Kate R. Pfile

Intrarater reliability of the functional movement screen.

Abstract Gribble, PA, Brigle, J, Pietrosimone, BG, Pfile, KR, and Webster, KA. Intrarater reliability of the functional movement screen. J Strength Cond Res 27(4): 978–981, 2013—The Functional Movement Screen (FMS) is a tool that quantifies movement patterns as a way to detect performance asymmetries. Although previous study has investigated the reliability of FMS, no current research has examined intrarater reliability or how clinical experience plays a role in the reliability of this tool. In this controlled laboratory study design, repeated measures were used to investigate how experience using the FMS and clinical experience as an athletic trainer (AT) affects the intrarater reliability of FMS testing. Before the data collection, 3 individuals recruited from the university community provided signed informed consent to serve as videotaped models performing the FMS test. The participants (raters) in the study, with different levels of FMS and clinical experience, viewed each of the 3 videotaped models and rated the video models on each exercise of the FMS according to the script that was presented by one of the study investigators. A week later, the participants watched the same videos again, in a different randomized order, and rated each video model on each exercise. After the scores from the participants were collected from both sessions, the intersession scores of the FMS were examined to establish intrarater reliability of all the participants. Additionally, the intrarater reliability of different groups of clinicians and students was compared to make inferences about the influence of clinical experience as an AT along with previous experience using the FMS. The ATs with at least 6 months of experience using the FMS (ATExp group) had the strongest intrarater reliability [intraclass correlation coefficients, ICC (2,1): 0.946], followed by the AT group with moderate reliability [ICC (2,1): 0.771]. This study indicates that intrarater reliability is strong and seems to strengthen when the individuals have experience using the FMS in addition to clinical experience.

Different Exercise Training Interventions and Drop-Landing Biomechanics in High School Female Athletes

CONTEXT Anterior cruciate ligament (ACL) injuries are common in female athletes and are related to poor neuromuscular control. Comprehensive neuromuscular training has been shown to improve biomechanics; however, we do not know which component of neuromuscular training is most responsible for the changes. OBJECTIVE To assess the efficacy of either a 4-week core stability program or plyometric program in altering lower extremity and trunk biomechanics during a drop vertical jump (DVJ). DESIGN Cohort study. SETTING High school athletic fields and motion analysis laboratory. PATIENTS OR OTHER PARTICIPANTS Twenty-three high school female athletes (age = 14.8 ± 0.8 years, height = 1.7 ± 0.07 m, mass = 57.7 ± 8.5 kg). INTERVENTION(S) Independent variables were group (core stability, plyometric, control) and time (pretest, posttest). Participants performed 5 DVJs at pretest and posttest. Intervention participants engaged in a 4-week core stability or plyometric program. MAIN OUTCOME MEASURE(S) Dependent variables were 3-dimensional hip, knee, and trunk kinetics and kinematics during the landing phase of a DVJ. We calculated the group means and associated 95% confidence intervals for the first 25% of landing. Cohen d effect sizes with 95% confidence intervals were calculated for all differences. RESULTS We found within-group differences for lower extremity biomechanics for both intervention groups (P ≤ .05). The plyometric group decreased the knee-flexion and knee internal-rotation angles and the knee-flexion and knee-abduction moments. The core stability group decreased the knee-flexion and knee internal-rotation angles and the hip-flexion and hip internal-rotation moments. The control group decreased the knee external-rotation moment. All kinetic changes had a strong effect size (Cohen d > 0.80). CONCLUSIONS Both programs resulted in biomechanical changes, suggesting that both types of exercises are warranted for ACL injury prevention and should be implemented by trained professionals.

Inter-limb differences in quadriceps strength and volitional activation

Abstract In this crossover study, we wished to determine if normalized inter-limb differences in strength differed from inter-limb differences in voluntary activation at 30°, 70°, and 90° of knee flexion. We also assessed the relationship between inter-limb differences in torque with the inter-limb differences in activation. Twenty-five healthy volunteers were used for final data analyses; the order of leg tested, joint angle, and measurement technique (isokinetic strength, voluntary activation) were randomly assigned. Quadriceps strength was measured isokinetically at 1.05 rad · s−1, while quadriceps voluntary activation was assessed via the central activation ratio. Absolute values of inter-limb differences for both measures were calculated by subtracting the non-dominant leg values from those of the dominant leg. Inter-limb isokinetic strength differences were greater than inter-limb central activation ratio differences at all joint angles (P = 0.003). Interestingly, inter-limb deficits between measures were not strongly correlated, suggesting that these measurements may be evaluating completely different phenomena within the neuromuscular system. These measurement techniques may provide unique information regarding neuromuscular function, suggesting that researchers and clinicians must utilize information from both techniques to determine the true clinical nature of inter-limb deficits.

Different Modes of Feedback and Peak Vertical Ground Reaction Force During Jump Landing: A Systematic Review

CONTEXT Excessive ground reaction force when landing from a jump may result in lower extremity injuries. It is important to better understand how feedback can influence ground reaction force (GRF) and potentially reduce injury risk. OBJECTIVE To determine the effect of expert-provided (EP), self-analysis (SA), and combination EP and SA (combo) feedback on reducing peak vertical GRF during a jump-landing task. DATA SOURCES We searched the Web of Science database on July 1, 2011; using the search terms ground reaction force, landing biomechanics, and feedback elicited 731 initial hits. STUDY SELECTION Of the 731 initial hits, our final analysis included 7 studies that incorporated 32 separate data comparisons. DATA EXTRACTION Standardized effect sizes and 95% confidence intervals (CIs) were calculated between pretest and posttest scores for each feedback condition. DATA SYNTHESIS We found a homogeneous beneficial effect for combo feedback, indicating a reduction in GRF with no CIs crossing zero. We also found a homogeneous beneficial effect for EP feedback, but the CIs from 4 of the 10 data comparisons crossed zero. The SA feedback showed strong, definitive effects when the intervention included a videotape SA, with no CIs crossing zero. CONCLUSIONS Of the 7 studies reviewed, combo feedback seemed to produce the greatest decrease in peak vertical GRF during a jump-landing task.

Effects of Chronic Ankle Instability on Energy Dissipation in the Lower Extremity

PURPOSE This study aimed to investigate the influence of chronic ankle instability (CAI) on lower extremity joint energy dissipation patterns during a stop-jump task. METHODS Nineteen participants with self-reported CAI and 19 healthy control participants volunteered. Participants performed five double-leg vertical stop-jump tasks onto a force plate. Lower extremity kinetics and kinematics were examined with an electromagnetic tracking system interfaced with a nonconductive force plate. Lower extremity joint energy dissipations were calculated for the hip, knee, and ankle in the sagittal plane during 50, 100, 150, and 200 ms after initial contact with the force plate. Energy dissipation values were normalized to the product of body mass and height [J · (N · m)(-1)]. Individual joint contribution to total lower extremity energy dissipation by the ankle, knee, and hip was reported as the percentage of energy dissipation by each joint over the total energy dissipation of all three joints. Independent t-tests and standard mean differences were conducted to assess differences in each dependent variable between the CAI and the control groups. Significance was set a priori at P < 0.05. RESULTS The CAI group demonstrated significantly less percentage of knee energy dissipation (P = 0.04) and higher percentage of ankle energy dissipation (P = 0.035) of the total energy dissipation during the 100 ms immediately after initial contact compared with the control group. CONCLUSIONS We found altered energy dissipation patterns at the knee and ankle during a stop-jump task in the CAI group. These findings may provide insight into kinetic alterations that may be associated with CAI. Future research should consider this information as it may be used to develop more effective interventions to target these potentially modifiable energy dissipation patterns in those with CAI.

Neuromuscular changes after aerobic exercise in people with anterior cruciate ligament-reconstructed knees.

CONTEXT Anterior cruciate ligament (ACL) reconstructions are common, especially in young, active people. The lower extremity neuromuscular adaptations seen after aerobic exercise provide information about how previously injured patients perform and highlight deficits and, hence, areas for focused treatment. Little information is available about neuromuscular performance after aerobic exercise in people with ACL reconstructions. OBJECTIVE To compare dynamic balance, gluteus medius muscle activation, vertical jump height, and hip muscle strength after aerobic exercise in people with ACL-reconstructed knees. DESIGN Case-control study. SETTING Research laboratory. PATIENTS OR OTHER PARTICIPANTS Of 34 recreationally active volunteers, 17 had a unilateral primary ACL reconstruction at least 2 years earlier and 17 were matched controls. INTERVENTION(S) All participants performed 20 minutes of aerobic exercise on a treadmill. MAIN OUTCOME MEASURE(S) We recorded dynamic, single-legged balance electromyographic gluteus medius muscle activation, single-legged vertical jump height, and maximum isometric strength for hip abduction, extension, and external rotation preexercise and postexercise. RESULTS Participants with ACL reconstructions exhibited shorter reach distances during dynamic balance tasks, indicating poorer dynamic balance, and less gluteus medius muscle electromyographic activation. Reductions in hip abduction and extension strength after exercise were noted in all participants; however, those with ACL reconstructions displayed greater hip extensor strength loss after aerobic exercise than did the control group. CONCLUSIONS Neuromuscular changes after aerobic exercise exist in both patients with ACL reconstructions and controls. The former group may experience greater deficits in hip extensor strength after aerobic exercise. Reduced reach distances in people with ACL reconstructions may represent a protective mechanism against excessive tibiofemoral rotation during dynamic balance. Clinicians should identify weaknesses in the resting state and after aerobic exercise in recreationally active patients and those with ACL reconstructions.

Longitudinal Changes in Hip Strength and Range of Motion in Female Youth Soccer Players: Implications for ACL Injury, A Pilot Study

CONTEXT Risk of anterior cruciate ligament (ACL) injuries in young female athletes increases with age, appearing to peak during maturation. Changes in hip muscle strength and range of motion (ROM) during this time may contribute to altered dynamic movement patterns that are known to increase risk of ACL injuries. Understanding the longitudinal changes in hip strength and ROM is needed to develop appropriate interventions to reduce the risk of ACL injuries. OBJECTIVE To examine the longitudinal changes in hip strength and ROM in female youth soccer players. DESIGN Longitudinal descriptive study. SETTING Field setting. PARTICIPANTS 14 female youth soccer athletes (14.1 ± 1.1 y, 165.8 ± 5.3 cm, 57.5 ± 9.9 kg) volunteered as part of a multiyear risk factor screening project. MAIN OUTCOME MEASURES Clinical measures of hip strength and ROM were collected annually over 3 consecutive years. Passive hip internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) ROM were measured with a digital inclinometer. Isometric hip ABD and extension (EXT) strength were evaluated using a hand-held dynamometer. Separate repeated-measures ANOVAs compared hip strength and ROM values across 3 consecutive years (P < .05). RESULTS As youth female soccer players increased in age, there were no changes in normalized hip ABD (P = .830) or EXT strength (P = .062) across 3 consecutive years. Longitudinal changes in hip ROM were observed with increases in hip IR (P = .001) and ABD (P < .001), while hip ADD (P = .009) and ER (P < .001) decreased. CONCLUSIONS Anatomical changes at the hip occur as youth female soccer players increase in age. While there are no changes in hip strength, there is an increase in hip IR and ABD ROM with a concomitant decrease in hip ER and ADD ROM. The resulting asymmetries in hip ROM may decrease the activation and force producing capabilities of the hip muscles during dynamic activities, contributing to altered lower extremity mechanics known to increase the risk of ACL injuries.

Nonlinear Dynamic Measures for Evaluating Postural Control in Individuals With and Without Chronic Ankle Instability

This study aimed to compare time-to-boundary and sample entropy during a single-leg balance task between individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. Twenty-two participants with CAI, 20 lateral ankle sprain copers, and 24 healthy controls performed a single-leg balance task during an eyes-closed condition. Participants with CAI exhibited lower time-to-boundary values compared with lateral ankle sprain copers and healthy controls. However, we did not find differences in sample entropy variables between cohorts. A decrease in time-to-boundary values in participants with CAI indicated that CAI may constrain the ability of the sensorimotor system to maintain the center of pressure within the boundaries of the base of support. However, the regularity of the center of pressure velocity time series appears not to be altered in the CAI cohort in this study.