Julie Kolesar is a Research Engineer in the Human Performance Lab, supporting teaching and interdisciplinary research at the crossroads of engineering, sports medicine, and athletics. Her work aims to understand the underlying mechanisms relating biomechanical changes with function and quality of life for individuals with musculoskeletal disorders and injuries. As part of the Wu Tsai Human Performance Alliance, Dr. Kolesar engages in collaborations which seek to optimize human health and performance across the lifespan. Her expertise and research interests include experimental gait analysis, musculoskeletal modeling and simulation, and clinical interventions and rehabilitation.

Academic Appointments

Professional Education

  • Ph.D., The Ohio State University, Mechanical Engineering (2013)
  • M.S., The Ohio State University, Mechanical Engineering (2009)
  • B.S., The Ohio State University, Mechanical Engineering (2008)

Clinical Trials

  • Long-Term Effectiveness of Walking Training in Patients With Knee Osteoarthritis Not Recruiting

    Nearly one out of every two Americans will develop knee osteoarthritis by age 85. Over 20 million Americans, including nearly three million Veterans, currently have painful knee arthritis that limits their daily activity or recreation. The vast majority of those individuals will be prescribed anti-inflammatory drugs that provide some pain relief but do not slow the progression of the disease. Often people with knee arthritis are told they must live with the pain until they become appropriate candidates for knee replacement surgery, but that can require tolerating the pain and limiting function for many years. Because of other health issues, some individuals are never acceptable surgery candidates. What is desperately needed are better conservative approaches for treating these patients. Two such approaches will be tested and compared in this study.

    Stanford is currently not accepting patients for this trial. For more information, please contact Julie Kolesar, PhD, 650-721-2547.

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All Publications

  • Can static optimization detect changes in peak medial knee contact forces induced by gait modifications? Journal of biomechanics Kaneda, J. M., Seagers, K. A., Uhlrich, S. D., Kolesar, J. A., Thomas, K. A., Delp, S. L. 2023; 152: 111569


    Medial knee contact force (MCF) is related to the pathomechanics of medial knee osteoarthritis. However, MCF cannot be directly measured in the native knee, making it difficult for therapeutic gait modifications to target this metric. Static optimization, a musculoskeletal simulation technique, can estimate MCF, but there has been little work validating its ability to detect changes in MCF induced by gait modifications. In this study, we quantified the error in MCF estimates from static optimization compared to measurements from instrumented knee replacements during normal walking and seven different gait modifications. We then identified minimum magnitudes of simulated MCF changes for which static optimization correctly identified the direction of change (i.e., whether MCF increased or decreased) at least 70% of the time. A full-body musculoskeletal model with a multi-compartment knee and static optimization was used to estimate MCF. Simulations were evaluated using experimental data from three subjects with instrumented knee replacements who walked with various gait modifications for a total of 115 steps. Static optimization underpredicted the first peak (mean absolute error = 0.16 bodyweights) and overpredicted the second peak (mean absolute error = 0.31 bodyweights) of MCF. Average root mean square error in MCF over stance phase was 0.32 bodyweights. Static optimization detected the direction of change with at least 70% accuracy for early-stance reductions, late-stance reductions, and early-stance increases in peak MCF of at least 0.10 bodyweights. These results suggest that a static optimization approach accurately detects the direction of change in early-stance medial knee loading, potentially making it a valuable tool for evaluating the biomechanical efficacy of gait modifications for knee osteoarthritis.

    View details for DOI 10.1016/j.jbiomech.2023.111569

    View details for PubMedID 37058768

  • Personalization improves the biomechanical efficacy of foot progression angle modifications in individuals with medial knee osteoarthritis. Journal of biomechanics Uhlrich, S. D., Kolesar, J. A., Kidzinski, L., Boswell, M. A., Silder, A., Gold, G. E., Delp, S. L., Beaupre, G. S. 2022; 144: 111312


    Modifying the foot progression angle during walking can reduce the knee adduction moment, a surrogate measure of medial knee loading. However, not all individuals reduce their knee adduction moment with the same modification. This study evaluates whether a personalized approach to prescribing foot progression angle modifications increases the proportion of individuals with medial knee osteoarthritis who reduce their knee adduction moment, compared to a non-personalized approach. Individuals with medial knee osteoarthritis (N=107) walked with biofeedback instructing them to toe-in and toe-out by 5° and 10° relative to their self-selected angle. We selected individuals' personalized foot progression angle as the modification that maximally reduced their larger knee adduction moment peak. Additionally, we used lasso regression to identify which secondary kinematic changes made a 10° toe-in gait modification more effective at reducing the first knee adduction moment peak. Seventy percent of individuals reduced their larger knee adduction moment peak by at least 5% with a personalized foot progression angle modification, which was more than (p≤0.002) the 23-57% of individuals who reduced it with a uniformly assigned 5° or 10° toe-in or toe-out modification. When toeing-in, greater reductions in the first knee adduction moment peak were related to an increased frontal-plane tibia angle (knee more medial than ankle), a more valgus knee abduction angle, reduced contralateral pelvic drop, and a more medialized center of pressure in the foot reference frame. In summary, personalization increases the proportion of individuals with medial knee osteoarthritis who may benefit from a foot progression angle modification.

    View details for DOI 10.1016/j.jbiomech.2022.111312

    View details for PubMedID 36191434

  • Muscle coordination retraining inspired by musculoskeletal simulations reduces knee contact force. Scientific reports Uhlrich, S. D., Jackson, R. W., Seth, A., Kolesar, J. A., Delp, S. L. 2022; 12 (1): 9842


    Humans typically coordinate their muscles to meet movement objectives like minimizing energy expenditure. In the presence of pathology, new objectives gain importance, like reducing loading in an osteoarthritic joint, but people often do not change their muscle coordination patterns to meet these new objectives. Here we use musculoskeletal simulations to identify simple changes in coordination that can be taught using electromyographic biofeedback, achieving the therapeutic goal of reducing joint loading. Our simulations predicted that changing the relative activation of two redundant ankle plantarflexor muscles-the gastrocnemius and soleus-could reduce knee contact force during walking, but it was unclear whether humans could re-coordinate redundant muscles during a complex task like walking. Our experiments showed that after a single session of walking with biofeedback of summary measures of plantarflexor muscle activation, healthy individuals reduced the ratio of gastrocnemius-to-soleus muscle activation by 25±15% (p=0.004, paired t test, n=10). Participants who walked with this "gastrocnemius avoidance" gait pattern reduced late-stance knee contact force by 12±12% (p=0.029, paired t test, n=8). Simulation-informed coordination retraining could be a promising treatment for knee osteoarthritis and a powerful tool for optimizing coordination for a variety of rehabilitation and performance applications.

    View details for DOI 10.1038/s41598-022-13386-9

    View details for PubMedID 35798755

  • Changes in foot progression angle during gait reduce the knee adduction moment and do not increase hip moments in individuals with knee osteoarthritis. Journal of biomechanics Seagers, K., Uhlrich, S. D., Kolesar, J. A., Berkson, M., Kaneda, J. M., Beaupre, G. S., Delp, S. L. 2022; 141: 111204


    People with knee osteoarthritis who adopt a modified foot progression angle (FPA) during gait often benefit from a reduction in the knee adduction moment. It is unknown, however, whether changes in the FPA increase hip moments, a surrogate measure of hip loading, which will increase the mechanical demand on the joint. This study examined how altering the FPA affects hip moments. Individuals with knee osteoarthritis walked on an instrumented treadmill with their baseline gait, 10° toe-in gait, and 10° toe-out gait. A musculoskeletal modeling package was used to compute joint moments from the experimental data. Fifty participants were selected from a larger study who reduced their peak knee adduction moment with a modified FPA. In this group, participants reduced the first peak of the knee adduction moment by 7.6% with 10° toe-in gait and reduced the second peak by 11.0% with 10° toe-out gait. Modifying the FPA reduced the early-stance hip abduction moment, at the time of peak hip contact force, by 4.3% ± 1.3% for 10° toe-in gait (p = 0.005, d = 0.49) and by 4.6% ± 1.1% for 10° toe-out gait (p < 0.001, d = 0.59) without increasing the flexion and internal rotation moments (p > 0.15). Additionally, 74% of individuals reduced their total hip moment at time of peak hip contact force with a modified FPA. In summary, when adopting a FPA modification that reduced the knee adduction moment, participants, on average, did not increase surrogate measures of hip loading.

    View details for DOI 10.1016/j.jbiomech.2022.111204

    View details for PubMedID 35772243

  • A neural network to predict the knee adduction moment in patients with osteoarthritis using anatomical landmarks obtainable from 2D video analysis. Osteoarthritis and cartilage Boswell, M. A., Uhlrich, S. D., Kidzinski, L., Thomas, K., Kolesar, J. A., Gold, G. E., Beaupre, G. S., Delp, S. L. 2021


    OBJECTIVE: The knee adduction moment (KAM) can inform treatment of medial knee osteoarthritis; however, measuring the KAM requires an expensive gait analysis laboratory. We evaluated the feasibility of predicting the peak KAM during natural and modified walking patterns using the positions of anatomical landmarks that could be identified from video analysis.METHOD: Using inverse dynamics, we calculated the KAM for 86 individuals (64 with knee osteoarthritis, 22 without) walking naturally and with foot progression angle modifications. We trained a neural network to predict the peak KAM using the 3-dimensional positions of 13 anatomical landmarks measured with motion capture (3D neural network). We also trained models to predict the peak KAM using 2-dimensional subsets of the dataset to simulate 2-dimensional video analysis (frontal and sagittal plane neural networks). Model performance was evaluated on a held-out, 8-person test set that included steps from all trials.RESULTS: The 3D neural network predicted the peak KAM for all test steps with r2=0.78. This model predicted individuals' average peak KAM during natural walking with r2=0.86 and classified which 15° foot progression angle modifications reduced the peak KAM with accuracy=0.85. The frontal plane neural network predicted peak KAM with similar accuracy (r2=0.85) to the 3D neural network, but the sagittal plane neural network did not (r2=0.14).CONCLUSION: Using the positions of anatomical landmarks from motion capture, a neural network accurately predicted the peak KAM during natural and modified walking. This study demonstrates the feasibility of measuring the peak KAM using positions obtainable from 2D video analysis.

    View details for DOI 10.1016/j.joca.2020.12.017

    View details for PubMedID 33422707

  • Bone changes in the lower limbs from participation in an FES rowing exercise program implemented within two years after traumatic spinal cord injury JOURNAL OF SPINAL CORD MEDICINE Lambach, R. L., Stafford, N. E., Kolesar, J. A., Kiratli, B., Creasey, G. H., Gibbons, R. S., Andrews, B. J., Beaupre, G. S. 2020; 43 (3): 306–14
  • SIX WEEKS OF PERSONALIZED GAIT RETRAINING TO OFFLOAD THE MEDIAL COMPARTMENT OF THE KNEE REDUCES PAIN MORE THAN SHAM GAIT RETRAINING Uhlrich, S. D., Kolesar, J. A., Silder, A., Berkson, M. Z., Presten, B., Montague-Alamin, H. A., Edouard, N., Willoughby, D., Finlay, A. K., Gold, G. E., Delp, S. L., Beaupre, G. S. ELSEVIER SCI LTD. 2019: S28
  • Bone changes in the lower limbs from participation in an FES rowing exercise program implemented within two years after traumatic spinal cord injury. The journal of spinal cord medicine Lambach, R. L., Stafford, N. E., Kolesar, J. A., Kiratli, B. J., Creasey, G. H., Gibbons, R. S., Andrews, B. J., Beaupre, G. S. 2018: 1–9


    OBJECTIVE: To determine the effect of a functional electrical stimulation (FES) rowing program on bone mineral density (BMD) when implemented within two years after SCI.DESIGN: Prospective.SETTING: Health Care Facility.PARTICIPANTS: Convenience sample; four adults with recent (<2 years) traumatic, motor complete SCI (C7-T12 AIS A-B).INTERVENTION: A 90-session FES rowing exercise program; participants attended 30-minute FES training sessions approximately three times each week for the duration of their participation.OUTCOME MEASURES: BMD in the distal femur and tibia were measured using peripheral Quantitative Computed Tomography (pQCT) at enrollment (T0) and after 30 (T1), 60 (T2), and 90 (T3) sessions. Bone stimulus was calculated for each rower at each time point using the average number of weekly loading cycles, peak foot reaction force, and bone mineral content from the previous time point. A regression analysis was used to determine the relationship between calculated bone stimulus and change in femoral trabecular BMD between time points.RESULTS: Trabecular BMD in the femur and tibia decreased for all participants in T0-1, but the rate of loss slowed or reversed between T1-2, with little-to-no bone loss for most participants during T2-3. The calculated bone stimulus was significantly correlated with change in femoral trabecular BMD (P=0.016; R2=0.458).CONCLUSION: Consistent participation in an FES rowing program provides sufficient forces and loading cycles to reduce or reverse expected bone loss at the distal femur and tibia, at least temporarily, in some individuals within two years after SCI.TRIAL REGISTRATION: NCT02008149.

    View details for PubMedID 30475172

  • Age Influences Biomechanical Changes After Participation in an Anterior Cruciate Ligament Injury Prevention Program AMERICAN JOURNAL OF SPORTS MEDICINE Thompson-Kolesar, J. A., Gatewood, C. T., Tran, A. A., Silder, A., Shultz, R., Delpt, S. L., Dragoo, J. L. 2018; 46 (3): 598–606


    The prevalence of anterior cruciate ligament (ACL) injuries increases during maturation and peaks during late adolescence. Previous studies suggested an age-related association between participation in injury prevention programs and reduction of ACL injury. However, few studies have investigated differences in biomechanical changes after injury prevention programs between preadolescent and adolescent athletes. Purpose/Hypothesis: The purpose was to investigate the influence of age on the effects of the FIFA Medical and Research Centre (F-MARC) 11+ injury prevention warm-up program on differences in biomechanical risk factors for ACL injury between preadolescent and adolescent female soccer players. It was hypothesized that the ACL injury risk factors of knee valgus angle and moment would be greater at baseline but would improve more after training for preadolescent athletes than adolescent athletes. It was further hypothesized that flexor-extensor muscle co-contraction would increase after training for both preadolescent and adolescent athletes.Controlled laboratory study.Institutional Review Board-approved written consent was obtained for 51 preadolescent female athletes aged 10 to 12 years (intervention: n = 28, 11.8 ± 0.8 years; control: n = 23, 11.2 ± 0.6 years) and 43 adolescent female athletes aged 14 to 18 years (intervention: n = 22, 15.9 ± 0.9 years; control: n = 21, 15.7 ± 1.1 years). The intervention groups participated in 15 in-season sessions of the F-MARC 11+ program 2 times per week. Pre- and postseason motion capture data were collected during 4 tasks: preplanned cutting, unanticipated cutting, double-legged jump, and single-legged jump. Lower extremity joint angles and moments were estimated through biomechanical modeling. Knee flexor-extensor muscle co-contraction was estimated from surface electromyography.At baseline, preadolescent athletes displayed greater initial contact and peak knee valgus angles during all activities when compared with the adolescent athletes, but knee valgus moment was not significantly different between age groups. After intervention training, preadolescent athletes improved and decreased their initial contact knee valgus angle (-1.24° ± 0.36°; P = .036) as well as their peak knee valgus moment (-0.57 ± 0.27 percentage body weight × height; P = .033) during the double-legged jump task, as compared with adolescent athletes in the intervention. Compared with adolescent athletes, preadolescent athletes displayed higher weight acceptance flexor-extensor muscle co-contraction at baseline during all activities ( P < .05). After intervention training, preadolescent athletes displayed an increase in precontact flexor-extensor muscle co-contraction during preplanned cutting as compared with adolescent intervention athletes (0.07 ± 0.02 vs -0.30 ± 0.27, respectively; P = .002).The F-MARC 11+ program may be more effective at improving some risk factors for ACL injury among preadolescent female athletes than adolescent athletes, notably by reducing knee valgus angle and moment during a double-legged jump landing.ACL prevention programs may be more effective if administered early in an athlete's career, as younger athletes may be more likely to adapt new biomechanical movement patterns.

    View details for PubMedID 29281799

  • Age-Related Differences in Gait Kinematics, Kinetics, and Muscle Function: A Principal Component Analysis. Annals of biomedical engineering Schloemer, S. A., Thompson, J. A., Silder, A., Thelen, D. G., Siston, R. A. 2017; 45 (3): 695-710


    Age-related increased hip extensor recruitment during gait is a proposed compensation strategy for reduced ankle power generation and may indicate a distal-to-proximal shift in muscle function with age. Extending beyond joint level analyses, identifying age-related changes at the muscle level could capture more closely the underlying mechanisms responsible for movement. The purpose of this study was to characterize and compare muscle forces and induced accelerations during gait in healthy older adults with those of young adults. Simulations of one gait cycle for ten older (73.9 ± 5.3 years) and six young (21.0 ± 2.1 years) adults walking at their self-selected speed were analyzed. Muscle force and induced acceleration waveforms, along with kinematic, kinetic, and muscle activation waveforms, were compared between age-groups using principal component analysis. Simulations of healthy older adults had greater gluteus maximus force and vertical support contribution, but smaller iliacus force, psoas force, and psoas vertical support contribution. There were no age-group differences in distal muscle force, contribution, or ankle torque magnitudes. Later peak dorsiflexion and peak ankle angular velocity in older adults may have contributed to their greater ankle power absorption during stance. These findings reveal the complex interplay between age-related changes in neuromuscular control, kinematics, and muscle function during gait.

    View details for DOI 10.1007/s10439-016-1713-4

    View details for PubMedID 27573696

  • Biomechanical Effects of an Injury Prevention Program in Preadolescent Female Soccer Athletes AMERICAN JOURNAL OF SPORTS MEDICINE Thompson, J. A., Tran, A. A., Gatewood, C. T., Shultz, R., Silder, A., Delp, S. L., Dragoo, J. L. 2017; 45 (2): 294-301


    Anterior cruciate ligament (ACL) injuries are common, and children as young as 10 years of age exhibit movement patterns associated with an ACL injury risk. Prevention programs have been shown to reduce injury rates, but the mechanisms behind these programs are largely unknown. Few studies have investigated biomechanical changes after injury prevention programs in children.To investigate the effects of the F-MARC 11+ injury prevention warm-up program on changes to biomechanical risk factors for an ACL injury in preadolescent female soccer players. We hypothesized that the primary ACL injury risk factor of peak knee valgus moment would improve after training. In addition, we explored other kinematic and kinetic variables associated with ACL injuries.Controlled laboratory study.A total of 51 female athletes aged 10 to 12 years were recruited from soccer clubs and were placed into an intervention group (n = 28; mean [±SD] age, 11.8 ± 0.8 years) and a control group (n = 23; mean age, 11.2 ± 0.6 years). The intervention group participated in 15 in-season sessions of the F-MARC 11+ program (2 times/wk). Pre- and postseason motion capture data were collected during preplanned cutting, unanticipated cutting, double-leg jump, and single-leg jump tasks. Lower extremity joint angles and moments were estimated using OpenSim, a biomechanical modeling system.Athletes in the intervention group reduced their peak knee valgus moment compared with the control group during the double-leg jump (mean [±standard error of the mean] pre- to posttest change, -0.57 ± 0.27 %BW×HT vs 0.25 ± 0.25 %BW×HT, respectively; P = .034). No significant differences in the change in peak knee valgus moment were found between the groups for any other activity; however, the intervention group displayed a significant pre- to posttest increase in peak knee valgus moment during unanticipated cutting (P = .044). Additional analyses revealed an improvement in peak ankle eversion moment after training during preplanned cutting (P = .015), unanticipated cutting (P = .004), and the double-leg jump (P = .016) compared with the control group. Other secondary risk factors did not significantly improve after training, although the peak knee valgus angle improved in the control group compared with the intervention group during unanticipated cutting (P = .018).The F-MARC 11+ program may be effective in improving some risk factors for an ACL injury during a double-leg jump in preadolescent athletes, most notably by reducing peak knee valgus moment.This study provides motivation for enhancing injury prevention programs to produce improvement in other ACL risk factors, particularly during cutting and single-leg tasks.

    View details for DOI 10.1177/0363546516669326

    View details for Web of Science ID 000394776900004

  • Muscle Forces and Their Contributions to Vertical and Horizontal Acceleration of the Center of Mass During Sit-to-Stand Transfer in Young, Healthy Adults JOURNAL OF APPLIED BIOMECHANICS Caruthers, E. J., Thompson, J. A., Chaudhari, A. M., Schmitt, L. C., Best, T. M., Saul, K. R., Siston, R. A. 2016; 32 (5): 487-503


    Sit-to-stand transfer is a common task that is challenging for older adults and others with musculoskeletal impairments. Associated joint torques and muscle activations have been analyzed two-dimensionally, neglecting possible three-dimensional (3D) compensatory movements in those who struggle with sit-to-stand transfer. Furthermore, how muscles accelerate an individual up and off the chair remains unclear; such knowledge could inform rehabilitation strategies. We examined muscle forces, muscleinduced accelerations, and interlimb muscle force differences during sit-to-stand transfer in young, healthy adults. Dynamic simulations were created using a custom 3D musculoskeletal model; static optimization and induced acceleration analysis were used to determine muscle forces and their induced accelerations, respectively. The gluteus maximus generated the largest force (2009.07 ± 277.31 N) and was a main contributor to forward acceleration of the center of mass (COM) (0.62 ± 0.18 m/s(2)), while the quadriceps opposed it. The soleus was a main contributor to upward (2.56 ± 0.74 m/s(2)) and forward acceleration of the COM (0.62 ± 0.33 m/s(2)). Interlimb muscle force differences were observed, demonstrating lower limb symmetry cannot be assumed during this task, even in healthy adults. These findings establish a baseline from which deficits and compensatory strategies in relevant populations (eg, elderly, osteoarthritis) can be identified.

    View details for DOI 10.1123/jab.2015-0291

    View details for Web of Science ID 000384950800008

    View details for PubMedID 27341083

  • Gluteus maximus and soleus compensate for simulated quadriceps atrophy and activation failure during walking JOURNAL OF BIOMECHANICS Thompson, J. A., Chaudhari, A. W., Schmitt, L. C., Best, T. M., Siston, R. A. 2013; 46 (13): 2165–72


    Important activities of daily living, like walking and stair climbing, may be impaired by muscle weakness. In particular, quadriceps weakness is common in populations such as those with knee osteoarthritis (OA) and following ACL injury and may be a result of muscle atrophy or reduced voluntary muscle activation. While weak quadriceps have been strongly correlated with functional limitations in these populations, the important cause-effect relationships between abnormal lower extremity muscle function and patient function remain unknown. As a first step towards determining those relationships, the purpose of this study was to estimate changes in muscle forces and contributions to support and progression to maintain normal gait in response to two sources of quadriceps weakness: atrophy and activation failure. We used muscle-driven simulations to track normal gait kinematics in healthy subjects and applied simulated quadriceps weakness as atrophy and activation failure to evaluate compensation patterns associated with the individual sources of weakness. We found that the gluteus maximus and soleus muscles display the greatest ability to compensate for simulated quadriceps weakness. Also, by simulating two different causes of muscle weakness, this model suggested different compensation strategies by the lower extremity musculature in response to atrophy and activation deficits. Estimating the compensation strategies that are necessary to maintain normal gait will enable investigations of the role of muscle weakness in abnormal gait and inform potential rehabilitation strategies to improve such conditions.

    View details for DOI 10.1016/j.jbiomech.2013.06.033

    View details for Web of Science ID 000324969500009

    View details for PubMedID 23915576

  • Biomechanical Effects of Total Knee Arthroplasty Component Malrotation: A Computational Simulation JOURNAL OF ORTHOPAEDIC RESEARCH Thompson, J. A., Hast, M. W., Granger, J. F., Piazza, S. J., Siston, R. A. 2011; 29 (7): 969–75


    Modern total knee arthroplasty (TKA) is an effective procedure to treat pain and disability due to osteoarthritis, but some patients experience quadriceps weakness after surgery and have difficulty performing important activities of daily living. The success of TKA depends on many factors, but malalignment of the prosthetic components is a major cause of postoperative complications. Significant variability is associated with femoral and tibial component rotational alignment, but how this variability translates into functional outcome remains unknown. We used a forward-dynamic computer model of a simulated squatting motion to perform a parametric study of the effects of variations in component rotational alignment in TKA. A cruciate-retaining and posterior-stabilized version of the same TKA implant were compared. We found that femoral rotation had a greater effect on quadriceps forces, collateral ligament forces, and varus/valgus kinematics, while tibial rotation had a greater effect on anteroposterior translations. Our findings support the tendency for orthopedic surgeons to bias the femoral component into external rotation and avoid malrotation of the tibial component.

    View details for DOI 10.1002/jor.21344

    View details for Web of Science ID 000290632900001

    View details for PubMedID 21567450