Coronary revascularization improves survival for patients with coronary artery disease (CAD). Despite successful coronary revascularization treatment, however, many patients with CAD are left suffering from poor exercise capacity and frequently experience difficulties in performing daily activities (e.g., getting dressed, sitting down or getting up from the toilet) because of diminished cardiovascular function and exercise tolerance. Decreased exercise capacity leads to a dramatic reduction in quality of life (QoL) and more severe depression symptoms. Low exercise capacity, poor quality of life (QoL) and severer depression symptoms heighten the risk of subsequent cardiovascular events and mortality.
Current guidelines recommend that persons with CAD who have undergone coronary artery bypass graft surgery (CABG) or percutaneous coronary intervention (PCI) participate in exercise-based cardiovascular rehabilitation (CR). Exercise-based CR is safe, effective and a class IA recommendation following CABG and PCI. Irrefutable evidence demonstrates that exercise-based CR including moderate-to-vigorous intensity continuous exercise training (MICT) improves exercise capacity, QoL, depression and reduces hospital readmissions and cardiovascular morbidity and mortality. MICT has long been used to manage the physical and mental health of CAD patients as per the Canadian Guidelines for Cardiovascular Rehabilitation and Cardiovascular Disease Prevention; however, such exercise may be less efficient and perceived as less motivating/enjoyable. Growing evidence suggests that non-conventional exercise interventions, such as high-intensity interval training (HIIT) and Nordic walking are more effective exercise modalities, and maybe more enjoyable, to improve clinical outcomes (e.g., exercise capacity, QoL, and depression symptoms) in patients with CAD.
HIIT (repeated bouts of brief high-intensity exercise interspersed with active recovery) is an effective and efficient exercise training paradigm. A recent meta-analysis (n=10 studies) comparing HIIT and MICT in patients with CAD suggests that: (1) HIIT is superior to MICT in improving cardiorespiratory fitness (V̇O2peak) of patients with CAD, an important clinical vital sign and strong predictor of mortality; and, (2) HIIT and MICT are equally effective in improving QoL and depression symptoms in patients including CAD. Increases in cardiorespiratory fitness decrease mortality risk -- every 3.5 ml/kg/min increase in V̇O2peak yields a 13% improvement in survival. Exercise training-induced increases in cardiorespiratory fitness are therefore highly desirable for the improvement of important patient outcomes.
Nordic walking is similar to Nordic skiing but uses specifically designed poles for walking. Nordic walking includes the recruitment of core, upper and lower body muscles, resulting in greater exergy expenditure while reducing loading stress at the knee joint. Regular participation in Nordic walking leads to increased exercise capacity. Although data is limited regarding the impact of Nordic walking in comparison to MICT on mental health in patients with CAD, some studies in patients with heart failure have shown superior improvements in QoL and fewer depressive symptoms following Nordic walking when compared to MICT. Our previous randomized controlled trial simultaneously comparing 12 weeks of supervised HIIT, MICT and Nordic walking in patients with CAD showed that Nordic walking was statistically and clinically superior in increasing functional capacity (i.e., distance walked over 6 minutes), and have similar effects on QoL and depression when compared to HIIT or MICT.
As many adults with cardiovascular disease consider lack of time a barrier to exercise, HIIT may be an appealing exercise training paradigm as cardiovascular health benefits can be achieved in less time when compared to MICT. HIIT may also address other frequently reported deterrents to MICT, including lack of interest and motivation, boredom, not challenging enough, and tailored for older people's needs. To date, HIIT used in CR settings has predominantly focused on lower body (e.g., leg cycling). There are few HIIT protocols that simultaneously target both upper and lower body, such as high-intensity interval Nordic walking (HIIT-NoW). Studies have shown that HIIT and Nordic walking are feasible, enjoyable and have similar or superior effects on physical and mental health when compared to MICT. By combining HIIT and Nordic walking, HIIT-NoW may offer an alternative time-efficient whole-body exercise to improve physical and mental health of patients with CAD.
