Long Run For 100km Trail Race

How to approach the long run for 100km trail race.

There’s an important concept we need to get our heads around. The speed we race a 100km race is relatively slow.

Compared to your 5km or half marathon speed, 100km is run significantly slower. This needs to be remembered when we are setting up our long run training.

How Long Is Long For 100km?

By following some principles we can get to an optimal long run distance.

Long is relative. It begins with a distance near the edge of what you can comfortably run. This could be 10km or it could be 40km. It depends on your training history and current fitness.

If you are looking at taking 16 weeks to train for a 100km race I recommend being comfortable at 25km.

You want to be able to build up to a peak of at least 40km or 4 hours. This will ensure you develop the physiology to go really long. The magic happens after 3 hours.

Referring back to 16 Weeks to 100km Training Plan, you want this peak run to be reached by 12 weeks. We start reducing the length of the long run after this.

Is it worth going longer?

The short answer is… maybe

That maybe depends on your ability to handle the extra distance. If you can handle, absorb and adapt to the extra distance then go for it.

However, any of the following will rule out going further:

  • Carrying an injury
  • Still feeling fatigued beyond 2 days after a long run
  • Recent long runs have a dramatic slow down in their second half
  • You struggle to perform the other key runs

Some runners may benefit from 1 to 4 long runs pushed out to 50km or 5-6 hours. Don’t under estimate the impact these runs have. Make sure you get in some sleep, eat well and focus on recovery afterward.

How Fast For The Long Run?

This is specific for a 100km ultra marathon. When training for shorter distances, it will be a different answer.

Now we get back to the concept that the speed we race a 100km race is relatively slow.

Be realistic. How fast will you really average over a 100km race?

Write the answer down.

Most of your long runs should be around this pace.

Take aiming  for under 12 hours to win the beer stein at Surf Coast Century. Giving 10 minutes buffer, 11hr 50min is a pace of 7:06/km or 11:21/mile. Most people in this chasing this time should be capable of a road marathon under 3hr 40min (5:12/km, 8:20/mile). In this example you want to make sure you are very comfortable at around 7:06/km over similar terrain to the race.

Is There Benefit To Going Faster?

You need to earn going faster.

To do so will require the following

  • At least 2 runs of 4 hours or more
  • Those runs must be completed at around 100km race pace
  • You need to feel comfortable in these runs
  • There is no big slow down towards the end

Going faster is best reserved for the peak phase of training. There are a few ways to approach this:

  • Start at usual pace then gradually and continuously increase the speed over the last 30-60min of run.
  • Start at usual pace then towards the end add 3-4 intervals of 10-20 minutes about 1 minute per kilometre faster than race pace. Take 10 minutes back at usual pace between intervals.
  • Negative split the long run with first half at usual pace and second half 15-20 seconds per kilometre faster.

These options look easier on paper. The pacing discipline required is hard.

Do you have the discipline to get the most from your long run?