Table 2.

Summary of exercise training-mediated skeletal muscle adaptations that contribute to improved exercise tolerance in patients with heart failure with reduced or preserved ejection fraction.

Variable	HFrEF	HFpEF
Morphology
Lean body mass	↔ [48, 89–92]	↔ [58••]
% type I fibers	↑ [29, 40, 48] ↔ [42, 44]	Not studied.
% type II fibers	↓ [29, 40] ↔ [42, 44]	Not studied.
Capillary density	↑ [29, 39, 42]	Not studied.
Mitochondrial volume density	↑ [29, 40, 41]	Not studied.
Mitochondrial enzyme density	↑ [29, 40–44, 48]	Not studied.
Function
Peak exercise a-vO2diff	↑ [29, 41, 93, 94] ↔ [57]	↑ [57, 61••]
Sub-maximal exercise oxidative metabolism	↑ [91, 95–97]	Not studied.

↑ = increase; ↓ decrease; ↔ stays the same; a-vO₂diff = arterial-venous oxygen content difference; HFpEF = heart failure with preserved ejection fraction; HFrEF = heart failure with reduced ejection fraction.