| Autor: |
Weavil JC; Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Thurston TS; Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah., Hureau TJ; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Gifford JR; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Kithas PA; Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Broxterman RM; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Bledsoe AD; Department of Anesthesiology, University of Utah, Salt Lake City, Utah., Nativi JN; Department of Internal Medicine, University of Utah, Salt Lake City, Utah., Richardson RS; Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.; Department of Internal Medicine, University of Utah, Salt Lake City, Utah.; Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah., Amann M; Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Salt Lake City, Utah.; Department of Internal Medicine, University of Utah, Salt Lake City, Utah.; Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, Utah.; Department of Anesthesiology, University of Utah, Salt Lake City, Utah. |
| Abstrakt: |
This study investigated the impact of HFpEF on neuromuscular fatigue and peripheral hemodynamics during small muscle mass exercise not limited by cardiac output. Eight HFpEF patients (NYHA II-III, ejection-fraction: 61 ± 2%) and eight healthy controls performed dynamic knee extension exercise (80% peak workload) to task failure and maximal intermittent quadriceps contractions (8 × 15 s). Controls repeated knee extension at the same absolute intensity as HFpEF. Leg blood flow (Q L ) was quantified using Doppler ultrasound. Pre/postexercise changes in quadriceps twitch torque (ΔQ tw ; peripheral fatigue), voluntary activation (ΔVA; central fatigue), and corticospinal excitability were quantified. At the same relative intensity, HFpEF (24 ± 5 W) and controls (42 ± 6 W) had a similar time-to-task failure (∼10 min), ΔQ tw (∼50%), and ΔVA (∼6%). This resulted in a greater exercise-induced change in neuromuscular function per unit work in HFpEF, which was significantly correlated with a slower Q L response time. Knee extension exercise at the same absolute intensity resulted in an ∼40% lower Q L and greater ΔQ tw and ΔVA in HFpEF than in controls. Corticospinal excitability remained unaltered during exercise in both groups. Finally, despite a similar ΔVA, ΔQ tw was larger in HFpEF versus controls during isometric exercise. In conclusion, HFpEF patients are characterized by a similar development of central and peripheral fatigue as healthy controls when tested at the same relative intensity during exercise not limited by cardiac output. However, HFpEF patients have a greater susceptibility to neuromuscular fatigue during exercise at a given absolute intensity, and this impairs functional capacity. The patients' compromised Q L response to exercise likely accounts, at least partly, for the patients' attenuated fatigue resistance. NEW & NOTEWORTHY The susceptibility to neuromuscular fatigue during exercise is substantially exaggerated in individuals with heart failure with a preserved ejection fraction. The faster rate of fatigue development is associated with the compromised peripheral hemodynamic response characterizing these patients during exercise. Given the role of neuromuscular fatigue as a factor limiting exercise, this impairment likely accounts for a significant portion of the exercise intolerance typical for this population. |
