What if all the training you do over 7 hours is making your heart and health worse not better? It’s possible.

Last week I published an article about the effects of alcohol on a cyclists’ body.

But what if I said the very thing we love doing is bad for us? That’s right cycling, or any endurance activity.

But before I get into that, let me discuss where this fits in the Semi-Pros life and training.

I’m sure there is at least some part of you that rides because of the health benefits? Am I right? If we go back to the scale between health and performance, the balance for longevity, or at least getting the health benefits of cycling relate to not pushing ourselves like crazy for performance gains all the time. Because high-performance to a large extent means hard training, and hard training can have adverse effects on the body.

My take is that the difference between health and performance is more like a u-shaped curve. Where health and performance are flagged at either end by unhealthy, or dangerous outcomes. Thinking that the dangers of too little exercise, and too much exercise could have the same outcome puts hard training into perspective over the long term.

There’s been a lot of hype around the results of this study, and in some ways, rightly so. Not that we should be running scared from one or two articles, but that we should be open to the possibility that there is a limit that we can cross in our cycling that will do our hearts bad.

Dr. O’Keefe suggest that chronic training for, and competing in, extreme endurance exercise such as marathons, ironman distance triathlons, and very long distance bicycle races (Tour de France) may cause structural changes to the heart and large arteries, leading to myocardial injury.

With the help of a great article on impruvism.com we are going to explore the question…Does cardio damage your heart?

The idea here is not to scare you, but rather just make you aware. The evidence is not conclusive, and there is no magic number of years or effort that the following information correlates to, but if you keep an eye on this material – then you will be better off.

Alright, down to the nitty gritty. Cardio the new evil which I will define as endurance or aerobic exercise. Which we know in cycling is pretty much the only type of training you will do. A bit of sprinting here or there, but really anything over a minute really is classed as aerobic, or for today – cardio. Also regarding the study, this is also referring to any activity that keeps your heart working at a moderate to high level for 30 minutes or more.

And here’s what they’re worried about, and what the study covers…

Their theory revolves around the idea that excessive cardio causes small amounts of damage in the short-term. Then these small injuries turn into more significant long-term changes that can hurt your heart, blood vessels, and even kill you.

This is thought to occur in a four step process:

  1. Endurance exercise places a higher than normal load on your heart. It increases your oxygen and energy needs. It raises stress hormones, heart rate, blood pressure, and strains the walls of your heart. It also causes oxidative stress and inflammation. The heart is starved for oxygen and overwhelmed with these demands, and in some cases is irreversibly scarred by the exertion.

  2. After each workout, your heart is tired from the effort and heart function drops. There are often changes in electrical activity, heart rate, and an increase in blood markers of heart damage. The inflammation and oxidative stress from the effort damages your heart, blood lipids, and blood vessels.

  3. With enough training, your heart increases in size, develops erratic electrical activity, loses some of its ability to function, and develops small patches of scar tissue that grow with more training. The blood vessels around the heart and throughout other parts of the body also become harder and develop thicker deposits of calcium and plaque.

  4. Over time, these long-term changes increase the risk of developing atherosclerosis, heart attack, coronary and peripheral artery disease, and in some cases, sudden cardiac arrest and early death.

Doing less than that is not considered to be harmful. So How Much is Too Much?

I imagine there are a lot of exercises can damage your heart under this theory, not just cycling. The study itself is based around running, and O’keefe suggests people don’t make a habit of running marathons. One thing I will point out is that O’Keefe talks about a greater risk to people over 45. Which for me comes back to the health scale, and why you ride. If you keep riding for a long time, I imagine that eventually you will be riding at 45 if you’re not there now. So it’s definitely something to keep in the back of your mind as the years tick away.

So if 3 or 4 hours may be dangerous – what’s the sweet spot? Keep in mind that yes he’s talking about running, it can easily be applied to cycling.

Sweet Spot:

  • 25 miles (40 kms) per week – benefits go away
  • Ideal 10-15 miles (16-24 kms) per week
  • But it’s not just distance – it’s speed as well. Too fast is over 8 miles (12 kms) an hour. 6-7 miles (9-11 kms) per hour pace.
  • And frequency 2-5 days are ideal.

Converting this to cycling is a little tricky. So I’ll just go back to what the researchers suggest time wise, avoid anything over an hour, and not more than seven hours weekly of hard endurance training.

That’s not enough to be serious at Cat 3 or higher. Which I’m not going to stand behind this look at endurance training, and say forget about your cycling goals. There is some encouraging news if this all turns out to be proven at some point in the future.



There may not be any concrete takeaways from this study, but what it does do it open the door to a mindset shift.

In some ways it’s about finding your why first, then your balance – if you ride a bike for health – here’s the lesson…

What are your plans? We’ve discussed age and performance on Semi-Pro before, if you’re plans are to work hard then fade out into the long tail – then it’s unknown, if you work hard then stop, it’s unknown, if you just want to stay active…

What does any of this have to do with performance? O’Keefe has this crazy notion that it’s a clear cut choice between short term performance and long term health.

I’m not convinced yet, but would you be willing to give up your cycling goals to live longer?