait termination, both prior to and following the football season. A 2 (group) × 2 (time) repeated measures ANOVA compared performance across 32 dynamic postural outcomes. A linear regression was performed on postural control change scores with common head impact kinematics serving as the independent variables.

RESULTS

The football players experienced a mean of 538.1 ± 409.1 head impacts in the season with a mean linear acceleration of 27.8g ± 3.2g. There were no significant interactions for any of the ST or DT dynamic postural control tasks. There was a significant relationship between head impact kinematics and the lateral center of pressure displacement during the anticipatory postural adjustment phase (r = 0.26, P = 0.010) and transitional phase (r = 0.511, P = 0.042) during ST gait initiation. For both measures, the number of impacts exceeding 98g was the only significant predictor of decreased center of pressure displacement.

CONCLUSIONS

A single competitive football season did not adversely affect dynamic postural control when comparing football players to cheerleaders who do not experience repetitive head impacts. Furthermore, there were limited relationships with head impact kinematics suggesting that a single season of football does not adversely affect most outcome measures of instrumented dynamic postural control. These findings are consistent with most studies which fail to identify clinical differences related to repetitive head impacts.

Trouble Falling Asleep After Concussion Is Associated With Higher Symptom Burden Among Children and Adolescents

Our objective was to identify factors associated with trouble falling asleep postconcussion. Patients seen for care after sport-related concussion were assessed ≤10 days postinjury and were between 6 and 19 years of age. Outcomes included symptoms (Post-Concussion Symptom Scale), postural steadiness, missed school, and medical history. There were 261 patients (49% female; mean age=14.8±2.5 years): 45% reported trouble falling asleep. A greater proportion of patients who reported trouble falling asleep missed ≥2 days of school (64% vs 49%; P = .02). Patients who reported trouble falling asleep endorsed more severe symptom severity than those who did not (median=38 vs 18; P < .001). After covariate adjustment, confusion (aOR = 1.95, 95% CI = 1.131-3.375), missing ≥2 days of school (aOR = 4.52, 95% CI = 1.553-13.16), and noise sensitivity (aOR = 1.48, 95% CI = 1.1.042-2.010) were independently associated with trouble falling asleep. Sleep disturbances are associated with poorer clinical outcomes after concussion. Inclusion of sleep assessments may help to provide early therapeutic pathways for pediatric concussion patients.

Efficacy of Tandem Gait to Identify Impaired Postural Control after Concussion

PURPOSE

The purpose was to evaluate tandem gait (TG), Balance Error Scoring System (BESS), and modified Balance Error Scoring System (mBESS) performance acutely after concussion in collegiate student-athletes. In addition, we sought to evaluate the psychometric properties of TG, including minimal detectable change (MDC), sensitivity, and specificity.

METHODS

Seventy-six National Collegiate Athletic Association student-athletes performed TG and BESS tests: 38 acutely after concussion and 38 controls. Participants were tested at baseline (time 1) and again acutely after concussion, or the following year for controls (time 2). Ten controls, tested simultaneously by two researchers, established a TG interrater minimal detectable change. A 2 × 2 mixed-design ANOVA compared each outcome variable. An receiver operating characteristic curve analysis was used to evaluate sensitivity, specificity, and area under the curve (AUC).

RESULT

There was a significant interaction (F = 8.757, P = 0.004) for TG whereby the concussion group was slower after concussion (10.59 ± 1.53 vs 11.80 ± 2.67 s), whereas there was no difference for controls (10.13 ± 1.72 vs 9.93 ± 1.85 s). There was no significant interaction for BESS (F = 0.235, P = 0.630) or mBESS (F = 0.007, P = 0.935). TG had a sensitivity of 0.632, a specificity of 0.605, and an AUC of 0.704. BESS had a sensitivity of 0.447, a specificity of 0.500, and an AUC of 0.508. mBESS had a sensitivity of 0.474, a specificity of 0.632, and an AUC of 0.535.

CONCLUSIONS

Participants completed TG significantly slower after concussion, whereas no change across time was detected for controls. In contrast, BESS and mBESS performances were similar at both testing times in both groups. Our AUC analysis was acceptable for TG, but a failure for both BESS and mBESS; thus, TG may be a useful alternative for clinicians conducting postconcussion postural control assessments.

Decreased Anticipatory Postural Adjustments During Gait Initiation Acutely Postconcussion

OBJECTIVE

To investigate anticipatory postural adjustments (APAs) during the transitional movement task of gait initiation (GI) in individuals acutely after a concussion.

DESIGN

Cohort study.

SETTING

University research center.

PARTICIPANTS

A population-based sample of participants (N=84) divided into 2 equal groups of acutely postconcussion and healthy student athletes.

INTERVENTION

Participants were tested on 2 occasions: a preinjury baseline test and then the concussion group was retested acutely postconcussion and the healthy student athlete group again at a similar time. All participants completed 5 trials of GI on 4 forceplates.

MAIN OUTCOME MEASURES

The dependent variables were the displacement and velocity of the center of pressure (COP) during the APA phase and initial step kinematics. Comparisons were made with a 2 (group) × 2 (time) repeated-measures analysis of variance.

RESULTS

There was a significant interaction for COP posterior displacement (P<.001) and lateral displacement (P<.001). Posteriorly, post hoc testing identified a significant reduction in the concussion group (pretest: 5.7±1.6cm; posttest: 2.6±2.1cm; P<.001), but no difference in the healthy student athlete group (pretest: 4.0±1.6cm; posttest: 4.0±2.5cm; P=.921). Laterally, post hoc testing identified a significant reduction in the concussion group (pretest: 5.8±2.1cm; posttest: 3.8±1.8cm; P<.001), but no difference in the healthy student athlete group (pretest: 5.0±2.5cm; posttest: 5.2±2.4cm; P=.485).

CONCLUSIONS

The results of this study suggest difficulty in the planning and execution of GI acutely postconcussion, and posterior APA displacement and velocity are highly effective measures of impaired postural control. Finally, the APA phase is linked to the supplementary motor area, which suggests a supraspinal contribution to postconcussion impaired postural control.

Evidence of a conservative gait strategy in athletes with a history of concussions

BACKGROUND

A history of 3 or more concussions is frequently associated with numerous short- and long-term neuropathologies. Impairments in postural control are a known acute consequence of concussion; however, limited evidence exists on the effects of multiple concussions on gait. The purpose of this study was to assess gait stepping characteristics in collegiate aged student-athletes based on concussion history.

METHODS

There were 63 participants divided into 3 even groups based on concussion history: ≥3 concussions, 1-2 concussions, and 0 concussion. All participants completed 10 trials of gait on a 4.9 m instrumented walkway. The dependent variables of interest included both gait stepping characteristics (step velocity, length, and width, double support time, and the percentage of the gait cycle in stance) and coefficient of variability (CoV) measures (step length, time, and width). The gait stepping characteristics were compared first with a MANOVA with follow-up 1-way ANOVAs and Tukey post hoc tests as appropriate. The CoV measures were compared with 1-way ANOVAs and Tukey post hoc tests.

RESULTS

There were main effects for group for step velocity, length, width, and double support time. Overall, the 0 concussion group displayed typical healthy young gait parameters and performed significantly better than either concussion group. The 0 concussion group had a significantly greater step length CoV, but there were no differences in the step time or width CoV.

CONCLUSION

This finding provides evidence of subtle impairments in postural control during gait among individuals with prior history of concussion which could be an early indicator of future neurological deficiencies. The limited difference in the variability measures is consistent with prior static stance studies and could suggest the individuals constrain their motor systems to reduce variability. Taken together, these findings suggest a conservative gait strategy which is adopted by individuals with a history of concussions.

Normative Tandem Gait in Collegiate Student-Athletes: Implications for Clinical Concussion Assessment

BACKGROUND

Impaired balance is common after concussion. The third edition of the Sport Concussion Assessment Tool (SCAT-3) recommends the Balance Error Scoring System (BESS) and/or tandem gait for postconcussion balance assessment. The limitations of the BESS are well documented; however, tandem gait has received little attention throughout concussion literature. The purpose of this study was to provide normative data for tandem gait in collegiate student-athletes based on sport type, concussion history, and gender.

HYPOTHESIS

Tandem gait will be influenced by concussion history, sport, and gender.

STUDY DESIGN

Cohort study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Four hundred collegiate student-athletes from both collision/contact (n = 200) and limited contact/noncontact (n = 200) sports performed 4 tandem gait trials, consistent with SCAT-3 guidelines. The dependent variables included the best of the 4 trials (BEST), the mean of the 4 trials (MEAN), and the mean of each of the trials individually (ORDER). Separate multivariate analyses of variance were performed for each of the independent variables to determine effect on BEST and MEAN trial times. Significant main effects were followed up with a 1-way analysis of variance (ANOVA). A separate 1-way ANOVA was used to assess ORDER differences.

RESULTS

The mean BEST was 10.37 ± 1.76 seconds, and the MEAN was 11.32 ± 0.70 seconds. There were no significant differences in BEST or MEAN tandem gait times, respectively, between those with and without concussion history ( P = 0.41 and P = 0.69, respectively), sport type ( P = 0.57 and P = 0.42, respectively), or gender ( P = 0.73 and P = 0.49, respectively). There were significant differences ( P < 0.05) between ORDER of the 4 tandem gait trials across the population, with improved times at each trial.

CONCLUSION

The results of this study provide a normative data set for tandem gait in healthy collegiate student-athletes and suggest that common determinants of balance, including concussion history, collision sport participation, and gender do not appear to influence performance, but ORDER could have significant clinical implications.

CLINICAL RELEVANCE

Clinicians may use these data to distinguish important determinants of tandem gait performance and improve awareness when returning an individual to play after a concussion.

Altered dynamic postural control during gait termination following concussion

Impaired postural control is a cardinal symptom following concussion. Planned gait termination (GT) is a non-novel, dynamic task that challenges postural control in individuals with neurological deficits, and it could be an impactful measure for identifying dynamic postural control impairments following concussion. Therefore, the purpose of this study was to assess acute post-concussion dynamic postural control utilizing a planned GT task. The concussion participants (n=19, age: 19.0±0.8years, height: 177.0±10.1cm, weight: 83.3±20.0kg) completed five planned GT trials during preseason baseline testing (Baseline) and on Day 1 post-concussion (Day-1). Healthy control participants (n=19, age: 20.4±1.2years, height: 173.8±8.9cm, weight: 80.2±17.6kg) completed the same trials a week apart. The dependent variables of interest included COP displacement and velocity in the mediolateral (ML) and anteroposterior (AP) axes during the three phases (braking, transitional, stabilization) of planned GT. There were significant interactions observed in both the braking ML and transitional AP displacement (p=0.042, p=0.030) and velocity (p=0.027, p=0.030). These results suggest a conservative post-concussion motor control strategy during planned GT. Further, these results support the use of dynamic postural control tasks as measures of post-concussion impairments.

Postural control deficits identify lingering post-concussion neurological deficits

Concussion, or mild traumatic brain injury, incidence rates have reached epidemic levels and impaired postural control is a cardinal symptom. The purpose of this review is to provide an overview of the linear and non-linear assessments of post-concussion postural control. The current acute evaluation for concussion utilizes the subjective balance error scoring system (BESS) to assess postural control. While the sensitivity of the overall test battery is high, the sensitivity of the BESS is unacceptably low and, with repeat administration, is unable to accurately identify recovery. Sophisticated measures of postural control, utilizing traditional linear assessments, have identified impairments in postural control well beyond BESS recovery. Both assessments of quiet stance and gait have identified lingering impairments for at least 1 month post-concussion. Recently, the application of non-linear metrics to concussion recovery have begun to receive limited attention with the most commonly utilized metric being approximate entropy (ApEn). ApEn, most commonly in the medial-lateral plane, has successfully identified impaired postural control in the acute post-concussion timeframe even when linear assessments of instrumented measures are equivalent to healthy pre-injury values; unfortunately these studies have not gone beyond the acute phase of recovery. One study has identified lingering deficits in postural control, utilizing Shannon and Renyi entropy metrics, which persist at least through clinical recovery and return to participation. Finally, limited evidence from two studies suggest that individuals with a previous history of a single concussion, even months or years prior, may display altered ApEn metrics. Overall, non-linear metrics provide a fertile area for future study to further the understanding of postural control impairments acutely post-concussion and address the current challenge of sensitive identification of recovery.

Effects of dietary fat and season on steroid hormonal profiles before parturition and on hormonal, cholesterol, triglycerides, follicular patterns, and postpartum reproduction in Brahman cows

Spring-calving Brahman cows (S) artificially inseminated to Brahman, Angus, or Tuli sires and fall-calving Brahman cows (F) naturally bred to Brahman were allotted randomly to receive 3.74% (LF; n = 9 S and 6 F), 5.20% (MF; n = 8 S and 6 F), or 6.55% dietary fat (HF; n = 8 S). Diets were formulated to contain differing fatty acid concentrations and to be isocaloric and isonitrogenous. Cows were bled and fed twice daily from 2 wk before expected calving date through d 21 after calving. Ultrasonography was performed on d 14 and 21 after calving. From d 21 to 90 after calving a sterile bull equipped with a chin-ball marker was placed with the cows to aid in estrus detection. In both seasons progesterone decreased (P < .01) and estradiol-17 beta increased (P < .01) as parturition approached. Cows receiving MF and HF had increased (P < .01) total numbers of follicles compared to LF cows, and cows receiving MF had larger (P < .01) follicles. During the spring, cows receiving HF and cows bred to Brahman or Tuli sires had longer (P < .01) gestation lengths. Progesterone concentrations before calving were affected (P < .01) by treatment x sire and estradiol-17 beta by a time x treatment interaction (P < .01). Cholesterol after calving was higher (P < .01) in HF cows than in LF or MF cows. In the fall, LF cows had heavier (P < .01) calves than cows receiving MF. Birth weight was also affected (P < .01) by treatment x sex of calf. Progesterone was affected (P < .01) by treatment x sex of calf. Estradiol-17 beta was affected (P < .01) by sex of calf and treatment x sex of calf. Across seasons, by d 90 after calving, 9 of 15 (60%) LF and 11 of 15 (73.3%) MF cows showed estrual behavior. Cows in the spring had increased (P < .01) numbers and larger follicles compared to the fall. In conclusion, dietary fat may influence steroid hormone concentrations before calving, calf birth weight and postpartum follicular populations; furthermore, follicular populations may also be influenced by season.