TY - JOUR

T1 - Left ventricular mechanical limitations to stroke volume in healthy humans during incremental exercise

AU - Stöhr, Eric J.

AU - González-Alonso, José

AU - Shave, Rob

PY - 2011/8/1

Y1 - 2011/8/1

N2 - During incremental exercise, stroke volume (SV) plateaus at 40-50% of maximal exercise capacity. In healthy individuals, left ventricular (LV) twist and untwisting ("LV twist mechanics") contribute to the generation of SV at rest, but whether the plateau in SV during incremental exercise is related to a blunting in LV twist mechanics remains unknown. To test this hypothesis, nine healthy young males performed continuous and discontinuous incremental supine cycling exercise up to 90% peak power in a randomized order. During both exercise protocols, end-diastolic volume (EDV), end-systolic volume (ESV), and SV reached a plateau at submaximal exercise intensities while heart rate increased continuously. Similar to LV volumes, two-dimensional speckle tracking-derived LV twist and untwisting velocity increased gradually from rest (all P ≤ 0.001) and then leveled off at submaximal intensities. During continuous exercise, LV twist mechanics were linearly related to ESV, SV, heart rate, and cardiac output (all P ≤ 0.01) while the relationship with EDV was exponential. In diastole, the increase in apical untwisting was significantly larger than that of basal untwisting (P ≤ 0.01), emphasizing the importance of dynamic apical function. In conclusion, during incremental exercise, the plateau in LV twist mechanics and their close relationship with SV and cardiac output indicate a mechanical limitation in maximizing LV output during high exercise intensities. However, LV twist mechanics do not appear to be the sole factor limiting LV output, since EDV reaches its maximum before the plateau in LV twist mechanics, suggesting additional limitations in diastolic filling to the heart.

AB - During incremental exercise, stroke volume (SV) plateaus at 40-50% of maximal exercise capacity. In healthy individuals, left ventricular (LV) twist and untwisting ("LV twist mechanics") contribute to the generation of SV at rest, but whether the plateau in SV during incremental exercise is related to a blunting in LV twist mechanics remains unknown. To test this hypothesis, nine healthy young males performed continuous and discontinuous incremental supine cycling exercise up to 90% peak power in a randomized order. During both exercise protocols, end-diastolic volume (EDV), end-systolic volume (ESV), and SV reached a plateau at submaximal exercise intensities while heart rate increased continuously. Similar to LV volumes, two-dimensional speckle tracking-derived LV twist and untwisting velocity increased gradually from rest (all P ≤ 0.001) and then leveled off at submaximal intensities. During continuous exercise, LV twist mechanics were linearly related to ESV, SV, heart rate, and cardiac output (all P ≤ 0.01) while the relationship with EDV was exponential. In diastole, the increase in apical untwisting was significantly larger than that of basal untwisting (P ≤ 0.01), emphasizing the importance of dynamic apical function. In conclusion, during incremental exercise, the plateau in LV twist mechanics and their close relationship with SV and cardiac output indicate a mechanical limitation in maximizing LV output during high exercise intensities. However, LV twist mechanics do not appear to be the sole factor limiting LV output, since EDV reaches its maximum before the plateau in LV twist mechanics, suggesting additional limitations in diastolic filling to the heart.

KW - Diastole

KW - Torsion

KW - Twist

KW - Untwisting

UR - http://www.scopus.com/inward/record.url?scp=79961041006&partnerID=8YFLogxK

U2 - 10.1152/ajpheart.00314.2011

DO - 10.1152/ajpheart.00314.2011

M3 - Article

C2 - 21572016

AN - SCOPUS:79961041006

VL - 301

SP - H478-H487

JO - American Journal of Physiology - Heart and Circulatory Physiology

JF - American Journal of Physiology - Heart and Circulatory Physiology

SN - 0363-6135

IS - 2

ER -