Editor’s note: This article deals with the same general topic as one just posted in this blog. This article reflects the timeliness of work being performed by faculty at the United States Sports Academy. Dr. Moon and Dr. Ric Esposito are currently doing grant work in the area of human performance as well as teaching USSA students in their areas of specialty.
Yes, it’s true… Well, kind of.
Two recently published articles found that long-term endurance training may result in cardiac fibrosis and remodeling, which causes abnormal changes in heart tissue, including cardiac remodeling and fibrosis, which can lead to heart failure. One study compared veteran endurance athletes over 50 years old to young endurance athletes and older non-trained adults. Their results are below:
“…veteran athletes had a significantly larger absolute and indexed LV (left ventricle) and RV (right ventricle) end-diastolic and systolic volumes, intra-ventricular septum thickness during diastole, posterior wall thickness during diastole, and LV and RV stroke volumes (p<0.05), together with significantly reduced LV and RV ejection fractions (p<0.05) compared to veteran controls. In 6 (50%) of the veteran athletes LGE of CMR (like MRI, a type of cardiac imaging) indicated the presence of myocardial fibrosis (4 veteran athletes with LGE of non-specific cause, 1 probable previous myocarditis and 1 probable previous silent myocardial infarction).” This article concluded that there may be a “link between life-long endurance exercise and myocardial fibrosis…”
However, life-long endurance exercisers may not be the only ones at risk. Another article looked at rats that were forced to vigorously run for 4, 8, and 16 weeks. The results, in my opinion, were alarming.
“In this animal model, we documented cardiac fibrosis after long-term intensive exercise training (16 weeks), together with changes in ventricular function and increased arrhythmia inducibility. If our findings are confirmed in humans, the results would support the notion that long-term vigorous endurance exercise training may in some cases promote adverse remodeling and produce a substrate for cardiac arrhythmias.”
Does this mean that as little as 16 weeks of intense cardio training may increase my risk for cardiac arrythmias? I thought doing cardio was supposed to help the heart. Well, apparently there is a fine line between benefiting the heart and possibly hurting the heart. The American College of Sports Medicine (ACSM) recommends doing cardio at an intensity of 40-60% of your VO2 reserve (maximum oxygen uptake minus resting oxygen uptake) or your heart rate reserve (max HR minus resting HR). This intensity is considered to be the minimal intensity to achieve health and fitness benefits by the ACSM. However, the ACSM guidelines also state that “…a combination of moderate- and vigorous-intensity (>60% VO2 Reserve) exercise is ideal for the attainment of improvements in health/fitness in most adults.“ However, the recent data above does not support this idea. Even more interesting is that recently data has been published indicating that strength training is better for the heart when compared to cardio exercise. Specifically, resistance (strength) exercise was shown to increase limb blood flow and increase post-exercise hypotension at 40 minutes compared to cardiovascular exercise.
However, the subjects lifted 65% of their maximum 10 times for three sets, and according to the National Strength and Conditioning Association, less than 67% should result in 12 or more repetitions. Therefore, the subjects were not lifting until failure, but rather voluntarily stopping at 10 reps when they could have done more.
Applying the principle of moderation (in terms of intensity) appears to be the key to heart health. Exercising at a moderate intensity during both cardio and strength training should result in the best improvements in heart health. The take-home message here is that you don’t need to go to the extreme during exercise to improve your heart health. However, if you want to increase muscular strength and size, you need to train at a higher intensity Also, if you want to improve your endurance performance, you need to up the intensity of your cardio training.
What is your training goal: To improve health or improve performance? Research suggests you can’t do them both. This may explain why many athletes have heart problems in middle and older age, despite having been in great shape their entire lives. In one such case, an outstanding American marathon runner Alberto Salazer almost died of a heart attack at the age of 49 in 2007.
So, if you want to exercise to improve your heart health, it appears that moderate strength and cardio are the best way. If you want to increase strength, muscle size, and endurance performance, you will need to up the intensity of both with the potential risk of causing harm to the heart.
We still do not know what exercises are best for the heart, but we do know that good nutrition, moderate physical activity, and low body fat can help reduce cardiovascular risks. The extent as to what damage high intensity training does to the heart is still not known. Just remember to keep everything in moderation, including food and high-intensity exercise, and your heart will thank you.
Jordan Moon, PhD, CPS, CSCS*D, HFS
Dr. Moon is the Department Head of Sports Health and Fitness at the United States Sports Academy. He has trained athletes at all levels including professionals in Major League Baseball, the National Football League, and the National Hockey League, as well as college athletes and teams in addition to youth and fitness clients.