The Modified Reactive Strength Index Is a Valid Measure of Lower-Body Explosiveness in Male and Female High School Athletes.

ABSTRACT: Witte, BC, Schouten, TC, Westphal, JA, VanZile, AW, Jones, DD, Widenhoefer, TL, Dobbs, WC, Jagim, AR, Luedke, JA, and Almonroeder, TG. The modified reactive strength index is a valid measure of lower-body explosiveness in male and female high school athletes. J Strength Cond Res XX(X): 000-000, 2024-The modified reactive strength index (mRSI) is a commonly used metric to quantify lower-body explosiveness during countermovement jump (CMJ) performance. However, few studies have attempted to examine its validity as a measure of explosiveness, particularly among high school athletes. The purpose of this study was to examine the validity of the mRSI as a measure of lower-body explosiveness among a relatively large sample of male and female high school athletes from various sports. As part of this study, male (n = 132) and female (n = 43) high school athletes performed CMJs, while ground reaction forces were recorded using a force platform. The vertical ground reaction force data collected during the CMJs were used to derive the following variables: peak force (PF), peak power, time to PF, time to take-off, peak rate of force development, and the mRSI. Principal component analysis was applied and reduced these variables into 2 components related to "force" and "speed." The mRSI loaded on both the force (loading = 0.82) and speed (loading = -0.46) components, indicating that it incorporates elements of both force and speed, although it loaded more strongly on the force component than the speed component. The observed pattern of cross-loading suggests that the mRSI is generally a valid measure of lower-body explosiveness for male and female high school athletes.

Spatial Abilities and Performance in Anatomy for Occupational Therapy and Physical Therapy Doctoral Students.

Spatial ability is the capacity to comprehend three-dimensional structures and positional relationships and to mentally manipulate these structures and relationships to predict the outcome correctly. Spatial ability, which requires extensive knowledge of three-dimensional relationships, contributes to success in endeavors such as studying human anatomy, a foundational component of rehabilitation science curricula. This investigation explored relationships between anatomy course grades, learning preferences, and spatial abilities of graduate healthcare students from two fields of rehabilitation science. We administered the Mental Rotation Test to 95 Doctor of Physical Therapy students and 66 Occupational Therapy students at the start of the anatomy course in the first semester of their professional programs. The spatial abilities of doctoral students in physical therapy and occupational therapy programs reflect consistently reported trends for gender and anatomy performance. Physical therapy students demonstrated higher spatial ability scores than occupational therapy students, which could result from differences in life experience or academic preparation. Awareness of students' spatial abilities, the factors that influence them, and their relationships to student success have important implications for teaching, learning, advising, and retention.

Intra-rater reliability of goniometry to measure scapular protraction and retraction.

STUDY DESIGN: Observational, descriptive design. BACKGROUND: Despite scapular mobility being essential for the completion of activities of daily living (ADLs), there is currently no established, a reliable goniometric technique to measure scapular protraction and retraction. A proposed method has shown clinically significant inter-rater reliability for a goniometric technique for these measurements. PURPOSE: This observational descriptive study examined the intra-rater reliability of a goniometric technique to assess scapular protraction and retraction among a sample of healthy adults. METHODS: An occupational therapist who is a certified hand therapist (CHT) and an occupational therapy student used goniometry to measure the neutral (resting), protracted, and retracted positions of the right and left scapula for a sample of healthy young adults (n = 54; a total of 108 data points for each measurement). These measurements were compared to analyze intra-rater and inter-rater reliability. RESULTS: For measurements of the scapula in neutral, protraction, and retraction, the standard error of measure (SEM) for repeat measures by the expert and novice raters was < 4.5° and < 3.9° respectively and ICC values ranged from poor to moderate (0.37-0.63). The SEM for measures between evaluators was < 5.0° and the ICC was poor (0.16-0.35). Minimum detectable change (MDC) values as a percentage of the mean (% MDC) ranged between 15.9 and 43.7% for intra-rater reliability and 21.9-52.8% for inter-rater reliability. DISCUSSION: The results of the study were mixed; variance of less than 5° for repeat measures by the same rater and measures between raters suggest clinically acceptable reliability. However, variance as a proportion of available motion (%MDC) demonstrates a broader range both above and below the threshold of 30% suggested for rehabilitation assessments. CONCLUSION: There are few efficient, reliable techniques to measure scapular mobility in clinical practice. The absolute reliability of goniometry to measure scapular protraction and retraction is similar to measurements of other joints. However, additional research and possible refinement of the technique is recommended to further address relative reliability and validity.

Examining the Influence of Attentional Focus on the Effects of a Neuromuscular Training Program in Male Athletes.

ABSTRACT: Ghanati, HA, Letafatkar, A, Almonroeder, TG, and Rabiei, P. Examining the influence of attentional focus on the effects of a neuromuscular training program in male athletes. J Strength Cond Res 36(6): 1568-1575, 2022-Neuromuscular training programs that incorporate lower extremity strengthening, plyometric exercises, balance training, and movement retraining are recommended for anterior cruciate ligament injury prevention; however, there is a need to improve their effectiveness. The purpose of this study was to examine how athletes' attentional focus during training influences the effects of an 8-week neuromuscular training program on hip strength, single-leg landing mechanics, and hop performance. Sixty-six male athletes were randomly allocated to a group that trained with an internal focus, a group that trained with an external focus, or a control group. All athletes completed testing before (baseline) and after (posttesting) the 8-week period. Isokinetic hip strength, hip and knee kinematics and ground reaction forces during landing, and hop distance were examined as part of this study. Analysis of covariance was used to compare posttesting outcomes among the groups while accounting for group differences in baseline performance. The neuromuscular training program resulted in improved hip abduction strength, reduced hip adduction and internal rotation motion during landing, and increased hop distance for athletes who trained with an external focus. However, the program did not seem to influence hip strength, landing kinematics, or hop performance for athletes who trained with an internal focus. Our findings indicate that male athletes may benefit from completing a neuromuscular training program with an external focus vs. an internal focus. Trainers, coaches, and clinicians should consider using instructions that promote an external focus when implementing neuromuscular training programs with male athletes.

Kinetic Asymmetry During a Repetitive Tuck Jump Task in Athletes with a History of Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Athletes who have undergone anterior cruciate ligament reconstruction typically exhibit relatively high/rapid loading of their uninvolved limb during bilateral landing and jumping (vs. their limb that underwent reconstruction), which may place their uninvolved limb at risk for injury. However, previous studies have only examined forces and loading rates for tasks involving an isolated land-and-jump. PURPOSE: The purpose of this study was to examine bilateral landing and jumping kinetics during performance of a repetitive tuck jump task in athletes who had undergone anterior cruciate ligament reconstruction and completed rehabilitation. STUDY DESIGN: Cross-sectional study. METHODS: Nine athletes (four males, five females) participated in this study. All participants had undergone successful unilateral anterior cruciate ligament reconstruction, had completed post-operative rehabilitation, and were in the process of completing return-to-sport testing. Athletes performed a repetitive tuck jump task for 10 seconds, while ground reaction forces were recorded for their uninvolved and involved limbs via separate force platforms. Two-way analysis of variance, for within-subjects factors of limb and cycle, was performed for the impact forces, loading rates, and propulsive forces from the first five land-and-jump cycles completed. RESULTS: There was not a limb-by-cycle interaction effect or main effect of cycle for the impact forces, loading rates, or propulsive forces; however, there was a main effect of limb for the impact forces (F(1, 8) = 14.64; p=0.005), loading rates (F(1, 8) = 5.60; p=0.046), and propulsive forces (F(1, 8) = 10.38; p=0.012). Impact forces, loading rates, and propulsive forces were higher for the uninvolved limb, compared to the involved limb, over the five land-and-jump cycles analyzed. CONCLUSION: The athletes in this study consistently applied higher and more rapid loads to their uninvolved limb over multiple land-and-jump cycles. This may help to explain the relatively high injury rates for the uninvolved limb in athletes who have returned to sport following anterior cruciate ligament reconstruction.

The influence of step-down technique on lower extremity mechanics during curb descent.

When stepping down from a curb, individuals typically make initial ground contact with either their rearfoot or forefoot. The purpose of this study was to compare vertical ground reaction forces, lower extremity mechanics, and intra-limb work distribution when individuals adopt a rearfoot technique vs. a forefoot technique, during simulated curb descent. Sixteen subjects stepped down from a platform with both a rearfoot and a forefoot technique. Vertical ground reaction forces and sagittal plane joint kinematics and kinetics were examined for the lead limb during the step-down task. Paired t-tests were used for comparison. Subjects demonstrated greater ankle joint power and negative work, and less hip joint power and negative work, with the forefoot technique vs. the rearfoot technique. Total lower extremity negative work was greater for the forefoot technique vs. the rearfoot technique. The percent contribution to the total negative work was greater for the ankle joint, and less for the hip and knee joints, with the forefoot technique vs. the rearfoot technique. The results of this study may provide insight into how curb descent technique can be modified to alter lower extremity loading.

Establishing Normative Values for Inter-Limb Kinetic Symmetry During Landing in Uninjured Adolescent Athletes.

BACKGROUND: Assessment of inter-limb kinetic symmetry during landing could provide valuable insights when working with athletes who have undergone anterior cruciate ligament reconstruction. However, it is difficult to determine if the asymmetry exhibited by an injured athlete is excessive or within a range that is similar to uninjured athletes, until normative values are established. PURPOSE: The purpose of this study was to establish normative values for inter-limb impact force symmetry in uninjured adolescent athletes. In addition, an example is provided of how these normative values could be used to identify athletes who exhibit atypically high levels of asymmetry following anterior cruciate ligament reconstruction. STUDY DESIGN: Cross-sectional study. METHODS: One hundred and thirty-six uninjured athletes completed drop vertical jumps and countermovement jumps while force plates recorded ground reaction forces. Symmetry indices captured inter-limb symmetry in impact forces during landing for both tasks. These symmetry indices were also combined to create an index that captured symmetry across both tasks. Normative values were established using the uninjured athletes' data. Eleven athletes who had undergone anterior cruciate ligament reconstruction and been cleared to return to landing and jumping performed the same tasks and their data were compared to the results for the uninjured group. RESULTS: Measures of central tendency, variability, percentiles, and outliers were calculated/identified based on the uninjured athletes' symmetry indices. Six of the 11 injured athletes exhibited atypically high symmetry index values. CONCLUSION: The normative values established as part of this study may serve as a basis for identifying athletes who exhibit atypically high levels of inter-limb impact force asymmetry during jumping tasks following anterior cruciate ligament reconstruction. LEVEL OF EVIDENCE: 3b.

Neuromuscular training programs predominantly include instructions that promote an internal focus.

Neuromuscular training programs that include movement pattern retraining and strengthening, plyometric, and balance exercises are recommended for anterior cruciate ligament injury prevention. Recent evidence suggests that the effectiveness of these programs may be enhanced when athletes train with an external focus; however, clinicians typically rely predominantly on instructions encouraging an internal focus. The aim of this study was to examine the types of instructions provided as part of popular neuromuscular training programs used for anterior cruciate ligament injury prevention. The technique-related instructions provided as part of the FIFA 11+, HarmoKnee, Knakontroll, and Prevent Injury and Enhance Performance programs were categorized as either promoting an internal focus or an external focus. Instructions provided during movement pattern retraining tasks and strengthening, plyometric, and balance training exercises were specifically examined. Next, the percentage of technique-related instructions that promoted an internal focus, versus the percentage that promoted an external focus, were compared for the various program components. Across all programs examined, the vast majority of technique-related instructions for the movement pattern re-training tasks (≥83.3%) and the strengthening, balance, and plyometric exercises (≥75.0%) appeared to promote an internal focus. Despite evidence suggesting that the effectiveness of neuromuscular training programs may be enhanced by encouraging an external focus, most technique-related instructions provided as part of popular neuromuscular training programs appear to promote an internal focus. Modifying neuromuscular training programs to promote a more external focus could help to improve the effectiveness of these programs for anterior cruciate ligament injury prevention.

The effects of drop vertical jump technique on landing and jumping kinetics and jump performance.

The drop vertical jump is a popular plyometric exercise. Two distinct techniques are commonly used to initiate the drop vertical jump. With the 'step-off' technique, athletes step off a raised platform with their dominant limb, while their non-dominant limb remains on the platform. In contrast, with the 'drop-off' technique, athletes lean forward and drop off the platform, with both feet leaving the platform more simultaneously. The purpose of this study was to compare landing and jumping kinetics, inter-limb kinetic symmetry, and jump performance when individuals used the step-off and drop-off techniques, and to examine whether potential differences between these techniques are affected by platform height. Sixteen subjects completed drop vertical jumps with the drop-off and step-off techniques, from relatively low and high platform heights. Ground reactions forces were recorded for the dominant and non-dominant limbs during the land-and-jump phase of the drop vertical jump. Subjects demonstrated greater inter-limb asymmetry in peak impact forces when using the step-off technique, vs. the drop-off technique. This difference between the techniques was consistent across platform heights. The step-off technique appears to result in greater asymmetry in limb loading, which could contribute to the development of neuromuscular asymmetries between the limbs and/or asymmetric landing patterns.

Muscle force characteristics of male and female collegiate cross-country runners during overground running.

Males and females demonstrate unique running mechanics that may contribute to sex-related differences in common running related injuries. Understanding differences in muscle forces during running may inform intervention approaches, such as gait retraining addressing muscle force distribution. The purpose of this study was to compare muscle force characteristics and inter-trial variability between males and females during running. Twenty female and 14 male collegiate cross-country runners were examined. Three-dimensional kinetic and kinematic data were collected during overground running and used to estimate muscle forces via musculoskeletal modelling. Principle components analysis was used to capture the primary sources of variance from the muscle force waveforms. The magnitude of the forces for the hamstrings, gastrocnemius, and soleus muscles were higher across the majority of stance in male runners regardless of footstrike pattern. Males also demonstrated greater inter-trial variability in the timing of the peak gluteus maximus force and the magnitude of local peaks in the gastrocnemius force waveform. Male and female collegiate cross-country runners appear to employ unique lower extremity muscle force characteristics during overground running.

Verbal Instruction Reduces Patellofemoral Joint Loading During Bodyweight Squatting.

CONTEXT: The bodyweight squat exercise is a common component for treatment and prevention of patellofemoral pain; however, it can also place a high load on the patellofemoral joint. Restricting anterior motion of the knees relative to the toes during squatting appears to reduce patellofemoral loading. However, exercise professionals typically rely on verbal instructions to alter squat technique. OBJECTIVE: To evaluate the influence of verbal instructions regarding squat technique on patellofemoral joint loading. DESIGN: Cross-sectional study. SETTING: Motion analysis laboratory. PARTICIPANTS: Eleven uninjured females. INTERVENTION: Participants performed bodyweight squats before (baseline) and after receiving verbal instructions to limit anterior knee motion. Two different types of verbal instruction were used, one intended to promote an internal focus of attention and the other intended to promote an external focus of attention. Three-dimensional kinematics and kinetics were recorded using a multicamera system and force plate. MAIN OUTCOME MEASURES: Sagittal plane patellofemoral joint forces and stress were estimated using a musculoskeletal model. RESULTS: Participants demonstrated a reduction in patellofemoral joint forces (35.4 vs 31.3 N/kg; P = .01) and stress (10.7 vs 9.2 mPa; P = .002) after receiving instructions promoting an internal focus of attention, compared with their baseline trials. Participants also demonstrated a reduction in patellofemoral joint forces (35.4 vs 32.3 N/kg; P = .03) and stress (10.7 vs 9.6 mPa; P = .04) after receiving instructions promoting an external focus of attention (vs baseline). However, there were no significant differences in patellofemoral forces (P = .84) or stress (P = .41) for trials performed with an internal versus external attentional focus. CONCLUSION: It appears that verbal instruction regarding knee position influences patellofemoral joint loading during squatting.

The effects of habitual foot strike patterns on Achilles tendon loading in female runners.

BACKGROUND: Female runners that habitually use a forefoot/midfoot strike pattern (non-rearfoot runners) may be at greater risk for Achilles tendinopathy compared to runners that habitually use a rearfoot strike pattern. Differences in Achilles tendon loading between non-rearfoot and rearfoot strike runners may be a contributing factor. RESEARCH QUESTION: Our purpose was to determine if there were differences in Achilles tendon loading and cross-sectional area between female habitual rearfoot and non-rearfoot strike runners. METHODS: Thirty-five female runners participated in this cross-sectional study (17 rearfoot strike runners, 18 non-rearfoot strike runners). Ultrasound images of the Achilles tendon were used to measure cross-sectional area. Kinematic and kinetic data were collected at a set running speed and used in a muscloskeletal model to calculate Achilles tendon force. Achilles tendon stress was determined from specific Achilles tendon cross-sectional area. Principal components (PC) analysis was performed to identify/characterize the primary sources of variability in the Achilles tendon stress time series. The PC scores and cross-sectional area where compared using independent t-tests. RESULTS: PC 1 reflected variability in the Achilles tendon stress magnitude from 25 to 100% of stance, PC 2 reflected timing variability, and PC 3 reflected variability in the magnitude during early stance (0-25%). The non-rearfoot strike runners demonstrated higher PC scores for PC 1 and PC 3 compared to the rearfoot strike runners. This reflected greater Achilles tendon stress during mid/late stance (PC 1) and early stance (PC 3) for the non-rearfoot strike runners. For PC 2, there was a trend toward higher PC scores in the non-rearfoot strike runners. Achilles tendon cross-sectional area for the rearfoot and non-rearfoot strike runners were not different. SIGNIFICANCE: Habitual non-rearfoot strike runners did not have greater cross-sectional area despite higher Achilles tendon loading, which may pose a higher risk for Achilles tendinopathy.

Sex differences in lower extremity kinematics and patellofemoral kinetics during running.

The incidence of patellofemoral pain (PFP) is 2 times greater in females compared with males of similar activity levels; however, the exact reason for this discrepancy remains unclear. Abnormal mechanics of the hip and knee in the sagittal, frontal, and transverse planes have been associated with an increased risk of PFP. The purpose of this study was to compare the mechanics of the lower extremity in males and females during running in order to better understand the reason(s) behind the sex discrepancy in PFP. Three-dimensional kinematic and kinetic data were collected as male and female participants completed overground running trials at a speed of 4.0 m · s-1 (±5%). Patellofemoral joint stress (PFJS) was estimated using a sagittal plane knee model. The kinematics of the hip and knee in the frontal and transverse planes were also analysed. Male participants demonstrated significantly greater sagittal plane peak PFJS in comparison with the female participants (P < .001, ES = 1.9). However, the female participants demonstrated 3.5° greater peak hip adduction and 3.4° greater peak hip internal rotation (IR). As a result, it appears that the sex discrepancy in PFP is more likely to be related to differences in the kinematics of the hip in the frontal and transverse planes than differences in sagittal plane PFJS.

Quantifying knee mechanics during balance training exercises.

Patellofemoral pain (PFP) is common among runners and those recovering from anterior cruciate ligament reconstruction. Training programs designed to prevent or treat injuries often include balance training, although balance interventions have been reported to coincide with more knee injuries. Knowledge of the effect of balance exercises on knee mechanics may be useful when designing training programs. High knee abduction moment has been implicated in the development of PFP, and imbalance between vastus lateralis (VL) and vastus medialis oblique (VMO) may contribute to patellofemoral stress. The purpose was to quantify knee abduction moment and vasti muscle activity during balance exercises. Muscle activity of VMO and VL, three-dimensional lower-extremity kinematics, and ground reaction forces of healthy recreational athletes (12M, 13F) were recorded during five exercises. Peak knee abduction moment, ratio of VMO:VL activity, and delay in onset of VMO relative to VL were quantified for each exercise. The influence of sex and exercise on each variable was determined using a mixed-model ANOVA. All analyses indicated a significant main effect of exercise, p<0.05. Follow-up comparisons showed low peak knee abduction moment and high VMO:VL ratio for the task with anterior-posterior motion. Delay of VMO relative to VL was similar among balance board tasks.

The Influence of a Prefabricated Foot Orthosis on Lower Extremity Mechanics During Running in Individuals With Varying Dynamic Foot Motion.

Study Design Controlled laboratory study, cross-sectional. Background Orthotic prescription is often based on the premise that the mechanical effects will be more prominent in individuals with greater calcaneal eversion. Objective To compare the effects of a prefabricated foot orthosis on lower extremity kinematics and kinetics between recreational athletes with high and low calcaneal eversion during running. Methods Thirty-one recreational athletes were included in this study. Three-dimensional kinematic and kinetic data were collected while running with and without a foot orthosis. Participants were grouped based on the degree of calcaneal eversion during the running trials relative to a standing trial (dynamic foot motion). The effects of the orthosis on the frontal and transverse plane angles and moments of the hip and knee were compared between the 10 participants with the greatest and least amount of dynamic foot motion. Results There were no significant interactions (group by orthotic condition) for any of the kinematic or kinetic variables of interest. Conclusion The effects of an orthosis on the mechanics of the hip and knee do not appear to be dependent on an individual's dynamic foot motion. J Orthop Sports Phys Ther 2016;46(9):749-755. Epub 5 Aug 2016. doi:10.2519/jospt.2016.6253.

The effects of fatigue and anticipation on the mechanics of the knee during cutting in female athletes.

BACKGROUND: Unanticipated cutting tasks which do not allow for pre-planning of a movement have been reported to promote knee mechanics which may increase the risk of anterior cruciate ligament injury. Fatigue has also been reported to have similar effects. Athletes must often perform unanticipated tasks when they are fatigued. Previous studies have reported that the effects of anticipation become more prominent as an athlete progresses through a fatigue protocol. However, the protocols previously utilized may not mimic the demands of sports participation. METHODS: Three-dimensional knee joint kinematics and kinetics were collected from 13 female athletes while they performed a run-and-cut task, before and after completion of an intermittent shuttle run. Trials were further divided (pre-planned, unanticipated) to assess the effects of anticipation. FINDINGS: There were no significant interactions between the effects of fatigue and anticipation for the peak knee angles or moments of the knee joint in any plane. Subjects did demonstrate a 68% increase in their peak knee abduction angles following completion of the intermittent shuttle run. Anticipation also had a significant effect on the mechanics of the knee in all planes. Most notably, there was a 23% increase in peak knee abduction angles and a 33% increase in the peak internal knee adduction moments. INTERPRETATION: Both fatigue and anticipation promoted knee mechanics which are associated with an increased risk of knee injury. However, it does not appear that their effects combine when athletes are at a level of fatigue which is thought to reflect sports participation.

CHANGES IN PATELLOFEMORAL JOINT STRESS DURING RUNNING WITH THE APPLICATION OF A PREFABRICATED FOOT ORTHOTIC.

BACKGROUND: Foot orthotics are commonly utilized in the treatment of patellofemoral pain (PFP) and have shown clinical benefit; however, their mechanism of action remains unclear. Patellofemoral joint stress (PFJS) is thought to be one of the main etiological factors associated with PFP. HYPOTHESIS/PURPOSE: The primary purpose of this study was to investigate the effects of a prefabricated foot orthotic with 5 ° of medial rearfoot wedging on the magnitude and the timing of the peak PFJS in a group of healthy female recreational athletes. The hypothesis was that there would be significant reduction in the peak patellofemoral joint stress and a delay in the timing of this peak in the orthotic condition. STUDY DESIGN: Cross-sectional. METHODS: Kinematic and kinetic data were collected during running trials in a group of healthy, female recreational athletes. The knee angle and moment data in the sagittal plane were incorporated into a previously developed model to estimate patellofemoral joint stress. The dependent variables of interest were the peak patellofemoral joint stress as well as the percentage of stance at which this peak occurred, as both the magnitude and the timing of the joint loading are thought to be important in overuse running injuries. RESULTS: The peak patellofemoral joint stress significantly increased in the orthotic condition by 5.8% (p=.02, ES=0.24), which does not support the initial hypothesis. However, the orthotic did significantly delay the timing of the peak during the stance phase by 3.8% (p=.002, ES=0.47). CONCLUSIONS: The finding that the peak patellofemoral joint stress increased in the orthotic condition did not support the initial hypothesis. However, the finding that the timing of this peak was delayed to later in the stance phase in the orthotic condition did support the initial hypothesis and may be related to the clinical improvements previously reported in subjects with PFP. LEVEL OF EVIDENCE: Level 4.

THE EFFECTS OF ANTICIPATION ON THE MECHANICS OF THE KNEE DURING SINGLE-LEG CUTTING TASKS: A SYSTEMATIC REVIEW.

BACKGROUND: ACL injuries are common in sports, which has resulted in the development of risk screening and injury prevention programs to target modifiable neuromuscular risk factors. Previous studies which have analyzed single-leg cutting tasks have reported that the anticipation status of the task (pre-planned vs. unanticipated) has a significant effect on the mechanics of the knee. HYPOTHESIS/PURPOSE: The purpose of this systematic review is to assess the effect of anticipation on the mechanics of the knee in the sagittal, frontal, and transverse planes during tasks which athletes frequently perform during competition. STUDY DESIGN: Systematic Review. METHODS: The following databases were searched using relevant key words and search limits: Pub Med, SPORTDiscus, CINAHL, and Web of Science. A modified version of the Downs and Black checklist was used to assess the methodological quality of the articles by two independent reviewers. RESULTS: 284 articles were identified during the initial database search. After a screening process, 34 articles underwent further review. Of these articles, 13 met the criteria for inclusion in this systematic review. CONCLUSIONS: It appears that tasks which do not allow a subject to pre-plan their movement strategy promote knee mechanics which may increase an athlete's risk of injury. CLINICAL RELEVANCE: Clinicians involved in the development and implementation of ACL injury risk screening and prevention programs may want to consider incorporating tasks which do not allow time for pre-planning. These unanticipated tasks may more closely mimic the demands of the sports environment and may promote mechanics which increase the risk of injury. LEVEL OF EVIDENCE: Level 1b.

The effect of a prefabricated foot orthotic on frontal plane joint mechanics in healthy runners.

The mechanism of action of a foot orthotic is poorly understood. The purpose of this study was to use principal components analysis (PCA) to analyze the effects of a prefabricated foot orthotic on frontal plane knee and ankle mechanics during running. Thirty-one healthy subjects performed running trials with and without a foot orthotic and PCA was performed on the knee and ankle joint angles and moments to identify the dominant modes of variation. MANOVAs were conducted on the retained principal components of each waveform and dependent t tests (P < .05) were performed in the case of significance. Mechanics of the ankle were not affected by the foot orthotic. However, mechanics of the knee were significantly altered as subjects demonstrated an increase in the magnitude of the knee abduction moment waveform in an orthotic condition. Subjects also demonstrated a significant shift in the timing of the knee abduction moment waveform toward later in the stance phase in the orthotic condition. These orthotic effects were not related to subject's foot mobility, measured using the navicular drop test. The mechanism of action of a foot orthotic may be related to their effect on the timing of frontal plane knee loading.