But these key sessionswhich took place in the final few weeks of the planwound up being entirely manageable.

They just werent quite possibleyet.

That process is why we train.

It allows you to improve incrementally, and ultimately to do things you didnt think you could.

And it all depends onpatterning, or properly varying effort throughout a given training week.

Most runners have heard of the easy/hard rule, where effort alternates from day to day.

This general rule always formed the backbone of our training programs.

And this patterning reflects a concept calledtraining density.

And once you understand density, youll be able to plan your own training much more effectively.

What is training density?

Training density reflects the pattern of effort throughout a certain time period.

If density is low, the overall workload is spread thinner with fewer high-quality training sessions.

High training density doesnt just mean that there are more challenging workouts and long runs.

It means that those key training sessions are closer together, resulting in less recovery between hard days.

This necessitates 1-2 days of recovery between each quality day, resulting in a denser schedule.

In other words, density is either too high or too low.

But this goal requires a Goldilocks-like level of densityand getting it just right is tricky.

High-density schedules can be objectively too difficult, but they can also berelativelytoo difficult.

And any schedule that includes back-to-back hard days with no easy days for recovery is almost always a mistake.

That said, certain schedules that arent inherently too dense could be too difficult based on your fitness level.

There wont be enough stress to spur those beneficial adaptations, which then leads to stagnating performances.

There simply isnt enough hard work in their regimen spurring them to move forward and improve.

If youre a beginner or intermediate runner, its best to limit yourself to one faster workout per week.

Lets look at two different examples of optimal training weeks.

This will help you plan your own training schedule, and hopefully find that Goldilocks sweet spot.

Theyre as evenly spaced as possible, allowing for 2-3 easy or rest days to allow for ample recovery.

They are also spaced as evenly as possible, allowing for 1-2 easy days in between each hard session.

They dont include back-to-back hard days.

Which sounds just right to me.