Global and regional left ventricular circumferential strain during incremental cycling and isometric knee extension exercise

Background: The objective of this study was to investigate left ventricular (LV) circumferential strain responses to incremental cycling and isometric knee extension exercises. Methods: Twenty-six healthy male participants (age = 30 ± 6 years) were used to study LV global (GCS) and regional circumferential strain at the apex (ACS) and base (BCS) during incremental cycling at 30% and 60% work rate maximum (W_max) and short-duration (15 seconds contractions) isometric knee extensions at 40% and 75% maximum voluntary contraction (MVC) using two-dimensional speckle tracking echocardiography. Results: During cycling (n = 22), GCS increased progressively from rest to 60% W_max (−22.85 ± 3.26% to −29.87 ± 2.59%, P <.01). ACS increased from rest to 30% W_max (−26.29 ± 4.84% to −36.84 ± 6.94%, P <.01) and then remained unchanged to 60% W_max (−40.72 ± 4.06%, P =.068). BCS decreased from rest to 30% W_max (−19.41 ± 2.79 to −17.51 ± 4.66%, P =.05) and then remained unchanged to 60% W_max. During isometric knee extension (n = 23), GCS decreased from rest to 40% MVC (−22.63 ± 3.46 to −20.10 ± 2.78%, P <.05) and then remained unchanged to 75% MVC. Similarly, BCS decreased from rest to 40% MVC (−19.21 ± 2.58% to −13.55 ± 3.45%, P <.01) and then remained unchanged, whereas ACS did not change with exercise intensity (rest, −26.05 ± 5.34%; 40% MVC, −26.64 ± 4.53% and 75% MVC −27.22 ± 5.34%, all P >.05). Conclusion: Global circumferential strain increased stepwise during incremental cycling, mediated by the apex with trivial changes at the base. In contrast, GCS decreased during the isometric knee extension to 40% MVC and then plateaued, due to decreased BCS as ACS was maintained. A novel finding is that the GCS response appears to be exercise modality dependant and is the consequence of region-specific changes.