Quadriceps Muscle Strength and Body Mass Index are Associated with Estimates of Physical Activity Postheart Transplantation

BACKGROUND: Although exercise capacity improves postheart transplantation (HTx), it remains unclear if the level of physical activity (PA) shows similar improvement. The purpose of this study was to (1) describe PA levels and (2) identify factors which may be associated with levels of PA post-HTx. METHODS: A prospective observational cross-sectional study was conducted at a single center HTx outpatient clinic. Medically stable adult recipients 6 months or longer post-HTx were recruited. Physical activity level (PAL) and average daily time spent at least moderately active (≥3 metabolic equivalents) were estimated using a multisensor device. Factors investigated were demographic (age, sex, body mass index [BMI], time post-HTx, and reason for HTx), corticosteroid use, exercise capacity (6-min walk distance), and quadriceps muscle strength corrected for body weight (QS%). RESULTS: The mean post-HTx time of the 75 participants was 9.2 ± 7.0 years (0.5-26 y). Twenty-seven (36%) participants were classified as extremely inactive (PAL, <1.40), 26 (34.6%) sedentary (1.40 ≤ PAL ≤ 1.69), and 22 (29.3%) active (PAL, ≥1.70). Multivariable analysis showed greater QS% (β = 0.004 (0.002-0.006) P = 0.001) to be independently associated with increased PAL. For increased time, 3 or more metabolic equivalents both greater QS% (β = 0.0164 [0.003-0.029]; P = 0.014) and lower BMI (β = -0.0626 [-0.115 to -0.0099]; P = 0.021) were independently associated. CONCLUSIONS: The degree of observed sedentary behavior post-HTx is surprising, with the majority of participants not reaching levels of PA recommended for health benefits. QS% and BMI were the only factors found to be independently associated with estimates of PA. Further quality trials are required to demonstrate the long-term benefits of regular PA and investigate ways of increasing adherence to PA post-HTx.