Sex Impacts Leg Stiffness When Increasing Stride Length to Run with Body Borne Load

Military personnel routinely run at a fixed cadence with body borne load, which may increase leg stiffness and potential injury risk - particularly for females. Seventeen males and ten females had leg stiffness quantified when running with four loads (20, 25, 30, and 35 kg) and three stride lengths (preferred, and ±15% of preferred). Participants increased leg stiffness (P=0.006), and potentially injury risk when running with load. But, a sex dimorphism in stiffness was evident with changes in stride length. Males exhibited reduced leg stiffness with longer strides (P\u3e0.05)

Sex and Limb Impact Biomechanics Associated with Risk of Injury During Drop Landing with Body Borne Load

Increasing lower limb flexion may reduce risk of musculoskeletal injury for military personnel during landing. This study compared lower limb biomechanics between sexes and limbs when using normal and greater lower limb flexion to land with body borne load. Thirty-three participants (21 male, 12 female, age: 21.6±2.5 years, height: 1.7±0.1 m, weight: 74.5±9.0 kg) performed normal and flexed lower limb landings with four body borne loads: 20, 25, 30 and 35 kg. Hip and knee biomechanics, peak vertical ground reaction force (GRF), and the magnitude and direction of the GRF vector in frontal plane were submitted to two separate repeated measures ANOVAs to test the main and interaction effects of sex, load, and landing, as well as limb, load, and landing. Participants increased GRFs (between 5 and 10%) and hip and knee flexion moments when landing with body borne load, but decreased vertical GRF 19% and hip adduction and knee abduction joint range of motion and moments during the flexed landings. Both females and the non-dominant limb presented greater risk of musculoskeletal injury during landing. Females exhibited larger GRFs, increased hip adduction range of motion, and greater knee abduction moments compared to males. Whereas, the non-dominant limb increased knee abduction moments and exhibited a more laterally-directed frontal plane GRF vector compared to the dominant limb during the loaded landings. Yet, increasing lower limb flexion during landing does not appear to produce similar reductions in lower limb biomechanics related to injury risk for both females and the non-dominant limb during landing

Sex Impact on Knee and Ankle Muscle Extensor Forces During Loaded Running

Background: This study determined whether the knee and ankle muscle extensor forces increase when running with a body-borne load and whether these forces differ between the sexes. Methods: Thirty-six (twenty male and sixteen female) adults had the knee and ankle extensor force quantified when running 4.0 m/s with four body-borne loads (20, 25, 30, and 35 kg). Peak normalized (BW) and unnormalized (N) extensor muscle force, relative effort, and joint angle and angular velocity at peak muscle force for both the ankle and the knee were submitted to a mixed model ANOVA. Results: Significant load by sex interactions for knee unnormalized extensor force (p = 0.025) and relative effort (p = 0.040) were observed, as males exhibited greater knee muscle force and effort than females and increased their muscle force and effort with additional load. Males also exhibited greater ankle normalized and unnormalized extensor force (p = 0.004, p \u3c 0.001) and knee unnormalized force than females (p = 0.005). The load increased the normalized ankle and knee muscle force (p \u3c 0.001, p = 0.030) and relative effort (p \u3c 0.001, p = 0.044) and the unnormalized knee muscle force (p = 0.009). Conclusion: Running with a load requires greater knee and ankle extensor force, but males exhibited greater increases in muscle force, particularly at the knee, than females

TRANSFERABILITY OF A PREVIOUSLY VALIDATED IMU SYSTEM FOR LOWER EXTREMITY KINEMATICS

This study tested transferability and validity of an Inertial Measurement Unit (IMU) system for estimation of lower limb kinematics. Peak hip, knee, and plantarflexion angles and sagittal plane range of motion (ROM) were compared during body weight squats (BWSQ) and countermovement jumps (CMJ) in 16 participants using root mean square error (RMSE) and intraclass correlation coefficients (ICC). RMSE wa

Sex and Stride Impact Joint Stiffness During Loaded Running

This study determined changes in lower limb joint stiffness when running with body-borne load, and whether they differ with stride or sex. Twenty males and 16 females had joint stiffness quantified when running (4.0 m/s) with body-borne load (20, 25, 30, and 35 kg) and 3 stride lengths (preferred or 15% longer and shorter). Lower limb joint stiffness, flexion range of motion (RoM), and peak flexion moment were submitted to a mixed-model analysis of variance. Knee and ankle stiffness increased 19% and 6% with load (P \u3c .001, P = .049), but decreased 8% and 6% as stride lengthened (P = .004, P \u3c .001). Decreased knee RoM (P \u3c .001, 0.9°–2.7°) and increased knee (P = .007, up to 0.12 N.m/kg.m) and ankle (P = .013, up to 0.03 N.m/kg.m) flexion moment may stiffen joints with load. Greater knee (P \u3c .001, 4.7°–5.4°) and ankle (P \u3c .001, 2.6°–7.2°) flexion RoM may increase joint compliance with longer strides. Females exhibited 15% stiffer knee (P = .025) from larger reductions in knee RoM (4.3°–5.4°) with load than males (P \u3c .004). Stiffer lower limb joints may elevate injury risk while running with load, especially for females

Sex and Limb Associated with Risk of Injury During Drop Landing with Load

Increasing lower limb flexion may reduce risk of musculoskeletal injury for military personnel during landing. This study compared lower limb biomechanics between sexes and limbs when using normal and greater lower limb flexion to land with body borne load. Thirty-three participants (21 male, 12 female, age: 21.6±2.5 years, height: 1.7±0.1 m, weight: 74.5±9.0 kg) performed normal and flexed lower limb landings with four body borne loads: 20, 25, 30 and 35 kg. Hip and knee biomechanics, peak vertical ground reaction force (GRF), and the magnitude and direction of the GRF vector in frontal plane were submitted to two separate repeated measures ANOVAs to test the main and interaction effects of sex, load, and landing, as well as limb, load, and landing. Participants increased GRFs (between 5 and 10%) and hip and knee flexion moments when landing with body borne load, but decreased vertical GRF 19% and hip adduction and knee abduction joint range of motion and moments during the flexed landings. Both females and the non-dominant limb presented greater risk of musculoskeletal injury during landing. Females exhibited larger GRFs, increased hip adduction range of motion, and greater knee abduction moments compared to males. Whereas, the non-dominant limb increased knee abduction moments and exhibited a more laterally-directed frontal plane GRF vector compared to the dominant limb during the loaded landings. Yet, increasing lower limb flexion during landing does not appear to produce similar reductions in lower limb biomechanics related to injury risk for both females and the non-dominant limb during landing

Sex and Stride Length Impact Leg Stiffness and Ground Reaction Forces When Running with Body Borne Load

This study quantified leg stiffness and vGRF measures for males and females using different stride lengths to run with four body borne loads (20, 25, 30, and 35 kg). Thirty-six participants (20 males and 16 females) ran at 4.0 m/s using either: their preferred stride length (PSL), or strides 15% longer (LSL) and shorter (SSL) than PSL. Leg stiffness and vGRF measures, including peak vGRF, impact peak and loading rate, were submitted to a RM ANOVA to test the main effect and interactions of load, stride length,and sex. Leg stiffness was greater with the 30 kg (p = 0.016) and 35 kg (p \u3c 0.001) compared to the 20 kg load, but decreased as stride lengthened from SSL to PSL (p \u3c 0.001) and PSL to LSL (p\u3c 0.001). Males exhibited greater leg stiffness than females with SSL (p = 0.029). Yet, males decreased leg stiffness with each increase in stride length (p \u3c 0.001; p \u3c 0.001), while females only decreased leg stiffness between PSL and LSL (p = 0.014). Peak vGRF was greater with the addition of body borne load (p \u3c 0.001) and increase in stride length (p \u3c 0.001). Both impact peak and loading rate were greater with the 30 kg (p = 0.034; p = 0.043) and 35 kg (p = 0.004; p = 0.015) compared to the 20 kg load, and increased as stride lengthened from SSL to PSL (p = 0.001; p = 0.004) and PSL to LSL (p \u3c 0.001; p \u3c 0.001). Running with body borne load may elevate injury risk by increasing leg stiffness and vGRFs. Injury risk may further increase when using longer strides to run with body borne load

Sex and Limb Differences During a Single-Leg Cut with Body Borne Load

Background: Military personnel don body borne loads that produce maladaptive lower limb biomechanics, increasing risk of musculoskeletal injury during common training tasks. Female personnel have over twice theinjury risk as males, but it is unknown if a sex dimorphism in lower limb biomechanics exists during commontraining-related tasks. Research Question: To determine whether lower limb biomechanics exhibited during a single-leg cut with military body borne loads differ between sexes. Methods: Sixteen females and 20 males had lower limb biomechanics quantified during five single-leg cuts off each limb with four loads (20, 25, 30 and 35 kg). Each cut required participants run 4 m/s, before planting their foot on a force platform and cut 45° towards the opposite limb. Lower limb biomechanics related to musculoskeletal injury were submitted to a repeated measures ANOVA to test for main and interaction effects of load, sex, and limb. Results: During the cut, load increased peak proximal anterior tibial shear force (p \u3c 0.001) and peak hip flexion (p = 0.010) and knee abduction (p = 0.045) moments, but decreased peak knee flexion angle (p = 0.032). Females exhibited greater peak proximal anterior tibial shear (p = 0.014), and peak hip adduction (p \u3c 0.001) and knee external rotation (p = 0.001) moment than males. Dominant limb exhibited larger peak hip adduction (p = 0.002); whereas, the non-dominant limb exhibited greater peak hip internal (p = 0.002) and knee external (p = 0.007) rotation moments. Only the non-dominant limb increased peak knee abduction moment (p = 0.001) with additional load. Significance: During the cut, adding body borne load produced maladaptive biomechanics that may increase knee musculoskeletal injury risk. Load increased peak proximal tibial shear and potential strain of knee’s soft-tissues. Females exhibited a sex dimorphism in lower limb biomechanics that may further elevate their injuryrisk. Both limbs exhibited biomechanics that may increase injury risk, but only the non-dominant limb further increased injury risk with load

Effect of Body-Borne Load on Lateral Trunk Flexion and Its Relation to Knee Abduction Biomechanics During a Single-Leg Cut

Body-borne load reportedly increases incidence of military-related knee injury by altering trunk and lower limb biomechanics. This investigation determined whether body-borne load impacts lateral trunk flexion during a single-leg cut, and whether greater lateral trunk flexion exaggerates knee abduction biomechanics. Thirty-six participants had trunk and knee biomechanics quantified during a single-leg cut with four body-borne loads (20, 25, 30 and 35 kg). To evaluate the impact of load on lateral trunk flexion and its relation with knee abduction biomechanics, peak stance lateral trunk flexion was submitted to a linear mixed model with load (20, 25, 30, and 35 kg) and sex (male, female) as fixed effects, and dominant limb peak stance knee abduction joint angle and moment considered as covariates. During the cut, there was a significant sex by load interaction for peak stance lateral trunk flexion (p = 0.038), and peak stance lateral trunk flexion angle exhibited a significant association with peak stance knee abduction angle (p \u3c 0.001) and moment (p = 0.014). Adopting lateral trunk flexion during loaded single-leg cuts may increase knee biomechanics related to ACL injury, but adding load only decreased lateral trunk flexion for female participants and did not further exaggerate knee abduction biomechanics

Load and Stride Increase Knee Adduction Velocity

Introduction: Service members often run at a fixed cadence with heavy body-borne loads (greater than 20 kg), which may lead to larger, faster knee adduction and risk of knee osteoarthritis. Although service members exhibit larger knee adduction walking with heavy load, it is unknown whether they use larger, faster knee adduction when running with load. Methods: Thirty-six participants had knee adduction quantified while running 4 m/s with four loads (20kg, 25kg, 30kg, 35kg) and three stride lengths (preferred, and 15% longer and shorter than preferred). For analysis, knee adduction angle and velocity were submitted to a RM ANOVA to test the main effect and interaction between body-borne load and stride. Results: Load and stride length had a significant effect on average velocity (p=0.050, p \u3c 0.001) and time to peak for knee adduction (p=0.010, p\u3c0.001), but only stride (p\u3c0.001) impacted range of knee adduction. A significant load versus stride length interaction was observed for average varus thrust velocity (p=0.006), and both load and stride impacted magnitude of varus thrust (p=0.014; p \u3c 0.001). Conclusion: Running with load and fixed cadence may elevate service member’s risk of knee OA, as increases in load and alterations in stride led to larger, faster knee adduction