Why Time-Trialists should consider Anaerobic Training

It may sound counter-intuitive to suggest that Time-Trialists work on their anaerobic system, the system that delivers a boost of energy when we work very, very hard, above our anaerobic threshold.  These kinds of efforts can only last up to a few minutes and therefore, may not seem relevant to time-trialling.

Most Time-trialists will know that Time trials are mostly an aerobic endeavour, meaning that the power to fuel this kind of riding comes mostly from “burning” fat in the presence of oxygen (hence the term aerobic). So why bother with anaerobic training?

In this article I will try to show why this is a good idea, what happens when we do it, and some example training exercises.

First we need to understand the aerobic system and the limitations to TT performance improvement.


When riding hard, there is a physiological turning point at which if we go too hard, or “into the red” or “into oxygen debt” we will be using our anaerobic system – burning sugar (glucose), which creates lactic acid. As we all know, do this too long and you soon tire and cannot maintain such a high pace.  We then have no choice but to ride along at a slower pace.  We can only ride to the maximum capacity of our aerobic system at this point. It is all we have left, the anaerobic system by this point is depleted. We will have to ride even slower if we are to re-charge it for use again later.

This turning point is known by many names, but the most commonly known is “threshold”.  The power at which this happens is a rider’s FTP – their Functional Threshold Power – the magic number that Time-Trialists love to talk about.  It’s the number we want to see going up if we are going to go faster in our races.  However this isn’t everything…

Aerobic Engine

To train FTP is generally well known.  We need to do a lot of work to improve the capacity of the “aerobic engine”:  lots of time spent doing long slow(ish) miles, and interval work at or around threshold power or HR level.

This is a great but very slow way to improve FTP.  However the gains from this approach accumulate year after year and fade fairly slowly, so it should definitely be the main-stay of your training. 

This approach to training is “pushing up your FTP from below”.  In time, we find that we start to bump up against a ceiling and improvements to FTP get harder and harder to come by.  We need to increase the volume of low intensity work more and more to see bigger improvements – that means even more time riding at a fairly low intensity (HR zone 2 in the 6-zone system)…doesn’t it?

Professional athletes have the time to do this, and it is this time they have available to do a *lot* of low intensity miles per week that gives them a superior aerobic system and hence better aerobic capacity than an amateur.  A pro will ride perhaps 25-35 hours per week or more vs and amateur riding 4-6 hours per week.  *Mostly in HR zone 2*, nice and easy.  Generally 80% of their bike time will be spent like this in fact.  The other 20% is spent doing hard, very, very hard, “quality” intervals at or above threshold (zones 4, 5 and above).

Notice very little work in the “dead zone” in zone 3 where most amateurs tend to gravitate towards!  Making the easy days easy and the hard days very hard is the “secret sauce” to really effective endurance training that leads to great performance.  An additional ingredient to the sauce is that you must “rest hard” on the rest days!  It is during this time that the body gets the opportunity to take the stimulus given to it in training to adapt and rebuild the body to cope with the higher demands being put on it.

The Ceiling

The ceiling we start to hit that limits FTP improvement is a critical component of the cyclist’s physiology that you don’t seem to hear talked about so much in amateur circles.  Namely, VO2 Max.

What is VO2 Max?  It is the maximum amount of oxygen an athlete can deliver to working muscles and make productive use of.  It is measured scientifically as volume of Oxygen (O2) in mL per minute, per kg of rider weight, mL-O2/min/kg.  A pro cyclist will tend to have a VO2 max in the range 75-85, with Greg Lemond supposedly hit 90 mL/min/kg.  A decent club rider may be in the 45-55 mL/min/kg range.

Maximum FTP can be expressed as a percentage of VO2 – mainly in the lab due to difficulties in measuring VO2 “in the field”.  Most well trained cyclists may see their FTP at around 75% of VO2 Max.

Therefore, it follows if we improve VO2 max, we create headroom for FTP to improve.  In fact FTP will tend to follow VO2 gains upwards once a good aerobic base fitness has been established.


In order to understand what workouts are beneficial to the  improvement of VO2 max, it is useful to understand the physiology that underpins it.  If you are not interested in the physiology of VO2 max, feel free to skip ahead to the next section.

Below are the physiological items that affect the delivery of oxygen to our muscles, which are what together contribute to our VO2 max.

  • Lungs – This is obviously where Oxygen comes into and CO2 goes out of the blood stream.  Not a huge amount of trainability unfortunately.  We get what genetics our parents have given us here.  Smoking and lung diseases can obviously have detrimental effects here.
  • Heart.  Stroke volume and stroke force. Aerobic training at low intensity will increase the size of your heart – this is why very fit people of a low resting heart rate – it doesn’t have to beat so much to deliver the basic oxygen needs of the body.  The thickness of the heart walls make it a more powerful pump able to drive the oxygen into the arteries and capillaries in our muscles.  Long-duration low-intensity aerobic exercise will increase heart stroke volume.  Very high intensity exercise will improve the power of the heart and increase muscle thickness.
  • Blood cells/Haemoglobin/Haematocrit/EPO/Bone Marrow: Red blood cells carry the oxygen in our blood. Not a lot we can do here but eat a good balanced diet with plenty of micronutrients (vitamins, minerals), get good sleep, and stay well hydrated.  Your bone marrow produces new red blood cells constantly as they only live for 120 days.  Iron is important for this process as are other vitamins and minerals.  Giving blood will definitely hinder aerobic performance for a few weeks whilst red blood cell production catches up.
  • Arteries, veins, capillaries: These carry the blood to the muscles.  Long-duration low intensity aerobic exercise *will* increase their number as will high intensity exercise.
  • Mitochondria.  These are the magic cells in the body that “burn” fat with oxygen and produce the energy to power our muscles.  They are also responsible for converting lactic acid (technically it’s a different compound, that later on leads to lactic acid production) back to re-usable energy – so recovery from lactic acid is done mainly via the aerobic system.  Another good reason for a good “aerobic base/engine”.  We can create more of these wonder cells by (yes you guessed it) doing Long-duration low-intensity aerobic exercise. With high intensity exercise we make the mitochondria more efficient.
  • Muscle Fibres.  We can convert some type 2 fibres into aerobic fibres with training, thus giving us more aerobic capacity.  Long-duration anaerobic intervals will achieve this.
  • Efficiency improvements in the aerobic system.  Anaerobic workouts will do this.

Anaerobic training

How do we improve VO2 max?  This is where (finally you say) the anaerobic training comes in.

In a nutshell we need to stimulate the improvements in cardio-vascular system, namely the heart, blood capillaries.  This means high intensity exercise.

This kind of exercise should only be scheduled in your plan after establishing a good solid aerobic base and some time working at threshold.  Useful for 4-8 weeks before an important race or start of a season.

To develop VO2 max, we need to spend time at a high heart rate, 90% of maximum to provide the required stimulus.

Before we get into training specifices, some health warnings.  Sorry to be a bore, but this is very important.

  • High intensity exercise of this nature should not be undertaken if you have heart problems.  You should check with your doctor that you are ok to start this kind of training.  I would suggest seeing your doctor if you’ve never done high-intensity training before, even if you don’t think you have any issues, especially those over 40.
  • Do not undertake this kind of training if you haven’t been training for a while.
  • You must already have a very strong base of aerobic fitness and be in good health and condition – i.e. no injuries that may be aggravated by the training.
  • If you feel faint or ill when doing the workouts.  Stop immediately!

Also some advice on performing high-intensity training;

  • Be well rested before doing the training.  Do these after a rest day.  It is the quality of the efforts that will lead to improvement.
  • Keep well hydrated and cool (use a fan if on a turbo trainer.)
  • Don’t do them when hungry.  Be well fuelled before starting.  Have a small carbohydrate snack 1hr to 30 mins before if necessary.  You also may want to have a carbohydrate drink with you when doing a high intensity workout.
  • Don’t attempt them if you are feeling tired or under the weather, especially if you have a cold or flu!
  • Only do these once or twice per week, for up to 8 weeks.  More is not more in this case!  These are very effective but are very fatiguing and you will soon hit your physiological limits.  Carrying on beyond this will only lead to chronic fatigue and illness.  You won’t get any fitter and you will get slower!  Move to a maintenance level through the season.
  • Concentrate on safety if doing these on the road!  Find a safe and quiet place to work.
  • You need to be very well motivated to do these intervals.  If you’re not feeling energetic or motivated, you could make a start and see how you feel but it is easier to get through these if you are “up for it.”

Suggested Workouts

Now for the section I suspect many of you will skip straight to.  Well I hope you’re proud of yourselves!  For those who did read through, thank you, I hope you learnt something.

Remember to warm-up for at least 15-20 minutes before doing these workouts.  Start with 5-10 minutes riding steady at a fairly gentle pace (HR zone 1-2).  Then start to ramp up the resistance/HR and include a few short “bursts” of power every 30-60 seconds, then at the end ride easy for a further 5 minutes.

30s Micro-intervals

  • Go “all out” as fast and hard as you can for 30 seconds, in a reasonably heavy gear and accelerate up to and hold 120 rpm if you can.  The pedal pressure should not feel easy but fairly hard.  If you start to bounce in the saddle, increase resistance or change to harder gear and/or lower the cadence.  Do these in the saddle but as a variation you could do the first 5-10 seconds out of the saddle.
  • Ride in an easy gear at a gentle pace and low cadence for 30 seconds. 
  • Repeat until you cannot put in a really good productive effort.  Should probably be around 3-6 repetitions.  You will find that your HR will rise rapidly.
  • Recover for 4-5 minutes (or as long as you need) and repeat the above.  Try to do 3 sets if you can.  If you can’t that’s fine that’s something to work towards next time.
  • Cool down with an easy ride HR zone 1 for 10-15 minutes
  • Have a good stretch, get some carbs on board or a recovery shake within 30 minutes of the workout for the most effective recovery.

For those with a power meter, you should be looking to do at least 120% of FTP on these if you can. Certainly above 110%.  If you cannot do it at that level, then you will need to do an FTP test to get the correct level set for your FTP.

Effort level should feel 8-9 out of 10. We’re looking to empty the tank with these, which is why the recoveries between each effort are short and won’t feel like they are enough.  The “draining of the tank” is what causes the stimulus to improve, so you can’t go making these easy on yourself – they have to be brutally hard, sorry.

If you find these too difficult, you could try increasing the recovery between each effort to 45 or 60 seconds, but be aware, the idea is to drain the anaerobic tank in about 4-5 minutes.  The efforts should feel progressively harder.

If on the other hand it is too easy for you, you may need to increase the power or resistance level.  You can shorten the recovery time to 20 or even 15 seconds if you find that you are hitting the target HR zone, and recovering very quickly or not draining the tank very quickly, i.e. those with a very large anaerobic capacity – over 22kJ FRC/W’ for example.

For a more advanced workout you can try 40s on 20s off.  Another advanced alternative is “tabata” intervals at 20s “on” and 10s “off” at 170% FTP.  Beware this should only be attempted by those who can do the intervals above at around 140-150% FTP.

Vo2 Max Long Intervals

These will pull up your VO2 max, but will also improve you anaerobic endurance – your ability to ride harder for longer.

Ride as hard as you can for 4 minutes.  Try not to “peak and fade” but pace the effort like a very short time trial – an even effort over the time.  It may take a few goes to get a feel for the effort level required. 

Effort level should feel 8 out of 10 – harder than a 10 TT effort.

For those with a power meter you should expect to ride these at around 110-120% of FTP. 

Because HR lags somewhat behind the effort, it’s not so easy to give a HR range, but your HR should get to around 90% of maximum by the end of each interval.

Between intervals ride very easy with little resistance for 4-5 minutes, until you feel ready to go again.

Repeat these 3-6 times as you feel you can manage.  If in doubt, start at the low end.


You can treat these as a “mini TT”.  You can see how far you can get in 4 minute or time how long it takes you to ride 2 or 2.5 miles.  See if you can improve on this next time, make a game of it.

Try adding a 15 second sprint at the start of each interval.

If you are struggling to hold the intensity for 4 minutes, reduce to 3 minutes (no shorter than this though) and build up from there each week, 3:15, 3:30, etc.  If you cannot hold the intensity for this shortened duration, you probably are lacking in base aerobic training so I advise working on this first.


Time-trialling is an *almost* 100% aerobic endeavour.  The longer the time-trial, the more this is the case in percentage terms.  It follows that shorter races have more of a contribution from the anaerobic system, but this is still only a few percentage points. 

Even so, as we discussed, it is of benefit for all time-trialists to do some anaerobic training after establishing a good aerobic base,  leading into the season or an important race, and for maintenance throughout the season, not only because they are likely to push into the red on harder sections of a course, but as the science shows that it leads to “pulling up the FTP from above” by raising the ceiling to FTP, VO2 max.

I hope you enjoyed this article.  If you have any questions or would like to discuss your training plans, please get in touch via coach@velo121.com