Medial Ground Reaction Force Research Articles

Effect of thoracolumbosacral braces on running ground reaction force components in male individuals with kyphosis

Background & aimsBraces are one of the methods for kyphosis treatment, but they can relocate the center of gravity of the trunk, affecting the ground reaction force (GRF) during running. Therefore, this study aimed to investigate the effects of two types of thoracolumbosacral braces on running GRF components in individuals with kyphosis. Materials & methodsParticipants were 15 males diagnosed with kyphosis who volunteered in this quasi-experimental study. Each subject performed the barefoot running trials on the force plate with one simple brace, with a sensor brace, and without the brace condition. The ground reaction forces components were calculated in the stance phase. Statistical analysis was done with repeated measures test with a significant level of 0.05. ResultsPeak medial ground reaction force when running with a sensor brace was lower than running with a simple brace (p = 0.017). Free moments were similar during three running conditions (p > 0.05). ConclusionLower maximum medial ground reaction force while using a sensor brace may possibly demonstrate the beneficial effects of a sensor brace in individuals with kyphosis.

Effects of shoe collar height and limb dominance on landing knee biomechanics in female collegiate volleyball players

ABSTRACT Volleyball-specific footwear with higher collar heights (a mid-cut shoe) are worn to restrict ankle motion. Reduced ankle dorsiflexion has been associated with increased frontal plane motion and injury risk at the knee. With the high frequency of unilateral landings in volleyball, the purpose of this study was to determine the effect of volleyball-specific shoes and limb dominance on knee landing mechanics in collegiate volleyball players. It was hypothesized that participants would exhibit smaller sagittal plane and greater frontal plane knee joint mechanics in mid-cut and dominant limb and that vertical and posterior directed ground reaction forces would be greater wearing mid-cut, yet similar between limbs. Seventeen female volleyball players performed unilateral landings on each limb in mid-cut and low-top volleyball shoes. For shoe main effects, smaller peak dorsiflexion angle and internal peak plantarflexion moment and greater peak medial ground reaction force were found in the mid-cut but with no impact on knee mechanics. For limb main effects, the internal peak knee abduction moment was greater in the dominant limb. Greater peak lateral ground reaction force was found in the interaction between the non-dominant limb and low-top. Further research is warranted to better understand shoe and limb impact in volleyball players.

Two-Experiment Examination of Habitual and Manipulated Foot Placement Angles on the Kinetics, Kinematics, and Muscle Forces of the Barbell Back Squat in Male Lifters.

This two-experiment study aimed to examine the effects of different habitual foot placement angles and also the effects of manipulating the foot placement angle on the kinetics, three-dimensional kinematics and muscle forces of the squat. In experiment 1, seventy lifters completed squats at 70% of their one repetition maximum using a self-preferred placement angle. They were separated based on their habitual foot angle into three groups HIGH, MEDIUM and LOW. In experiment 2, twenty lifters performed squats using the same relative mass in four different foot placement angle conditions (0°, 21°, 42° and control). Three-dimensional kinematics were measured using an eight-camera motion analysis system, ground reaction forces (GRF) using a force platform, and muscle forces using musculoskeletal modelling techniques. In experiment 1, the impulse of the medial GRF, in the descent and ascent phases, was significantly greater in the HIGH group compared to LOW, and in experiment 2 statistically greater in the 42° compared to the 21°, 0° and control conditions. Experiment 2 showed that the control condition statistically increased quadriceps muscle forces in relation to 0°, whereas the 0° condition significantly enhanced gluteus maximus, gastrocnemius and soleus forces compared to control. In experiment 1, patellofemoral joint stress was significantly greater in the HIGH group compared to LOW, and in experiment 2, patellar and patellofemoral loading were statistically greater in the control compared to the 42°, 21°, 0° and control conditions. Owing to the greater medial GRF’s, increased foot placement angles may improve physical preparedness for sprint performance and rapid changes of direction. Reducing the foot angle may attenuate the biomechanical mechanisms linked to the aetiology of knee pathologies and to promote gluteus maximus, gastrocnemius and soleus muscular development. As such, though there does not appear to be an optimal foot placement angle, the observations from this study can be utilised by both strength and conditioning and sports therapy practitioners seeking to maximise training and rehabilitative adaptations.

A Multi-Experiment Investigation of the Effects Stance Width on the Biomechanics of the Barbell Squat.

This two-experiment study aimed to explore habitual and manipulated stance widths on squat biomechanics. In experiment one, 70 lifters completed back squats at 70%, 1 repetition maximum (1RM), and were split into groups (NARROW < 1.06 * greater trochanter width (GTW), MID 1.06–1.18 * GTW and WIDE > 1.37 * GTW) according to their self-selected stance width. In experiment two, 20 lifters performed squats at 70%, 1RM, in three conditions (NARROW, MID and WIDE, 1.0, 1.25 and 1.5 * GTW). The three-dimensional kinematics were measured using a motion capture system, ground reaction forces (GRF) using a force platform, and the muscle forces using musculoskeletal modelling. In experiment two, the peak power was significantly greater in the NARROW condition, whereas both experiments showed the medial GRF impulse was significantly greater in the WIDE stance. Experiment two showed the NARROW condition significantly increased the quadriceps forces, whereas both experiments showed that the WIDE stance width significantly enhanced the posterior-chain muscle forces. The NARROW condition may improve the high mechanical power movement performance and promote the quadriceps muscle development. Greater stance widths may improve sprint and rapid change-of-direction performance and promote posterior-chain muscle hypertrophy. Whilst it appears that there is not an optimal stance width, these observations can be utilized by strength and conditioning practitioners seeking to maximize training adaptations.

The Effect of Arm Dominance on Knee Joint Biomechanics During Basketball Block Shot Single-Leg Landing.

Single arm blocking is a key component of successful basketball defence. The player uses either their dominant or non-dominant arm to block the ball landing on a common leg. Understanding how the bio-physical loads of the landing leg change as a function of the blocking arm will provide insights into potential injury risk of the lower limb. The aim of this study was to investigate the effects of arm dominance on the biomechanical variables of injury risk of the lower limb, specifically the knee joint during the single-leg landing in female basketball players. Kinematic and kinetic data were collected from fourteen female basketball athletes (20.85 ± 1.35 years, 1.69 ± 0.06 m, 60.37 ± 7.75 kg), each performing three trials of a dominant arm and non-dominant block jump landing on the dominant leg. The results showed significantly higher anterior and medial ground reaction force, knee joint flexion and abduction and lateral knee force during the dominant arm landing (p < 0.05). These findings highlight potential injury risk and the need for the player to be more proficient at dominant arm block-shot landing. The player should aim to develop a larger landscape of technique to meet the demands of the game and facilitate a more effective and safer landing strategy.

Softball Pitching Propulsion and Performance Differences According to Body Fat Percentage.

Softball pitchers with a high body-fat percentage (bf%) can often be successful, despite the heightened risk of injury associated with high bf%. Given the importance of propulsion during pitching, those with high bf% may have an advantage performance-wise. Therefore, the purpose of this study was to examine the differences in ground reaction force (GRF) development between two groups of pitchers: those with a high-fat percentage (≥32 bf%) and a healthy-fat percentage (<32 bf%). Thirty-two female high-school softball pitchers (1.70±.06 m, 76.09±17.50 kg, 15±1 yrs) completed dual-energy x-ray absorptiometry (DEXA) scans. GRF data were collected during pitch propulsion via a force plate, pitch speed was captured using a radar gun, BMI was calculated from pitcher height and mass, and fat free mass index (FFMI) and fat mass index (FMI) were calculated using DEXA data and pitcher height. Multivariate analysis of variance revealed pitcher group GRFs differed significantly (F3,30=3.45, p=.030). Univariate follow-up analyses showed healthy bf% pitchers presented greater weight-normalized peak medial GRF (F1,30=7.17, p=.012). BMI and FFMI were positively associated with pitch speed while bf% and FMI were negatively associated with pitch speed. While pitchers can be successful and carry excess bf%, results indicate potential performance disadvantages associated with having an increased bf%.

Knee and ankle biomechanics in 90° side cutting on synthetic turf with shock pad

The purpose of this study was to examine differences in knee and ankle biomechanics on synthetic turf with and without a shock pad in two approach velocities during a 90° cutting movement. Twelve recreational male American football or soccer players performed five trials of 90° side cutting in each of four conditions: turf only and turf with shock pad at approach velocity of 3.0 and 4.0 m/s. A two-way (surface × approach velocity) ANOVA was used to analyse selected variables. Knee and ankle variables were generally similar across surface conditions. However, peak knee frontal-plane loading eccentric power was greater (p = 0.013) while peak knee frontal-plane push-off eccentric power was reduced on the shock pad (p = 0.020). A surface × approach velocity interaction was detected for peak knee sagittal-plane eccentric power (p = 0.018), and a post-hoc analysis found a significant increase of peak knee sagittal-plane eccentric power at a faster approach speed on the turf only condition compared to the turf with the shock pad. There were increases in the knee extension moments (p = 0.004), peak push-off medial ground reaction force (GRF, p = 0.025), peak ankle eversion moment (p < 0.001), and ankle inversion ROM (p = 0.001) as approach velocity increased while peak push-off vertical GRF decreased (p = 0.011). The effects of the inclusion of a shock pad on lower extremity loading during a 90° cutting movement are limited. The results indicate that the turf with the shock pad absorbs more kinetic energy as speed increases than the turf alone.

Influence of sidestepping expertise and core stability on knee joint loading during change of direction

ABSTRACT The aims of this study were twofold: first, to compare core stability and knee joint loading between sidestepping experts and nonexperts; secondly, to determine core predictors of knee joint loading. Thirteen handball male players (experts) and 14 karatekas (nonexperts) performed six unanticipated 45° sidestepping manoeuvers, while trunk and pelvis 3D kinematics as well as ground reaction forces were measured, and peak knee abduction moment (PKAM) was determined. Student t-tests enabled a comparison of both groups and a linear mixed model approach was used to identify PKAM predictors. Sidestepping experts demonstrated significantly lower pelvis rotation towards the new movement direction at the initial contact than nonexperts (4.9° vs. 10.8°) and higher PKAM (0.539 vs. 0.321 Nm/kg-bwt). Trunk medial lean, trunk axial rotation and pelvis anterior tilt at the initial contact predicted PKAM, while trunk axial rotation, pelvis medial lean and posterior ground reaction force predicted PKAM during the weight acceptance phase. Despite higher PKAM, handball players might not be at a higher risk of anterior cruciate ligament injury as the knee joint loading remained at a relatively low level during this sidestepping task. Core stability, in its three dimensions, is a key determinant of knee joint loading.

Force Production Patterns of Muscles Surrounding Knee During Running and Cutting Maneuvers: A Musculoskeletal Modeling Approach

OBJECTIVES The purpose of this study was to investigate the force production patterns of individual muscles surrounding the knee during running (RUN) and cutting (CUT) tasks.METHODS Thirteen women (24.2±3.5 yrs, 162.8±6.0 cm, 55.3±6.2 kg) performed a series of running and cutting tasks. Running and cutting motions were recorded using a motion capture system and ground reaction force (GRF) was recorded using a force plate. Three-dimensional knee angle, ground reaction force, and knee joint moment were calculated using Visual3D software. OpenSim musculoskeletal modeling software was used to calculate the force of individual muscles including the medial hamstring, biceps femoris long head, biceps femoris short head, rectus femoris, vastus medialis, vastus lateralis, gastrocnemius medialis, and gastrocnemius lateralis. All data were analyzed for loading response (or weight acceptance), mid-stance, and final push-off periods, respectively and were compared between two tasks.RESULTS At loading response: external rotation angle, medial and vertical GRFs, and valgus moment for the CUT task were greater than those of the RUN task. Compared to the RUN task, the CUT task showed: 1) an increase in lateral hamstring muscle force at weight acceptance, 2) a decrease in hamstring muscle force and an increase in medial vastus muscle force at mid-stance, and 3) an increase in lateral gastrocnemius muscle force at final push-off.CONCLUSIONS Selective force production patterns of muscles surrounding the knee seem to offset the external load caused by the cutting motion. We anticipate that our results will provide basic data for future training programs designed to prevent noncontact knee injuries.

Overall Greater Demands on the Musculoskeletal System at Multiple Walking Speeds in Service Members With Lower Limb Loss.

Individuals with lower limb loss often walk with altered/asymmetric movement mechanics, postulated as a catalyst for development of low back and knee pain. Here, the authors simultaneously investigated trunk-pelvic movement patterns and lower limb joint kinematics and kinetics among 38 males with traumatic, unilateral lower limb loss (23 transtibial and 15 transfemoral), and 15 males without limb loss, at a self-selected and 2 standardized (1.0 and 1.6m/s) speeds. Individuals with versus without lower limb loss walked with greater trunk range of motion in the frontal and transverse planes at all speeds (despite ∼10% slower self-selected speeds). At all speeds, individuals with versus without limb loss exhibited +29% larger medial ground reaction forces, and at 1.6m/s also exhibited +50% to 110% larger vertical hip power generation, +27% to 80% larger vertical hip power absorption, and +21% to 90% larger medial-lateral hip power absorption. Moreover, pervasive biomechanical differences between transtibial versus transfemoral limb loss identify amputation-level movement strategies. Overall, greater demands on the musculoskeletal system across walking speeds, particularly at the hip, knee, and low back, highlight potential risk factors for the development/recurrence of prevalent secondary musculoskeletal conditions (eg,joint degeneration and pain) following limb loss.

Recreational runners who recovered from COVID-19 show different running kinetics and muscle activities compared with healthy controls

BackgroundSocial isolation through quarantine represents an effective means to prevent COVID-19 infection. A negative side-effect of quarantine is low physical activity. Research questionWhat are the differences of running kinetics and muscle activities of recreational runners with a history of COVID-19 versus healthy controls? MethodsForty men and women aged 20–30 years participated in this study and were divided into two experimental groups. Group 1 (age: 24.1 ± 2.9) consisted of participants with a history of COVID-19 (COVID group) and group 2 (age: 24.2 ± 2.7) of healthy age and sex-matched controls (controls). Both groups were tested for their running kinetics using a force plate and electromyographic activities (i.e., tibialis anterior [TA], gastrocnemius medialis [Gas-M], biceps femoris [BF], semitendinosus [ST], vastus lateralis [VL], vastus medialis [VM], rectus femoris [RF], gluteus medius [Glut-M]). ResultsResults demonstrated higher peak vertical (p = 0.029; d=0.788) and medial (p = 0.004; d=1.119) ground reaction forces (GRFs) during push-off in COVID individuals compared with controls. Moreover, higher peak lateral GRFs were found during heel contact (p = 0.001; d=1.536) in the COVID group. COVID-19 individuals showed a shorter time-to-reach the peak vertical (p = 0.001; d=3.779) and posterior GRFs (p = 0.005; d=1.099) during heel contact. Moreover, the COVID group showed higher Gas-M (p = 0.007; d=1.109) and lower VM activity (p = 0.026; d=0.811) at heel contact. SignificanceDifferent running kinetics and muscle activities were found in COVID-19 individuals versus healthy controls. Therefore, practitioners and therapists are advised to implement balance and/or strength training to improve lower limbs alignment and mediolateral control during dynamic movements in runners who recovered from COVID-19.

Biomechanics Differ for Individuals With Similar Self-Reported Characteristics of Patellofemoral Pain During a High-Demand Multiplanar Movement Task.

Patellofemoral pain (PFP) is often categorized by researchers and clinicians using subjective self-reported PFP characteristics; however, this practice might mask important differences in movement biomechanics between PFP patients. To determine whether biomechanical differences exist during a high-demand multiplanar movement task for PFP patients with similar self-reported PFP characteristics but different quadriceps activation levels. Cross-sectional design. Biomechanics laboratory. A total of 15 quadriceps deficient and 15 quadriceps functional (QF) PFP patients with similar self-reported PFP characteristics. In total, 5 trials of a high-demand multiplanar land, cut, and jump movement task were performed. Biomechanics were compared at each percentile of the ground contact phase of the movement task (α = .05) between the quadriceps deficient and QF groups. Biomechanical variables included (1)whole-body center of mass, trunk, hip, knee, and ankle kinematics; (2)hip, knee, and ankle kinetics; and (3)ground reaction forces. The QF patients exhibited increased ground reaction force, joint torque, and movement, relative to the quadriceps deficient patients. The QF patients exhibited: (1)up to 90, 60, and 35N more vertical, posterior, and medial ground reaction force at various times of the ground contact phase; (2)up to 4° more knee flexion during ground contact and up to 4° more plantarflexion and hip extension during the latter parts of ground contact; and (3)up to 26, 21, and 48 N·m more plantarflexion, knee extension, and hip extension torque, respectively, at various times of ground contact. PFP patients with similar self-reported PFP characteristics exhibit different movement biomechanics, and these differences depend upon quadriceps activation levels. These differences are important because movement biomechanics affect injury risk and athletic performance. In addition, these biomechanical differences indicate that different therapeutic interventions may be needed for PFP patients with similar self-reported PFP characteristics.

Effect of sports shoe mileage on running mechanics and lower limb muscular activities in male individuals with and without genu varus

The aim of the present study was to evaluate the long-term effects of shoes wearing on lower limb kinetics and electromyography activity of selected muscles of genu varus males compared with healthy age-matched controls during running. Equipment and methods Fifteen healthy males (age: 23.20 ± 1.78 years) and 14 males with genu varus (age: 21.57 ± 2.34 years) were eligible for inclusion in this study. Participants received new shoes before the baseline test and were measured with the same shoes (used shoes) after six months in the post-test. Ground reaction forces and muscle activities were recorded in both pre-test and post-test during running. Irrespective of the groups, pair-wise comparisons revealed that peak medial ground reaction force (p = 0.002; d = 0.316) values were higher at post-test. Furthermore, peak negative free moment (p = 0.008; d = 0.235) and peak positive free moment (p < 0.002; d = 0.298) were higher and lower respectively at the post-test. For electromyography activity at the loading phase, the tibialis anterior and vastus medialis muscle activities were higher in the post-test, while the vastus medialis, vastus lateralis, and rectus femoris muscles activities were higher at the mid-stance phase. The gluteus medius muscle activity was reduced at the push-off phase in the post-test. Shoe mileage appears to have an impact on ground reaction force and selected muscle activities in healthy male individuals with and without genu varus. Together with the observed findings on shoe stiffness, it seems appropriate to change running shoes after a great wearing time of approximately six months with walking and to run mileage about 17 km/week. Le but de la présente étude était d’évaluer les effets à long terme du port de chaussures sur la cinétique des membres inférieurs et l’activité électromyographique de certains muscles de genu varus mâles par rapport à des témoins sains en fonction de l’âge pendant la course. Quinze hommes en bonne santé (âge: 23,20 ± 1,78 ans) et 14 hommes atteints de genu varus (âge: 21,57 ± 2,34 ans) étaient éligibles à l’inclusion dans cette étude. Les participants ont reçu de nouvelles chaussures avant le test de base et ont été mesurés avec les mêmes chaussures (chaussures usagées) après six mois dans le post-test. Les forces de réaction au sol et les activités musculaires ont été enregistrées à la fois avant et après les tests pendant la course. Indépendamment des groupes, des comparaisons par paires ont révélé que les valeurs maximales de la force de réaction au sol médiane (p = 0,002; d = 0,316) étaient plus élevées au post-test. De plus, le moment libre négatif maximal (p = 0,008; d = 0,235) et le moment libre positif maximal (p <0,002; d = 0,298) étaient respectivement plus élevés et plus faibles au post-test. Pour l’activité d’électromyographie à la phase de chargement, les activités musculaires du tibial antérieur et du vaste médial étaient plus élevées dans le post-test, tandis que les activités des muscles du vaste médial, du vaste latéral et du rectus fémoral étaient plus élevées à la phase intermédiaire. L’activité musculaire du fessier moyen a été réduite lors de la phase de poussée dans le post-test. Le kilométrage des chaussures semble avoir un impact sur la force de réaction au sol et certaines activités musculaires chez les individus masculins en bonne santé avec et sans genu varus. Parallèlement aux résultats observés sur la rigidité des chaussures, il semble approprié de changer de chaussures de course après une grande durée de port d’environ six mois avec un kilométrage à pied et à pied d’environ 17 km/semaine.

Toe-out gait decreases knee load during stair descent in healthy individuals

IntroductionBoth toe-out (TO) and toe-in (TI) gaits decrease knee load during walking and stair ascent. However, few reports have focused on stair descent, which requires a higher load compared with walking. ObjectivesThe purpose of this study was to investigate the effect of foot progression angle (FPA) on knee joint load and related variables during stair descent. MethodsTwenty-two healthy young adults performed a stair descent task at a predefined speed of 90 steps/min with normal gait, TO gait (15° > normal), and TI gait (15° < normal). 3D motion analysis was conducted. In addition, the ground reaction force (GRF) with 3 components, center of pressure (COP) positions, and sagittal and frontal plane hip and knee joint kinematic and kinetic variables were recorded during stair descent. ResultsThe medial GRF increased, and the COP position was more lateral in TO gait compared with normal and TI gait during stair descent. TO gait exhibited a significant decrease in the peak knee adduction moment by ∼20% compared with normal gait and by ∼23% compared with TI gait. In addition, the knee flexion moment in TI gait significantly increased compared with normal and TO gait. ConclusionsTO gait decreases knee joint load during stair descent. Our results might have important implications for patients with knee osteoarthritis (OA) or those at risk of developing knee OA. Moreover, it will be of great interest to those involved in the research or clinical practice dealing with the role of gait in pathologic conditions, such as OA.

Unilateral above-knee amputees achieve symmetric mediolateral ground reaction impulse in walking using an asymmetric gait strategy

The ability to sustain steady straight-ahead walking is one goal of gait rehabilitation for individuals with unilateral above-knee (UAK) amputation. Despite the morphological and musculoskeletal asymmetry resulting from unilateral limb loss, the mediolateral ground-reaction-impulse (GRI) should be counterbalanced between the affected and unaffected limbs during straight-ahead walking. Therefore, we investigated the strategies of mediolateral ground-reaction-force (GRF) generation adopted by UAK prosthesis users walking along a straight path. GRFs of 15 participants with UAK amputation were measured during straight-ahead walking. Then, the mediolateral GRI, stance time, and mean mediolateral GRF during the stance phase of the affected and unaffected limbs were compared. To better understand the GRF generation strategy, statistical-parametric-mapping (SPM) was applied to assess the phase-dependent difference of the mediolateral GRFs between two limbs. The results showed that UAK prosthesis users can achieve symmetric mediolateral GRI during straight-ahead walking by adopting an asymmetric gait strategy: shorter stance time and higher mean mediolateral GRF over the stance phase for the affected than for the unaffected limb. In addition, the analysis using SPM revealed that the affected limb generates a higher mean medial GRF component than the unaffected limb, especially during the single-support phase. Thus, a higher medial GRF during the single-support phase of the affected limb may allow UAK prosthesis users to achieve mediolateral GRI that are similar to those of the unaffected limb. Further insights on these mechanics may serve as guidelines on the improved design of prosthetic devices and the rehabilitation needs of UAK prosthesis users.

Effects of an elastic resistance band exercise program on kinetics and muscle activities during walking in young adults with genu valgus: A double-blinded randomized controlled trial

BackgroundThis double-blinded randomized-controlled-trial aimed to identify the effects of an elastic band resistance training on walking kinetics and muscle activities in young adults with genu valgus. MethodsForty-two male young adults aged 22.5(2.7) years with genu valgus were randomly allocated to two experimental groups. The intervention group (n = 21) conducted a 14-weeks elastic band resistance training. The control group was passive during the intervention period and received the same treatment after the post-tests. Pre and post training, ground reaction forces and lower limb muscle activities were recorded during walking. FindingsResults revealed significant group-by-time interactions for peak medial ground reaction force and time-to-peak for posterior ground reaction force in favor of the intervention group (p < 0.012; d = 0.83–3.76). Resistance training with elastic bands resulted in significantly larger peak medial ground reaction force (p < 0.001; d = 1.45) and longer time-to-peak for posterior ground reaction force (p < 0.001; d = 1.85). Finding showed significant group-by-time interactions for peak positive free moment amplitudes in favor of the intervention group (p < 0.001; d = 1.18–2.02). Resistance training resulted in a lower peak positive free moment amplitude (p = 0.001; d = 1.46). With regards to muscle activities, the analysis revealed significant group-by-time interactions for rectus femoris and gluteus medius activities during the push-off phase in favor of the intervention group (p < 0.038; d = 0.68–0.89). Resistance training induced higher rectus femoris (p = 0.038; d = 0.84) and gluteus medius (p = 0.007; d = 0.54) activities. InterpretationThis study proved the effectiveness of resistance training using elastic bands on kinetics and muscle activities during walking in male adults with genu valgus disorder. Given that this training regime is low cost, effective, and easy-to-administer, we suggest that it should be implemented as a rehabilitative or preventive means for young adults with genu valgus.

Effects of Increased Step-Width on Knee Biomechanics During Inclined and Declined Walking.

The purpose of this study was to investigate effects of preferred step width and increased step width modification on knee biomechanics of obese and healthy-weight participants during incline and decline walking. Seven healthy-weight participants and 6 participants who are obese (body mass index ≥ 30) performed 5 walking trials on level ground and a 10° inclined and declined instrumented ramp system at both preferred and wide step-widths. A 2 × 2 (step-width × group) mixed-model analysis of variance was used to examine selected variables. There were significant increases in step-width between the preferred and wide step-width conditions for all 3 walking conditions (all P < .001). An interaction was found for peak knee extension moment (P = .048) and internal knee abduction moment (KAM) (P = .025) in uphill walking. During downhill walking, there were no interaction effects. As step-width increased, KAM was reduced (P = .007). In level walking, there were no interaction effects for peak medial ground reaction force and KAM (P = .007). There was a step-width main effect for KAM (P = .007). As step-width increased, peak medial ground reaction force and peak knee extension moment increased, while KAM decreased for both healthy weight and individuals who are obese. The results suggest that increasing step-width may be a useful strategy for reducing KAM in healthy and young populations.

Whole-body dynamic stability in side cutting: Implications for markers of lower limb injury risk and change of direction performance

Control of the centre of mass (CoM) whilst minimising the use of unnecessary movements is imperative for successful performance of dynamic sports tasks, and may indicate the condition of whole-body dynamic stability. The aims of this study were to express movement strategies that represent whole-body dynamic stability, and to explore their association with potentially injurious joint mechanics and side cutting performance. Twenty recreational soccer players completed 45° unanticipated side cutting. Five distinct whole-body dynamic stability movement strategies were identified, based on factors that influence the medial ground reaction force (GRF) vector during ground contact in the side cutting manoeuvre. Using Statistical Parametric Mapping, the movement strategies were linearly regressed against selected performance outcomes and peak knee abduction moment (peak KAM). Significant relationships were found between each movement strategy and at least one selected performance outcome or peak KAM. Our results suggest excessive medial GRFs were generated through sagittal plane movement strategies, and despite being beneficial for performance aspects, poor sagittal plane efficiency may destabilise control of the CoM. Frontal plane hip acceleration is the key non-sagittal plane movement strategy used in a corrective capacity to moderate excessive medial forces. However, whilst this movement strategy offered a way to retrieve control of the CoM, mitigating reduced whole-body dynamic stability, it also coincided with increased peak KAM. Overall, whole-body dynamic stability movement strategies helped explain the delicate interplay between the mechanics of changing direction and undesirable joint moments, providing insights that might support development of future intervention strategies.

Effects of Shock Pad and Synthetic Turf on Ankle Biomechanics in a 90° Cutting Movement

Shock pad (PAD) is a popular choice underlayment installed under a synthetic turf (TURF) field. The effects of PAD on impact attenuation and injury risks of human movements are still relatively unknown. PURPOSE: To examine impact attenuation related ankle biomechanical characteristics of a 90° cutting movement on synthetic turf with shock pad compared to synthetic turf only. METHODS: Twelve recreational football and soccer players performed five successful trials of 90° cutting movement in each of two approaching speed conditions: 3.0±0.3 (SLOW) and 4.0±0.4 (FAST) m/s on each of TURF and PAD surface conditions. Three-dimensional kinematic and ground reaction force (GRF) data were collected simultaneously. A 2” monofilament synthetic turf with 1/2” stitch gauge was used in TURF and PAD conditions. A foam-based shock pad was used in PAD condition. RESULTS: No significant surface main effect or surface by speed interactions were found for any ankle kinematic and kinetic variables and peak GRFs (p > 0.05). Increased peak ankle eversion moment (0.65 vs. 0.84 Nm/kg, p<0.001) and inversion loading range of motion (ROM, 13.7 vs. 18.6 deg, p=0.001) were seen in FAST compared to SLOW. Increases for peak ankle sagittal-plane concentric pushoff power, and frontal-plane eccentric and concentric power were also observed in FAST compared to SLOW. Peak vertical (2.04 vs. 2.31 BW, p=0.023) and medial loading (0.79 vs. 1.11 BW, p=0.002) GRFs were higher in FAST than SLOW. Additionally, peak pushoff medial GRFs were increased from SLOW to FAST (0.91 vs. 1.20 BW, p=0.025), but pushoff vertical GRFs were decreased slightly (2.24 vs. 2.11 BW, p=0.011). CONCLUSIONS: The lack of significant differences between TURF and PAD and their interactions for examined ankle and GRF variables suggest that adding a form-based shock pad does not impede cutting performance. These results also seem to indicate there is a neuromuscular accommodation in cutting mechanics on PAD surface, which cannot be reflected loading variables using inverse dynamics. As cutting speed increased, greater increases in medial peak GRFs, and frontal-plane peak ankle moment and ROM were observed compared to those in sagittal-plane, suggesting increased mediolateral loading to ankle complex in fast cut movement. Supported in part by Brock International.

Altered Movement Biomechanics in Chronic Ankle Instability, Coper, and Control Groups: Energy Absorption and Distribution Implications.

Patients with chronic ankle instability (CAI) exhibit deficits in neuromuscular control, resulting in altered movement strategies. However, no researchers have examined neuromuscular adaptations to dynamic movement strategies during multiplanar landing and cutting among patients with CAI, individuals who are ankle-sprain copers, and control participants. To investigate lower extremity joint power, stiffness, and ground reaction force (GRF) during a jump-landing and cutting task among CAI, coper, and control groups. Cross-sectional study. Laboratory. A total of 22 patients with CAI (age = 22.7 ± 2.0 years, height = 174.6 ± 10.4 cm, mass = 73.4 ± 12.1 kg), 22 ankle-sprain copers (age = 22.1 ± 2.1 years, height = 173.8 ± 8.2 cm, mass = 72.6 ± 12.3 kg), and 22 healthy control participants (age = 22.5 ± 3.3 years, height = 172.4 ± 13.3 cm, mass = 72.6 ± 18.7 kg). Participants performed 5 successful trials of a jump-landing and cutting task. Using motion-capture cameras and a force plate, we collected lower extremity ankle-, knee-, and hip-joint power and stiffness and GRFs during the jump-landing and cutting task. Functional analyses of variance were used to evaluate between-groups differences in these dependent variables throughout the contact phase of the task. Compared with the coper and control groups, the CAI group displayed (1) up to 7% of body weight more posterior and 52% of body weight more vertical GRF during initial landing followed by decreased GRF during the remaining stance and 22% of body weight less medial GRF across most of stance; (2) 8.8 W/kg less eccentric and 3.2 W/kg less concentric ankle power, 6.4 W/kg more eccentric knee and 4.8 W/kg more eccentric hip power during initial landing, and 5.0 W/kg less eccentric knee and 3.9 W/kg less eccentric hip power; and (3) less ankle- and knee-joint stiffness during the landing phase. Concentric power patterns were similar to eccentric power patterns. The CAI group demonstrated altered neuromechanics, redistributing energy absorption from the distal (ankle) to the proximal (knee and hip) joints, which coincided with decreased ankle and knee stiffness during landing. Our data suggested that although the coper and control groups showed similar landing and cutting strategies, the CAI group used altered strategies to modulate impact forces during the task.