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Threshold Intervals versus Speed-Work

By Donovan van Gelder - Cybercoach

One of the more interesting aspects of a training session is the ratio of interval length to recovery time. How we plan this changes the characteristics of the session, the perceived effort and the potential outcome.

I thought of this post when I downloaded my 20 X 100 swim session last week and could clearly see the impact of different recovery times. This particular session had a reducing recovery. I started leaving every 2:00 and then reduced the recovery time by :10 every 5 reps so that the last five were leaving off 1:30. Looking at the screenshot of the HR curve from Polar Flow, you can see what an impact this had on my recovery HR.

A short recovery period does not allow the body enough time to totally process metabolites, and completely resupply the working muscles with oxygen and nutrients before we go again. So we are giving the body stimulus that will force it to adapt to performing under a constant stress and improving it's performance at a consistently high effort level, such as it experiences when we are holding a high effort for extended periods.

A long recovery period in relation to the interval time allows the body to recover more between each repetition. This will allow a higher exertion level in each interval. There will therefore be less adaption to the 'Threshold' or sustainable effort but that is not what we are training in a session like this. This is 'Speed Work', where we are looking at more of a muscular and neural stress. We are providing the body an opportunity to improve it's force, speed and mechanics. To do that we need to go fast and then give the body enough time to recover properly so that we can repeat that level of exertion again. Without enough recovery time, the quality of the effort would drop, we would lose form and the muscles will fail to produce the force of the interval before.

So as an example we can look at a set of 10 X 400 on the track. Looking to improve our ability to hold a high pace for an extended time, like running a fast 10km or half marathon we would look at running at around 5km race pace, which is not that hard to hold for one lap of the track but, we would want to limit the recovery to around half of the time it takes us to run the interval. Your HR will get slightly higher with each interval and not drop as low between each one. It will also move in quite a narrow range between the minimum and maximum achieved during the set.

If you are happy with your ability to hold a hard pace for a long time but feel that you cannot accelerate from that pace or you don't see a significant difference between your pace per kilometre in your 5; 10 or 21.1km races, you would want to improve your speed, pick up your cadence and improve running mechanics. Then you would want to run the 400s fast, not far off a maximum effort for the distance but then allow yourself what feels like complete recovery, around double the time that it takes you to do the interval or even slightly more.

When I say it 'seems like complete recovery' I mean you feel fresh again and your HR will have dropped to recovery-session levels before the next interval. So you will see a wider range between your maximum and minimum HR achieved during the set. The recovery will obviously not be complete because the muscles will not be recovering completely and they will eventually not be able to sustain the effort.

So the same set of 10 X 400 can have different outcomes as far as how it affects the body when we alter the recovery periods and the intensity of the efforts. As triathletes we are aerobic animals. Pretty much all of our racing and therefore training efforts are below the anaerobic threshold and we need to train ourselves to maintain that uncomfortable effort. However, adding speed-work at the appropriate times in our schedules can make a big difference to the speed that we can maintain at that uncomfortable effort.

We just need to convince ourselves that we are not being lazy when we have a long rest between intervals