Ankle instability (AI) and fatigue impair neuromuscular control as well as dynamic joint stability of the lower extremity. No one has comprehensively examined the effects of AI and fatigue on neuromechanics of the lower extremity during a functional activity. Deficits associated with AI and fatigue could be additive in increasing the risk for injury in patients with AI. PURPOSE: To examine the interaction of AI and fatigue on lower extremity muscle activity, kinematic, and kinetic patterns during a forward-side jump. METHODS: 25 AI (23.3 ± 1.9 yrs, 176.5 ± 10.5 cm, 70.9 ± 11.4 kg), and 25 matched control subjects (23.7 ± 2.5 yrs, 175.0 ± 10.8 cm, 70.3 ± 12.8 kg) were categorized according to the Foot and Ankle Ability Measure (FAAM) (ADL: 84.3 ± 7.6%, Sport: 63.6 ± 8.6%) and the Modified Ankle Instability Instrument (MAII) (3.7 ± 1.2). Fifty-nine reflective markers were place over anatomical landmarks and eight electromyography (EMG) electrodes were placed on tibialis anterior (TA), peroneus longus (PL), medial gastrocmedius (MG), medial hamstring (MH), vastus lateralis (VL), adductor longus (AL), gluteus medius (GMed), and gluteus maximus (GMax) muscles in the involved leg. Subjects performed five forward-side jumps on a force plate before and after functional fatiguing exercises. To induce fatigue, subjects began 5-min incremental running on a treadmill between 5 and 6 mph. Next, subjects performed 20-second lateral counter movement jumps (CMJ), and 20 vertical CMJs. After each fatigue cycle, subjects performed one max vertical jump. Subjects repeated three exercises until Borg's rating of perceived exertion (RPE) reached 17 and the vertical jump height fell below 80% of their max jump height. Functional analysis of variance (FANOVA) (p < 0.05) was used to evaluate differences (a group by fatigue interaction) between two conditions (pre- vs post-fatigue) in each group (AI and control) for lower-extremity kinematic, kinetic and neuromuscular patterns. Pairwise comparison functions as well as 95% confidence interval (CI) bands were plotted to determine specific differences. If 95% CI bands did not cross the zero line, we considered the difference significant. RESULTS: Compared to the control group, the AI group demonstrated less range of dorsiflexion, knee and hip flexion motions during early phase of landing after fatigue. For sagittal-plane hip kinetics, subjects with AI decreased the hip extension moment while control subjects increased hip extension moments during landing following functional fatiguing exercise. The AI group showed less reduction of anterior-posterior ground reaction force (AP GRF) during transition phase of a forward-side jump after fatigue compared to control subjects. The AI group decreased EMG amplitude of PL, MH, and GMed while increased VL and GMax during landing after fatigue compared to control subjects. CONCLUSION: AI subjects demonstrated greater impairments in neuromechanical control patterns than a matched control group during a sport movement as fatigue progressed. Compared to AI group, control subjects showed a coordinated joint control strategy after fatigue, increasing joint angles from distal (ankle) to proximal (hip) joints by increasing hip extensor moments during landing from a forward-side jump in an attempt to reduce ground impact force. EMG alterations were consistent with patterns observed in injured patients, which may predispose patients to poor positions associated with lower extremity joint injury. These interactions between neuromuscular fatigue and AI may predispose individuals to lower extremity injuries.

archives@tulane.edu / Background Ankle brachial index (ABI) is a noninvasive measure of subclinical cardiovascular disease (CVD) and atherosclerosis of the lower extremities. Low and high levels of ABI are associated with cardiovascular mortality and vascular calcification in dialysis chronic kidney disease (CKD) patients. However, the association of the spectrum of vascular calcification with low and high ABI is not well studied in pre-dialysis CKD patients. The purpose of this study is to investigate the association of both low and high ABI with the risk of vascular calcification in CKD patients. Methods We recruited 243 patients with pre-dialysis CKD from the great New Orleans area between 2010 and 2012. Our study used a cross-sectional design with ABI and CAC measured at the same visit. Continuous ABI measurements were taken and further classified into four categories : <=0.9 (low ABI) >0.9-<1.0 (borderline), 1.0-<1.4 (normal), >=1.4 (high). Level of vascular calcification were considered as the outcome and calculated by agatston score. Three categories of CAC is defined as: CAC agaston score=0, 0-100, >100. Three cumulative logit models were applied to the data. The first is an unadjusted univariate model, the second adjusts for baseline demographics, and the third adjusts for baseline demographics and covariates that are associated with CAC. Logistic regression methods were used to calculate the odds ratio of having a higher CAC score for CKD patients. Results We found a significant association between ABI and vascular calcification. All three models returned consistently significant result (p=0.0005, 0.0005, 0.0037, respectively) for the association between ABI and CAC. In addition, low ABI (ABI≤0.9) is also associated with an increased risk of CAC and severe CAC (OR=6.183, 95%CI(1.085, 35.228)). High ABI (>1.4) is also associated with an increase in CAC and severe CAC (OR=5.064, 95%CI (1.696, 15.122)). Borderline ABI (0.9<ABI<1.0) is not associated with an increase in CAC or severe CAC (OR=2.704, 95% CI (0.702, 10.418). Conclusion Compared to normal ABI level, low and high ABIs are both significantly associated with an increased risk of coronary artery calcification and severe coronary artery calcification in CKD patients. / 1 / Shuo Bai

Contact stress exposure is thought to play a significant role in many aspects of joint degradation and pathology. Effective and accurate contact stress computation in native or pathological subject specific joints is an important tool in determining the role of contact stress in OA onset and worsening as well as eventually developing and monitoring interventions to prevent joint degradation. In the past FEA modeling has allowed for studies to be completed which relate contact stress exposure human ankle joint to the presence of radiographic OA. While promising, contact FEA for subject specific models is significantly limited by the number of cases that can be computed due to the difficulty of FEA modeling, as well as numerical convergence issues present in contact FEA. To obtain truly statistically powerful conclusions about the causes of joint degradation and OA onset large numbers of subject specific models will need to be created, run and analyzed. Rigid body spring modeling or RBSM has proven to be an effective method of contact stress measurement for both expedited evaluation of PTOA risk following tibial plafond fractures as well as for evaluation of BMLs worsening in a cohort of 38 at risk patients. RBSM treats cartilage as a bed of springs attached to an underlying rigid bone surface. It is a significant simplification from FEA in that it does not allow computation of internal stresses of an object, elaborate material treatments, or true deformation of an object. This simplification comes with the benefit of reduced computational and investigator burden due to the lack of numerical convergence issues as well as no FEA meshing step. A custom written RBSM algorithm was created in MATLAB which works in conjunction with a load balancing algorithm to iteratively solve contact solutions in both load and displacement control. This algorithm was first validated against a previously done physical validation study using two human cadaver ankles in a custom built fixture. The RBSM method was then used to replicate previously obtained FEA results in a study of 22 human ankle joints following tibial plafond fracture. FEA models and loadings were adapted for the RBSM method and run. The RBSM offered a significant speed increase while maintaining comparable results to the FEA. The ability of RBSM to predict PTOA development using a contact stress-time-area exposure metric was virtually unchanged (95% KL grade concordance and 100% OA concordance vs. 94% KL grade concordance and 100% OA concordance, for RBSM and FEA, respectively). The RBSM method was then combined with a feature based 3D-2D alignment routine custom written in MATLAB. This alignment routine uses a ray casting method to recreate a virtual x-ray silhouette edge for a 3D model. This model is then aligned to a 2D edge tracing based off an input radiograph depicting a functional pose of the bone. A global optimizer (simulated annealing) is used to determine the best Euler transform to place the bone in an accurate position in the recreated virtual scene. 38 subject specific knee models segmented from the MOST cohort were aligned to functional appositions bases off of fixed flexion standing radiographs. Contact stresses were then obtained from these aligned joints using RBSM to evaluate the relationship between contact stress level and bone marrow lesion worsening. It was found that as contact stress level increases so does the risk of BMLs worsening. As the worsening of BMLs is associated with joint pain, degradation, and pathology an expedited contact stress method which can accurately predict BML worsening is especially valuable.

With over 7% (20 million) people in the United States affected by diabetes mellitus (DM), DM has emerged as a significant health problem. The hallmark of DM is multi-system involvement and the lower limbs are frequently involved in the form of foot ulcers. Inability to heal foot ulcers and maintain healing contributes to the high rate of amputation seen in individuals with DM. The development of foot ulcers has been strongly linked with mechanical stress. Changes in muscle characteristics and segmental foot mobility have been postulated to limit forward progression of the leg on the fixed foot during walking. This in turn may result in prolonged and excessive loading on the ball of the foot. However the extent and site of the impairments and their functional consequences are not well understood. The purpose of this work is to examine determinants of dynamic foot function and plantar loading in individuals with DM. Our results revealed that in spite of differences in passive ankle dorsiflexion and stiffness, subjects with DM demonstrated ankle motion, stiffness and plantar pressures, similar to control subjects, while walking at the identical speed, 0.89 m/s (2 mph). In terms of segmental mobility, reductions were particularly dramatic in the calcaneus (20%) compared to the forefoot and first metatarsal. Decreases in frontal plane calcaneal motion were accompanied by reduced midfoot mobility. Sagittal motion of the first metatarsal and forefoot, and frontal motion of the calcaneus, in subjects with DM, was negatively associated with the magnitude of plantar loading under the respective segment. This information is important because it may help elucidate underlying mechanisms and add to our understanding of the disease process and its effects. In addition, these results may help develop more focused intervention strategies.

The effect of a preseason conditioning program of balance and jump landing training exercises was studied to evaluate its influence on static and dynamic balance and the occurrence of ankle and knee injuries in Basketball. Fifty-eight female representative Basketball players (aged 9 – 17 years) were studied over one season. Twenty-nine of these players participated in a six week training program implemented during the preseason. Pre and post tests measured balance and injuries documented over one season. The experimental group’s static and dynamic balance improved significantly as measured by a stork stand test and a multiple single-leg hop-stabilisation test In a post hoc analysis of dynamic balance, participants in the 12 – 13 years experimental group performed significantly better on dynamic balance, whereas the 12 – 13 years control group performed poorest compared with all other age cohorts. The lower limb injury rate for the 29 experimental group participants was .78 injuries per 1 000 hours, while the control group sustained no lower limb injuries in the 2001 season, based on the injury definition utilised in the study. This finding was statistically significant although three of the four injuries sustained were contact injuries. The study findings indicate that appropriately defined balance training can be beneficial for improving balance ability in female Basketball players. Evidence was found in the study for the existence of a critical age when balance training should be introduced to maximise the benefit for young female adolescent Basketball players. / Master of Education (Hons)

Ankle injuries comprise more than 15% of all sports injuries worldwide. The efficacy of the ankle taping for injury prevention has long been under scrutiny as numerous studies have shown that tape rapidly loses its ability to constrain ankle motion with exercise. Consequently, ankle braces (orthoses) are being used with increasing frequency for the prevention and functional management of ankle injuries. However, the motion restraining qualities of ankle orthoses have not been widely evaluated in closed kinetic chain environments under physiologic loads. The primary purpose of this study was to compare the abilities of four ankle orthoses (ankle taping, lace-up brace, semirigid orthosis and hybrid brace) against a control condition (no brace or tape) to control subtalar and talocrural motion during running on a laterally-tilted treadmill at 16.2 km/h before and after exercise. It has been hypothesized that ankle orthoses make a secondary contribution to injury prevention through enhanced proprioception. The secondary purpose of this study was to quantify the effects of the aforementioned ankle orthoses on postural stability during single-limb stance following a bout of exercise. Fifteen healthy university students (8 men and 7 women) with no history of significant ankle injuries (age, mean �� SD: 22.9 �� 3.9 years) volunteered to participate in this study. Three-dimensional kinematic data were captured with an active infrared digital camera system sampling at 120 Hz. To address the first question, data analyses were performed using 2way univariate (Ankle Orthoses x Pre/Post-Exercise x Subjects) (5 x 2 x 15) repeated measures analysis of variance (ANOVA) to determine the existence of differences among three closed and four open kinematic chain dependent measures before and after exercise. Maximum inversion angles (MAXINV) were similar for all ankle orthoses, with no orthosis limiting inversion during tilted treadmill running significantly more than another, or compared to the control condition, either before or after exercise (p>.05). Pre-exercise MAXINV group means and standard deviations during treadmill running ranged from 6.8 �� 3.4 deg with the Royce Medical Speed Brace to 9.5 �� 4.1 deg in the tape condition; post-exercise MAXINV mean values ranged from 7.6 �� 3.2 deg for the Aircast Sport Stirrup to 9.1 �� 4.6 deg with closed basketweave tape. While not statistically significant (p=0.10), ankle taping provided the least amount of inversion restraint, both before and after the exercise bout. The MAXINV angles measured during treadmill running (8.2 �� 4.0 deg) and open chain inversion AROM measured with a goniometer (34.5 �� 6.2 deg) were not related (r=-0.0003). The compressive forces present during closed kinetic chain activity are known to increase joint stability and thus may explain why MAXINV under dynamic varus loads was so much less in magnitude than inversion AROM measured under open kinetic chain conditions. The nonlinear relationship of these two variables supports our contention that reports of the motion controlling properties of ankle orthoses measured in open kinetic chain environments should not be used to infer the response characteristics of these same orthoses under dynamic, physiologic loads. To address the second question, data were analyzed using 3-way univariate (Ankle Orthoses x Pre/Post-Exercise x Eyes Open/Closed x Subjects) (5 x 2 x 2 x 15) repeated measures ANOVAs. Subjects' postural stability was assessed using a Biodex Balance System with eyes open and eyes closed conditions, before and after an exercise bout. The ankle orthoses evaluated did not influence postural stability as measured by mediolateral sway index, anteroposterior sway index, and overall sway index. Removal of visual perception via blindfolding resulted in significant decreases in all three measures of postural stability (p=.001). There was poor association among the closed chain postural stability parameters and the open chain AROM measures. These correlations ranged from r=.04 to .17, indicating minimal relationship between the amount of AROM permitted by the orthoses and postural stability as quantified by this method. / Graduation date: 2000

Gait biomechanics of forty male subjects was evaluated at normal and fast walking speeds. The forty subjects composed four groups based on their body mass index, with ten subjects in each of the groups: underweight, normal weight, overweight and obese. To our knowledge this is the first comprehensive 3-dimensional kinetic and kinematic gait analysis of all four groups based on body mass index. The obese subjects walked with significantly slower gait speed by taking shorter steps and strides, while having significantly higher step widths and longer gait cycle times than the other subjects. The obese subjects spent significantly less time in single support and more time in double support than their non-obese counterparts. These adjustments in temporal characteristics for the obese participants may be as a result of the gait compensation for the additional body weight in order to give them the most efficient, stable and balanced walking ability. Body mass index affected significantly the forces and moments at the ankle, knee and hip in the medial-lateral plane while speed effects were more prominent in the sagittal and transverse planes. These results suggest that an increase in the body weight would affect the gait stability while increasing the speed will affect the gait progression. Contrary to most researchers beliefs that an increase of the body weight would increase the forces and moments of the knee in all three planes, this study was able to prove that the actual forces and moments in the medial-lateral plane for the knee joint decrease while the ones in the sagittal plane increase. On the other hand, the hip joint in the medial-lateral plane displays the highest forces and moment for the obese subjects. These results are indicative of a gait compensation related to increasing body weight in the medial-lateral compartment of the lower extremity joints. Recommendations for further studies and follow up experiments are enclosed.

The purpose of this study was to examine the effects of landing on a combined inverted and plantarflexed surface on the ankle kinematics and electromyographic (EMG) activities of the medial gastrocnemius (MG), peroneal longus (PL) and anterior tibialis muscles (TA). Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to each of these surfaces: a flat surface, a 25° inversion surface (inverted), and a combined surface (combined) of 25° inversion and 25° plantarflexion. The three dimensional kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using one-way repeated measures analysis of variance (ANOVA, p < 0.05) and a 3 × 3 (surface × muscle) ANOVA, respectively. The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG and ankle plantarflexion angle were significantly higher for the combined surface compared to the inverted surface. These findings suggest that compared to inversion, a combination of plantarflexion and inversion provides a more realistic surface for simulating lateral ankle sprains.

The purpose of this study was to examine the effects of landing on a combined inverted and plantarflexed surface on the ankle kinematics and electromyographic (EMG) activities of the medial gastrocnemius (MG), peroneal longus (PL) and anterior tibialis muscles (TA). Twelve recreational athletes performed five drop landings from an overhead bar of 30 cm height on to each of these surfaces: a flat surface, a 25° inversion surface (inverted), and a combined surface (combined) of 25° inversion and 25° plantarflexion. The three dimensional kinematic variables and integrated EMG (IEMG) of the three muscles were assessed using one-way repeated measures analysis of variance (ANOVA, p < 0.05) and a 3 × 3 (surface × muscle) ANOVA, respectively. The IEMG results showed a significant muscle by surface interaction. The flat surface induced higher TA activity than the two tilted surfaces. The inverted surface produced significantly higher inversion peak angle and velocity than the flat surface, but similar PL activity across the surfaces. The MG IEMG and ankle plantarflexion angle were significantly higher for the combined surface compared to the inverted surface. These findings suggest that compared to inversion, a combination of plantarflexion and inversion provides a more realistic surface for simulating lateral ankle sprains.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 141-148).