||BACKGROUND: Left ventricular (LV) systolic long-axis shortening can be measured as Mitral Annular Plane Systolic Excursion (MAPSE). Global longitudinal strain (GLS) is relative LV shortening, equivalent to normalizing MAPSE for LV length (MAPSEn). The objective of this study was to test whether normalizing LV shortening reduced biological variability of MAPSE due to normalizing for heart size and, possibly BSA. Secondly to provide normal reference values for MAPSE. METHODS AND RESULTS: A total of 1266 subjects from the Nord-Trondelag Health Study (HUNT), without evidence of heart disease were examined. MAPSE and wall lengths were measured in all three standard apical views, while GLS has been published previously. Mean MAPSE was 1.58 (0.25) cm, MAPSEn 16.3 (2.4)%, and GLS 16.7 (2.4)%. All measures declined with age, correlations between -0.50 and -0.41. MAPSE was gender independent, and less BSA dependent than MAPSEn and GLS, while relative standard deviations (SDs) were similar for all three measures. CONCLUSIONS: MAPSE, MAPSEn, and GLS have similar biological variability, which is mainly due to age variation, indicating they are equivalent in normal, and normalizing for BSA will not reduce the variability. Normalizing MAPSE for LV length (MAPSEn and GLS) normalizes for one dimension only, inducing a systematic error, which increases BSA and gender dependence. Normal age-related, gender-independent values for MAPSE are provided.