No matter whether you train four or fourteen times a week, the goal should always be to train at a lower intensity for 80% and a higher intensity for 20%. This is what Dr Stephen Seiler recommends, one of the world's leading sports scientists from the University of Agder in Norway. These percentages don't refer to the overall training time, but rather the number of sessions to be completed at 80% lower intensity and 20% higher intensity.

However, the reality is often quite different. Many recreational runners feel like they have to put in maximum effort whenever they get the chance to train. This actually means that they end up training neither fast enough nor slow enough – simply hovering somewhere in the middle. Although improvements might be seen at first, things soon plateau. The problem is that they are always too exhausted when it comes to the high-intensity workouts.

Does 80:20 lead to the desired result?

Why should we aim for this extreme ratio of 80:20? Don’t we get faster by running faster?

Running at a low intensity teaches the cardiovascular and respiratory system to work more efficiently. As a result, you'll find it easier to run at a higher intensity. Slow runs also exercise the slow-twitch muscle fibres that help with aerobic training. They support adjustments that then make us better endurance runners. If your training plan doesn’t include these runs, you will struggle to achieve the aerobic load required for long-distance runs.

By contrast, both moderate and high-intensity training put too much strain on the body to be carried out in large amounts. This increases the risk of injury and you'll need longer to recover. As a rule, you won’t have recovered sufficiently before the next high-intensity training session to be able to achieve the desired training effect.

What does this mean in practice?

• Seiler emphasises that the 80:20 ratio is to be understood as a general guideline and not as a strict rule. The ratio could also be 85:15 or 75:25.
• The rule is based on categories. A training session should be difficult or easy. If a training week is made up of four sessions and one of them involves interval training or sprints, this is a ratio of 75:25.
• "Hard" doesn't mean that you have to run yourself into the ground. 90 to 95 percent is perfectly sufficient and lets you recover faster.
• Remember to include low-intensity sessions in between the hard sessions. This is especially true for athletes over 50, as they'll need more time to recover between intensive sessions.