The Heart of the Matter

Running may delay the effects of age, but it cannot deny them. The human body weakens with time, and all the miles and gym sessions in the world will not indefinitely forestall its decline. For better or worse, our mortality is a fact (at least for now) and though many things can take us out of the game of life, the degradation of our organs and cells over time is the chaser that will always catch us, no matter how far or how fast we run. An unhappy byproduct of this gradual decay is an age-related decline in endurance performance. 

The blood pump we call a heart is no exception to this rule.  As runners, we maintain a special relationship with the heart - we train it, we monitor it, we try to understand its secrets. In the end, however, it tends to let us down.

A few distinct things happen to our hearts as we age and most of them are not good if judged by their impact on performance. On the positive side, the heart remains quite trainable into our later years. We can stress it with interval sessions or tempo runs and the heart will return the favor by super-compensating in response to the stress - e.g., strengthening, pumping more efficiently, sometimes enlarging. In general, the heart is durable and fit for purpose - it has a lot of work to do over a lifetime and it holds up pretty well.  

Unfortunately, the good news mostly ends there. As for the bad news, I will tick off only a few of the key age-related issues with heart function. To begin with the catastrophic, we have an increased risk of suffering an acute myocardial infarction (aka a heart attack). Advanced age (particular being older than 45) is the biggest uncontrollable risk for heart disease of all types. Short of that severe severe performance-inhibiting issue, advanced age can cause the heart to emit confused electrical signals that lead to arrhythmias like atrial fibrillation. A-fib and other arrhythmias are typically performance dampeners and lifestyle inhibitors. (My father was setting age-group indoor rowing records into his 70s until a-fib eventually slowed down his ergometer times.) Though these disorders are partly attributable to genetic predisposition and lifestyle, our odds of suffering from these problems increase substantially as we age.  

Apart from these issues, there is one performance limitation that the heart bestows on all of us without fail: our maximum heart rate, the highest number of beats our heart can deliver per minute, drops as we get older. If there is perhaps one reason why the shorter running events (800m to 3000m) are considered a young man’s or woman's game, declining max heart rate is it. I recently learned this the hard way when I underwent some physiological testing and was told that my maximum heart rate had declined from 182 beats per minute ("bpm") to something in the mid 170s. Not a huge decline, of course, but knowing that those extra beats are never coming back, no matter how hard I train, is a bit of a bummer. At least now when I listen to “For Reasons Unknown” by The Killers (a staple of my treadmill playlist), I can relate more directly to the lyrics: “But my heart, it don’t beat, it don’t beat the way it used to….”

In the spirit of preparing myself for negative developments that are both inevitable and relatively imminent, I decided to learn a bit more about declining maximum hear rate (HRmax for short). To understand more about why the heart slows down, and what if anything we runners can do about it, I put some questions to Dr. Ramzy Ross, a Dubai-based sports scientist and owner of First Performance Consultancy. Dr. Ross works with elite UAE athletes and local companies to test and improve health and to maximize athletic performance.

What causes HRmax to decline as we age?

RR: There are several contributors to this and research is still on-going. Key points include: a reduction in elasticity of the heart’s walls, depression in electrical activity of the heart's natural pacemaker, as well as decreased responsiveness to certain neurotransmitters, such as adrenaline, which increases heart rate in times of stress. 

How does a decline in HRmax impact endurance performance, particularly when it comes to running?

RR: Heart rate is part of a more complex integrated engine so there are several considerations to take into account including heart-related factors such as stroke volume (the amount of blood your heart can pump per beat).  For example, if one’s stroke volume and other remaining components were to remain unchanged then a decline in heart rate would result in a decrease in the body's ability to use oxygen, particularly at higher intensities.   

Is the decline in HRmax the reason that VO2max starts to decline as we move into our thirties and forties?

RR: This is certainly a contributing factor - yes. However, in the context of endurance performance, assuming VO2max is of a required minimum, VO2max is not the be all and end all as other components (such as one’s blood lactate profile) become more important. The best physiological predictor of endurance performance capabilities is still linked to blood lactate measures.

Is there anything we can do to prevent or counteract a decline in HRmax?

RR: Keeping fit certainly won't do any harm. Doing activities that 'stress' the heart over a period of time may be particularly beneficial and such activities can include continuous and interval based training.  Unfortunately, however, the aging process, which is something that we are still learning about, ultimately causes a decline in HRmax regardless. The key is to be at the top of the expected decline. 

Should older runners consider changing their training habits or race distances to work around HRmax decline -- i.e., are marathon/triathlon better bets for older athletes who want to stay competitive?

RR: Again, there are many variables that will impact one’s ability to remain competitive - not just max heart rate. For example, ones max heart rate may decline but other performance-related markers remain 'competitive' and these can compensate for the HRmax decline. You may want to change your event-type for various reasons - but I wouldn't suggest this based on HRmax alone. 

Is a decline in HRmax the biggest issue that aging endurance athletes face, or are other aspects of aging (e.g., muscle loss, etc.) more important to performance?

RR: Master-level athletes should understand the physiological changes the body undergoes − assuming no debilitating health and/or psychological related conditions − when getting older and how they may need to modify their training accordingly. Physiological changes may include:

• Reduced cardiovascular function, flexibility, and muscular strength;
• Decline in lactate threshold – the exercise intensity at which lactic acid accumulates in the bloodstream – and maximal oxygen uptake (VO2 max );
• Longer recovery times between training sessions.

Reductions in muscular strength are linked to prolonged periods of disuse, rather than the aging process alone -  so keep training … but train smart! This helps arrest a decline performance.

There you have it, fellow runners. A dose of reality from the world of sports science, mixed with some cause for optimism. If that's not enough, we can draw further inspiration from the Olympic appearances of fortysomethings Meb Keflezighi and Bernard Lagat in Rio last year. As a loose paraphrase Dr. Ross’s recommendation that we “keep training” and avoid “prolonged periods of disuse," I will only offer this: never stop running.

Learn more about Dr. Ramzy Ross and First Performance Consultancy.