The Physical Fitness of Pediatric Kidney and Liver Transplant Recipients

Abstract

PURPOSE: A cross-sectional study was performed to assess laboratory and field test measures of physical fitness after kidney (KTX, 3.4 ± 4.1 yrs post) or liver transplantation (LTX, 10.9 ± 4.4 yrs post) during childhood. METHODS: Laboratory testing included assessment of cardiorespiratory fitness (CRF, VO2peak), quadricep muscle strength (peak torque), and body composition (%fat). Field testing was adopted from the FITNESSGRAM® and included the PACER, curl-up and sit and reach tests. Values obtained from field testing were compared to sex and age-based criterion-referenced standards (Healthy Fitness Zone, HFZ). The Previous Day Physical Activity Recall (PDPAR) was used to assess after-school activity participation. Independent t-tests were used to determine the differences between the KTX and LTX recipients with p-values <0.05 indicating statistical significance. KTX and LTX recipient data was compared to FITNESSGRAM® criterion-referenced standards by calculating the percent of KTX and LTX children that attained values within the HFZ. RESULTS: Twenty-five KTX (16 boys, 9 girls; age 15.7 ± 2.3 yrs) and 11 LTX (5 boys, 6 girls; age 14.5 ± 2.6 yrs) recipients completed all assessments. No differences were detected between the KTX and LTX groups in any of the laboratory or field physical fitness testing. However, both groups demonstrated below normative age and sex values for VO2peak (KTX 30.1 ± 8.9; LTX 33.4 ± 8.2 ml/kg/min) and peak torque (KTX 73.8 ± 26.8; LTX 67.5 ± 20.1 Nm). Only 4% of the KTX and 9% of the LTX recipients achieved the HFZ for the PACER and 24% of the KTX and 45% LTX attained the HFZ for the curl-up test. Twenty percent of the KTX group and 45% of the LTX group had percent body fat values greater than the upper criterion value of the HFZ. Both the KTX and LTX recipients reported spending less than 10% of their after-school time participating in physical activity, 35% performing self-care tasks and greater than 55% physically inactive. CONCLUSION: Pediatric solid organ transplant recipients may be at increased risk for cardiovascular problems and loss of bone density. These risks may be due to the immunosuppressive therapy. However, the present findings of significantly reduced exercise capacity and physical activity in pediatric solid organ transplant recipients warrants counseling and encouragement for increased physical activity. A randomized clinical trial of diet and exercise intervention after pediatric transplantation is warranted to determine the impact of such lifestyle interventions on improving physical fitness and cardiovascular health.