Examining the Dynamic Nature of Anterior Cruciate Ligament Injury Risk Factors in Women's Collegiate Soccer.

CONTEXT: Anterior cruciate ligament (ACL) injuries are a common and devastating injury in women's soccer. Several risk factors for ACL injury have been identified, but have not yet been examined as potentially dynamic risk factors, which may change throughout a collegiate soccer season. DESIGN: Prospective cohort study. METHODS: Nine common clinical screening assessments for ACL injury risk, consisting of range of motion, movement quality, and power, were assessed in 29 Division I collegiate women's soccer players. Preseason and midseason values were compared for significant differences. Change scores for each risk factor were also correlated with cumulative training loads during the first 10 weeks of a competitive soccer season. RESULTS: Hip external rotation range of motion and power had statistically significant and meaningful differences at midseason compared with preseason, indicating they are dynamic risk factors. There were no significant associations between the observed risk factor changes and cumulative training load. CONCLUSIONS: Hip external rotation range of motion and power are dynamic risk factors for ACL injury in women's collegiate soccer athletes. Serial screening of these risk factors may elucidate stronger associations with injury risk and improve prognostic accuracy of screening tools.

Epidemiology of Cervical Muscle Strains in Collegiate and High School Football Athletes, 2011-2012 Through 2013-2014 Academic Years.

CONTEXT: Cervical muscle strains are an often-overlooked injury, with neck- and spine-related research typically focusing on spinal cord and vertebral injuries. OBJECTIVE: To examine the rates and distributions of cervical muscle strains in collegiate and high school football athletes. DESIGN: Descriptive epidemiology study. SETTING: Collegiate and high school football teams. PATIENTS OR OTHER PARTICIPANTS: The National Collegiate Athletic Association Injury Surveillance Program (NCAA-ISP) collected data from collegiate football athletes. The High School National Athletic Treatment, Injury and Outcomes Network (HS NATION) and High School Reporting Information Online (HS RIO) collected data from high school football athletes. Data from the 2011-2012 through 2013-2014 academic years were used. MAIN OUTCOME MEASURE(S): Athletic trainers collected injury and exposure data for football players. Injury counts, injury rates per 10 000 athlete-exposures (AEs), and injury rate ratios with 95% confidence intervals (CIs) were calculated. RESULTS: The NCAA-ISP reported 49 cervical muscle strains (rate = 0.96/10 000 AEs), of which 28 (57.1%) were TL (time loss; rate = 0.55/10 000 AEs). High School NATION reported 184 cervical muscle strains (rate = 1.66/10 000 AEs), of which 33 (17.9%) were TL injuries (rate = 0.30/10 000 AEs). The HS RIO, which collects only TL injuries, reported 120 TL cervical muscle strains (rate = 0.51/10 000 AEs). The overall injury rate was lower in the NCAA-ISP than in HS NATION (injury rate ratio = 0.58; 95% CI = 0.42, 0.79); when restricted to TL injuries, the overall injury rate was higher in the NCAA-ISP (injury rate ratio = 1.83; 95% CI = 1.11, 3.03). No differences were found when comparing TL injuries in HS RIO and the NCAA-ISP. Cervical muscle-strain rates were higher during competitions than during practices across all 3 surveillance systems for all injuries. Most cervical muscle strains were due to player contact (NCAA-ISP = 85.7%, HS NATION = 78.8%, HS RIO = 85.8%). CONCLUSIONS: The incidence of cervical muscle strains in football players was low compared with other injuries. Nonetheless, identifying and implementing interventions, particularly those aimed at reducing unsafe player contact, are essential to further decrease the risk of injury and associated adverse outcomes.

Neuromuscular fatigue alters postural control and sagittal plane hip biomechanics in active females with anterior cruciate ligament reconstruction.

BACKGROUND: Females with history of anterior cruciate ligament (ACL) injury and subsequent ligament reconstruction are at high risk for future ACL injury. Fatigue may influence the increased risk of future injury in females by altering lower extremity biomechanics and postural control. HYPOTHESIS: Fatigue will promote lower extremity biomechanics and postural control deficits associated with ACL injury. STUDY DESIGN: Descriptive laboratory study. METHODS: Fourteen physically active females with ACL reconstruction (mean age, 19.64 ± 1.5 years; mean height, 163.52 ± 6.18 cm; mean mass, 62.6 ± 13.97 kg) volunteered for this study. Postural control and lower extremity biomechanics were assessed in the surgical limb during single-leg balance and jump-landing tasks before and after a fatigue protocol. Main outcome measures were 3-dimensional hip and knee joint angles at initial contact, peak angles, joint angular displacements and peak net joint moments, anterior tibial shear force, and vertical ground reaction force during the first 50% of the loading phase of the jump-landing task. During the single-leg stance task, the main outcome measure was center of pressure sway speed. RESULTS: Initial contact hip flexion angle decreased (t = -2.82, P = 0.01; prefatigue, 40.98° ± 9.79°; postfatigue, 36.75° ± 8.61°) from pre- to postfatigue. Hip flexion displacement (t = 2.23, P = 0.04; prefatigue, 45.19° ± 14.1°; postfatigue, 47.48° ± 14.21°) and center of pressure sway speed (t = 3.95, P < 0.05; prefatigue, 5.18 ± 0.96 cm/s; postfatigue, 6.20 ± 1.72 cm/s) increased from pre- to postfatigue. There was a trending increase in hip flexion moment (t = 2.14, P = 0.05; prefatigue, 1.66 ± 0.68 Nm/kg/m; postfatigue, 1.91 ± 0.62 Nm/kg/m) from pre- to postfatigue. CONCLUSION: Fatigue may induce lower extremity biomechanics and postural control deficits that may be associated with ACL injury in physically active females with ACL reconstruction. CLINICAL RELEVANCE: Rehabilitation and maintenance programs should incorporate activities that aim to improve muscular endurance and improve the neuromuscular system's tolerance to fatiguing exercise in efforts to maintain stability and safe landing technique during subsequent physical activity.

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

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

Dehydration and performance on clinical concussion measures in collegiate wrestlers.

CONTEXT: The effects of dehydration induced by wrestling-related weight-cutting tactics on clinical concussion outcomes, such as neurocognitive function, balance performance, and symptoms, have not been adequately studied. OBJECTIVE: To evaluate the effects of dehydration on the outcome of clinical concussion measures in National Collegiate Athletic Association Division I collegiate wrestlers. DESIGN: Repeated-measures design. SETTING: Clinical research laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty-two Division I healthy collegiate male wrestlers (age = 20.0 ± 1.4 years; height = 175.0 ± 7.5 cm; baseline mass = 79.2 ± 12.6 kg). INTERVENTION(S): Participants completed preseason concussion baseline testing in early September. Weight and urine samples were also collected at this time. All participants reported to prewrestling practice and postwrestling practice for the same test battery and protocol in mid-October. They had begun practicing weight-cutting tactics a day before prepractice and postpractice testing. Differences between these measures permitted us to evaluate how dehydration and weight-cutting tactics affected concussion measures. MAIN OUTCOME MEASURES: Sport Concussion Assessment Tool 2 (SCAT2), Balance Error Scoring System, Graded Symptom Checklist, and Simple Reaction Time scores. The Simple Reaction Time was measured using the Automated Neuropsychological Assessment Metrics. RESULTS: The SCAT2 measurements were lower at prepractice (P = .002) and postpractice (P < .001) when compared with baseline. The BESS error scores were higher at postpractice when compared with baseline (P = .015). The GSC severity scores were higher at prepractice (P = .011) and postpractice (P < .001) than at baseline and at postpractice when than at prepractice (P = .003). The number of Graded Symptom Checklist symptoms reported was also higher at prepractice (P = .036) and postpractice (P < .001) when compared with baseline, and at postpractice when compared with prepractice (P = .003). CONCLUSIONS: Our results suggest that it is important for wrestlers to be evaluated in a euhydrated state to ensure that dehydration is not influencing the outcome of the clinical measures.

The influence of hip strength on gluteal activity and lower extremity kinematics.

The effects of hip muscle strength and activation on anterior cruciate ligament injury biomechanics, particularly knee valgus loading, have been reported in isolation and with equivocal results. However, the combination of these factors influences joint biomechanics. This investigation evaluated the influence of hip strength on gluteal activation and knee valgus motion. Maximal isometric hip abduction (ABD) and external rotation (ER) contractions were used to define High and Low strength groups. Knee kinematics and gluteus maximus (GMax) and medius (GMed) EMG amplitudes obtained during landing were compared between High and Low strength groups after controlling for the potential confounding influence of sex. Knee valgus motion did not differ between the High and Low hip ABD and ER strength groups. However, the Low ABD and ER strength groups displayed greater GMed and GMax EMG amplitudes, respectively, compared to the High strength groups. These findings suggest that weaker individuals compensate for a lack of force production via heightened neural drive. As such, hip muscle strength influences knee valgus motion indirectly by determining neural drive requirements.

Effects of a single-task versus a dual-task paradigm on cognition and balance in healthy subjects.

CONTEXT: Recent evidence has revealed deficiencies in the ability to divide attention after concussion. OBJECTIVE: To examine the effects of a single vs a dual task on cognition and balance in healthy subjects and to examine reliability of 2 dual-task paradigms while examining the overall feasibility of the tasks. DESIGN: Pretest-posttest experimental design. SETTING: Sports medicine research laboratory. PATIENTS: 30 healthy, recreationally active college students. INTERVENTION: Subjects performed balance and cognitive tasks under the single- and dual-task conditions during 2 test sessions 14 d apart. MAIN OUTCOME MEASURES: The procedural reaction-time (PRT) test of the Automated Neuropsychological Assessment Metrics (eyes-closed tasks) and an adapted Procedural Auditory Task (PAT; eyes-open tasks) were used to assess cognition. The NeuroCom Sensory Organization Test (SOT) and the Balance Error Scoring System (BESS) were used to assess balance performance. Five 2-way, within-subject ANOVAs and a paired-samples t test were used to analyze the data. ICCs were used to assess reliability across 2 test sessions. RESULTS: On the SOT, performance significantly improved between test sessions (F1,29 = 35.695, P < .001) and from the single to the dual task (F1,29 = 9.604, P = .004). On the PRT, performance significantly improved between test sessions (F1,29 = 57.252, P < .001) and from the single to the dual task (F1,29 = 7.673, P = .010). No differences were seen on the BESS and the PAT. Reliability across test sessions ranged from moderate to poor for outcome measure. CONCLUSIONS: The BESS appears to be a more reliable and functional tool in dual-task conditions as a result of its increased reliability and clinical applicability. In addition, the BESS is more readily available to clinicians than the SOT.

The effects of an exercise intervention on forward head and rounded shoulder postures in elite swimmers.

OBJECTIVES: To examine the correction of posture, increase in strength and decrease in shoulder pain and dysfunction in varsity swimmers. DESIGN AND SETTING: Randomised clinical trial. PARTICIPANTS: Twenty-eight National Collegiate Athletic Association division I varsity swimmers. MEASUREMENTS: Two testing sessions were conducted before and after an 8-week time period. Posture, strength and shoulder pain and function were assessed. Forward head angle was measured using a digital inclinometer, forward head translation was measured using a ruler and total scapular distance was measured with unmarked string. Average and peak values (N) of strength were measured with the hand-held dynamometer. The intervention subjects then participated in an 8-week exercise training programme to correct posture. The procedures were then repeated in the post-test. RESULTS: Significant group by time interactions (p<0.05) were found in forward head angle and forward shoulder translation indicating a decrease in forward head angle and forward shoulder translation. Significant main effects for time (p<0.05) were found in strength measures for all muscle groups indicating increased strength for shoulder girdle muscles tested. CONCLUSIONS: The exercise intervention was successful at decreasing forward head and rounded shoulder postures in elite swimmers. This study supports the theoretical basis for clinical rehabilitation of posture and the shoulder.

Effect of ice hockey helmet fit on cervical spine motion during an emergency log roll procedure.

OBJECTIVE: To investigate cervical spine motion during a log roll technique in ice hockey players under different helmet fit conditions. DESIGN: Prospective counterbalanced design. SETTING: University research laboratory. PARTICIPANTS: Eighteen club ice hockey players were recruited to participate in this study. ASSESSMENT OF RISK FACTORS: A standard emergency log roll was performed 3 times under each of 3 different helmet fit conditions: properly fit, improperly (competition) fit, and helmet-removed. MAIN OUTCOME MEASUREMENTS: Frontal, sagittal, and transverse plane cervical spine motion were used as outcome measures. RESULTS: Significantly less sagittal and transverse plane motion occurred during the helmet-removed condition. No differences in frontal plane motion among the 3 conditions were observed. CONCLUSIONS: Presence of helmet (whether properly fit or not) resulted in increased of sagittal and transverse plane movement. This suggests that when an ice hockey helmet is stabilized, the head within it is not. We recommend the helmet and face shield be removed before performing an emergency prone log roll.

Muscle activation during side-step cutting maneuvers in male and female soccer athletes.

CONTEXT: Female soccer athletes are at greater risk of anterior cruciate ligament (ACL) injury than males. Sex differences in muscle activation may contribute to the increased incidence of ACL injuries in female soccer athletes. OBJECTIVE: To examine sex differences in lower extremity muscle activation between male and female soccer athletes at the National Collegiate Athletic Association Division I level during 2 side-step cutting maneuvers. DESIGN: Cross-sectional with 1 between-subjects factor (sex) and 2 within-subjects factors (cutting task and phase of contact). SETTING: Sports medicine research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty males (age = 19.4 +/- 1.4 years, height = 176.5 +/- 5.5 cm, mass = 74.6 +/- 6.0 kg) and 20 females (age = 19.8 +/- 1.1 years, height = 165.7 +/- 4.3 cm, mass = 62.2 +/- 7.2 kg). INTERVENTION(S): In a single testing session, participants performed the running-approach side-step cut and the box-jump side-step cut tasks. MAIN OUTCOME MEASURE(S): Surface electromyographic activity of the rectus femoris, vastus lateralis, medial hamstrings, lateral hamstrings, gluteus medius, and gluteus maximus was recorded for each subject. Separate mixed-model, repeated-measures analysis of variance tests were used to compare the dependent variables across sex during the preparatory and loading contact phases of each cutting task. RESULTS: Females displayed greater vastus lateralis activity and quadriceps to hamstrings coactivation ratios during the preparatory and loading phases, as well as greater gluteus medius activation during the preparatory phase only. No significant differences were noted between the sexes for muscle activation in the other muscles analyzed during each task. CONCLUSIONS: The quadriceps-dominant muscle activation pattern observed in recreationally active females is also present in female soccer athletes at the Division I level when compared with similarly trained male soccer athletes. The relationship between increased quadriceps activation and greater incidence of noncontact ACL injury in female soccer athletes versus males requires further study.

Neuropsychological performance, postural stability, and symptoms after dehydration.

CONTEXT: Dehydration and concussion are common in athletic performance. Some experts have speculated that dehydration may negatively influence performance on tests commonly used for concussion assessment. OBJECTIVE: To determine how the signs and symptoms, neuropsychological performance, and postural stability are affected by dehydration. DESIGN: Repeated-measures design assessing subjects in the euhydrated and dehydrated conditions. SETTING: Sports Medicine Research Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-four healthy, male recreational athletes participated in the study. INTERVENTION(S): Subjects participated in 2 counterbalanced sessions (euhydrated and dehydrated) separated by at least 7 days. Subjects were dehydrated using fluid restriction and an exercise task. No direct intervention was provided for the euhydrated condition. MAIN OUTCOME MEASURE(S): We used the Standardized Assessment of Concussion to test mental status, the Automated Neuropsychological Assessment Metrics (ANAM) to evaluate neuropsychological performance, the NeuroCom Sensory Organization Test and Balance Error Scoring System to test postural stability, the Graded Symptom Checklist to assess symptom presence and severity in our participants, and urine specific gravity and body mass to determine hydration status. RESULTS: No differences were noted for the Standardized Assessment of Concussion, total Balance Error Scoring System errors, composite Sensory Organization Test, and composite ANAM scores between conditions. Subjects in the dehydrated condition had significant deterioration in visual memory (t(23) = 2.130, P < .001) and fatigue measures (t(23) = -7.880, P < .001) as assessed by ANAM. The dehydrated condition resulted in subjects reporting a significantly higher number (t(23) = -8.585, P < .001) and severity (t(23) = -7.673, P < .001) of symptoms than the euhydrated subjects on the Graded Symptom Checklist. CONCLUSIONS: Our results suggest that moderate dehydration (-2.5 +/- 0.63%) significantly influenced the self-report of symptoms commonly associated with concussion. Dehydration resulted in a deterioration of visual memory and increases in the self-report of fatigue. Despite these findings, dehydration did not affect other neuropsychological and postural stability objective testing measures for concussion.