The 80/20 Rule Of Endurance Training

The 80/20 Rule Of Endurance Training

Posted by Kyle Williams on Mar 26, 2018

Estimated reading time: 2mins

Whether you’re a triathlete, ultra runner, or do a lot of endurance training, you’ll get the best results if you follow the ‘80/20’ rule: Train easy 80% of the time and train hard the other 20%.

Why follow this?

Quite simply, scientific studies have clearly demonstrated that endurance adaptations are maximized when your training is split between 80% easy work and 20% hard efforts.

In relation to the 80% easy, you get your greatest aerobic adaptations at training intensities below 70% of your maximum heart rate. And yes, training at the 80% ‘easy’ level means training slower for the most part.

The effort/intensity level linked to this is below lactate threshold. If you don’t use a heart-rate monitor, that’s the level of effort/intensity where you can comfortable hold a conversation and not noticeably hear your breathing.

The 20% hard is the opposite: Above 85% maximum heart rate, where it feels uncomfortable, hard, and you are unable to hold a conversation.

Why train ‘easy’?

While training primarily ‘easy’ might seem counter intuitive to be able to race fast, it works.

However, most endurance athletes lack the patience or discipline to follow this tried and true training tenet. The reality is it takes YEARS to properly adapt the body to the loading of endurance training.

Can you improve endurance fitness with HIIT?

Whilst intervals and HIIT (High Intensity Interval Training) might seem like the ‘hack’ or ‘shortcut’ to get quicker results and improve your fitness, your gains will quickly taper off.

Too much HIIT creates consistent high training stress which will wreck your hormone levels and put you on a one-way ticket to a soft-tissue injury.

I’ve seen it time and time again. Did you know that 80% of runners will suffer a training related injury within any 12-month period?

Endurance training success comes from playing the long game – So train easy for most of the time, go hard for a little bit, and you’ll be primed for endurance success.

Don’t risk an injury. Train smart for endurance.


  1. Stöggl, T. and Sperlich, B., 2015. The training intensity distribution among well-trained and elite endurance athletes. Frontiers in Physiology, [online] 6, p.295. Available at:The training intensity distribution among well-trained and elite endurance athletes.

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