Energy Sources: Why it gets hard after a minute

Source: Edington & Edgerton '76
Source: Edington & Edgerton ’76

In you last parkrun or duathlon or bike TT, maybe you started off feeling great? Maybe that new coach had worked wonders? Maybe the new taper was working wonders too? You were FLYING! You hardly needed to breathe really. Awesome!

But after a minute you reverted to normal.

🙁 Sigh.


The first 10 seconds of work uses energy within the muscles from PCr and ATP – this is achieved ANaerobically.

Maybe that’s why they still have the 100m and 200m at the Olympics? – subtly different

Doing intervals here is fine but you need significant recovery periods of over 3 minutes to replenish the PCr and ATP.

If we keep going up to the minute mark then we use glycosis. That is still ANaerobic and converts glucose to the fabled lactate. (Most of the lactate produced in your session can be cleared in 10 minutes with a light jog/spin).

OK we’re 61 seconds into the race…let’s get AEROBIC. (It’s after about a minute not literally 61 seconds).

Maybe that’s why the 400m is kept in the Olympics? Different again to 200m

When doing aerobic work after the minute mark we use aerobic glycosis (‘good’) and lipolysis (‘bad’ – sort of).

The amount of aerobic glycosis that can happen depends on the fuel and oxygen available. The fuel is still glucose; when that’s gone you hit the ‘wall’/bonk and that’s YOUR fault because you haven’t sufficiently refuelled. The amount of oxygen involved is of course your parents’ fault as it’s limited by your VO2max which has a genetic component as well as, naturally, how effectively you train!

Despite being a slow energy producer, lipolysis is not totally bad of course. If we can get good at this ‘fat burning’ malarky then we can make life MUCH easier for the glycosis. Lipolysis relies on both your fat stores, which nearly all of us have in abundance, AND WATER. This is one reason why proper hydration is important. Lipolysis takes about 7 minutes to get going (maybe that’s why warming up is a good idea).

Of course, if you get good at lipolysis then your body will use that process of ‘fat burning’ much more than other people do. That’s why you won’t get fat so easily.

So, that’s why 5k is a bit tricky. You need to train all of the above as those 30 seconds, 1 minute, 7 minute physiological marks are a significant part of your time. Even a significant part of Mo or Glenn’s times. And that’s why marathons are a bit more straightforward to train for; ‘all’ you have to do is enable that aerobic glycosis to last for the full race…whilst going as fast as you can. Easy! Sort of. 🙂

Now you know.


Reader-Powered Content

This content is not sponsored. It’s mostly me behind the labour of love which is this site and I appreciate everyone who follows, subscribes or Buys Me A Coffee ❤️ Alternatively please buy the reviewed product from my partners. Thank you! FTC: Affiliate Disclosure: Links pay commission. As an Amazon Associate, I earn from qualifying purchases.