Active Voice: Backpedaling on Heart Disease
By Lauren C. Chasland, B.Sc. (Hons), Louise H. Naylor, Ph.D., and Daniel J. Green, Ph.D.
Lauren C. Chasland, B.Sc. (Hons), is an accredited exercise physiologist, trainee vascular sonographer and a Ph.D. student at the University of Western Australia. Lauren’s honors research investigated the oxygen demand of eccentric and concentric cycling in people with chronic heart failure. Lauren has a keen interest in using exercise as medicine across the lifespan.
Louise H. Naylor, Ph.D., is an early career researcher in the School of Human Sciences (Exercise and Sport Science) at the University of Western Australia in Perth. She is an expert vascular sonographer and accredited exercise physiologist. She also works part-time in the Western Australia Cardiac Transplant Service. Dr. Naylor has worked with elite athletes, healthy non-athletes and chronically ill individuals to generate a multifaceted understanding of cardiac and vascular exercise physiology.
Daniel J. Green, Ph.D., is Winthrop Professor in the School of Human Sciences (Exercise and Sport Science) at the University of Western Australia in Perth. He also holds an appointment as professor of cardiovascular physiology with the Research Institute for Sport and Exercise Sciences (RISES) at Liverpool John Moores University in the United Kingdom. Professor Green is a human integrative and cardiovascular physiologist whose research focuses on the prevention of cardiovascular diseases.
This commentary presents the authors’ views on the topic of their research article that they had published with other colleagues. Their article appears in the April 2017 issue of Medicine & Science in Sports & Exercise® (MSSE).
Chronic heart failure (HF) is a common and debilitating disease, with a high cost for care, and is associated with a prognosis that remains poorer than for most cancers. In the USA, 6.5 million adults live with this condition and the burden of HF care is about $30 billion, principally attributable to hospital costs. In contrast to other cardiovascular diseases, deaths and hospitalizations for HF have risen for both men and women across the last decade.
Heart failure is a systemic disease. Although impaired cardiac function initiates the syndrome, research has identified an intriguing paradox associated with HF, in that the primary locus of exercise intolerance often lies in the skeletal muscle, rather than the heart itself. As such, exercise is a highly effective “medicine” as it treats multiple peripheral effects of the disease. For this reason, exercise training is strongly advocated in contemporary clinical HF guidelines (Class I Level A Evidence). More than 20 years ago, our group in Western Australia introduced novel approaches to personalized exercise training in HF, focusing on circuit-style sessions of combined aerobic and resistance exercises, in which small muscle groups are focally trained at higher intensity. This approach has generated excellent results in our transplant unit and advanced heart failure management setting and has been adopted widely elsewhere.
Eccentric exercise is a novel form of exercise that has unique impacts, promising enhanced functional benefits at a lower cardiovascular burden. These characteristics are particularly relevant in HF, because impaired functional capacity often limits the ability to prescribe exercise at an intensity high enough to induce substantive physiological and clinical benefit. Eccentric cycling can be performed using an ergometer with a motor that powers the cranks in reverse. Participants exert force in the forwards direction – effectively trying to slow the pedals down while eccentrically contracting the quadriceps muscle group.
In our study, published in the April 2017 MSSE, we examined differences in oxygen demand between eccentric and concentric cycling in a group of 11 patients (one female) with low ejection fraction chronic heart failure. The principal finding was that oxygen demand was significantly lower (13 percent) during eccentric cycling compared to traditional concentric cycling, despite the sessions being matched for power output. Heart rate and blood pressure responses were similar between the two modalities. Achieving a similar workload with less oxygen demand is a clinically relevant finding in HF, as patients often experience dyspnea at low exercise intensities. The corollary is that when HF patients perform eccentric exercise, they may be able to perform higher exercise workloads for a given oxygen uptake.
In an accompanying study reported elsewhere, we demonstrated the impact of eccentric cycling on platelet and endothelial function in people with HF. We found that both conventional and eccentric cycling can be performed without acute increases in the risk of platelet-mediated thrombosis or detrimental impacts on vascular function.
If replicated and extended, the findings of our modest study may eventually have implications for cardiovascular rehabilitation. This eccentric exercise modality enables a greater localized stimulus to the muscle, without increased cardiovascular demand or risk for selected HF patients. This represents a promising alternative to attenuate the skeletal muscle abnormalities that are so important in HF. Randomized controlled trials of eccentric exercise training in HF are required to assess the extent to which peripheral limitations to function are impacted and to determine the feasibility of incorporating this exercise modality into routine cardiovascular rehabilitation.