Exercise and Heart Health: How Much is Too Much?

by Joe Giandonato, MBA, MS, CSCS

The age old debate of cardiovascular exercise versus strength training continues to rage on, gulfing a divide among clinicians, fitness professionals, and fitness enthusiasts.  What modality is superior? What yields the greatest improvement in athletic performance or body composition? And lastly, which is the safest? If you are a member of lay public and not an acronymized academic or someone who’s spent time in the trenches, you lay vulnerable to sensationalized news reports at face value. Fads come and go as do the people that attempt to ascribe to them. Few offer a semblance of longevity. The fitness industry mirrors that of professional football – trends like players have a tremendously short shelf life.
Outlasting the onslaught of gimmicks and the charlatans that pitch them to make a quick buck (yes, I am looking at you, Tracy Anderson), are the constants of cardiovascular exercise and strength training.
Each packs a bevy of benefits. However, in excessive amounts, each may pose a series of health risks, specifically, cardiovascular risks. The intention of this article is not to scare, but to help you better understand the myocardial remodeling and protective effects that each modality yields.
Cardiovascular exercise and strength training render a number of transformative effects on the heart. 
Acutely, the commencement of physical activity or the mere anticipation of engaging in movement elicits activity of the sympathetic branch of autonomic nervous system which increasing heart rate. Moreover, autonomic nervous system activity coupled with exercise elevates blood pressure, increasing the amount of blood which is ejected during ventricular contraction, also known as stroke volume. Collectively, these physiological responses to exercise increase cardiac output, which is the product of heart rate and stroke volume. Elevations in stroke volume during exercise have been reported to be five to six times greater than rest. 
While consistent engagement in cardiovascular exercise and/or strength training results in the strengthening of myocardial structures giving rise to increases in angiogenesis and vascularization and a reduction in aortic stiffness, inappropriate intensities and/or durations may increase left ventricular wall thickness. 
Cardiovascular exercise imparts a volume load on the left ventricle, since it ejects vast amounts of oxygen enriched blood through the arterial system to working musculature. A pressure load is also imparted since the rate pressure product, an expression of systolic blood pressure and heart rate, is higher during exercise. 
Strength training imparts a far greater pressure load on the left ventricle than cardiovascular exercise does. During circa maximal efforts and intense isometric activities, blood pressure exponentially increases, creating a significant afterload effect which stresses the walls of the myocardium thereby inducing a hypertrophic response. A larger left ventricle will impede cardiac perfusion and is typically accompanied by aortic stenosis and systemic hypertension.
The amount to which the myocardium responds depends not only on workload, but it’s interaction with genetic predispositions, diet, and drug consumption, including drugs used for recreational and performance enhancement purposes.
Echocardiographic imaging revealed enlarged hearts among highly trained endurance athletes (3,4). Left ventricular wall thickness was noted among endurance athletes (3,4), including rowers (3). Electrocardiographic tests involving an individual with an enlarged left ventricle may display increased voltages, specifically, tall R waves and deep S waves (1).
A Pulse of Prevention
Rather than gamble your cardiovascular health, it would be prudent to eliminate excessive stimulant usage, which includes nicotine, and incorporate sounder nutritional strategies, such as ones that reduce sodium intake. As it pertains to exercise, inter -and intra- session recovery needs to be closely monitored, especially among younger athletes whose cardiovascular systems are more sensitive to stress. For power and strength activities which involve a significant spike in blood pressure, a lengthened recovery period is suggested prior to a subsequent bout. Power and strength activities should never be taken to metabolic fatigue and stress throughout one’s training program should undulate, accounting for competing physiological stressors such as occupational, competitive, and recreational activities.
1. Sokolow, M. & Lyon, T.P. (1949). The ventricular complex in left ventricular hypertrophy as obtained by unipolar precordial and limb leads. American Heart Journal, 37, 161.
2. Urhausen, A., & Kindermann, W. (1992). Echocardiographic findings in strength and endurance trained athletes. Sports Medicine, 13, 270-284.
3. Urhausen, A., Monz, T., & Kindermann, W. (1996). Sports-specific adaptation of left ventricular muscle mass in athlete’s heart. An echocardiographic study with combined isometric and dynamic exercise trained athletes (male and female rowers). International Journal of Sports Medicine, S3, 145-151.
4. Whyte, G., Sharma, S., George, K., & McKenna, W.J. (1999). Alterations in cardiac morphology and function in elite multidisciplinary athletes. International Journal of Sports Medicine, 20, 220-226.