Table 1.

Key variables used in studies of physical activity and endocrine/metabolic effects

OUTCOME VARIABLES
Insulin Resistance (8-10)
HOMA-IR (10)	Computer model of insulin secretion and glucose metabolism, using serum fasting glucose and insulin to predict beta cell function.
Glucose Tolerance Test(8)	Measurement of serial serum glucose levels following oral or intravenous glucose load; often includes calculation of area under the curve (AUC) as measure of insulin resistance.
Metabolic Syndrome
Continuous Metabolic Risk Score (cMetS)(11)	Standardized, continuous score derived from sum of z-scores of metabolic syndrome risk factors, including fasting cholesterol (LDL, HDL, total cholesterol), triglycerides, waist circumference, glucose, and systolic blood pressure. Variations of this score used by several studies. (12-15)
Others	Carotid artery intima-media thickness, body composition quantified using DXA, percent body fat (using bioelectrical impedance analysis), triceps skin-fold test, indirect calorimetry, brachial-ankle pulse wave velocity, BDNF, leptin, adiponectin and markers of inflammation (CRP, cytokines).
PREDICTOR VARIABLES
Physical Activity	Measured via accelerometer or pedometer, with associated classifications as light, moderate, and vigorous physical activity based on movement counts over defined time interval. Thresholds vary by study.
Physical Fitness	VO2 Max (16, 17) Heart rate recovery (18) 20 meter Shuttle Run (12, 19, 20) 4 × 10 meter Shuttle Run (12, 21) Speed-agility test (20)
Muscular Fitness	Isometric Handgrip (12, 15, 22) Standing Long Jump (12, 15, 22)