Ground Reaction Force Asymmetry Research Articles

Relationships of lower extremity and trunk asymmetries in elite soccer players.

In light of previous research highlighting the prevalence of asymmetries in soccer players and possible links to injury risks, there is a crucial gap in the biomechanical understanding of complex relationships between lower extremity and trunk asymmetries in elite soccer players. The purpose of this study was to investigate the level, relationships, and differences among twelve different parameters of strength, morphological, and neuromuscular asymmetries in elite soccer players. Methods: Elite male soccer players (n = 25, age 21.7 ± 3.9years) were tested in the following tests: bilateral fluid distribution, hip flexor range of motion, postural stability, isokinetic strength of knee extensors and flexors, isometric lateral trunk rotation strength, eccentric strength of knee flexors, isometric bilateral strength of hip adductors, and vertical ground reaction force in counter-movement jump-free arms, counter-movement jump, squat jump, and drop jump tests. One-way ANOVA, Pearson's coefficient (r), and partial eta squared (η p 2) were used for data analysis. Results: Significant differences in asymmetries were found in elite soccer players (F11,299 = 11.01, p < .01). The magnitude of asymmetry over 10% was in postural stability and drop jump parameters. The lowest magnitudes of asymmetries were in the fluid distribution of the lower limbs and the vertical ground reaction force during the take-off phase in squat jumps. The highest asymmetries between the dominant and non-dominant sides were found in postural stability and drop jump. A total of eleven significant correlations (p < 0.05, r = 0.41-0.63, R2 = 0.17-0.40) were detected between the analyzed asymmetries in elite soccer players. The lateral trunk rotation asymmetries were significantly correlated to vertical ground reaction force asymmetries and knee extensors. Conclusion: Long-term exposure in elite soccer leads to unilateral biomechanical loading that induces abnormal strength and morphological adaptations in favor of the dominant side while linking lower limb and trunk strength asymmetries. By unraveling these complex relationships, we strive to contribute novel methods that could inform targeted training regimens and injury prevention strategies in the elite soccer community. The data should encourage future researchers and coaches to monitor and develop trunk strength linked to lower body kinematics.

Editorial Expression of Concern: Vertical ground reaction force and knee muscle activation asymmetries in patients with ACL reconstruction compared to healthy individuals.

Editorial Expression of Concern: Vertical ground reaction force and knee muscle activation asymmetries in patients with ACL reconstruction compared to healthy individuals.

Differences in hip musculoskeletal loads between limbs during daily activities in patients with 3D-printed hemipelvic reconstructions following tumor surgery

BackgroundAnatomical custom-made prostheses, thanks to computer-aided design and 3D-printing technology, help improve osseointegration and reduce mechanical complications in bone reconstructions following bone tumors. A recent quantitative analysis of long-term recovery in patients with 3D-printed reconstructions following pelvic tumor surgery showed asymmetries in ground reaction forces between limbs during different motor activities, while standing very good motor performance and quality of life. Research questionWe analyzed hip contact forces and muscle forces in that cohort of six patients with an innovative custom-made reconstruction of the hemipelvis, and we tested the hypothesis that asymmetries in ground reaction forces would result in more marked differences in musculoskeletal forces. MethodsState-of-the-art musculoskeletal modeling in an optimization-based inverse-dynamics workflow was used to calculate hip contact forces and muscle forces during five motor activities, and the differences between limbs were statistically evaluated across the motor activity cycles and on the force peaks. ResultsThe musculoskeletal loads were found to be not symmetric, as hip loads were generally higher in the contralateral limb. We found significant differences in considerable portions of the motor activities cycles except squat, load symmetry indices indicating a load increase (median up to 25%) on the contralateral limb, especially during stair descent and chair rise/sit, and significantly higher values in the contralateral limb at force peaks. SignificanceWe confirmed the hypothesis that residual asymmetries found in ground reaction forces were amplified when hip musculoskeletal loads were investigated, reflecting a shift of the loads toward the intact limb. Despite the general trend of higher loads found in the contralateral hip, this cannot be considered a risk of overloading, as both hips supported loads in a physiological range or lower, indicating a likely optimal recovery.

Using trunk kinematics to predict kinetic asymmetries during double-leg jump-landings in collegiate athletes following anterior cruciate ligament reconstruction

BackgroundBilateral vertical ground reaction force (VGRF) and knee extension moment asymmetries are commonly observed during jumping and landing tasks following anterior cruciate ligament (ACL) reconstructions (ACLR) in collegiate athletes. Kinetic asymmetries during landings are associated with increased ACL re-injury risk. Efforts have been made to predict bilateral kinetic asymmetries using trunk kinematics during squats but not during jump-landings. Research questionTo determine the correlations between trunk kinematics (medial-lateral shoulder positions, medial-lateral hip positions, and lateral trunk bending angles) and bilateral kinetic asymmetries (VGRF and knee extension moments) during double-leg jump-landings in collegiate athletes following ACLR. MethodsFifteen National Collegiate Athletic Association Division I athletes who had ACLR in the past 24 months participated. Eleven of them performed two assessments over the study period for a total of 26 assessments for data analyses. Athletes performed three double-leg countermovement jumps. Kinematics and kinetics data were collected. Medial-lateral shoulder and hip positions relative to ankle positions, lateral trunk bending angles, and kinetic asymmetries were calculated during the jumping (the lowest hip position until takeoff) and landing (the first 100 ms after initial contact) phases. ResultsMedial-lateral shoulder positions correlated with VGRF (r = 0.63, p < 0.001) and knee moment asymmetries (r = 0.53, p = 0.006) in the jumping phase. Medial-lateral hip positions correlated with VGRF (r = 0.61, p < 0.001; r = 0.52, p = 0.006) and knee moment asymmetries (r = 0.55, p = 0.004; r = 0.61, p < 0.001) in both jumping and landing phases. SignificanceMedial-lateral hip positions correlated with kinetic asymmetries during double-leg jump-landings in collegiate athletes following ACLR. A 2D assessment using a standard video camera might be used as a low-cost and clinically applicable tool to assess bilateral kinetic asymmetries by quantifying medial-lateral hip positions during jump-landings following ACLR.

Ground reaction forces during double limb stances while walking in individuals with unilateral transfemoral amputation.

The asymmetrical gait of individuals with unilateral transfemoral amputation has been well documented. However, there is not a wealth of investigation into asymmetries during the double limb stance depending on whether the intact or prosthetic limb is leading. The first aim of this study was to compare ground reaction forces during the double limb stance of individuals with unilateral transfemoral amputation depending on whether their intact (initial double limb stance) or prosthetic (terminal double limb stance) limb was leading. The second aim of this study was to compare the asymmetry ratio of ground reaction forces during the double limb stance between individuals with and without unilateral transfemoral amputation. Thirty individuals, fifteen with unilateral transfemoral amputation and fifteen who were able-bodied, were recruited for this study. Each individual walked on an instrumented treadmill for 30s at eight different speeds, ranging from 2.0km/h to 5.5km/h with .5km/h increments. Ground reaction force parameters, temporal parameters, and asymmetry ratios of all parameters were computed from the data collected. The appropriate statistical analyses of all data based on normality were conducted to investigate the aims of this study. Significant main effects of speed, double limb stance, and their interactions were found for most parameters (p < .01 or p < .05). Individuals with unilateral transfemoral amputation spent a longer duration in terminal double limb stance than initial double limb stance at all tested speeds. They also experienced significantly higher peak vertical ground reaction force during initial double limb stance compared to terminal double limb stance with increasing walking speed. However, during terminal double limb stance, higher anteroposterior ground reaction force at initial contact was found when compared to initial double limb stance. Significant differences between individuals with unilateral transfemoral amputation and able-bodied individuals were found in asymmetry ratios for peak vertical ground reaction force, anteroposterior ground reaction force, anteroposterior shear, and mediolateral shear at all tested speeds. Asymmetrical loading persists in individuals with unilateral transfemoral amputation during double limb stance. Increasing walking speed increased ground reaction force loading asymmetries, which may make individuals with unilateral transfemoral amputation more susceptible to knee osteoarthritis or other musculoskeletal disorders. Further study is necessary to develop ideal gait strategies for the minimization of gait asymmetry in individuals with unilateral transfemoral amputation.

Bilateral Ground Reaction Force Asymmetry During Supramaximal Drop Landings

Bilateral vertical ground reaction forces (vGRF) asymmetries have not been investigated during supramaximal drop heights. The first purpose of this study was to investigate the influence of drop height on impact and attenuation vGRF impulses. 19 young adults completed the protocol (14 males, 5 females, age: 21.3 ± 0.75 years, mass: 75.1 ± 10.2 kg, height: 171.4 ± 7.9 cm, 1RM back squat relative to mass: 1.72 ± 0.4), which included bilateral drop landings starting at 0.3 m going up to 1.52 m in increments of 0.152 m. Asymmetries were calculated from impact impulse, loading rate, peak vGRF, attenuation impulse, and total impulse. Linear regressions analyzed these variables with respect to drop height at the group and individual levels. All dependent variables measuring asymmetrical force production produced negative regression slopes at the group level, but the adjusted R2 values ranging 0.06 to 0.15 indicate drop height accounted for minimal variance in asymmetry variables. However, examination of individual asymmetry responses reveals noteworthy adjusted R2 values for athlete monitoring and return to play considerations in competitive sport. Seven participants displayed significant reductions in asymmetry values as drop height increased with R2 values ranging from 0.23-0.64. Practitioners and coaches using landing asymmetry measurements to support return to play decisions should consider the inclusion of larger drop heights to avoid false positive asymmetry results and encourage participants to land as quickly as possible with maximal effort.

Unilateral symptomatic Achilles tendinopathy has limited effects on bilateral lower limb ground reaction force asymmetries and muscular synergy attributes when walking at natural and fast speeds

BackgroundAchilles tendinopathy (AT) may affect ground reaction force (GRF) and muscle synergy (MS) during walking due to pain, biological integrity changes in the tendon and neuroplastic adaptations. The objective of this study was to compare GRF asymmetries and MS attributes between symptomatic and asymptomatic lower limbs (LL) during walking at natural and fast speeds in adults with unilateral AT.MethodsA convenience sample consisting of twenty-eight participants walked on an instrumented treadmill at natural (1.3 m/s) and fast (1.6 m/s) speeds. Peak GRF were measured in mediolateral, anteroposterior and vertical directions. Individualized electromyography (EMG) activation profiles were time- and amplitude-normalized for three consecutive gait cycles and MS were extracted using non-negative matrix factorization algorithms. MS were characterized by the number, composition (i.e., weighting of each muscle) and temporal profiles (i.e., duration and amplitude) of the MS extracted during walking. Paired Student’s t-tests assessed peak GRF and MS muscle weighting differences between sides whereas Pearson correlation coefficients characterized the similarities of the individualized EMG and MS activation temporal profiles within sides.ResultsAT had limited effects on peak GRF asymmetries and the number, composition and temporal profiles of MS between symptomatic and asymptomatic LL while walking on a level treadmill at natural and fast speeds. In most participants, four MS with a specific set of predominantly activated muscles were extracted across natural (71 and 61%) and fast (54 and 50%) walking speeds for the symptomatic and asymptomatic side respectively. Individualized EMG activation profiles were relatively similar between sides (r = 0.970 to 0.999). As for MS attributes, relatively similar temporal activation profiles (r = 0.988 to 0.998) and muscle weightings (p < 0.05) were found between sides for all four MS and the most solicited muscles. Although the faster walking speed increased the number of merged MS for both sides, it did not significantly alter MS symmetry.ConclusionFaster walking speed increased peak GRF values but had limited effects on GRF symmetries and MS attribute differences between the LL. Corticospinal neuroplastic adaptations associated with chronic unilateral AT may explain the preserved quasi-symmetric LL motor control strategy observed during natural and fast walking among adults with chronic unilateral AT.

Effects of walking speed on magnitude and symmetry of ground reaction forces in individuals with transfemoral prosthesis

Individuals with unilateral transfemoral amputation (uTFA) walk asymmetrically. Investigating gait symmetry in ground reaction force (GRF) is critical because asymmetric loading on the residual limb can result in injury. The aim of this study was to investigate the GRF of individuals with uTFA by systematically controlling their walking at eight speeds(2.0–5.5 km/h with increments of 0.5 km/h) on a treadmill. Forty-eight individuals participated in this study, which included 24 individuals with uTFA (K3 and K4) and 24 individuals without amputation. GRFs (anteroposterior, mediolateral, and vertical) of the prosthetic and intact limb steps were collected for the individuals with uTFA and those of the right limb were collected for the control group. Peak force values of the GRF components, temporal parameters, impulses, and their asymmetry ratios were investigated and statistically analyzed. With an increasing walking speed, the magnitude of GRF changed gradually; individuals with uTFA exhibited increased GRF asymmetry in the vertical and mediolateral components, while that of the anteroposterior component remained constant. uTFA individuals typically maintained a constant asymmetry ratio in the mediolateral and anteroposterior (braking and propulsive) GRF impulses across a wide range of walking speeds. This result suggests that individuals with uTFA may cope with various walking speeds by maintaining symmetric mediolateral and anteroposterior impulses. The data provided in this study can serve as normative data for the GRF and its symmetry across a range of walking speeds in individuals with uTFA.

Medial-lateral hip positions predicted kinetic asymmetries during double-leg squats in collegiate athletes following anterior cruciate ligament reconstruction

ACL re-injury rates are high in collegiate athletes, and double-leg squats have been used as a functional weight-bearing exercise to strengthen the lower extremities and assess bilateral kinetic asymmetries. The primary purpose was to quantify the correlations between medial–lateral shoulder/hip positions and lateral bending angles and bilateral asymmetries in vertical ground reaction forces (VGRF) and knee extension moments during double-leg squats in collegiate athletes at two assessments following anterior cruciate ligament reconstruction (ACLR). Seventeen National Collegiate Athletic Association Division I athletes performed double-leg squats between 0 and 6 months and/or between 6 and 12 months following their ACLR while kinematic and kinetic data were collected. Medial-lateral shoulder positions strongly and significantly correlated with VGRF asymmetries at both assessments (p ≤ 0.007, r ≥ 0.68). Medial-lateral hip positions strongly and significantly correlated with VGRF asymmetries and knee moment asymmetries at both assessments (p ≤ 0.018, r ≥ 0.62). Additionally, participants demonstrated decreased VGRF asymmetries and knee moment asymmetries, more neutral shoulder and hip positions, and increased knee moments for the injured leg at the second assessment compared to the first assessment with large effect sizes (p ≤ 0.008, Cohen’s d ≥ 1.06). In conclusion, medial–lateral hip positions correlated and predicted VGRF and knee moment asymmetries during double-leg squats in collegiate athletes at two assessments (0–6 and 6–12 months) following ACLR. The bilateral asymmetries support the need for an individual approach for kinetic asymmetry assessments. A commercially available camera can be utilized as a low-cost and convenient tool to monitor and potentially train bilateral kinetic symmetries during double-leg squats in patients following ACLR.

Reliability and Validity of the Ground Reaction Force Asymmetric Index at Seat-Off as a Measure of Lower Limb Functional Muscle Strength: A Preliminary Study

This study examined the reliability of the newly developed ground reaction force asymmetry index (GRF AI) at seat-off using a low-cost force plate and the validity of this new test by comparing it with other muscle strength-measuring methods and walking speed. This study was a cross-sectional design in general hospital setting. A convenience sample of 47 community-dwelling adults aged ≥40 years was performed. GRF AI is the measurement value obtained by shifting the weight to the right and left while performing sit-to-stand (STS). GRF AI assessed using GRF data at seat-off during an STS test with maximal weight shift to the right and left side and repeated 4 weeks later. Hip and knee extensor strength were measured using hand-held dynamometry; hand grip strength and walking speed were measured using a standardized method. Intrasessional intrarater reliability of the right and left side at Sessions 1 and 2 were high (intraclass correlation coefficients [ICC] = 0.947 and 0.974; 0.931 and 0.970, respectively). In addition, the intersessional intrarater reliability of a single test trial (ICC = 0.911 and 0.930) and the mean of three test trials (ICC = 0.965 and 0.979) was also high. There was a low correlation between right-side GRF AI and right hand grip strength (r = 0.268) and between left-side GRF AI and left hand grip strength (r = 0.316). No significant correlations were found between the GRF AI and other parameters. Although the reliability of the GRF AI was high, the validity was poor. To be clinically useful, this test should be further refined by modifying the test protocol.

Gait asymmetries are exacerbated at faster walking speeds in individuals with acute anterior cruciate ligament reconstruction.

Previous research suggests more biomechanically demanding tasks (e.g., stair descent, hopping) magnify biomechanical asymmetries compared with walking after anterior cruciate ligament (ACL) reconstruction. However, it is unclear if modifying task-specific constraints, like walking speed also elicits greater biomechanical asymmetries in this population. We examined the effects of manipulating walking speed on ground reaction force (GRF) asymmetries in individuals with ACL reconstruction and uninjured controls. Thirty individuals with ACL reconstruction (age = 20.6 ± 5.4 years, body mass index [BMI] = 23.9 ± 3.3 kg/m2 ) and 15 controls (age = 23.1 ± 4.5 years, BMI = 23.6 ± 2.7 kg/m2 ) were tested on an instrumented treadmill at three speeds (100%, 120%, and 80% self-selected speed). Bilateral vertical and posterior-anterior GRFs were recorded at each speed. GRF asymmetries were calculated by subtracting the uninjured from the injured limb at each percent of stance. Statistical parametric mapping was used to evaluate the effects of speed on GRF asymmetries across stance. We found vertical and posterior GRF asymmetries were exacerbated at faster speeds and reduced at slower speeds in ACL individuals but not controls (p < .05). No differences in anterior GRF asymmetries were observed between speeds in either group (p > .05). Our results suggest increasing walking speed magnifies GRF asymmetries in individuals with ACL reconstruction. Statement of Clinical Significance: Evaluating both preferred and fast walking speeds may aid in characterizing biomechanical asymmetries in individuals with ACL reconstruction which may be valuable in earlier rehabilitative time points when more difficult tasks like hopping and running are not feasible.

Biomechanical upper-extremity performance tests and isokinetic shoulder strength in collision and contact athletes

ABSTRACT The aim of this study was threefold (1) to assess the reliability of three upper-extremity performance tests: a countermovement push up, press jump and drop box land, performed on a set of dual-force plates (2) to examine whether there was an association between isokinetic dynamometry and the performance tests in a non-injured cohort of collision/contact athletes and (3) to establish a normal descriptive profile of the vertical ground reaction forces from the performance tests, in a cohort of contact/collision athletes. The study was split into two sub-sections; the inter-day reliability of three upper-extremity performance tests (n = 21) and a descriptive, correlation study investigating the relationship between isokinetic dynamometry and performance tests metrics (n = 39). We used intraclass correlation coefficients (absolute agreement, 2-way mixed-effects model) with 95% confidence intervals to quantify inter-day reliability of all variables. We used Pearson correlation coefficients to investigate associations between isokinetic strength and vertical ground reaction force asymmetry variables. Inter-day reliability was moderate-to-excellent for the upper-extremity performance tests (ICC 0.67–0.97). There was no statistically significant correlation between external and internal rotational peak torque and the variables of CPMU, PJ and BDL (r range = .02–.24).These upper-extremity tests are reliable for use with male contact/collision athletes.

Asymmetries in Ground Reaction Forces During Turns by Elite Slalom Alpine Skiers Are Not Related to Asymmetries in Muscular Strength.

The ground reaction forces (GRF) associated with competitive alpine skiing, which are relatively large, might be asymmetric during left and right turns due to asymmetries in the strength of the legs and torso and the present investigation was designed to evaluate this possibility. While skiing a symmetrical, 20-gate slalom course, the asymmetries of 9 elite alpine skiers were calculated on the basis of measurements provided by inertial motion units (IMU), a Global Navigation Satellite System and pressure insoles. In addition, specialized dynamometers were utilized to assess potential asymmetry in the strength of their legs and torso in the laboratory. In total, seven variables related to GRF were assessed on-snow and eight related to strength of the legs and torso in the laboratory. The asymmetries in these parameters between left and right turns on snow were expressed in terms of the symmetry (SI) and Jaccard indices (JI), while the asymmetries between the left and right sides of the body in the case of the laboratory measurements were expressed as the SIs. The three hypotheses to be tested were examined using multivariable regression models. Our findings resulted in rejection of all three hypotheses: The asymmetries in total GRF (H1), as well as in the GRF acting on the inside and outside legs (H2) and on the rear- and forefeet GRF (H3) during left and right turns were not associated with asymmetries in parameters related to muscular strength. Nevertheless, this group of elite slalom skiers exhibited significant asymmetry between their right and left legs with respect to MVC during ankle flexion (0.53 ± 0.06 versus 0.60 ± 0.07 Nm/kg, respectively) and hip extension (2.68 ± 0.39 versus 2.17 ± 0.26 Nm/kg), as well as with respect to the GRFs on the inside leg while skiing (66.8 ± 7.39 versus 76.0 ± 10.0 %BW). As indicated by the JI values, there were also large asymmetries related to GRF as measured by pressure insoles (range: 42.7–56.0%). In conclusion, inter-limb asymmetries in GRFs during elite alpine skiing are not related to corresponding asymmetries in muscular strength. Although our elite athletes exhibited relatively small inter-limb asymmetries in strength, their asymmetries in GRF on-snow were relatively large.

Acute and Delayed Effects of Fatigue on Ground Reaction Force, Lower Limb Stiffness and Coordination Asymmetries During a Landing Task.

Landing is a critical phase of movement for injury occurrence, in which lower limbs should be used equally to better absorb the shock. However, it has been suggested that fatigue can lead to the appearance of asymmetries. The aim of this study was to verify the acute and delayed effects of fatigue on the lower limb asymmetry indexes of peak ground reaction force, leg stiffness and intra-limb coordination during a landing task. Fifteen physically active men performed a fatigue protocol composed of 14 sets of 10 continuous vertical jumps, with a one-minute rest interval between the sets. A step-off landing task was performed before, immediately after, 24 h and 48 h after the fatigue protocol. Two force plates and a video analysis system were used. The symmetry index equation provided the asymmetry indexes. For statistical analysis, ANOVA and effect size analysis were utilized. Inferential statistics did not show the effect of fatigue in the asymmetry indexes for any variable or condition (p > .05). Moderate effect sizes were observed for peak ground reaction force (0.61) and leg stiffness (0.61) immediately after the application of the protocol. In conclusion, fatigue does not seem to significantly change the asymmetries of lower limbs, especially regarding intra-limb coordination. The moderate effects observed for peak ground reaction force and leg stiffness asymmetries suggest that these variables may be acutely affected by fatigue.

Quantifying Asymmetry in Gait: The Weighted Universal Symmetry Index to Evaluate 3D Ground Reaction Forces.

Though gait asymmetry is used as a metric of functional recovery in clinical rehabilitation, there is no consensus on an ideal method for its evaluation. Various methods have been proposed to analyze single bilateral signals but are limited in scope, as they can often use only positive signals or discrete values extracted from time-scale data as input. By defining five symmetry axioms, a framework for benchmarking existing methods was established and a new method was described here for the first time: the weighted universal symmetry index (wUSI), which overcomes limitations of other methods. Both existing methods and the wUSI were mathematically compared to each other and in respect to their ability to fulfill the proposed symmetry axioms. Eligible methods that fulfilled these axioms were then applied using both discrete and continuous approaches to ground reaction force (GRF) data collected from healthy gait, both with and without artificially induced asymmetry using a single instrumented elbow crutch. The wUSI with a continuous approach was the only symmetry method capable of identifying GRF asymmetry differences in different walking conditions in all three planes of motion. When used with a continuous approach, the wUSI method was able to detect asymmetries while avoiding artificial inflation, a common problem reported in other methods. In conclusion, the wUSI is proposed as a universal method to quantify three-dimensional GRF asymmetries, which may also be expanded to other biomechanical signals.

Relationships Between Highly Skilled Golfers' Clubhead Velocity and Vertical Ground Reaction Force Asymmetry During Vertical Jumps and an Isometric Midthigh Pull

Wells, JET, Mitchell, ACS, Charalambous, LH, and Fletcher, IM. Relationships between highly skilled golfers' clubhead velocity and vertical ground reaction force asymmetry during vertical jumps and an isometric midthigh pull. J Strength Cond Res 34(10): 2824-2831, 2020-Clubhead velocity (CHV) is a commonly measured variable within golf due to strong associations with increased drive distance. Previous research has revealed significant relationships between CHV and vertical ground reaction force (vGRF) variables during bilateral tasks including a countermovement jump (CMJ), squat jump (SJ), drop jump (DJ), and isometric midthigh pull (IMTP). Asymmetries have been linked to performance outcomes in a number of sports; however, few studies have assessed asymmetries within golf. The current study, therefore, examined the relationships between CHV and vGRF asymmetries for CMJ positive impulse, SJ positive impulse, DJ positive impulse, and IMTP peak force (PF). Furthermore, the level of agreement for asymmetries between protocols was assessed by using Kappa coefficients. Fifty highly skilled (handicap ≤5) male golfers attended laboratory and range-based testing sessions. Positive impulse and PF were measured using a dual force platform system, with CHV measured using a TrackMan 3e launch monitor. There was no significant relationship (r = -0.14 to 0.22) between CHV and each of the vGRF asymmetry measures. Of the golfers tested, 26 had a "real" asymmetry in the CMJ, 18 had a "real" asymmetry in the SJ, 25 had a "real" asymmetry in the DJ, and 27 had a "real" asymmetry in the IMTP. Kappa coefficients indicated that asymmetries rarely favored the same limb (k = 0.06 to 0.39) with asymmetries varying for individual golfers between protocols. As such, asymmetries are neither beneficial nor detrimental to CHV but are inherently individual and dependent on the task.

Restricted Unilateral Ankle Dorsiflexion Movement Increases Interlimb Vertical Force Asymmetries in Bilateral Bodyweight Squatting.

Crowe, MA, Bampouras, TM, Small, K, and Howe, LP. Restricted unilateral ankle dorsiflexion movement increases interlimb vertical force asymmetries in bilateral bodyweight squatting. J Strength Cond Res 34(2): 332-336, 2020-The purpose of this study was to investigate the effect of unilateral restrictions in ankle-dorsiflexion range of motion (DF-ROM) on interlimb vertical ground reaction force (vGRF) asymmetries. Twenty healthy and physically active volunteers (age 23 ± 3 years; height 1.72 ± 0.1 m; mass 74.9 ± 20.3 kg) performed 3 barefoot bodyweight squats (control condition) and with a 10° custom-built forefoot wedge under the right foot to artificially imitate ankle DF-ROM restriction (wedge condition). Force data were used to calculate the mean asymmetry index score for the upper descent phase, lower descent phase, lower ascent phase, and upper ascent phase during the bilateral squat. Significant differences were found for comparisons for each phase between conditions, with effect sizes ranging between 0.7 and 1.1. Asymmetry index scores indicated that for all phases, the unrestricted limb in the wedge condition produced greater vGRF. Therefore, interlimb differences in ankle DF-ROM can cause interlimb asymmetries in vGRF during bilateral squatting. As such, athletes with asymmetrical squat mechanics should be screened for interlimb differences in ankle DF-ROM to ascertain whether it is a contributing factor.

Validity and Reliability of the Rear Foot Elevated Split Squat 5 Repetition Maximum to Determine Unilateral Leg Strength Symmetry.

Helme, M, Bishop, C, Emmonds, S, and Low, C. Validity and reliability of the rear foot elevated split squat 5 repetition maximum to determine unilateral leg strength symmetry. J Strength Cond Res 33(12): 3269-3275, 2019-The purpose of this study was to examine the validity and reliability of the rear foot elevated split squat (RFESS) 5 repetition maximum (5RM) test as a field method for measuring unilateral leg strength symmetry. As a validated method of testing symmetry, the RFESS 5RM may be used by strength and conditioning coaches and sports medicine staff to measure the presence of imbalances with minimal equipment and time. Twenty-six subjects (age = 23.8 ± 4.6 years, mass = 88.1 ± 10.7 kg, and height = 1.79 ± 0.1 m) with a minimum 2 years of strength and conditioning experience were recruited. After a familiarization session, subjects performed an incremental 5RM protocol on both legs, on 2 occasions where 3D motion and force data were collected. Moderate reliability of bar load symmetry was found between test and retest conditions correlation (intraclass coefficient = 0.73, 0.33-0.91) with no proportional bias between sessions. Validation of the exercise was analyzed using a correlation between asymmetries in mean set vertical ground reaction forces (vGRF) of the lead foot during the concentric phase, with bar load. When all maximal trials, from both test conditions, were analyzed, a most likely large positive correlation (0.57, 0.30-0.76) was found for mean set concentric lead foot vGRF. When a threshold level of load symmetry (96.54-103.46%) was applied, a most likely large positive correlation (r = 0.59, 0.14-0.84) between symmetry in lead foot vGRF was found in subjects who exceeded this limit. Conversely, analysis of subjects within the threshold produced unclear correlations. Findings of this study suggest the RFESS is a valid and reliable measure of unilateral leg strength symmetry. Practitioners are recommended to use this exercise to investigate the strength symmetry of athletes, but are guided to note that a threshold level of symmetry (96.54-103.46%) may be required to have been exceeded to indicate a true difference in vGRF production.

Human Gait Analysis Metric for Gait Retraining.

The combined gait asymmetry metric (CGAM) provides a method to synthesize human gait motion. The metric is weighted to balance each parameter's effect by normalizing the data so all parameters are more equally weighted. It is designed to combine spatial, temporal, kinematic, and kinetic gait parameter asymmetries. It can also combine subsets of the different gait parameters to provide a more thorough analysis. The single number quantifying gait could assist robotic rehabilitation methods to optimize the resulting gait patterns. CGAM will help define quantitative thresholds for achievable balanced overall gait asymmetry. The study presented here compares the combined gait parameters with clinical measures such as timed up and go (TUG), six-minute walk test (6MWT), and gait velocity. The comparisons are made on gait data collected on individuals with stroke before and after twelve sessions of rehabilitation. Step length, step time, and swing time showed a strong correlation to CGAM, but the double limb support asymmetry has nearly no correlation with CGAM and ground reaction force asymmetry has a weak correlation. The CGAM scores were moderately correlated with TUG and strongly correlated to 6MWT and gait velocity.

Anterior cruciate ligament reconstructed females who pass or fail a functional test battery do not exhibit differences in knee joint landing biomechanics asymmetry before and after exercise.

A functional test battery (FTB) has been proposed to evaluate the readiness of return to activity after ACLR. However, there is limited evidence documenting the usefulness of an FTB. Therefore, the purpose of the current investigation was to compare knee joint landing biomechanics asymmetry during double-leg jump landing (DLJL) and single-leg jump cutting (SLJC) between healthy females and ACLR females who pass (ACLR-pass) or fail (ACLR-fail) an FTB before and after the completion of a sustained exercise protocol. Eighteen ACLR females (ten ACLR-pass and eight ACLR-fail) and twelve healthy females performed an FTB including The 2000 International Knee Documentation Committee Subjective Knee Evaluation Form, the Knee Outcome Survey Activities of Daily Living Scale, quadriceps strength, and single-leg hop tests. DLJL and SLJC knee joint biomechanics asymmetry were measured before and after exercise. During DLJL, there were significant main effects of group on peak anterior tibial shear force (ATSF) asymmetry [F(2,27) = 3.86, p < 0.05, [Formula: see text] = 0.214] and peak vertical ground reaction force (vGRF) asymmetry [F(2,27) = 3.34, p = 0.05, [Formula: see text] = 0.198]. During SLJC, there was a significant group main effect for peak ATSF asymmetry [F(2,27) = 3.494, p = 0.04, [Formula: see text] = 0.206]. ACLR-fail exhibited greater asymmetry in peak ATSF during DLJL and SLJC compared to healthy females. In addition, ACLR-pass exhibited greater asymmetry in peak ATSF and peak vGRF during DLJL and SLJC, respectively, compared to healthy females. However, ACLR-fail did not exhibit any significant differences in landing biomechanics asymmetry during either task compared with ACLR-pass. Furthermore, the completion of a sustained exercise protocol did not affect knee joint landing biomechanics asymmetry across groups. II.