Escalating numbers of adults have now embraced the notion that more exercise is invariably better. However, vigorous exercise, particularly when performed by inactive, unfit individuals can trigger acute cardiac events. Accelerated coronary artery calcification, exercise-induced cardiac biomarker release, atrial fibrillation and higher rates of cardiac events have also been reported in the most active population cohorts. Plus, concern over the safety of HIIT for clients with known or suspected congenital heart defects suggest that it should not be recommended, especially in unsupervised, non-medical settings. Learn about the practical implications of this data for health fitness professionals and the clients they serve.