Thomas G. Almonroeder

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

ABSTRACT 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.

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.

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 subjects 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.

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 individuals dynamic foot motion. J Orthop Sports Phys Ther 2016;46(9):749-755. Epub 5 Aug 2016. doi:10.2519/jospt.2016.6253.

The influence of fatigue on decision-making in athletes: a systematic review

Abstract A potential challenge associated with sports is that athletes must often perform the cognitive processing associated with decision-making (i.e., movement selection) when fatigued. The purpose of this systematic review was to summarise studies that have analysed the extent to which fatigue influences the effects of decision-making on lower extremity mechanics during execution of common sports manoeuvres. We specifically focused on mechanics associated with ACL injury risk. Reviewers searched the PubMed, SPORTDiscus, CINAHL and Web of Science databases. The search identified 183 unique articles. Five of these articles met our eligibility criteria. Two of the studies incorporated fatigue protocols where athletes progressed to exhaustion and found that the effects of decision-making on mechanics were more pronounced with fatigue. The nature of the results appears to indicate that fatigue may compromise an athlete’s cognitive processing in a manner that diminishes their ability to control movement when rapid decision-making is required. However, three subsequent studies utilised fatigue protocols designed to mimic sports participation and found that fatigue did not influence the effects of decision-making on mechanics. In general, these findings appear to indicate that fatigue may only affect the cognitive processing associated with decision-making when athletes approach a state of exhaustion.

Cognitive Demands Influence Lower Extremity Mechanics During a Drop Vertical Jump Task in Female Athletes

&NA; • STUDY DESIGN: Cross‐sectional study. • BACKGROUND: The drop vertical jump task is commonly used to screen for anterior cruciate ligament injury risk; however, its predictive validity is limited. The limited predictive validity of the drop vertical jump task may be due to not imposing the cognitive demands that reflect sports participation. • OBJECTIVES: To investigate the influence of additional cognitive demands on lower extremity mechanics during execution of the drop vertical jump task. • METHODS: Twenty uninjured women (age range, 18‐25 years) were required to perform the standard drop vertical jump task, as well as drop vertical jumps that included additional cognitive demands. The additional cognitive demands were related to attending to an overhead goal (ball suspended over‐head) and/or temporal constraints on movement selection (decision making). Three‐dimensional ground reaction forces and lower extremity mechanics were compared between conditions. • RESULTS: The inclusion of the overhead goal resulted in higher peak vertical ground reaction forces and lower peak knee flexion angles in comparison to the standard drop vertical jump task. In addition, participants demonstrated greater peak knee abduction angles when trials incorporated temporal constraints on decision making and/or required participants to attend to an overhead goal, in comparison to the standard drop vertical jump task. • CONCLUSION: Imposing additional cognitive demands during execution of the drop vertical jump task influenced lower extremity mechanics in a manner that suggested increased loading of the anterior cruciate ligament. Tasks utilized in anterior cruciate ligament injury risk screening may benefit from more closely reflecting the cognitive demands of the sports environment.

Decision Making Influences Tibial Impact Accelerations During Lateral Cutting

Lower-extremity musculoskeletal injuries are common in sports such as basketball and soccer. Athletes competing in sports of this nature must maneuver in response to the actions of their teammates, opponents, etc. This limits their ability to preplan movements. The purpose of this study was to compare impact accelerations during preplanned versus unplanned lateral cutting. A total of 30 subjects (15 males and 15 females) performed preplanned and unplanned cuts while the authors analyzed impact accelerations using an accelerometer secured to their tibia. For the preplanned condition, subjects were aware of the movement to perform before initiating a trial. For the unplanned condition, subjects initiated their movement and then reacted to the illumination of one of 3 visual stimuli which dictated whether they would cut, land, or land-and-jump. A mixed-model analysis of variance with a between factor of sex (male and female) and a within factor of condition (preplanned and unplanned) was used to analyze the magnitude and variability of the impact accelerations for the cutting trials. Both males and females demonstrated higher impact accelerations (P = .01) and a trend toward greater intertrial variability (P = .07) for the unplanned cutting trials (vs preplanned cuts). Unplanned cutting may place greater demands on the musculoskeletal system.

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.

Divided attention during cutting influences lower extremity mechanics in female athletes

Abstract Anterior cruciate ligament (ACL) injuries in basketball appear to be more common when players are in possession of the ball. The greater risk of ACL injury when in possession of the ball may result from the athlete’s inability to fully attend to their movement. However, it is also possible that having to carry/manipulate the ball restricts the athlete’s ability to utilise their upper extremities for stability during a manoeuvre. The purpose of this study was to explore how possession of a basketball and divided attention influence lower extremity mechanics during cutting and landing. Twenty uninjured females with basketball experience performed a baseline lateral cutting task, as well as lateral cuts while carrying a basketball, with and without a subsequent chest pass. Requiring participants to carry the basketball in isolation (i.e., without the additional pass) had minimal influence on lower extremity mechanics compared to baseline. However, participants demonstrated less knee flexion (40.9° vs. 47.3°) and greater knee abduction (12.2° vs. 10.1°) for trials that included the additional pass (divided attention condition) compared to trials conducted while carrying the basketball in isolation. Athletes may be at greater risk for ACL injury when they are unable to solely attend to their movement.