Regular physical activity is undoubtedly beneficial for humans. Over the years there has been numerous studies conducted to prove this. In both men and women, those who presented with high levels of physical activity were linked to a reduced risk of death by up to 50%! More importantly (and more relevant to todays society), those who had a physically active lifestyle and also had a risk factor for cardiovascular disease (smoking, obesity, diabetes, hypertension) are shown to have a lower risk of premature death then those who had the same risk factors and were sedentary.
Although, the question that is passed around is “Is more always better?” Now, to put this question into context, for someone that is sedentary most of the day and doesn’t meet the guidelines for physical activity, yes more is better. But with the rise of competitive endurance sports such as triathlons, marathons and ironman events, this is where there is a fine line. Of course, as an exercise physiologist I’m going to explain this on a physiological level first then we will talk more wholistic later. So if you don’t want the science, skip to the end (but you’re going to miss all the good stuff).
Arrhythmias
In terms of the general population, atrial fibrillation (AF) is the most common arrhythmia. Numerous studies however have shown that athletes are more susceptible to AF than non-athletes. This has been believed to be because of the chronic intense physical training regimes athletes engage in which predisposes this arrhythmia due to the left atrial enlargement, increased vagal tone, and increased left ventricle mass. Metabolic changes and adrenergic activation due to intense exercise has also been known to trigger arrhythmias. A 2.5-fold greater risk of sudden cardiac death was observed in competitive athletes and these were related to structural heart disease such as ischaemic heart disease, coronary artery anomalies, and arrhythmogenic right ventricle cardiomyopathy.
Hemodynamics & Right Ventricle Dysfunction
A study conducted on the Boston marathon participants showed that those who completed the marathon had an association with impaired RV systolic function, increased RV dimensions and increased pulmonary artery pressure. Another study has shown that athletes who completed ultra-marathons, had undergone trans thoracic echocardiography which had revealed increased RV dysfunction, reduced tricuspid annular plan systolic excursion (TAPSE) and a reduced RV functional area change. This might all be foreign terms to you, but these alter the physiological processes of the heart and its biomechanics.
Cardiac Remodelling
A group of well trained endurance athletes were tested and results showed that the athletes had arrhythmias originating from the RV. In the same study, the same group of athletes were shown to have reduced ejection fraction and increased end-systolic volume. In most cases, exercise-induced arrhythmogenic RV cardiomyopathies were shown to be present due to the repeated excessively intense exercise in conjunction with inadequate regeneration periods. The RV is more susceptible to volume and pressure overloads bought on by intense and/or endurance training. As its main function is to eject unoxygenated blood to the lungs to become useful to the body and working muscles, its role is quite important.
To sum everything up, it is yet to be proven in studies that too much exercise is bad for your cardiovascular health however there is supporting literature to suggest that excessive high-intensity endurance training continued over long periods of time can have a negative structural influence on your heart.
Layman’s Terms & Mitch’s Suggestion
Although AF and other arrhythmias (abnormal heart rhythms) brought on by exercise sound like a serious event, however some arrhythmias occur to us everyday and they often go un-noticed due to their severity being so low. For something like a change in harm-dynamics to occur (dynamics of blood flow) or cardiac remodelling (alteration in the hearts structure), the heart has to go through an excessive amount of chronic stress for this to happen.
My suggestion is to monitor your exercise load throughout the week and ensure you’re listening to your body and getting enough rest when it needs it. You’re heart is a muscle is an autonomic muscle so it needs to ‘chill out’ once in a while too. Other external stimulus affect your heart also that will lead to these events happening such as stress at work, anxiety and hereditary disease, so exercise alone does not solely increase your risk of these alterations occurring.
Now in terms of how much is too much, there’s no correct answer but you can easily monitor your own exercise load until it becomes too much. The first thing you do is determine your exercise load for the week by multiplying your time spent exercising by your rate of perceived exertion (RPE) and this equals your load (this comes out as an arbitrary number, it doesn’t mean anything special). As you either increase the amount of time exercising or the intensity of your exercise, this number should become higher. For example, if you run for 100minutes and you rate it a 5/10, your load is 500.
As you increase the time spent exercising or the intensity of your sessions this number will increase. This is where you need to monitor for signs of over-training such as persistent muscle soreness and an elevated heart rate. Another specific sign of over training is the increased incidence of injuries. An injury can usually be picked up by looking at the month prior to the injury occurring and noticing any major spikes in load.
Take Home Message
Monitor your exercise throughout the week as total load arbitrary number and notice when there are large spikes because this is where you’re most likely to have an injury occur. If you’re getting fatigued easily in exercise or finding it harder and harder to become motivated about exercise, look at your total load arbitrary number at that current time and keep just below this number for a while until you become accustomed to the work load. Have regular check-ups with your GP to ensure your heart health is adequate. Also, come see an Exercise Physiologist to get the right exercise plan to suit you and your goals.
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