Effect of Exercise Training on Pulmonary Oxygen Uptake Kinetics in Heart Transplant Recipients

Pulmonary oxygen uptake ( V ˙ O 2 p ) at exercise onset is severely delayed in heart transplant recipients (HTRs). The role of exercise training to improve V ˙ O 2 p kinetics in HTRs has not been studied. We examined V ˙ O 2 p kinetics before and after 12 weeks of aerobic and strength training (HTR-T; n = 19, mean ± SD age: 57 ± 10 years) or usual care (HTR-UC; n = 16, mean age: 58 ± 12 years). Phase II V ˙ O 2 p kinetics, reflecting the rate of muscle metabolic adaptation, improved 37% after training compared with usual care (HTR-UC, 15 ± 19 vs 2 ± 13 seconds improvement, p = 0.02). The change in rest to steady-state heart rate reserve before and after 12 weeks was not different in HTR-T (−2 ± 9 beats/min) and HTR-UC (−1 ± 7 beats/min; p = 0.78). No significant relation was found between the change in V ˙ O 2 p kinetics and rest to steady-state heart rate reserve. Changes in leg lean tissue mass and V ˙ O 2 p kinetics were significantly related (r = −0.46, p = 0.008). In conclusion, a favorable adaptation in skeletal muscle oxidative function may underpin our finding of faster V ˙ O 2 p kinetics in HTRs after exercise training.