Chronic Adaptations On The Oxygen Uptake Kinetics In Trained Older Adults With Coronary Artery Disease

Abstract

Previous studies have reported that slower VO2 kinetics typically observed in healthy older individuals can be prevented by long-term endurance training interventions. However, the chronic adaptations on the VO2 kinetics and muscle deoxygenation ([HHb]) kinetics response in trained older adults with coronary artery disease (CAD) remains unknown. PURPOSE: to compare VO2 and [HHb] kinetics response in moderate exercise in older adults with CAD and a control group (CG) of healthy active age- and gender-matched individuals. Both groups did at least 6 months the following exercise training (ET) prescription, 3 d.wk-1 x 60-min: 30 min at 60-70% heart rate reserve + 2 x 8-12 repetitions in 6 major muscle groups. METHODS: thirty-two male participants (age: 63.5 ± 8.3 years; n= 17 CAD and n=15 CG) completed the following assessments: 1) incremental symptom-limited cycling cardiopulmonary exercise test; 2) square-wave transitions from rest to moderate-intensity exercise. Pulmonary VO2 was collected breath-by-breath and [HHb] data of the vastus lateralis was determined by near-infrared spectroscopy. The parameters of the VO2 and [HHb] kinetics were determined using a monoexponential model. Differences between groups was assessed with the independent-samples t-test. RESULTS: Peak oxygen consumption and peak work load were lower in CAD compared to CG (CAD: 23.2 ± 6.2, CG: 30.4 ± 7.5 ml/kg/min, p<0.05; and CAD: 158 ± 47, CG: 193 ± 50 W, p<0.05). For the square-wave transition, VO2 amplitude was significantly lower in CAD patients than CG group (10.1 ± 2.9 vs 13.1 ± 3.8 ml/kg/min, p<0.05). In contrast, VO2 baseline, time constant of the primary phase, gain and mean response time were not significant (p>0.05). The effective deoxy-[Hb+Mb] was not statistically different between groups (p>0.05). CONCLUSIONS: Long term ET in CAD participants had lower measured VO2peak and work load compared to age- and gender matched. However, both pulmonary and muscular oxygen kinetics were not slower in older adults with CAD compared to their training-matched counterparts. These findings support the importance on the referral of elderly patients to community-based cardiac rehabilitation ET program to maintain their submaximal pulmonary and muscle [HHb] kinetics to continue their ability to perform daily activities.