Ask the Coach: Why do my long runs leave me wiped out for days?

Hi Mike, my long runs leave me wiped out for days. Is that normal at my age (39), or am I training wrong?  

Sam

Running coach answer: Why do my long runs leave me wiped out for days?

Firstly, you are not too old for a distance runner; there are lots of runners, even in their 60s and 70s, who are still producing remarkable performances, which require a high level of training. The men’s world best for the male masters age 60+ was beaten in the Seville Marathon 2026 with a 2.28 performance!

While age is ultimately a performance factor, experience counts for more. 

The athletes who produce these fast marathons will have spent three or so years building up their training volume. Endurance running is a long-term gain activity. 

As a novice runner, I suspect you are running your long runs too fast. Or you may have built up the distance too quickly. Either way, you haven’t given your body time to adapt to the load you are asking it to do. 

From a physiological adaptation point of view, you adapt best to becoming an efficient long-distance runner by developing the oxygen delivery to your muscles. These developments take a long time to happen and happen incrementally over months rather than weeks. 

This aerobic development is achieved most efficiently by running at a slower, comfortable pace. At slower paces, you will increase your blood stroke volume (the amount of blood pumped from your heart), increase the capillary network of blood vessels that take the oxygenated blood to your muscles, and develop mitochondria, the engine that creates energy in your muscle cells by combining the glucose in your muscles with oxygen. 

If you use a GPS watch, you will see that your aerobic speed is shown as running in zone 1 or zone 2. These are the speeds at which your body can deliver sufficient oxygen to your muscles to keep contracting. When you run at faster speeds, you can’t supply sufficient oxygen to mix with glycogen, and lactate is produced.

You feel the buildup of lactate when you are breathing very heavily during exercise, and your legs start to feel heavy, ultimately causing you to slow down. 

If you don’t have a GPS watch, you can gauge your aerobic level when you can breathe relatively normally and hold a conversation while you’re running, which is often called conversation pace running. 

Stay in this area of easy to steady running, where you can breathe normally, while also building up the distance of the long run gradually over many months, and you should find that your long run switches from being a hard run to a moderate effort run, where, apart from some inevitable muscle fatigue, from being out running for a long time, you recover fairly quickly within 24 hours.

What I find with beginners is that at these zone 1 or zone 2 speeds, you can be running very slowly, and in some cases, could be at walking speed. 

It’s a problem, as you naturally want to feel that you are running. The result is that to try to feel that you are running, you end up running too fast.

One way around this, and which Runner’s World Magazine finds to be a very efficient way to train for endurance, is to plan from the outset to run for a few minutes, then walk for a few minutes. Over time, as you get fitter, you will be able to reduce the walking stretches and increase the time running. 

The key is to build up the long run gradually over many months and keep the pace down. 

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