1. ABSTRACT CONCLUSIONS BACKGROUND Heart Rate Recovery: An Indicator of Fitness Among Middle School Children Daniel Simhaee, Roopa Gurm, Susan Aaronson, Jean DuRussel-Weston, Catherine Fitzgerald, Shannon Flynn, Zachary Geiger, Nicole Corriveau, Julia Winfield, Caren Goldberg, Kim A. Eagle, Elizabeth A. Jackson, University of Michigan, Ann Arbor, MI RESULTS METHODS Background: Heart Rate Recovery (HRR) has been used in adults to evaluate cardiovascular fitness and is a strong predictor of morbidity and mortality. We sought to determine if HRR is associated with body mass index (BMI), blood pressure, lipid levels, and lifestyle behaviors such as physical activity among middle school children. Methods: Data from 1276 participants in Project Healthy Schools, a school-based intervention program in southeast Michigan, were collected. In addition to demographic characteristics, data on physiologic factors were collected including lipid and glucose levels, BMI, blood pressure, and heart rate. Standardized questionnaires were used to collect information on behaviors including diet, physical activity and sedentary behaviors. HRR was determined by measurement of heart rate after a 3 minute step test. Using quartiles of HRR as a marker of fitness, associations with demographic, physiologic and behavioral factors were explored using Chi-squared and t-tests. Results: Compared to children in the lowest quartile of HRR (i.e. most fit), those in the upper quartile of HRR (i.e. less fit) had higher mean LDL cholesterol (93.0 mg/dL vs. 86.7 mg/dL; P=0.02), lower mean HDL cholesterol (50.9 mg/dL vs. 55.9 mg/dL; P<0.001), and higher mean triglycerides (132.4 mg/dL vs. 111.74 mg/dL; P=0.004). Children in the upper 95% of BMI had higher mean HRR compared to those in the normal BMI range (5 to 85%) (116.6 kg/m2 vs. 100.3 kg/m2). Children in the upper quartile of HRR reported fewer days of strenuous to moderate exercise per week compared to children in the lowest quartile of HRR (4.8 vs. 4.1; P<0.001 for moderate exercise, and 3.6 vs. 3.0; P=0.001, for strenuous exercise). Conclusions: We observed that longer HRR times were associated with a less favorable lipid profile and higher BMI, suggesting HRR can identify middle school children at risk for obesity and increased cardiovascular risk. Longer HRR was also associated with decreased physical activity suggesting HRR may be a clinical useful tool to measure fitness in children. Disclosures: None Heart Rate Recovery (HRR) has been used in adults to evaluate cardiovascular fitness and is a strong predictor of morbidity and mortality. We sought to determine if HRR is associated with body mass index (BMI), blood pressure, lipid levels, and lifestyle behaviors such as physical activity among middle school children. Age (years)11.55±.41 Male (Percent)47.9 Female (Percent)52.1 Resting Heart Rate (bpm)80.79±11.15 Heart Rate Recovery (bpm)103.70±17.44 Table 1: Baseline Characteristics Data from 1276 participants in Project Healthy Schools, a school-based intervention program in southeast Michigan, were collected. In addition to demographic characteristics, data on physiologic factors were collected including lipid and glucose levels, BMI, blood pressure, and heart rate. Standardized questionnaires were used to collect information on behaviors including diet, physical activity and sedentary behaviors. HRR was determined by measurement of heart rate after a 3 minute step test. Using quartiles of HRR as a marker of fitness, associations with demographic, physiologic and behavioral factors were explored using Chi-squared and t-tests. We observed that higher HRR levels were associated with a less favorable lipid profile and higher BMI. This suggests that HRR can identify middle school children at risk for obesity and increased cardiovascular risk. Longer HRR was also associated with decreased physical activity suggesting HRR may be a clinical useful tool to measure fitness in children. Figure 1: Higher HRR Correlated with Various Physiological Measures HDL* Triglycerides* Cholesterol** LDL** Figure 3: Children Who are More Physically Active have Lower HRR Mean HRR* *p<.001 Strenuous activity: physical activity for >20 minutes that makes heart beat fast Figure 4: Higher HRR in Students from Lower Socioeconomic Status Schools Mean HRR *p<.001 Schools classified as low SES include: Scarlett, E. Ypsilanti, W. Ypsilanti Schools classified as high SES include: Clague, Forsythe, Slauson, Tappan The socioeconomic class was based on the number of students on free lunches Program among the seven schools. Figure 2: Positive Association Between HRR Levels and BMI Mean HRR* *p<.001. Center for Disease Control and Prevention. BMI Percentile Calculator for Child and Teen. http://www.cdc.gov *p<.001 **p=.02 1Q 2Q 3Q 4Q