• Dr. Gabriel is cross-trained in exercise physiology and epidemiology with over a decade of experience implementing physical fitness and physical activity measures in large, observational studies. Her research interests focus on two key areas of inquiry. First is the development and evaluation of methodological strategies to optimize the precision of physical fitness, physical activity and sedentary behavior measures for use in population-based studies. The second is to examine the timing of these exposure variables and risk of subsequent disease and disability using a life-course perspective with a strong focus on midlife women. She has served as principal investigator on projects funded by the American College of Sports Medicine (2007-08), American Institute for Cancer Research (2010-12), American Heart Association (2014-15), and National Heart, Lung and Blood Institute (2015-16) and National Institute on Aging (2015-16).

    She also actively collaborates on several large observational studies, providing consultation and support specific to: study design, strategies for physical activity and sedentary behavior assessment, computation/derivation of summary estimates, data reduction and processing of accelerometer data, statistical handling of physical activity and sedentary behavior data, statistical methods to examine associations of physical activity and sedentary behavior with health risk factors and outcomes and data interpretation and dissemination of findings. These collaborations include several large, federally funded prospective cohort studies including Coronary Artery Risk Development in Young Adults, the Study of Women’s Health Across the Nation and Atherosclerosis Risk in Communities. In addition, her scholarly work includes over 100 peer-reviewed publications and four book chapters.
  • Selected Publications

    Academic Article

    Year Title Altmetric
    2021 Physical Activity, Sleep, and Sedentary Behavior among Successful Long-Term Weight Loss Maintainers: Findings from a U.S. National Study.International Journal of Environmental Research and Public Health.  18. 2021
    2021 Dual trajectories of physical activity and blood lipids in midlife women: The Study of Women's Health Across the NationMaturitas.  146:49-56. 2021
    2021 Prospective Analysis of Leisure-Time Physical Activity in Midlife and Beyond and Brain Damage on MRI in Older AdultsNeurology.  96:e964-e974. 2021
    2021 A Pilot and Feasibility Mobile Health Intervention to Support Healthy Behaviors in African American Breast Cancer SurvivorsJournal of Racial and Ethnic Health Disparities.  8:157-165. 2021
    2021 Disentangling individual, school, and neighborhood effects on screen time among adolescents and young adults in the United StatesPreventive Medicine.  142. 2021
    2021 In-school, out-of-school, and weekend physical activity levels vary across sociodemographic subgroups of US adolescentsJournal of Physical Activity and Health.  18:418-425. 2021
    2021 Longitudinal associations of midlife accelerometer determined sedentary behavior and physical activity with cognitive function: The cardia study 2021
    2021 Physical activity-related metabolites are associated with mortality: Findings from the atherosclerosis risk in communities (aric) studyMetabolites.  11:1-13. 2021
    2020 Transit environments for physical activity: Relationship between micro-scale built environment features surrounding light rail stations and ridership in Houston, TexasJournal of Transport and Health.  19. 2020
    2020 Adiposity, cardiovascular, and health-related quality of life indicators and the reallocation of waking movement behaviors in preschool children with overweight and obesity: An isotemporal data analysisPLoS ONE.  15. 2020
    2020 Bikeability: Assessing the Objectively Measured Environment in Relation to Recreation and Transportation BicyclingEnvironment and Behavior.  52:861-894. 2020
    2020 Peripheral nerve impairment and recurrent falls among women: Results from the study of women’s health across the nation 2020
    2020 Sedentary behavior, physical inactivity, and metabolic syndrome: Pilot findings from the rapid assessment disuse index studyJournal of Physical Activity and Health.  17:1042-1046. 2020
    2020 Body mass index versus bioelectrical impedance analysis for classifying physical function impairment in a racially diverse cohort of midlife women: the Study of Women’s Health Across the Nation (SWAN)Aging Clinical and Experimental Research.  32:1739-1747. 2020
    2020 Screen Time for Children and Adolescents During the Coronavirus Disease 2019 Pandemic 2020
    2020 The role of military experience on officer-involved shootings: Towards a constructive research agenda 2020
    2020 The impact of breast cancer on physical activity from midlife to early older adulthood and predictors of change post-diagnosisJournal of Cancer Survivorship.  14:545-555. 2020
    2020 Association between Objective Activity Intensity and Heart Rate Variability: Cardiovascular Disease Risk Factor Mediation (CARDIA)Medicine and Science in Sports and Exercise.  52:1314-1321. 2020
    2020 Associations of accelerometer-measured physical activity and sedentary time with chronic kidney disease: The Framingham Heart StudyPLoS ONE.  15. 2020
    2020 Associations of physical activity and sleep with cardiometabolic risk in older womenPreventive Medicine Reports.  18. 2020
    2020 Life-course reproductive history and cardiovascular risk profile in late mid-life: The cardia study 2020
    2020 Bidirectional 10-year associations of accelerometer-measured sedentary behavior and activity categories with weight among middle-aged adultsInternational Journal of Obesity.  44:559-567. 2020
    2020 Sedentary Time and Physical Activity Across Occupational ClassificationsAmerican Journal of Health Promotion.  34:247-256. 2020
    2020 Individualized Relative-Intensity Physical Activity Accelerometer Cut PointsMedicine and Science in Sports and Exercise.  52:398-407. 2020
    2020 Differential use of strategic constructs of the transtheoretical model across accelerometer-determined sedentary timeAmerican Journal of Health Behavior.  44:18-25. 2020
    2020 Mid- And Late-Life Leisure-Time Physical Activity and Global Brain Amyloid Burden- And Atherosclerosis Risk in Communities (ARIC)-PET StudyJournal of Alzheimer's Disease.  76:139-147. 2020
    2020 The association of physical activity with carotid intima media thickening in a healthy older population: Cooper center longitudinal studyJournal of Aging and Physical Activity.  28:448-454. 2020
    2020 The association of self-reported muscle-strengthening activities with carotid intima-media thickness in older adults: Cooper center longitudinal studyJournal of Aging and Physical Activity.  28:534-539. 2020
    2019 Multi-ancestry study of blood lipid levels identifies four loci interacting with physical activityNature Communications.  10. 2019
    2019 Risk Estimates for Diabetes and Hypertension with Different Physical Activity MethodsMedicine and Science in Sports and Exercise.  51:2498-2505. 2019
    2019 Does military veteran status and deployment history impact officer involved shootings? A case-control study 2019
    2019 The feasibility of using real-time, objective measurements of physiological stress among law enforcement officers in Dallas, TexasPolicing: An International Journal of Police Strategies and Management.  42:701-710. 2019
    2019 Perceived and objective characteristics of the neighborhood environment are associated with accelerometer-measured sedentary time and physical activity, the CARDIA StudyPreventive Medicine.  123:242-249. 2019
    2019 Cost-effectiveness of improvements to the built environment intended to increase physical activityJournal of Physical Activity and Health.  16:308-317. 2019
    2019 A semiparametric model for wearable sensor-based physical activity monitoring data with informative device wear 2019
    2019 Physical activity trajectories and subsequent fall risk: ARIC StudyPreventive Medicine.  121:40-46. 2019
    2019 Prevalence and Likelihood of Meeting Sleep, Physical Activity, and Screen-Time Guidelines among US YouthJAMA Pediatrics.  173:387-389. 2019
    2019 The association of midlife cardiorespiratory fitness with later life carotid atherosclerosis: Cooper Center Longitudinal StudyAtherosclerosis.  282:137-142. 2019
    2019 iAmHealthy: Rationale, design and application of a family-based mHealth pediatric obesity intervention for rural childrenContemporary Clinical Trials.  78:20-26. 2019
    2019 Foot-based audit of streets adjacent to new light rail stations in Houston, Texas: Measurement of health-related characteristics of the built environment for physical activity researchBMC Public Health.  19. 2019
    2019 Leisure-time physical activity sustained since midlife and preservation of cognitive function: The Atherosclerosis Risk in Communities StudyAlzheimer's and Dementia.  15:273-281. 2019
    2019 Associations of accelerometer-measured sedentary time and physical activity with prospectively assessed cardiometabolic risk factors: The CARDIA study 2019
    2019 Factors associated with civilian and police officer injury during 10 years of officer-involved shooting incidentsInjury Prevention2019
    2019 Precancer diagnosis cardiorespiratory fitness, physical activity and cancer mortality in men 2019
    2018 Physical Activity and Physical Function: Moving and AgingObstetrics and Gynecology Clinics of North America.  45:723-736. 2018
    2018 Effect of media use on adolescent body weight 2018
    2018 Long-Term Weight Loss and Metabolic Health in Adults Concerned With Maintaining or Losing Weight: Findings From NHANESMayo Clinic Proceedings.  93:1611-1616. 2018
    2018 Perceived social and built environment correlates of transportation and recreation- Only bicycling among adults 2018
    2018 The utility and cross-validation of a composite physical activity score in relation to cardiovascular health indicators: Coronary artery risk development in young adultsJournal of Physical Activity and Health.  15:847-856. 2018
    2018 Utilization of Chiropractic Care in US Children and Adolescents: A Cross-Sectional Study of the 2012 National Health Interview SurveyJournal of Manipulative and Physiological Therapeutics.  41:725-733. 2018
    2018 Ten-Year Changes in Accelerometer-Based Physical Activity and Sedentary Time during MidlifeAmerican Journal of Epidemiology.  187:2145-2150. 2018
    2018 Comparison of Two Generations of ActiGraph Accelerometers: The CARDIA StudyMedicine and Science in Sports and Exercise.  50:1333-1340. 2018
    2018 The Association Among Overweight, Obesity, and Low Back Pain in U.S. Adults: A Cross-Sectional Study of the 2015 National Health Interview SurveyJournal of Manipulative and Physiological Therapeutics.  41:294-303. 2018
    2018 Relationship between Homocysteine and Muscle Strength Decline: The Baltimore Longitudinal Study of Aging 2018
    2018 Transit use and physical activity: Findings from the Houston travel-related activity in neighborhoods (TRAIN) studyPreventive Medicine Reports.  9:55-61. 2018
    2018 Clinical importance of non-participation in a maximal graded exercise test on risk of non-fatal and fatal cardiovascular events and all-cause mortality: CARDIA studyPreventive Medicine.  106:137-144. 2018
    2017 Physical activity trajectories during midlife and subsequent risk of physical functioning decline in late mid-life: The Study of Women's Health Across the Nation (SWAN)Preventive Medicine.  105:287-294. 2017
    2017 Sedentary Time, Physical Activity, and Adiposity: Cross-sectional and Longitudinal Associations in CARDIAAmerican Journal of Preventive Medicine.  53:764-771. 2017
    2017 Vitamin B12 and homocysteine associations with gait speed in older adults: The Baltimore Longitudinal Study of AgingJournal of Nutrition, Health and Aging.  21:1321-1328. 2017
    2017 25-Year Physical Activity Trajectories and Development of Subclinical Coronary Artery Disease as Measured by Coronary Artery Calcium: The Coronary Artery Risk Development in Young Adults (CARDIA) StudyMayo Clinic Proceedings.  92:1660-1670. 2017
    2017 Income, physical activity, sedentary behavior, and the ‘weekend warrior’ among U.S. adultsPreventive Medicine.  103:91-97. 2017
    2017 The Importance of Mid-to-Late-Life Body Mass Index Trajectories on Late-Life Gait Speed 2017
    2017 Sedentary behavior patterns in non-pregnant and pregnant womenPreventive Medicine Reports.  6:97-103. 2017
    2017 Association of cardiorespiratory fitness and adiposity with inflammatory biomarkers in young adultsAmerican Journal of Human Biology.  29. 2017
    2017 Relationship Between Midlife Cardiovascular Health and Late-Life Physical Performance: The ARIC StudyJournal of the American Geriatrics Society.  65:1012-1018. 2017
    2017 Application of the transtheoretical model to sedentary behaviors and its association with physical activity statusPLoS ONE.  12. 2017
    2017 Bidirectional associations of accelerometer-determined sedentary behavior and physical activity with reported time in bed: Women's Health StudySleep Health.  3:49-55. 2017
    2017 Evaluation of a shelter-based diet and physical activity intervention for homeless adultsJournal of Physical Activity and Health.  14:88-97. 2017
    2017 U.S. military service and the prevalence of metabolic syndrome: Findings from a cross-sectional analysis of the Cooper Center Longitudinal Study, 1979–2013Preventive Medicine.  95:52-58. 2017
    2017 Completion of multidisciplinary treatment for persistent postconcussive symptoms is associated with reduced symptom burdenJournal of Head Trauma Rehabilitation.  32:1-15. 2017
    2017 Ecological momentary assessment of physical activity: Validation studyJournal of Medical Internet Research.  19. 2017
    2016 Strategic Priorities for Physical Activity Surveillance in the United StatesMedicine and Science in Sports and Exercise.  48:2057-2069. 2016
    2016 The association of trip distance with walking to reach public transit: Data from the California Household Travel SurveyJournal of Transport and Health.  3:154-160. 2016
    2016 Association between sitting time and cardiometabolic risk factors after adjustment for cardiorespiratory fitness, cooper center longitudinal study, 2010-2013 2016
    2016 Impact of a mobile phone intervention to reduce sedentary behavior in a community sample of adults: A quasi-experimental evaluationJournal of Medical Internet Research.  18. 2016
    2016 Promoting healthy lifestyles during the menopausal transition 2016
    2016 Sitting time, physical activity, and cardiorespiratory fitness: Cooper center longitudinal study cohortJournal of Physical Activity and Health.  13:17-23. 2016
    2016 Transit use by children and adolescents: An overlooked source of and opportunity for physical activity?Journal of Physical Activity and Health.  13:861-866. 2016
    2015 Cross-sectional and longitudinal associations between objectively measured sedentary time and metabolic Disease: The coronary artery risk development in young adults (CARDIA) StudyDiabetes Care.  38:1835-1843. 2015
    2015 Grasping the 'teachable moment': Time since diagnosis, symptom burden and health behaviors in breast, colorectal and prostate cancer survivors 2015
    2015 Accelerometer determined sedentary behavior and dietary quality among US adultsPreventive Medicine.  78:38-43. 2015
    2015 Measuring the bias, precision, accuracy, and validity of self-reported height and weight in assessing overweight and obesity status among adolescents using a surveillance systemInternational Journal of Behavioral Nutrition and Physical Activity.  12. 2015
    2015 Youth and young adult physical activity and body composition of young adult women: Findings from the dietary intervention study in childrenPediatric Exercise Science.  27:140-150. 2015
    2015 Bone mineral density across a range of physical activity volumes: NHANES 2007-2010Medicine and Science in Sports and Exercise.  47:326-334. 2015
    2015 Do short spurts of physical activity benefit cardiovascular health? The CARDIA studyMedicine and Science in Sports and Exercise.  47:2353-2358. 2015
    2015 Independent and joint effects of sedentary time and cardiorespiratory fitness on all-cause mortality: The Cooper Center Longitudinal StudyBMJ Open.  5. 2015
    2015 Standing, obesity, and metabolic syndrome findings from the cooper center longitudinal studyMayo Clinic Proceedings.  90:1524-1532. 2015
    2015 Taking the next step: a systematic review and meta-analysis of physical activity and behavior change interventions in recent post-treatment breast cancer survivorsBreast Cancer Research and Treatment.  149:331-342. 2015
    2014 Application of the American Heart Association/American College of Sports Medicine adult preparticipation screening checklist to a nationally representative sample of US adults aged ≥40 years from the National Health and Nutrition Examination Survey 2001 to 2004Circulation.  129:1113-1120. 2014
    2014 Sedentary behaviour and physical inactivity assessment in primary care: The rapid assessment disuse index (RADI) studyBritish Journal of Sports Medicine.  48:250-255. 2014
    2014 Convergent validity of a brief self-reported physical activity questionnaireMedicine and Science in Sports and Exercise.  46:1570-1577. 2014
    2014 Sedentary and active: Self-reported sitting time among marathon and half-marathon participantsJournal of Physical Activity and Health.  11:165-172. 2014
    2014 Sedentary behavior, cardiorespiratory fitness, physical activity, and cardiometabolic risk in men: The cooper center longitudinal studyMayo Clinic Proceedings.  89:1052-1062. 2014
    2014 Sleep and executive function in older women: The moderating effect of physical activity 2014
    2014 The association between physical fitness and academic achievement in Texas state house legislative districts: An ecologic studyJournal of School Health.  84:533-542. 2014
    2014 The impact of change in physical activity on change in arterial stiffness in overweight or obese sedentary young adults 2014
    2014 Utility of actiwatch sleep monitor to assess waking movement behavior in older womenMedicine and Science in Sports and Exercise.  46:2301-2307. 2014
    2014 Utility of computer-assisted approaches for population surveillance of physical activityJournal of Physical Activity and Health.  11:1111-1119. 2014
    2013 Temporal relationships between physical activity and sleep in older womenMedicine and Science in Sports and Exercise.  45:2362-2368. 2013
    2013 Assessing sitting across contexts: Development of the multicontext sitting time questionnaireResearch Quarterly for Exercise and Sport.  84:323-328. 2013
    2013 Adolescent and young adult exposure to physical activity and breast densityMedicine and Science in Sports and Exercise.  45:1515-1523. 2013
    2013 Associations between accelerometer-derived physical activity and regional adiposity in young men and women 2013
    2013 TV Viewing and BMI by Race/Ethnicity and Socio-Economic StatusPLoS ONE.  8. 2013
    2013 Depressive symptoms and serum lipid levels in young adult womenJournal of Behavioral Medicine.  36:143-152. 2013
    2013 Physical activity intensity and cardiovascular risk by ankle-brachial index 2013
    2013 Sensation-seeking genes and physical activity in youthGenes, Brain and Behavior.  12:181-188. 2013
    2013 Self-reported and accelerometer-derived physical activity levels and coronary artery calcification progression in older women: Results from the Healthy Women Study 2013
    2013 Family history of chronic disease and meeting public health guidelines for physical activity: The cooper center longitudinal studyMayo Clinic Proceedings.  88:588-592. 2013
    2012 Cardiorespiratory fitness, alcohol intake, and metabolic syndrome incidence in menMedicine and Science in Sports and Exercise.  44:2125-2131. 2012
    2012 Experimenting with cigarettes and physical activity among Mexican origin youth: A cross sectional analysis of the interdependent associations among sensation seeking, acculturation, and genderBMC Public Health.  12. 2012
    2012 Height, adiposity and body fat distribution and breast density in young womenBreast Cancer Research.  14. 2012
    2012 Association of leisure physical activity and sleep with cardiovascular risk factors in postmenopausal women 2012
    2012 The Women on the Move through Activity and Nutrition (WOMAN) study: Final 48-month results 2012
    2012 Cardiorespiratory fitness, alcohol, and mortality in men: The Cooper Center Longitudinal StudyAmerican Journal of Preventive Medicine.  42:460-467. 2012
    2012 Framework for physical activity as a complex and multidimensional behavior.Journal of Physical Activity and Health.  9 Suppl 1. 2012
    2012 Patterns of accelerometer-derived estimates of inactivity in middle-age womenMedicine and Science in Sports and Exercise.  44:104-110. 2012
    2012 Reported physical activity and sedentary behavior: why do you ask?Journal of Physical Activity and Health.  9 Suppl 1. 2012
    2012 Short- and Long-Term Eating Habit Modification Predicts Weight Change in Overweight, Postmenopausal Women: Results from the WOMAN StudyJournal of the Academy of Nutrition and Dietetics.  112. 2012
    2011 Adolescent diet and metabolic syndrome in young women: Results of the Dietary Intervention Study in Children (DISC) follow-up studyJournal of Clinical Endocrinology and Metabolism.  96. 2011
    2011 The Relationship Between Media Use and Psychological and Physical Assets Among Third- to Fifth-Grade GirlsJournal of School Health.  81:749-755. 2011
    2011 Physical activity self-monitoring and weight loss: 6-month results of the SMART trialMedicine and Science in Sports and Exercise.  43:1568-1574. 2011
    2011 The impact of weight and fat mass loss and increased physical activity on physical function in overweight, postmenopausal women: Results from the Women on the Move Through Activity and Nutrition study 2011
    2011 Reliability and convergent validity of the past-week Modifiable Activity QuestionnairePublic Health Nutrition.  14:435-442. 2011
    2011 Comprehensive evaluation of a single-stage submaximal treadmill walking protocol in healthy, middle-aged womenEuropean Journal of Applied Physiology.  111:47-56. 2011
    2011 Girls on the Run: a quasi-experimental evaluation of a developmentally focused youth sport program.Journal of Physical Activity and Health.  8 Suppl 2. 2011
    2010 Physical activity and coronary artery calcification in two cohorts of women representing early and late postmenopause 2010
    2010 Issues in accelerometer methodology: The role of epoch length on estimates of physical activity and relationships with health outcomes in overweight, post-menopausal womenInternational Journal of Behavioral Nutrition and Physical Activity.  7. 2010
    2010 Adolescent diet and subsequent serum hormones, breast density, and bone mineral density in young women: Results of the dietary intervention study in children follow-up studyCancer Epidemiology, Biomarkers and Prevention.  19:1545-1556. 2010
    2010 Association between self-reported resistance training and self-rated health in a national sample of U.S. men and womenJournal of Physical Activity and Health.  7:289-298. 2010
    2010 Test-retest reliability and validity of the 400-meter walk test in healthy, middle-aged womenJournal of Physical Activity and Health.  7:649-657. 2010
    2009 Psychometric properties of the Commitment to Physical Activity ScaleAmerican Journal of Health Behavior.  33:425-434. 2009
    2009 Physical fitness and carotid atherosclerosis in menInternational Journal of Sports Medicine.  30:672-676. 2009
    2009 Changes in Psychosocial Factors and Physical Activity Frequency among Third- to Eighth-Grade Girls Who Participated in a Developmentally Focused Youth Sport Program: A Preliminary StudyJournal of School Health.  79:474-484. 2009
    2009 Evaluation of physical activity measures used in middle-aged womenMedicine and Science in Sports and Exercise.  41:1403-1412. 2009
    2009 The reliability of a survey question on television viewing and associations with health risk factors in US adults 2009
    2009 Monthly variation in physical activity levels in postmenopausal womenMedicine and Science in Sports and Exercise.  41:322-327. 2009
    2008 Weight regain and health-related quality of life in postmenopausal women 2008
    2008 A Lifestyle Approach for Primary Cardiovascular Disease Prevention in Perimenopausal to Early Postmenopausal WomenAmerican Journal of Lifestyle Medicine.  2:421-431. 2008
    2008 Gait speed and step-count monitor accuracy in community-dwelling older adultsMedicine and Science in Sports and Exercise.  40:59-64. 2008
    2007 Lapses and psychosocial factors related to physical activity in early postmenopauseMedicine and Science in Sports and Exercise.  39:1858-1866. 2007
    2007 Discontinuing Hormone Replacement Therapy. Attenuating the Effect on CVD Risk With Lifestyle ChangesAmerican Journal of Preventive Medicine.  32:483-489. 2007
    2007 Associations among walking performance, physical activity, and subclinical cardiovascular disease.Preventive Cardiology.  10:134-140. 2007
    2007 The relationship between physical activity and lipoprotein subclasses in postmenopausal women: The influence of hormone therapy 2007
    2006 Erratum: Lifestyle intervention and coronary heart disease risk factor changes over 18 months in postmenopausal women: The Women on the Move through Activity and Nutrition (WOMAN Study) clinical trial (Journal of Women's Health 15, 8 (962-974))Journal of Women's Health.  15:1101-1102. 2006
    2006 Lifestyle intervention and coronary heart disease risk factor changes over 18 months in postmenopausal women: The women on the move through activity and nutrition (WOMAN study) clinical trialJournal of Women's Health.  15:962-974. 2006
    2006 Influence of marital status on physical activity levels among older adultsMedicine and Science in Sports and Exercise.  38:541-546. 2006
    2005 Fishes, whales, and fishing tips: Hooking an active lifestyleDiabetes Spectrum.  18:114-118. 2005
    2004 Lifestyle intervention for the prevention of type 2 diabetes: Translation and future recommendationsCurrent Diabetes Reports.  4:113-118. 2004
    2001 Brief Muscle Hypoperfusion/Hyperemia: An Ergogenic Aid?Journal of Strength and Conditioning Research.  15:362-366. 2001
    Associations between longitudinal trajectories of insomnia symptoms and sleep duration with objective physical function in postmenopausal women: the Study of Women’s Health Across the NationSLEEP


    Year Title Altmetric
    2009 Measurement of Physical Activity and Inactivity in Epidemiologic Studies 2009

    Research Overview

  • physical activity, sedentary behavior, chronic disease epidemiology
  • Teaching Activities

    Education And Training

  • Doctor of Philosophy in Epidemiology, University of Pittsburgh 2006
  • Master of Science in Exercise Physiology, Northeastern University 1999
  • Bachelor of Science or Mathematics in Athletic Training and Sports Medicine, Ithaca College 1996
  • Full Name

  • Kelley Gabriel