Effects of a 12-Week Home-Based Resistance Training Intervention on Peripheral Muscle Oxygenation and Exercise Tolerance in Children with Congenital Heart Disease

Abstract

Congenital heart disease (CHD) is the most common birth defect occurring in approximately 1 in 100 live births. A hallmark feature of children with CHD is exercise intolerance, despite successful surgical intervention and medical management. Although central mechanisms have been shown to play a role in reduced exercise tolerance in children with CHD, information regarding the influence of peripheral mechanisms is lacking. Exercise rehabilitation programs have been shown to improve exercise tolerance in children with CHD; however, exercise tolerance is still limited compared to healthy matched controls. Whether a home-based exercise intervention including primarily strength activities improves muscle oxygenation (as measured by tissue oxygenation index, TOI) in children with CHD compared to healthy children is unknown. PURPOSE: To determine whether a 12-week home-based exercise intervention can improve TOI, V̇O2 and heart rate (HR) during submaximal and maximal exercise in children with CHD compared to healthy children. METHODS: 14 children with simple and complex lesions (f/m: 5/9; mean ± SD age: 12±2 yrs) and nine healthy controls (f/m: 5/4; mean ± SD age: 12±3 yrs) were studied. Children with CHD completed a home-based exercise program 3 times/week for 12 weeks, in addition to 6 biweekly in-person sessions. Exercise tolerance was assessed with peak V̇O2 testing to volitional fatigue on a cycle ergometer. Vastus lateralis TOI was continuously sampled during the peak V̇O2 test via near-infrared spectroscopy (NIRS). Peak TOI, V̇O2 and HR were analyzed as the average value over 30-s within the last 1-minute of exercise. Submaximal TOI, V̇O2 and HR were analyzed as the average of the last 30-s of stage 1 (25W) and stage 2 (50W). TOI was expressed as a percentage scaled to the total liable signal (TLS). Pre- vs post- training changes in children with CHD were analyzed using paired t-tests. Pre- and post- training CHD data compared to healthy control data were analyzed using one-way ANOVAs with Holm-Sidak post-hoc testing. Significance was accepted when p < 0.05. RESULTS: TOI at peak V̇O2 was significantly lower post-training compared to control (20±13% vs 41±11%; p = 0.02). Peak V̇O2 was significantly lower pre-training (35±7 mL/kg/min vs 48±7 mL/kg/min; p = 0.006) and post-training (36±9 mL/kg/min vs 48±7 mL/kg/min; p = 0.005) in children with CHD compared to control. Although not significant, HR at peak V̇O2 was lower pre- training (175±23 bpm vs 189±12 bpm; p = 0.06) and post-training (169±21 bpm vs 189±12 bpm; p = 0.06) in children with CHD compared to control. CONCLUSION: Despite no change in V̇O2 and HR, TOI is lower during submaximal and maximal exercise after home-based exercise in children with CHD compared to healthy children. Our findings suggest that peripheral mechanisms (such as oxygen uptake and utilization) can be improved using a strength-based exercise intervention, and may influence exercise intolerance in children with CHD.