Background: After lung transplantation (LTx) exercise capacity frequently remains limited, despite significantly improved pulmonary function. The aim of this study was to evaluate maximal exercise capacity and peripheral muscle force before and 1 year after LTx, and to determine whether peripheral muscle force and lactate threshold (LT) limit exercise capacity 1 year after LTx. Methods:Twenty-five subjects (mean age 43 years, 8 women and 17 men, 4 single-lung transplantations) were included in the study. Measurements included maximal exercise capacity, lactate threshold (symptom-limited bicycle ergometer test) and muscle force test (hand-held dynamometer) were performed before and 1 year after LTx. Results:Before LTx, all patients showed severe exercise intolerance (mean Ϯ SD): work capacity (W peak ), 11.6 Ϯ 18 W; peak oxygen uptake (VO 2 ), 8.6 Ϯ 3.6 ml/min/kg. After LTx, exercise capacity improved significantly: W peak , 69 Ϯ 27 W (p Ͻ 0.001); peak VO 2 , 15.7 Ϯ 4.3 ml/min/kg (p Ͻ 0.001). Ventilatory factors did not appear to limit exercise capacity. Quadriceps muscle force pre-vs post-LTx was: 248 Ϯ 73 N vs 281 Ϯ 68 N (p Ͻ 0.05). Post-LTx, a significant correlation was found between LT and exercise capacity (r ϭ 0.76, p Ͻ 0.001), between muscle force and exercise capacity (r ϭ 0.41, p Ͻ 0.05) and between the LT and muscle force (r ϭ 0.53, p Ͻ 0.01). Conclusions:The occurrence of an early and pathologic LT and peripheral muscle weakness contributes to the limitation of exercise capacity and reflects a peripheral deficit post-LTx.

Peripheral muscle strength predicted 6-minute walking distance; this finding suggests that quadriceps strength training should be included in physical training to increase functional exercise capacity. Attention should be paid to further increasing 6-minute walking distance between 6 and 12 months after transplantation.