Fatigue is a case of interaction between different factors and is characterized by the increase in the perceived effort to exercise and produce force. However, the effect on balancing tasks are not completely understood, especially the time course of the postural sway parameters during the recovery phase. Twenty female handball athletes participated in this study. They stood upright in a one-leg posture supported by the non-dominant limb on a force plate. The center of pressure (COP) and the maximum propulsion force (FMAX) were obtained at baseline, immediately after the exhaustion due to the fatigue protocol and every minute during the first 10 min of the recovery phase. For the postural-sway measures, participants stood on the force plate for 30 s with eyes opened looking to a target. Based on the COP displacement, the ellipse area containing 95% of the COP data points (Area) was computed. The FMAX was measured during a countermovement jump. Specific handball actions composed the fatigue protocol in the format of a circuit with the gradual increment of laps. The force decreased ~9.5% after the fatigue protocol (p = 0.01) and returned to baseline values during the recovery phase at the fifth minute. For the postural sway, the Area decreased during the recovery phase until the fourth minute (p = 0.007). The fatigue protocol affected postural sway and force variables, which returned to baseline values after four minutes of the protocol. Therefore, we suggest that future fatigue analyses should be tested during this time window.
Listed In: Biomechanics, Posturography, Sports Science

The anterior cruciate ligament (ACL) stabilizes the lower limb against translational and rotational loads while the knee is is multiple postures. Surgical reconstruction, the most common treatment for ACL tears, is intended to replicate the biomechanical function of the native ACL in the postures and activities related to daily living and high-impact activities. In order to improve outcomes from ACL reconstructions in patients in pediatric and adolescent age groups, we need to improve our understanding of the knee posture dependent biomechanical function of the ACL. As such, the objective of this study was to quantify flexion angle dependent changes in the response of the ACL and the total knee to applied loads in the anterior-posterior and varus-valgus directions using a skeletally immature porcine model. To do this, we collected stifle (knee) joints from female Yorkshire-cross pigs at ages ranging from 1.5 to 18 months (n=30 total). The joints were tested using a 6 degree-of-freedom universal force sensing robotic system under applied anterior-posterior loads and varus-valgus moments at 40° and 60° of flexion. Studied parameters included anterior-posterior tibial translation (APTT), varus-valgus rotation (VVR), and anterior force carried by the ACL and its anteromedial and posterolateral bundles. We found increased knee laxity (APTT and VVR) was associated with both younger age and increased knee flexion. Greater anterior force carried in the ACL, and specifically in the anteromedial bundle, was associated with increased flexion, regardless of age. These findings have implications in intraoperative graft assessment and biomechanical models.
Listed In: Biomechanical Engineering, Biomechanics, Orthopedic Research, Sports Science

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

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

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