Biomechanics

The Influence of Body Mass Index and Sex on Frontal and Sagittal Plane Joint Moments During Walking.

Obesity and female sex are considered independent risk factors for the development of knee osteoarthritis (KOA) which may be due to aberrant gait biomechanics. Few data exist on the interaction of obesity and female sex despite their independent influence on KOA risk. The purpose of this study was to examine the influence of sex and BMI on knee joint sagittal and frontal plane gait mechanics. Dependent variables included the knee flexion moment (KFM) and first peak knee adduction moment (KAM1). Gait biomechanics were assessed in 42 obese and 39 normal weight participants that were matched on age and sex. Kinematic and kinetic data were sampled using a 9-camera Qualisys system and 2 AMTI force-plates. Participants completed walking trials in laboratory standard neutral-cushion footwear at self-selected speed and the external KFM and KAM1 during the first 50% of stance was extracted and normalized to a product of bodyweight (N) and height (m). A 2 (BMI) by 2 (Sex) analysis of co-variance (α=0.05) was used to examine dependent variables with gait speed as a covariate. The BMI by sex interaction was not significant for KFM (p=0.073) or KAM1 (p=0.703). A main effect was observed for sex and females exhibited smaller KFM (p=0.05) and greater KAM1 (p=0.004) compared to males. No differences were found in normalized knee moments between BMI groups. Regardless of BMI, females exhibited aberrant gait mechanics that are indicative of KOA progression. Further studies are needed examining the influence of altered gait in young, healthy females on knee cartilage morphology.
Listed In: Biomechanics, Gait


Does Type of Unanticipated Stimulus Alter Knee Mechanics During Dynamic Tasks?

Noncontact ACL injuries occur during movements that involve sudden decelerations and changes in direction due to combined sagittal and frontal plane knee loading. Previous studies have shown altered knee mechanics when decision-making is involved, which may better simulate game-like scenarios in a lab setting. The purpose of this study was to determine how two unanticipated stimuli alter knee biomechanics during a dynamic task. Eight females and eight males, all recreationally-active, participated. Participants completed two unanticipated 45-degree cutting conditions (visual stimulus (VS); human defensive opponent (DO)). For the VS condition, a custom computer program presented one of three visual stimuli in a random order. For the DO condition, a research assistant attempted to “block” the participant’s running path with a defensive move, using the same three random-order tasks as in VS. For both conditions, participants had a reaction time range of 400-500 milliseconds. Separate 2×2 mixed-model repeated measures ANOVAs (condition×sex) were performed, with an alpha level of .05. Results showed a significant condition main effect for knee extension moments, which were greater in DO compared to VS (p=.009). Significant interactions were present for peak knee flexion angles and peak knee adduction moments. Females had greater flexion angles (p=.001) and adduction moments (p=.030) in VS compared to DO. Women had less knee flexion and more adduction moment in VS, possibly suggesting this stimulus amplifies ACL injury risk factors in females. A human defender increased sagittal plane loading in a manner that may better represent loading in game situations.
Listed In: Biomechanics, Sports Science


Effects of Increased Q-Factor on Knee Biomechanics During Stationary Cycling

Q-Factor (QF), the inter-pedal width, in cycling is the analog to step-width in gait. Increased step-width has been shown to reduce peak knee abduction moment (KabM), however no studies have examined the frontal plane biomechanics with increased QF in cycling. The purpose of this study was to investigate the effects of increased QF on frontal plane knee biomechanics during cycling in healthy participants. Sixteen healthy participants (age: 22.4 ± 2.6 yr, BMI: 22.78 ± 1.43 kg/m2) participated in this study. A motion analysis system and customized instrumented pedals were used to collect five trials of three-dimensional kinematic (240 Hz) and pedal reaction force (PRF, 1200 Hz) data in twelve testing conditions, four QF conditions of Q150 (150 mm), Q192 (192 mm), Q234 (342 mm), Q276 (276 mm), and three workrate conditions of 80 W, 120 W, and 160 W. A 3 × 4 (QF × workrate) repeated measures ANOVA was performed to analyze differences between conditions (p < 0.05). Increased QF increased peak KAbM 47, 56, and 56% from Q150 to Q276 at each workrate respectively. Mediolateral PRF increased 46, 57, and 57% from Q150 to Q276 at each workrate. Frontal plane knee angle and range of motion (ROM) decreased with increased QF. No changes were observed for peak vertical PRF, knee extension moment, sagittal plane peak knee joint angles or ROM. Conclusions: These results indicate increasing QF will increase peak KAbM. Future studies should examine the effects of increased QF on obese and knee osteoarthritis patients.
Listed In: Biomechanics, Sports Science


Lower Extremity Muscle Contributions to Ground Reaction Force during a Stop-Jump Task

Females commonly use a landing technique that creates higher impact forces when contacting the ground, thus leading to higher ground reaction force (GRF) acting upon the lower extremities, leading to an increased risk of injury. The lower extremity musculature plays a critical role in absorbing the energy of these impact forces during landing. Understanding how specific muscle groups contribute to ground reaction force may offer insight to creating more advanced landing retraining protocols. The purpose of this study was to observe how lower extremity muscle groups contribute to GRFs during an unanticipated stop-jump task. 3D musculoskeletal simulations of unanticipated stop-jump tasks were completed for five healthy females. Participant-specific scaled musculoskeletal models (modified gait2392) were generated. A pseudo-inverse induced-acceleration analysis was used to determine individual muscle group contribution to 3D GRFs. Means ± standard deviations were calculated for each muscle group during the landing phase. The vasti, soleus, and the gluteus maximus muscle groups were most responsible for bodyweight support, with the vasti and the soleus being the largest contributors (375.84±88.64 N; 267.39±103.70 N, respectively). The vasti group (165.63±74.94 N) were primarily responsible for braking and propulsion. Finally, the gluteus maximus, gluteus medius, and vasti group were the major generators in producing a medially-directed GRF, with the vasti group as the largest contributor (118.05±32.83 N). The vasti, soleus, and gluteus maximus appears to be the overall largest contributors to 3D GRFs. Landing retraining protocols may want to consider targeting these muscle groups specifically to improve landing performance and decrease injury risk.
Listed In: Biomechanics, Sports Science, Other


Sudden Ankle Inversion Perturbation During Walking Alters Gait Kinematics in Chronic Ankle Instability Patients.

Context: Individuals with chronic ankle instability (CAI) have demonstrated altered lower-extremity joint kinematics during walking. The purpose of this study was to examine feedback control of gait kinematics following repeated sudden ankle inversion perturbation during walking in CAI patients relative to matched controls. Methods: Twenty-one CAI patients, 21 matched controls participated. Subjects performed five walking trials at a preferred speed both before and after 10 sudden ankle inversion perturbations during walking while 3D joint kinematic data were collected using high-speed video and in-ground force plate. Main outcome measures were ankle- (sagittal and frontal planes), knee- (sagittal plane), and hip-angles (sagittal and frontal planes) from heel-strike to toe-off. Spatial trajectories of 44 markers were smoothed using a digital filter. Functional analysis was used to detect mean differences. Results: CAI group demonstrated (i) less ankle dorsiflexion, (ii) more ankle eversion, (iii) less knee flexion, (iv) less hip flexion, and (v) more adduction during walking trails, compared to the control group. The 10 sudden ankle inversion perturbations resulted in more ankle dorsiflexion only in the CAI group. However, both the CAI and control groups demonstrated no differences in frontal ankle, sagittal knee and sagittal and frontal hip kinematics between pre- and post-intervention measurements. Conclusions: Sudden ankle inversion perturbations did not affect gait kinematics in both CAI and control groups except sagittal ankle kinematics in the CAI group. Increased ankle dorsiflexion after inversion perturbation in the CAI group may be the result of a change in motor control to avoid self-perceived vulnerable positions of the foot during walking.
Listed In: Biomechanics, Gait


Gait as a Potential Marker of Cognitive Decrements in Type 2 Diabetes (T2DM): Early Results from the ENBIND Study

Background and Aim: Type 2 Diabetes (T2DM) in midlife represents a potent risk factor for the development of dementia in later life. Early indicators to highlight particular individuals with T2DM who are at risk of cognitive decline are lacking. Subtle abnormalities in gait (and particularly dual-task gait with a cognitive task) have emerged as a potential predictor of cognitive decline in older adults, but have not been investigated in patients with T2DM. The ENBIND Study (Exploring Novel Biomarkers of Brain health IN Diabetes) aims to assess patients with T2DM in midlife without cognitive impairment and follow participants over the course of several years to establish early predictors of cognitive decline in this poorly characterised yet high-risk group. Methods: Patients with midlife T2DM (40-65 yrs) were recruited at the time of their diabetic clinic appointment. Patients were excluded if they had a diagnosis of peripheral neuropathy, peripheral vascular disease, musculoskeletal disease, previous stroke, any form of diagnosed cognitive impairment or diabetic retinopathy/nephropathy. Patients underwent medical/diabetes assessment and examination by a physician. Cognition was screened using the Montreal Cognitive Assessment (MoCA) and assessed using a computerised cognitive battery designed for prodromal Alzheimer's Disease (CANTAB®). Gait was then assessed using both a raw clinical measure (stopwatch) and Shimmer® Inertial Measurement Units (IMUs) across four tasks: (i) 30 metre walk at a normal pace (turn at 15m), (ii) 30 metre fast walk (turn at 15m) (iii) dual cognitive-gait task (reciting alternate letters of the alphabet) and (iv) a long walk at a self-selected pace. Between group differences were assessed using t-tests and appropriate non-parametric equivalents Results: 20 participants with T2DM (52.05 yrs ± 2.13) and 10 matched healthy volunteers (mean age 52.2 yrs ± 2.74) were recruited. T2DM was associated with a significantly lower score on the MoCA (29.2 vs 27.6; p=0.0452). Participants with T2DM had slower but non-significant self-selected (0.87 ms-1 vs 0.8ms-1) and fast gait speed (0.66 ms-1 vs 0.59 ms-1). On the dual-cognitive task, participants with T2DM made more errors (1.1 vs 0.6), and had higher dual-task cost (9.17% vs 2.7%, p=0.014). Dual-task cost (the percentage decrement in walking speed due to introduction of the cognitive task) was significantly correlated with total MoCA score (R2 = 0.17, p =0.031). Discussion: Otherwise healthy participants with midlife T2DM display significantly poorer scores on MoCA. Performance on the dual-cognitive gait task was significantly correlated with MoCA score. Our study adds evidence to the presence of cognitive decrements in midlife T2DM, in-keeping with its role as a potent risk factor for the later development of dementia. We provide early data to support the utility of simple clinical gait analysis, particularly where a dual-cognitive paradigm is employed. Expansion of the sample size of patients in this study as well as longitudinal follow up should afford more detailed insight into using gait as a potential marker for cognition in this high risk cohort
Listed In: Biomechanical Engineering, Biomechanics, Gait, Neuroscience


Fluid load support in the migrating contact area: How much migration is necessary?

It is well-accepted that cartilage maintains interstitial fluid load support under long-term joint loading because contact migration leaves insufficient time for fluid exudation. However, it’s also evident that the benefits of migration dissipate as range of motion first approaches the contact length, a situation typical of moving diarthrodial joints, and then zero—typical of static joints. This study aims to elucidate the transition from full fluid load support to zero fluid load support under restricted ranges of motion. Testing was performed on osteochondral plugs using varied probe sizes, loads and track-lengths at Pe >> 1; fluid load support, contact area, and contact stress were quantified in-situ. Fluid load support depended primarily on the migration length per unit contact length (S*) and maintained maximal magnitude (F*=100%) at S* > 10. At S* < 10, it varied as a sigmoidal function of S*, falling to F* = 50% by S* = 0.1 on average. This transition migration length was independent of probe radius and varied slightly, yet significantly with contact area, load, and contact stress over the ranges tested. When migration length approached the contact length, the fluid load support of cartilage fell below that predicted by the established mechanics of migrating contacts. Based on our results, we propose a simple analytical correction that should be used when S*<10. These results demonstrate that fluid retention and load support are impaired by reduced activity and reduced ranges of motion, especially given the relatively short tracks of most joints at full range of motion.
Listed In: Biomechanical Engineering, Biomechanics, Biotribology


Can We Develop a Biomechanical Functional Score to Quantify the Joint Mechanics of THA Patients?

THA is a reliable method to improve the quality of life in osteoarthritis patients. However, it is still unclear whether it would lead to improved functional mobility. The purpose was to develop a biomechanical functional score to quantify the joint mechanics of THA patients compared to healthy participants (CTRL). Twenty-four THA patients and 12 CTRL (age-, sex-, and BMI-matched) participants were recruited and underwent motion analysis for different ADLs tasks prior and nine months after THA. Three-dimensional joint kinematics and ground reaction forces were collected and five kinematic and six kinetic variables were included in the analysis. The normalized root-mean-square-deviation (nRMSD) was calculated between the THA and the CTRL groups for both pre- and post-op conditions: nRMSD= √((∑_(t=1)^n(x_(1,t)- y_(1,t))^2)/n)⁄(x_max-x_min). Kinematics and kinetics improvement scores (KMIS and KNIS) were calculated to estimate pre/post-op differences: KMIS=∑_(i=1)^n〖〖(KM〗_(pre/ctrl i)-〖KM〗_(post/ctrl i))〗; KNIS=∑_(i=1)^n〖〖(KN〗_(pre/ctrl i)- 〖KN〗_(post/ctrl i))〗. THA patients experienced post-op improvements, with kinetics variables closely resembling the CTRLs, especially on hip and knee power production. Total improvement scores showed that THA experienced greater improvements during a squat task and this can be a practical approach to evaluate the change in biomechanical function and highlight small improvements that may go unnoticed with traditional statistical analysis.
Listed In: Biomechanics, Orthopedic Research


Could lowering the tackle height law to below the chest in rugby union reduce long-term brain degeneration?

The tackle height law in rugby union has been an area of concern for many years. It is currently set at the line of the ball carrier’s shoulder. The goal of this study is to use Model-Based Image-Matching (MBIM) and human volunteer tackles in a marker-based 3D motion analysis laboratory to examine the severity of a legal tackle to the shoulder/chest of the ball carrier (with no head contact) and the effect of tackles above and below the chest on ball carrier inertial head kinematics, respectively. From the real-world tackles, the estimated ball carrier peak resultant change in head angular velocity was 30.4 rad/s (23.1 rad/s, 14.0 rad/s and 21.8 rad/s in the coronal, sagittal and transverse direction, respectively). In the staged tackles, the median peak resultant head linear and angular acceleration and change in head angular velocity values for tackles above the chest were greater than for below the chest. The results support the proposition of lowering the current tackle height law. Due to the real-world tackle (MBIM), the ball carrier head kinematics indicated a greater than 75% chance of sustaining a concussion, based on the literature. This was the case even though no contact was made with the ball carrier’s head. Therefore, repeatedly engaging in this type of legal tackle may be detrimental for long-term brain health. However, by lowering the tackle height law to below the chest, ball carrier inertial head kinematics can be reduced significantly, thus reducing the repetitive loading placed on the brain.
Listed In: Biomechanical Engineering, Biomechanics, Sports Science


Kinetics and kinematics of the lower extremity during performance of two typical Tai Chi movements by the elders

Tai Chi (TC) has the rehabilitative potential to prevent falls in the elderly, however it is unclear how TC training improves postural control capacity. Fifteen male participants with more than 4 years of TC experience were asked to perform two TC movements, the “Repulse Monkey (RM)” and “Wave-hands in clouds (WHIC).” Three-dimensional (3-D) temporospatial, kinematic and kinetic data was collected using VICON motion analysis system with 10 infrared cameras and 4 force plates. Stride width, step length, step width, single- and double-support times, center of mass (COM) displacement, peak joint angles, range of motion, peak joint moments, time to peak moment, and ground reaction force (GRF) were analyzed. The differences in the measurements of the two TC movements were compared with walking using two-way ANOVA analysis. Compared with walking kinematics, both TC movements spent less time in single-support; RM and WHIC had larger mediolateral and vertical displacement of the COM. Compared with walking kinetics, both TC movements generated significantly smaller peak ground reaction forces in all directions, except the anterior; larger hip extension, adduction and internal rotational moments, knee adduction/abduction and internal rotation moments and eversion/inversion and external/internal moments of ankle–foot; and longer peak moment generation time for hip extension, adduction and internal rotation, knee extension and ankle dorsiflexion and inversion. The slow, gentle stepping-action and loading patterns that are consistent with the mechanical behavior of biological tissues. These two TC movements would be suitable training to help strengthen the lower extremities and prevent falls in the elderly.
Listed In: Biomechanics, Gait, Sports Science