Elevating VO2max through endurance training is important as it relates to cardiovascular disease, due to the association between poor cardiovascular fitness, a sedentary lifestyle and mortality risk.
J. Helgerud, T. Karlsen, W. Y. Kim, K. L. Høydal, A. Støylen, H. Pedersen,L. Brix, S. Ringgaard, J. Kværness, J. Hoff
Endurance training has been recognized to increase maximal oxygen-uptake (VO2max) in cardiovascular disease patients (CAD) while high intensity aerobic interval training, employing 4 × 4 min, is a more effective approach. Elevating VO2max through endurance training is important as it relates to cardiovascular disease, due to the association between poor cardiovascular fitness, a sedentary lifestyle and mortality risk. Similarly, low skeletal muscular strength is associated with increased mortality, and skeletal muscle strength decreases with age and inactivity.
Specific to the cardiac muscle itself, cardiovascular disease, aging and a sedentary lifestyle deteriorate cardiac function with left ventricular stiffness, decreased left ventricular compliance and diminished diastolic performance. Endurance training can improve maximal stroke volume (SV) of the heart and left ventricular function in CAD patients, but it has previously been recognized that, at least in healthy subjects, high intensity aerobic interval training at 90–95 % of maximal heart rate is superior to less intense exercise in terms of increasing maximal SV. This aerobic interval training-induced increase in SV is not only associated with an increased VO2max, but also a reversal of left ventricular remodelling, improving left ventricular function in heart failure patients.
There is a minimum muscular strength required for the activities of daily life such as walking or stair climbing and when lacking, may lead to disability. Low muscular strength is associated with reduced mechanical efficiency, the oxygen cost of generating a given work load, during endurance activities. It has been documented that CAD patients walk with mechanical inefficiency, which is likely a consequence of skeletal muscle weakness. Increased skeletal muscle strength and the subsequent improvement in the mechanical efficiency of a simple task such as walking could shift the stress of daily activity from severe, to tolerable and repeatable in such patients.
Although the importance of maintaining or improving skeletal muscle strength in CAD patients is clear, little is known about the impact of maximal strength training (MST) on this population. This study sought to study the effect of high intensity aerobic interval endurance training on maximal SV and MST on strength and mechanical efficiency in CAD patients.
8 CAD patients (average age 61 years) trained 30 interval training sessions with 4 × 4 min intervals at 85 – 95 % of peak heart rate while 10 CAD patients (average age 66 years) trained 24 sessions of maximal horizontal leg press. In the interval training group peak SV increased by 23% and VO2max increased by 17%. In contrast, there was no such exercise training-induced change in the MST group.
The MST group improved maximal leg press strength by 43% and rate of force development by 85% after training, with no changes in the 4x4 min interval group. Both the 4x4 min group and the MST group improved walking mechanical efficiency after training, indicating that different mechanisms explain the adaptation.
Conclusion: High aerobic intensity interval training significantly improves maximal SV and VO2max in CAD patients. In contrast, there was no such exercise training-induced change in maximal SV or VO2max in the MST group, despite a 35 % improvement in walking efficiency.
Read the full study: https://pubmed.ncbi.nlm.nih.gov/21072747/