Endurance 101: Zone 3 - Zone 3 Tempo and Sweetspot (SST) Made Simple

What is zone 3?

As we've discussed in earlier posts in this series, the "zone" system is a way of attempting to divide the range of possible power outputs for a given athlete over various durations into a progressive series of numbered zones, in ascending order of intensity. This helps provide a common language for both the description and prescription of training sessions and intervals. It does so by anchoring them to one or more underlying physiological parameters where possible, in order to make these numbered zones as objectively discrete as possible within complex biological systems.

The name "Zone 3" is sitting almost in the dead centre of our 7-zone model of exercise intensity. Unlike many of the other zones, it is not named after an energy system or physiological boundary but an old French and Italian term - "tempo" - that is inherited from the birth of modern cycling in Europe in the early twentieth century.

Where did tempo get its name?

The first competitive endurance cycling events, like the first Tour de France, competitors rode as privateers, individual and often solo efforts to handle routes. They often rode alone and at night, covering the huge distances not en masse or, as now, in formal daily stages but just in sections for as far as their legs could carry them before sleep overcame them. It perhaps bore more resemblance in that respect to modern ultra-endurance rides such as the 4,000km+ RAAM (Ride Across AMerica).

However, the evolution of the event and others that sprang up soon saw the introduction of changes and argued advances such as formal, initially national, latterly commercial teams, and grouped, "bunch" or "peloton" riding. It was within this context that the term "tempo" or "a tempo" evolved to describe the base pace or ride cadence of a group of riders in a race following some adjustment, such as settling into a steady but hard effort following a break, surge or sprint.

"Tempo" pace as a concept therefore predates more modern developments such as heart rate monitors, power meters, lactate testing and VO2 respiratory carts. It is just a "comfortably hard", reasonably high-speed cruising pace that a group of riders can maintain for many hours. Along with other terms like "peloton", "bidon", and "rouleur", "tempo" has been adopted into the international cycling vocabulary. In our 7-zone model it has been adopted to denote an intensity greater than endurance (all day) and threshold (FTP) pace.

What sets tempo apart from zone 2 and zone 4?

As we saw in our earlier post on "zone 2" riding - that is, riding in our endurance zone - zone 2 is the highest intensity at which we can ride such that our blood lactate levels hit an inflection point beyond which they no longer remain quasi-stable but start to increase slowly but steadily. In the same way, we saw in our "zone4" or threshold/FTP post how our threshold power was the maximum power output that we could sustain before our blood lactate levels hit a second inflection point - LT2 - and begin to climb very rapidly to an unsustainable level.

Since most of us are not fortunate enough to have the option of continuous and ongoing lactate monitoring while we ride, this definition is of limited practical use to us in the field. If you are in a steady-state ride-e.g., ERG mode on a turbo trainer-and have a power meter, then it is possible to accurately target tempo pace simply by selecting a pace that is around 10-20% under your determined FTP and sticking with it.

But outside of that, and elsewhere, it is very helpful to develop a "feel" for what riding at tempo feels like. In Zwift you might be able to train yourself on this by picking a RoboPacer one or two steps above the one which you can comfortably ride with at endurance-empty pouches-all day-pace but not so hard that you are forced to drop within 4060 minutes.

How does tempo pace feel?

Tempo riding feels like you are working hard but sustainably. You might have experienced it on a hard group ride of around 2 hours in duration, especially on a flat route. At least initially, and at the lower end of the intensity range, it doesn't feel cruel in the way that a hard threshold effort can do. Some find that toward the lower end of the tempo range, they reach a sort of "flow state"-an almost meditative experience in which they can somewhat dissociate from the effort and just push on.

Less poetically, tempo is highly aerobic in nature, so your breathing rate should be elevated, but remain deep and controlled, rather than lapse into harsh or laboured gasping. If using the "talk test" to help you assess your perception of exertion, you should be able to speak an individual long sentence though not multiple consecutive ones-without letting up on the pace.

Off the back of a long block of tempo, or at the higher tempo intensities that edge towards threshold, things might start to get a little tougher.

I've heard tempo called the "Grey zone" and been told never to ride in it?

Many will tell you that tempo pace is a "grey zone", "junk miles", or "no man's land" - an intensity that is counter-productive to effective training and must be avoided. Like many things you hear this isn't true, but rather an appropriate mis-communication of a somewhat more nuanced idea that holds some merit.

Wait, so tempo has positive training benefits?

Absolutely. In fact, tempo riding is super-effective for your cycling training. In fact, it would provide many of the exact same benefits that this highly-lauded and championed "zone 2" does, but more so. This is partially reflected in some of the recent coaching and research literature by moving away from using the terms "endurance" (zone 2) and "tempo" (zone 3) and instead recognizing the large degree of overlap and similarity that exists between them. Newer sources, as such, sometimes refer to zone 2 as "extensive aerobic" and zone 3 as "intensive aerobic", thereby identifying these two as tightly coupled training zones in nature.

Tempo's development is very good, particularly for aerobic power and endurance. Just as "zone 2" or endurance riding is very aerobic, riding at this intensity can stimulate mitochondrial development. However, the tempo pace includes an increase in effort and thus forces our bodies to cause a significant amount of extra lactate, some of which enters our blood stream. It may or may not be true-debated, although high blood lactate has been associated with possible acute blunting of adaptive signalling to mitochondria, which would be counter-adaptive. However, tempo riding is a good way to train our bodies in the optimisation of the processes involved in the clearance of excess lactate from working muscle and to recycle it as an energy substrate-fuel-for our cells. This would help to increase our effective lactate threshold, the holy grail of many cyclists.

Why does tempo get called the "Grey zone" then?

The original criticism levelled at tempo is not that is is ineffective as a training intensity. It is that training solely and exclusively at tempo is ineffective training. This is, of course, an entirely different claim. Riding in any one single zone - whichever zone that is - is likely sub-optimal for our training, after all.

The intention here is not to deconstruct criticism, but rather to grasp where the more refined criticism originates from and better understand whether it is valid. To do this, there are competing claims regarding optimal training intensity distribution that need to be understood.

What are training intensity distributions?

We have also already discussed how the intensity that we cycle at exists in an inverse relationship with duration, or in other words, we can do either a long time at low intensities-for example, an endurance ride-or a short time at high intensities, such as sprinting. Indeed, "zone3" is actually a numbered zone on this intensity-duration scale.

However, besides simply knowing each one of the zones covered in this series of posts individually, it is also very important to understand the amount of training we're doing-or want to do-in each intensity for meeting our own individual goals.

Training intensity distribution is the attempt to model or describe this either for descriptive or prescriptive purposes. The training intensity distribution summarises how much of the time that we spend cycling is spent in different intensity zones. This analysis can be done for the course of a single ride, the course of a single training week or block, or even for an entire season.

Whatever the range of time, from individual ride to entire season, we could end up with a distribution pattern such as "20% zone 1, 70% zone 2, 9% zone4, 1% zone 6". OK, but now what? That's quite a mouthful. And even if we aim to keep the same balance of intensity in our next ride or week, those numbers might be slightly different. And what if we want to compare our riding to others, or to investigate as a researcher what is optimal, amongst such a noisy set of data?

Researchers and coaches have therefore come up with names for a few common patterns of intensity distribution-such as "base", "polarised", "pyramidal" and "threshold"-which millions of unique exact permutations of training distributions can be lumped into.

Which intensity distribution involves riding all of the time at tempo?

Riding all of the time at tempo doesn't really have a name per se assigned to it, but is probably closest to what is known as a "threshold" intensity distribution, in which the greatest proportion of riding is performed at a moderately hard intensity.

Why does a threshold intensity distribution come under criticism?

The main opposition to threshold intensity distribution comes from those of the "polarised" intensity distribution model currently in vogue. In this model, training prescription is bifurcated into two highly contrasting training intensities and little or no time is spent around threshold and tempo intensities. This clearly constitutes a diametrically opposed training intensity distribution compared with a threshold intensity distribution.

Perhaps the best-known variant of polarized intensity training distribution would be that riders complete roughly 80% of their sessions-us note, not overall ride time-at a very low intensity, zones 1 and 2, to provide base aerobic fitness, allowing for recovery with minimal fatigue. These might then fill in the rest of the sessions-maybe once or twice per week-with very intense sessions: HIIT sessions, such as VO2max intervals, micro-intervals, or sprint interval training (SIT).

This pattern of distribution has also cropped up in the training distribution of many elite athletes at various times of their training calendar and has also been shown to be very effective in eliciting rapid improvements in untrained athletes unaccustomed to training.

Is a polarised intensity distribution optimal?

Yes. Also no. Oh, and "maybe", too. Whilst flame-wars and picking a hill to die on are as popular pastimes as ever, even among highly-regarded academic researchers and coaches, the truth is that a more nuanced answer is, as ever "it depends".

It depends on your training history, it depends on your power output, it depends on your time available, it depends on your life's stress, it depends on your training distribution to date and hence what offers a novel stimulus, it depends on your goals, it depends what you enjoy and will stick to in terms of training compliance.

Its OK to do tempo then?

Yes, provided your needs and requirements are met. The important thing is to understand what the benefits are that tempo can bring, and how to fit tempo into an overarching training plan.

When and how should I incorporate tempo into my training?

There are three primary ways I believe that threshold sessions are most commonly incorporated into a wider training plan.

First, when you are either in or transitioning out of a period of base training composed primarily of zone 2 riding. It is good, provided you can do this without incurring excessive fatigue, to gradually acclimate your body to high-intensity riding through a graduated ramp, moving the intensity progressively higher as you transition into a more focused "build" phase.

The second is when your target event is to be ridden at tempo pace and you need therefore to increase your specificity of riding at your intended pace as the event approaches. For example, if you are an Ironman athlete then you may find that your target event requires you to ride at a tempo pace for perhaps the entirety of-or at least a substantial percentage of-the bike leg. In this case, becoming comfortable riding at tempo is critical to success. In this way, an athlete in such a scenario may choose a reverse periodisation strategy for the intensity distribution of their season. That is, conducting a period of polarised or high-intensity training at the beginning of their season, before steadily transitioning their intensity distribution to a race-specific threshold intensity distribution which features a high volume of tempo work.

A third possibility is that we are what is commonly termed a "time-crunched" rider. Even the most ardent proponents of zone 2 or polarised training generally accept that there is a lower limit in terms of weekly duration in which an 80/20 or polarised intensity distribution remains optimal. Below this limit-which will depend on your age and training history, but may be in the neighborhood of 6 hours per week for many athletes-you could safely replace some or all of your zone 2 rides with tempo rides instead. This is because at such low volume, there is so to speak ample time for recovery or shedding fatigue from tempo rides before key or priority sessions will have to be made at high intensity.

There might be a variant of this sort of scenario where an athlete has more than 6 hrs available per week to train but is only able to train in-for example-45 minute blocks at any one time because of family and work constraints on scheduling. This athlete, too, would probably be best off performing non-key sessions at tempo rather than endurance pace, or using an entirely alternative intensity distribution.

You might realise by now that in all these three scenarios, an athlete is never alone riding at tempo pace. You should also notice that you do not have to pick a hill and die on it. You don't need to pick a camp and declare yourself a polarised training athlete and stick to it. Life's different week to week, and the knowledge to adapt to circumstances, and train in every and any zone when it's optimal, gives you an automatically huge key advantage over the less flexible athlete.

What Intensity Should I Ride Tempo At?

"Tempo" is a pretty broad range, normally given as being around 75% to 90% our threshold power. The very upper end of this range, as it blurs into our threshold zone - at around 85-95% of our FTP - is sometimes called the "Sweetspot", and training in this zone referred to as "SST - SweetSpot Training".

The name "Sweetspot" comes from the claim that, of all the possible training intensities, it offers the best "bang for the buck". That is, it reaches an optimum balance of a positive training stimulus against a negative fatigue value. By this point in the post, it's hopefully pretty clear there can't be one "optimal" zone in any absolute sense, and that what is needed is a more nuanced distribution of training intensity, particularly over time.

How does tempo get applied to workouts?

The first way in which tempo workouts can be performed is as a single, steady state effort for the entirety of the session-after warm-up, sometimes referred to in the research literature as "MICT-Mod­erate Intensity Continuous Training"". All you do is warm up, pick a tempo pace, and hold it until fatigued or until you run out of time.

A second variant of the above-more commonly seen in running than in cycling-is the so-called progressive aerobic session, in which you might start your warmup in zone1, continue ramping up the pace through zone 2 (endurance) pace, and then continue to gradually lift the pace until you are working in the tempo range, perhaps over the course of several house. This is also termed a positive split. You could hold this rhythm cadence for the entire ride, or continue to push the progression to at least threshold pace. This version is reportedly a particular favourite of the professional Kenyan runners, but so far has found very little popularity among cyclists.

Fifth, and most common, tempo pace may be divided into a series of intervals performed either evenly spaced throughout an otherwise zone 2, endurance, ride, or else bunched at the end of such a ride. This is theorised to stimulate increased resistance to muscular fatigue. It is also claimed to yield increases in muscular endurance through the simulation of the type I, or "fast twitch," muscle fiber recruitment seen in much longer purely zone 2, or endurance, rides-performed as it is at low cadence, particularly towards the end of a ride.

Similarly, tempo might be done in ad hoc longer endurance rides that are otherwise conducted at tempo. Coaching company CTS specifically differentiates longer aerobic rides into two subtypes: "foundation" rides performed exclusively in zone 2; and "endurance" rides which are more flexible and specifically allow both tempo and endurance paces throughout, in order to accommodate terrain changes and infrastructure changes outdoors, or maximizing engagement indoors.

Finally, and perhaps most commonly for so-called "over under" workouts, the tempo pace is used as the "not-quite recovery" pace between threshold lifts. Inclusion here is due to some research that suggests that the targeted lactate clearance from the muscles is best, most optimally trained at a mid-tempo pace ‌‌disputed, or at least open to interpretation‌‌.

What is the overall time in zone for tempo sessions?

In theory, it would be possible for an athlete to sustain endurance pace for 4-6 hours, but such an effort would require optimal fuelling and fatigue/rest state, and high mental fortitude. You would not normally see such efforts outside of key race performances.

Instead, tempo sessions are usually prescribed as 30-120 minutes or 0.5 to 2 hours, depending on the exact intensity range selected higher intensities near threshold have correspondingly shorter session durations.

What length should tempo blocks be if one is not continuously riding?

When done as intervals within a longer endurance ride, a tempo interval might be perhaps as short as 20 minutes for a high intensity SST interval, right up to 60 minutes for a typical lower intensity interval performed at around 75-80% of FTP.

For the very lowest end, a tempo interval could be as low as 5 minutes in duration when specifically targeting the low cadence, high torque for muscular endurance adaptations.

Should I go for a higher duration or higher power to introduce progressions?

We have discussed in previous posts the concept of progressive overload and the fact it's a pre-requisite if we want to improve as cyclists via training. In a nutshell, if we just do the same workouts, at the same power and for the same duration every time we go out and train, we are probably going to reach a point whereby we stop improving.

Any signaling for positive adaptation to training load must include a novel stimulus relative to power or duration over time in a given zone.

There is no completely right or wrong answer with tempo workouts, since this would depend upon the placement of the session within our overall training plan, an analysis of our current strengths and weaknesses, and how the session is aligned or targeting our goals and hence the required training outcomes.

For example, if we are working toward completing an ironman event, we might consider the event distance and likely duration at various points on our current power duration curve PDC. We can then decide on the best approach to optimize our race time via either increasing our pace-and hence power at tempo-or else training our TTE, time to exhaustion, if we cannot hold our tempo pace for the required duration.

Do I need to fuel tempo workouts?

Yes, at tempo intensity there is an increased demand on glycogen stores over zone 2 (endurance) riding. For optimal performance we should aim to replenish these reserves as we ride, through the consumption of exogenous carbohydrates.

Due to the increased intensity over zone 2endurance rides, gastrointestinal distress (stomach upset) may be more occurent than in longer rides at low intensity, since our bodies will divert more of our blood flow away to our working skeletal muscle. It is, therefore, even more important that we feed our stomachs with easily digested simple carbohydrates like simple sugars and avoid, as far as possible, either fats or high fibre during our tempo rides. Carbohydrates must always be taken with ample hydration.

For most, this can be done ad libitum-to thirst-but if you have trouble remembering to drink, a simple trick is to set a "lap counter" on your head unit-or mobile phone if cycling indoors on Zwift-to bleep every 10-15 minutes as a reminder to sip.