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

The objective of this study was to investigate left ventricular (LV) circumferential strain responses to incremental cycling and isometric knee extension exercises.

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.

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).

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.