Working with Function Threshold Power

Pushing your threshold

For triathlon, maximal aerobic capacity or VO2max is seen as an important determinant of endurance exercise performance. However, your ability to sustain a high percentage of your aerobic engine, for a prolonged period, is arguably a more important factor. Being able to sustain a high percentage of VO2max means that we must tolerate accumulating blood lactate at higher exercise intensities.

Your functional threshold power (FTP) represents the highest power output you can sustain for 1-hour without fatiguing, and is closely correlated to the second lactate threshold. Over recent years, FTP has been used as a key performance benchmark in both cycling and triathlon from which to measure training effectiveness and predict future performance.

Before we go any further, let’s clear up a few myths about lactate. Blood lactate is constantly being produced by our bodies, even at rest. It allows the regeneration of a substance called NAD which, in turn, enables glycolysis to continue to make a meaningful contribution to energy production. So rather than cause fatigue, lactate does its best to prevent fatigue. However, as we begin to increase our exercise intensity, blood lactate production does increase above resting levels, and this is generally referred to as the first lactate threshold. It can also be associated with a more rapid increase in heart rate and respiration. It represents a shift away from moderate exercise to heavier exercise.

If we continue to exercise at increasing intensities, the rate of lactate accumulation in our blood becomes greater than the rate of clearance. A second lactate threshold can be determined, and this tends to represent the boundary between heavy and severe exercise. It’s this threshold that is closely correlated to your FTP.

What is my FTP?

Before embarking on any training plan, it’s important to try and determine the intensity at which your FTP occurs. This is to ensure that your training is structured in a way to avoid accumulating fatigue and potentially over-training. You can determine your FTP by using a 20-minute test protocol or a sustained 60-minute effort. If you use a power meter then your FTP would be the normalized power for an all-out effort of 60 minutes. Alternatively, you can get a fairly accurate estimate of your FTP by doing an all-out 20-minute effort, then subtracting 5% from the average power value for that interval. If you use heart rate as a way of setting your training intensity, then you can use the average heart rate from the 20-minute test without subtracting the 5%.

An alternative way to determine your FTP is by blood lactate profiling, which we use at trainSharp. The 20 and 60-minute efforts provide an estimate of your functional threshold power whereas blood lactate profiling takes away the guess work and accurately identifies your body’s response to exercise at different work rates. In addition, it also identifies both lactate thresholds, which is important from a coaching point of view.

Whatever method you use to determine your FTP, being able to increase it will be key to improving your performances.

How can I boost my functional threshold power?

Quite simply, you need to train at, or near to the work rate associated with your FTP as well as increasing the duration of these efforts. For some of us, this will involve really working outside of our comfort zone for prolonged periods of time. Being able to increase the contribution of fat oxidation to energy supply during exercise (sparing muscle glycogen/blood glucose), reduce the recruitment of the faster type II muscle fibres and decrease the rate of accumulation of lactate are key training adaptations that you would expect from this type of training.

To get you started, I would recommend that you start with the following session:

Threshold ‘pushing’

  • Try starting with a 10-minute incremental warm up progressing through zones 1, 2 and 3.

  • Finish the warm up with 5 minutes easy spinning then straight in to the threshold pushing efforts which should be approx.. 90-95% of your FTP.

  • Try starting with two reps of 8 minutes with 10 minutes easy recovery between them. Find your rhythm and aim to hold a nice constant cadence and power.

  • Warm down 15 minutes

Aim to increase the duration of each rep by 2 minutes each week over a period of 6-weeks.

This session can be done indoors on a turbo or incorporated into a longer ride.

As you get towards the end of this 6-week threshold ‘pushing’ block, you can look to increase the intensity a bit. I’ve set out a session below that we use with some of our elite triathletes like the 2016 Ironman 70.3 World Champion, Holly Lawrence. This is a tough session so be prepared to push yourself outside of your comfort zone!

Threshold ‘pushing & pulling’

  • Try starting with a 10-minute incremental warm up progressing through zones 1, 2 and 3.

  • Finish the warm up with 5 minutes easy spinning then into the efforts alternating 2 minutes spent just above your FTP then aiming to recover for 2 minutes at or just below your FTP.

  • Aim for 2 reps, recovery for 5 minutes then go for another 2 reps.

  • Finish with a 10-minute warm down.

Aim to increase the numbers of reps by 1 each week over a period of 6-weeks.

The first time you ride this session it will feel very tough, perhaps bordering on an all-out effort by the end of each interval. Make sure you are well fuelled, hydrated and suitably motivated for a tough session.

Try not to spike the power in the first few seconds of the lifts, aim hold the power as consistent as possible whilst maintaining a nice, smooth cadence. After a few weeks, your body will adapt to the increasing training load.

Whilst training at, or just above your FTP is hard, it will reap rewards! Try to avoid the temptation to suddenly start increasing the duration of your higher intensity training sessions. Although you may feel this is important for building confidence, it’s likely to increase your recovery time and expose you to an increased risk of injury.

For more information on trainSharp coaching and fitness testing packages email or call us on 01892 577802.

Good luck!

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