Comparative Effects of Complex Contrast Training and Traditional Training Methods on Physical Performance Within Female, Semiprofessional Australian Rules Football Players.

ABSTRACT: Luders, J, Garrett, J, Gleadhill, S, Mathews, L, and Bennett, H. Comparative effects of complex contrast training and traditional training methods on physical performance within female, semiprofessional Australian Rules Football players. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to explore whether complex contrast training (CCT) would elicit greater strength and power adaptations than traditional (TRAD) training methods using a volume- and intensity-matched design. Fourteen semiprofessional female Australian Football players completed the study. Both CCT and TRAD saw improvements in all performance outcomes: 1 repetition maximum (1RM) back squat (21.3 ± 8.2 and 16.7 ± 6.8 kg), 1RM bench press (5.3 ± 3.6 and 2.1 ± 4.0 kg), 1RM trap bar deadlift (5.0 ± 6.6 and 11.3 ± 2.5 kg), 5 m sprint (0.002 ± 0.09 and 0.02 ± 0.2 s), 10 m sprint (0.04 ± 0.17 and 0.02 ± 0.1 s), 15 m sprint (0.009 ± 0.15 and 0.08 ± 0.2 s), countermovement jump (CMJ) height (230 ± 150 and 340 ± 390 cm), CMJ absolute peak power (158.5 ± 69.6 and 235.6 ± 229.6 N), CMJ relative peak power (3.46 ± 4.1 and 2.68 ± 1.4 N·kg-1)), and plyometric push-up peak relative power (20.5 ± 13.4 and 15.2 ± 13.5 N). There were no between-group differences except for TRAD recording slightly greater improvements in 1RM Trap bar deadlift (Bayes factor [BF10] = 1.210). Complex contrast training completed sessions on average ∼7 minutes quicker than TRAD (BF10 = 5.722), while both groups reporting similar ratings of perceived exertion (RPE) with CCT (±SD) 58.4 ± 6.7 minutes and TRAD 65.5 ± 4.8. Based on the results, CCT training provides the same performance outcomes as traditional training methods across a period of 8 weeks, while taking less time to achieve these outcomes and with similar RPE.

Musculoskeletal model degrees of Freedom: Frontal plane constraints are hindering our understanding of human movement.

Induced acceleration analyses have expanded our understanding on the contributions of muscle forces to center of mass and segmental kinematics during a myriad of tasks. While these techniques have identified a subset of major muscle that contribute to locomotion, most analyses have included models with only one frontal plane degree of freedom (dof) actuated by the hip joint. The purpose of this study was to define the impact of including knee and subtalar joint frontal plane dof on model superposition accuracy and muscle specific contributions to mediolateral accelerations. Induced acceleration analyses were performed using OpenSim with the Lai model on a freely available dataset of one subject running at 4 m/s. Analyses were performed on four models (standard, with subtalar joint, with frontal plane knee, and combined frontal plane knee with subtalar) with the kinematic constraint and perturbation analyses. Root mean square error and correlations were computed against experimental kinematics. Adding frontal plane dofs improved mediolateral acceleration correlations on average by > 0.25 while only minimally impacting errors. The constraints method performed better than the perturbation method for mediolateral accelerations. Including frontal plane knee dof resulted in muscle and method specific responses. All muscles presented with a complete flip of polarity for constraint method, imparted by allowing the medial/lateral muscles to contribute according to their anatomical function. Only the gluteus medius flipped for the perturbation method. This study provides significant support for the inclusion of frontal plane knee and subtalar dof and the need for reevaluation of muscle contributions via induced acceleration.

Predicting Knee Joint Contact Forces During Normal Walking Using Kinematic Inputs With a Long-Short Term Neural Network.

Knee joint contact forces are commonly estimated via surrogate measures (i.e., external knee adduction moments or musculoskeletal modeling). Despite its capabilities, modeling is not optimal for clinicians or persons with limited experience. The purpose of this study was to design a novel prediction method for knee joint contact forces that is simplistic in terms of required inputs. This study included marker trajectories and instrumented knee forces during normal walking from the "Grand Challenge" (n = 6) and "CAMS" (n = 2) datasets. Inverse kinematics were used to derive stance phase hip (sagittal, frontal, transverse), knee (sagittal, frontal), ankle (sagittal), and trunk (frontal) kinematics. A long-short term memory network (LSTM) was created using matlab to predict medial and lateral knee force waveforms using combinations of the kinematics. The Grand Challenge and CAMS datasets trained and tested the network, respectively. Musculoskeletal modeling forces were derived using static optimization and joint reaction tools in OpenSim. Waveform accuracy was determined as the proportion of variance and root-mean-square error between network predictions and in vivo data. The LSTM network was highly accurate for medial forces (R2 = 0.77, RMSE = 0.27 BW) and required only frontal hip and knee and sagittal hip and ankle kinematics. Modeled medial force predictions were excellent (R2 = 0.77, RMSE = 0.33 BW). Lateral force predictions were poor for both methods (LSTM R2 = 0.18, RMSE = 0.08 BW; modeling R2 = 0.21, RMSE = 0.54 BW). The designed LSTM network outperformed most reports of musculoskeletal modeling, including those reached in this study, revealing knee joint forces can accurately be predicted by using only kinematic input variables.

Rotation sequences for the calculation of shoulder kinematics of the volleyball attack.

Calculating upper extremity kinematics during overhead movements presents with problems typically not seen for the lower extremity due to the large range of motion. Due to these unique issues, different rotation sequences have been suggested to circumvent challenges due to gimbal lock (GL) and angle coherence (AC). The purpose of this study is to determine the most appropriate rotation sequence for shoulder angle calculation during a volleyball attack. METHODS: 15 healthy experienced volleyball players (women = 8) performed 5 attacks off a stationary ball. A 12-camera 3D motion capture system was utilized to record trunk and arm kinematics to compare joint angles calculated using the YXY, ZXY, XZY, YXZ, ZYX, and XYZ rotation sequences. Instances of GL and AC inconsistences were marked for each trial. The last 3 trials were used for analysis. RESULTS: The YXY and XYZ sequences presented with the least total number of errors (12 and 5, respectively). 5 instances of GL were present in the XYZ sequence while none were recorded for the YXY sequence. All other sequences returned incoherent angles that greatly exceeded known ranges of motion. CONCLUSION: When performing kinematic analyses during a volleyball attack, researchers should adhere to ISB recommendations and employ the Eulerian YXY sequence for calculations. If greater anatomical understanding is desired, the XYZ sequence may be utilized for most subjects.

A Comparison of Squat Depth and Sex on Knee Kinematics and Muscle Activation.

The squat is an essential exercise for strengthening lower body musculature. Although squats are frequently employed to improve lower extremity strength and neuromuscular control, differences between sexes and slight modifications, such as squat depth, can dramatically alter muscle recruitment and thus the foci of the exercise. The purpose of this study was to assess the effect of sex and squat depth on lower extremity coactivation and kinematics. Twenty recreationally active (female = 10) participants were recruited. The first visit consisted of one repetition maximum testing. For the second visit, muscle activation was recorded of the gluteus maximus (GM), semitendinosus, biceps femoris (BF), vastus medialis, vastus lateralis, rectus femoris, and gastrocnemius. Reflective markers were placed on the lower body for three-dimensional motion capture. Participants performed a series of squats to 90 deg knee flexion and 120 deg knee flexion. Benjamin-Hochberg procedure was employed and the alpha level was set at 0.05. Knee flexion (p < 0.001), adduction (p < 0.001), and external rotation (p = 0.008) were reduced during 90 deg compared to deep squats. Hip flexion, abduction, and external rotation were greater in deep squats (p < 0.001). Males had greater hip extensor to quad (HE:Q) cocontraction in 90 deg compared to deep squats (p = 0.007); females produced greater posterior chain activation in deep squats (p = 0.001) on ascent. When comparing sexes, males displayed greater HE:Q in the 90 deg squat during ascent (p = 0.013). The addition of deep squats into a preventative training program could be beneficial in reducing deficits prevalent in females and decrease injury incidence.

Lower extremity joint stiffness of autistic adolescents during running at dual speeds.

Running is one of the most common forms of physical activity for autistic adolescents. However, research examining their lower extremity dynamics is sparse. In particular, no information exists regarding lower extremity joint stiffness in autistic adolescents. This study compared knee and ankle joint stiffness during the absorption phase of running between autistic adolescents and non-autistic controls. Motion capture and ground reaction forces were recorded for 22 autistic adolescents and 17 non-autistic age, sex, and BMI matched peers who ran at self-selected and standardized (3.0 m/s) speeds. Group × speed knee and ankle joint stiffness, change in moment, and range of motion were compared using mixed-model ANOVAs. There were no group × speed interactions for any variable. Autistic adolescents presented with significant (12 % and 19 %) reduced knee and ankle joint stiffness, respectively. In addition, autistic adolescents had significant reduced changes in knee and ankle joint moments by 11 % and 21 %, respectively, compared to their non-autistic peers. Only knee joint stiffness and knee joint moments were sensitive to running speed, each significantly increasing with speed by 6 %. Current literature suggests joint stiffness is an important mechanism for stability and usage of the stretch shortening cycle (or elastic recoil); as such, it is possible that the reduced ankle plantar flexor and knee extensor stiffness found in autistic adolescents in this study could be indicative of reduced efficiency during running. As group differences existed across both speeds, autistic adolescents may benefit from therapeutic and/or educational interventions targeting efficient running mechanics.

The effect of subtalar joint axis location on muscle moment arms.

Most dynamic musculoskeletal models define the subtalar joint (STJ) as a one degree of freedom (DOF) hinge with a tri-planar axis. The orientation of this axis of rotation is often determined as a combination of inclination and deviation angles measured from the ground and midline of the foot, respectively. In defining the location of the axis, often the origin is found at the distal aspect of the heel instead of at the articulation of the talus and calcaneus. Key musculoskeletal modeling definitions, such as muscle moment arms, are dependent on the distance and relative location of muscle insertion to the axis of rotation. Since the axis orientation and origin location affect calculations of muscle moment arm and joint dynamics, there is much need for accurate characterization of the STJ axis to understand the STJ's role in dynamic weight-bearing motion. The purpose of this study is to explore how the STJ origin location and axis orientation affect muscle moment arms surrounding the ankle. Datasets from the Grand Knee Challenge, posted on the open-source SimTK website, were modeled using OpenSim. Modifying the location of the STJ axis from the original location closer to the articulation between the talus and calcaneus resulted in significant differences in STJ muscle moment arms and peak STJ moments. The findings of this study conclude that the location of the STJ axis origin needs to be considered and accurately defined, especially if the inclination/deviation angles of the rotational axis will be modified to represent a more subject-specific definition.

Evidence for the use of dynamic maximum normalization method of muscle activation during weighted back squats.

Electromyography (EMG) is a popular technique for analyzing muscle activation profiles during athletic maneuvers such as the back squat. Two methods are commonly implemented for normalizing EMG: a maximum voluntary isometric contraction (MVIC) and a dynamic maximum during the task being performed (DMVC). Although recent literature suggests DMVC may be superior, these suggestions havent been examined for weighted exercises. This study examined the influence of normalization method on rectus femoris, vastus medialis, and biceps femoris activations during back squats. Muscle activations were collected on twenty-seven participants (13 females, 14 males) performing one-repetition maximum (DMVC) and submaximum (80%) back squats. Data from submaximum squats were normalized to MVICs and DMVC. Data were compared using intra-class correlations over two testing days, variance ratio, and coefficients of variation. Mixed-model ANOVAs were used to elucidate the influence on intra-participant (method) and inter-participant (sex) variability. Reliability was "good" or "excellent" for MVIC and "excellent" for DMVC. Inter-subject variability was greater for MVIC compared to DMVC for all muscles. A significant normalization by sex interaction for both peak and mean biceps femoris activation was found. Based on our findings and current literature, normalization to DMVC is the superior method for weighted exercises.

Are Gait Biomechanics Related to Physical Activity Engagement? An Examination of Adolescents with Autism Spectrum Disorder.

PURPOSE: Adolescents with autism spectrum disorder (ASD) rarely meet physical activity (PA) guidelines, thus not reaping associated health benefits. Although many barriers exist, abnormal or inefficient gait biomechanics could negatively impact engagement in PA. This study has two purposes: first, to compare total body mechanical work between adolescents with ASD and neurotypical age-, sex-, and body mass index-matched controls, and second to determine whether gait biomechanics are significantly related to engagement in PA. METHODS: Twenty-five adolescents (age, 13-18 yr) with ASD and 17 neurotypical controls (eight with ASD had no match) participated in the study. Three-dimensional motion capture and force platforms were used to record and analyze gait biomechanics at self-selected speeds and a standardized 1.3 m·s-1. Total body mechanical work (sum of joint works across lower extremity, low back, torso, and shoulders) was compared between groups (n = 17 for each) and speeds using a mixed model analysis of variance. Average daily light PA, moderate to vigorous PA, and total PA was recorded for the entire data set with ASD using triaxial accelerometers worn for 1 wk. Regression analyses were performed between work, stride time variability, speed, and stride length with each PA variable. RESULTS: Adolescents with ASD generated 9% more work compared with the controls (P = 0.016). Speed and stride length were significant regressors of light PA, moderate to vigorous PA, and total PA, explaining greater than 0.20 variance (P < 0.02 for all regressions). CONCLUSIONS: Although adolescents with ASD walked with significantly greater work, the complex full-body variable is not significantly related to engagement in PA. In agreement with research spanning multiple populations and ages, speed and stride length are indicative of PA engagement in adolescents with ASD.

Coordination variability during running in adolescents with autism spectrum disorder.

LAY ABSTRACT: Walking and running are popular forms of physical activity that involve the whole body (pelvis/legs and arms/torso) and are coordinated by the neuromuscular system, generally without much conscious effort. However, autistic persons tend not to engage in sufficient amounts of these activities to enjoy their health benefits. Recent reports indicate that autistic individuals tend to experience altered coordination patterns and increased variability during walking tasks when compared to non-autistic controls. Greater stride-to-stride coordination variability, when the task has not changed (i.e. walking at same speed and on same surface), is likely indicative of motor control issues and is more metabolically wasteful. To date, although, research examining running is unavailable in any form for this population. This study aimed to determine if coordination variability during running differs between autistic adolescents and age, sex, and body mass index matched non-autistic controls. This study found that increased variability exists throughout the many different areas of the body (foot-leg, left/right thighs, and opposite arm-opposite thigh) for autistic adolescents compared to controls. Along with previous research, these findings indicate autistic persons exhibit motor control issues across both forms of locomotion (walking and running) and at multiple speeds. These findings highlight issues with motor control that can be addressed by therapeutic/rehabilitative programming. Reducing coordination variability, inherently lessening metabolic inefficiency, may be an important step toward encouraging autistic youth to engage in sufficient physical activity (i.e. running) to enjoy physiological and psychological benefits.

The effects of sex and landing task on hip mechanics.

Prevalence of femoroacetabular impingement syndrome is common in cutting sports. A first step to understanding the relationship between cutting sports and the development of femoroacetabular impingement is to investigate hip joint contact forces during such tasks. The purpose of this study was to explore sex and task differences in hip joint contact forces, estimated through musculoskeletal modeling, during single-leg drop landings and land-and-cuts. Kinematics and ground reaction forces were obtained from 38 adults performing drop landings and land-and-cut tasks. Simulations were performed in OpenSim to estimate lower extremity muscle forces and hip joint contact forces. Statistical parametric mapping was used to compare hip joint force waveforms between sex and task. There were no sex differences in hip joint forces, but landing trials were characterized by increased hip joint forces compared to land-and-cut trials. The hip joint force estimates obtained the current study could be used in future finite element models that incorporate bone growth models to understand the development of femoroacetabular impingement and design possible compensatory exercises.

Inter and intra-limb coordination variability during walking in adolescents with autism spectrum disorder.

BACKGROUND: Autism spectrum disorder, a neurodevelopmental disorder, is difficult to characterize from a gait biomechanics perspective, possibly due to increased inter and intra-individual variability. Previous research illustrates increased gait variability in young children with autism, but assessments in older adolescents or at varying speeds are unavailable. The purpose of this study was to determine if adolescents with autism demonstrate increased intra-limb and inter-limb coordination variability during walking compared to age, sex, and body mass index matched controls. METHODS: Seventeen adolescents with autism (age 13-18 years) and seventeen matched controls performed walking at two matched speeds: self-selected of adolescents with autism and at 1.3 m/s. Modified vector coding was used to determine the patterns of movement for foot-shank, left/right thigh, and contralateral thigh-arm coupling. Coordination variability, a measure of cycle-to-cycle variability, was determined across the full stride. Mixed-model analyses of variance were used to determine if group by speed interactions and/or main effects existed for coordination variability. FINDINGS: A significant interaction existed for foot-shank variability (p = 0.039). Adolescents with autism had greater variability at self-selected speeds (p = 0.018), but not at 1.3 m/s (p = 0.593) compared to controls. Thigh-thigh coordination was greater for adolescents with ASD compared to controls at both speeds (p = 0.021). Variability was decreased at 1.3 m/s for both foot-shank (p = 0.016) and thigh-thigh (p = 0.021) coupling. INTERPRETATION: This study illustrates that adolescents with autism perform walking with increased coordination variability at both proximal and distal segments. Thus, it is likely intra-individual variability drives the disparity of movement patterns in this population.

Lower Limb Proprioception and Strength Differences Between Adolescents With Autism Spectrum Disorder and Neurotypical Controls.

Autism spectrum disorder (ASD) is a complex diagnosis characterized primarily by persistent deficits in social communication/interaction and repetitive behavior patterns, interests, and/or activities. ASD is also characterized by various physiological and/or behavioral features that span sensory, neurological, and neuromotor function. Although problems with lower body coordination and control have been noted, little prior research has examined lower extremity strength and proprioception, a process requiring integration of sensorimotor information to locate body/limbs in space. We designed this study to compare lower limb proprioception and strength in adolescents with ASD and neurotypical controls. Adolescents diagnosed with ASD (n = 17) and matched controls (n = 17) performed ankle plantarflexion/dorsiflexion bilateral proprioception and strength tests on an isokinetic dynamometer. We assessed position-based proprioception using three targeted positions (5 and 20-degrees plantarflexion and 10-degrees dorsiflexion) and speed-based proprioception using two targeted speeds (60 and 120-degrees/second). We assessed strength at 60-degrees/second. Participants with ASD performed 1.3-times more poorly during plantarflexion position and 2-times more poorly during the speed-based proprioception tests compared to controls. Participants with ASD also exhibited a 40% reduction in plantarflexion strength compared to controls. These findings provide insight into mechanisms that underly the reduced coordination, aberrant gait mechanics, and coordination problems often seen in individuals with ASD, and the identification of these mechanisms now permits better targeting of rehabilitative goals in treatment programs.

Running Biomechanics of Adolescents With Autism Spectrum Disorder.

Research examining gait biomechanics of persons with autism spectrum disorder (ASD) has grown significantly in recent years and has demonstrated that persons with ASD walk at slower self-selected speeds and with shorter strides, wider step widths, and reduced lower extremity range of motion and moments compared to neurotypical controls. In contrast to walking, running has yet to be examined in persons with ASD. The purpose of this study was to examine lower extremity running biomechanics in adolescents (13-18-year-olds) with ASD and matched (age, sex, and body mass index (BMI)) neurotypical controls. Three-dimensional kinematics and ground reaction forces (GRFs) were recorded while participants ran at two matched speeds: self-selected speed of adolescents with ASD and at 3.0 m/s. Sagittal and frontal plane lower extremity biomechanics and vertical GRF waveforms were compared using two-way analyses of variances (ANOVAs) via statistical parametric mapping (SPM). Adolescents with ASD ran with reduced stride length at self-selected speed (0.29 m) and reduced vertical displacement (2.1 cm), loading-propulsion GRFs (by 14.5%), propulsion plantarflexion moments (18.5%), loading-propulsion hip abduction moments (44.4%), and loading knee abduction moments (69.4%) at both speeds. Running at 3.0 m/s increased sagittal plane hip and knee moments surrounding initial contact (both 10.4%) and frontal plane knee angles during midstance (2.9 deg) and propulsion (2.8 deg) compared to self-selected speeds. Reduced contributions from primarily the ankle plantarflexion but also knee abduction and hip abduction moments likely reduced the vertical GRF and displacement. As differences favored reduced loading, youth with ASD can safely be encouraged to engage in running as a physical activity.

Accelerometer measured physical activity among youth with autism and age, sex, and body mass index matched peers: A preliminary study.

BACKGROUND: While research has examined physical activity differences between youth with autism spectrum disorder (ASD) and neurotypical peers, they largely do not consider demographic or anthropomorphic variables when recruiting comparison group participants. OBJECTIVE: The purpose of this preliminary study was to compare light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA) between youth with ASD and age, sex, and body mass index (BMI) matched neurotypical peers from the same geographic region. METHOD: A sample of 36 participants, including youth aged 13-17 with ASD and age, sex, and BMI-matched neurotypical youth recruited from the same geographic location. Demographic information was obtained via parent report, and physical activity was measured using the ActiGraph GT3x accelerometer. Participants wore monitors for seven consecutive days during waking hours. Descriptive analyses were conducted for participant demographics, LPA, and MVPA, and paired-sample t-tests were employed to examine differences in LPA and MVPA between youth with ASD and age, sex, and BMI-matched neurotypical peers. RESULTS: Youth with ASD and their age, BMI, and sex matched neurotypical peers demonstrated no significant difference in average daily LPA (201.36 ± 63.50 v. 172.30 ± 54.98) or MVPA (33.54 ± 17.07 v. 37.63 ± 19.94). CONCLUSIONS: Results indicate that youth with ASD did not engage in significantly less MVPA than age, sex, and BMI-matched peers from the same geographic location. Not finding clear distinctions between youth with ASD and neurotypical peers in this study suggest that variability in other social or environmental factors may play a larger role in influencing MVPA than ASD itself.

Footwear Affects Conventional and Sumo Deadlift Performance.

Barefoot weightlifting has become a popular training modality in recent years due to anecdotal suggestions of improved performance. However, research to support these anecdotal claims is limited. Therefore, the purpose of this study was to assess the differences between the conventional deadlift (CD) and the sumo deadlift (SD) in barefoot and shod conditions. On day one, one-repetition maximums (1 RM) were assessed for thirty subjects in both the CD and SD styles. At least 72 h later, subjects returned to perform five repetitions in four different conditions (barefoot and shod for both CD and SD) at 70% 1 RM. A 2 × 2 (footwear × lifting style) MANOVA was used to assess differences between peak vertical ground reaction force (VGRF), total mechanical work (WORK), barbell vertical displacement (DISP), peak vertical velocity (PV) and lift time (TIME) during the concentric phase. The CD displayed significant increases in VGRF, DISP, WORK, and TIME over the SD. The shod condition displayed increased WORK, DISP, and TIME compared to the barefoot condition. This study suggests that lifting barefoot does not improve performance as no differences in VGRF or PV were evident. The presence of a shoe does appear to increase the DISP and WORK required to complete the lift, suggesting an increased work load is present while wearing shoes.

Walking lower extremity biomechanics of adolescents with autism spectrum disorder.

Although the literature indicates children with autism spectrum disorder (ASD) walk at slower speeds and altered kinematics compared to neurotypical controls, no research has examined walking at matched speeds. This study examined biomechanical differences between adolescents with ASD and matched (age, sex, and body mass index) neurotypical controls. Lower extremity biomechanics of seventeen adolescents with ASD and seventeen controls were compared at matched speeds: self-selected and a standardized 1.3 m/s. Controls exhibited greater eversion angles and hip abduction moments compared to those with ASD. This study found adolescents, which may have a more mature gait than young children, walk with a similar pattern in the propulsive plane (i.e. sagittal) as neurotypical controls, but with alterations in the supportive plane (i.e. frontal).

Effects of External Load on Sagittal and Frontal Plane Lower Extremity Biomechanics During Back Squats.

Previous literature suggests the sticking region, the transition period between an early peak concentric velocity to a local minimum, in barbell movements may be the reason for failing repeated submaximal and maximal squats. This study determined the effects of load on lower extremity biomechanics during back squats. Twenty participants performed the NSCA's one-repetition-maximum (1RM) testing protocol, testing to supramaximum loads (failure). After completing the protocol and a 10-min rest, 80% 1RM squats were performed. Statistical parametric mapping (SPM) was used to determine vertical velocity, acceleration, ankle, knee, and hip sagittal and frontal plane biomechanics differences between 1RM, submaximum, and supramaximum squats (105% 1RM). Vertical acceleration was a better discriminative measure than velocity, exhibiting differences across all conditions. Supramaximum squats emphasized knee moments, whereas 1RM emphasized hip moments during acceleration. Submaximum squats had reduced hip and knee moments compared to supramaximum squats, but similar knee moments to 1RM squats. Across all conditions, knee loads mirrored accelerations and a prominent knee (acceleration) to hip (sticking) transition existed. These results indicate that (1) submaximum squats performed at increased velocities can provide similar moments at the ankle and knee, but not hip, as maximal loads and (2) significant emphasis on hip strength is necessary for heavy back squats.

Intra- and inter-rater reliability of ultrasound measures of the anterior cruciate ligament.

Diagnostic ultrasound has accurately and reliably been utilized by clinicians to determine ACL morphology at the tibial insertion site, specifically measuring the entire ACL diameter, the anteromedial bundle (AM), and the posterolateral bundle. However, intra- and inter-rater reliability of these measures in a research setting is unknown. The purpose of this study was to determine intra- and inter-rater reliability of ultrasound measures of ACL diameter and AM diameter in researchers with low-to-moderate ultrasound experience. We hypothesized that intra- and inter-rater reliability of ACL and AM diameters would reach acceptable levels, a minimal intraclass correlation (ICC) of 0.6 and a desired ICC of 0.8 with an α of 0.05 and ß of 0.20. Fourteen volunteers participated in this study. During the ACL ultrasound measures, participants were seated with their knee flexed to at least 90°. Each rater recorded two images of both the right and left ACL and AM bundles. Next, participants were re-examined by rater one for intra-rater reliability analyses. Two-way random ICCs were conducted for intra-rater (between sessions) and inter-rater reliability for both the full ACL and the AM bundle diameters. Standard errors between sessions for Rater 1's AM bundle and ACL diameters were less than 0.03 cm. Intra-rater reliability was higher in AM bundles compared to full ACL, 0.76 versus 0.59, respectively. Standard errors between Rater 1 and Rater 2 were less than 0.03 cm. Inter-rater reliability was higher in AM bundles compared to full ACL, 0.71 versus 0.41, respectively. The results of the study indicate researchers with low-to-moderate training with ultrasound measures can locate and measure the ACL, but with greater reliability using the AM.

Foot Rotation Gait Modifications Affect Hip and Ankle, But Not Knee, Stance Phase Joint Reaction Forces During Running.

Alterations of foot rotation angles have successfully reduced external knee adduction moments during walking and running. However, reductions in knee adduction moments may not result in reductions in knee joint reaction forces. The purpose of this study was to examine the effects of internal and external foot rotation on knee, hip, and ankle joint reaction forces during running. Motion capture and force data were recorded of 19 healthy adults running at 3.35 m/s during three conditions: (1) preferred (normal) and with (2) internal and (3) external foot rotation. Musculoskeletal simulations were performed using opensim and the Rajagopal 2015 model, modified to a two degree-of-freedom knee joint. Muscle excitations were derived using static optimization, including muscle physiology parameters. Joint reaction forces (i.e., the total force acting on the joints) were computed and compared between conditions using one-way analyses of variance (ANOVAs) via statistical parametric mapping (SPM). Internal foot rotation reduced resultant hip forces (from 18% to 23% stride), while external rotation reduced resultant ankle forces (peak force at 20% stride) during the stance phase. Three-dimensional and resultant knee joint reaction forces only differed at very early and very late stance phase. The results of this study indicate, similar to previous findings, that reductions in external knee adduction moments do not mirror reductions in knee joint reaction forces.