Left ventricular mechanics in humans with high aerobic fitness: adaptation independent of structural remodelling, arterial haemodynamics and heart rate

Individuals with high aerobic fitness have lower systolic left ventricular strain, rotation and twist ('left ventricular (LV) mechanics') at rest, suggesting a beneficial reduction in LV myofibre stress and more efficient systolic function. However, the mechanisms responsible for this functional adaptation are not known and the influence of aerobic fitness on LV mechanics during dynamic exercise has never been studied. We assessed LV mechanics, LV wall thickness and dimensions, central augmentation index (AIx), aortic pulse wave velocity (aPWV), blood pressure and heart rate in 28 males (age: 21 ±2 years SD) with a consistent physical activity level (nochange >6months).Individualswereexaminedatrestandduringexercise(40%peakexercise capacity) and separated post hoc into a moderate and high aerobic fitness group ( u VO2peak :4 9±5 and 63 ±7mlkg −1 min −1 , respectively, P 0.05).However, for the same AIx, the high u VO2peak group had significantly lower LV apical rotation (P =0.002) and LV twist (P =0.003) while basal rotation and strain indices did not differ between groups (P >0.05).WeconcludethatyoungmaleswithhighaerobicfitnesshavelowerLVapicalrotationat restandduringsubmaximalexercisethatcanoccurwithoutchangesingrossLVstructure,arterial haemodynamics or heart rate. The findings suggest a previously unknown type of physiological adaptationoftheleftventriclethatmayhaveimportantimplicationsforexercisetraininginolder individuals and patient populations in which exercise training has previously failed to show clear benefits for LV function.