MTB Interval Training: A Comprehensive Guide
In this post, we’ll look at how to improve your interval training for MTB cross-country (XC) racing.
We’ll cover the essential topics and approaches you need to know to see greater adaptations from your MTB training time using structured interval workouts, including those that we’ve directly applied in our coaching to win national championship titles and achieve multiple UCI podium finishes internationally.
More specifically, this article will outline:
The modern-day demands of MTB XC racing
Why you want to use interval training to prepare for competition
Which areas of your MTB-specific fitness you can use interval training to improve
The most effective interval workouts you can utilise in your training program
Some additional suggestions that should help you get a few % greater results from your interval training.
So, let’s get started by understanding what MTB XC racing actually demands for success…
Demands of MTB XCO
Mountain bike XC (MTB XC) is one of the most aerobically taxing and technically demanding sports in the world. There are few others requiring a higher sustained utilisation of the aerobic capacity (a combination of a high VO2max and lactate threshold) as well as such a large contribution of the anaerobic energy systems for success.
MTB XC riding and racing differs from a lot of the other cycling disciplines insomuch as that whilst the sport is primarily aerobic in nature and races typically last around 90 minutes, it’s uniquely characterised by extremely “stochastic” power production, i.e. a highly variable wattage profile.
High supra-maximal efforts need to be produced repetitively and consistently throughout the duration of a race, yet must be recovered from extremely quickly, and done so with only a very partial recovery at best (often whilst descending technical downhill sections).
To illustrate this, here’s a power file from an Elite UCI Category 1 MTB race in Slovenia, a field that included some of the world’s best XC racers like World Cup race winner Gerhard Kerchbaumer and Italy’s Braidot twins, clearly revealing these huge spikes and recoveries:
Now, depending on how you interpret the data from an XC race, you can draw different conclusions as to what is going on at the athlete level. Let’s take a look at this file through a number of different lenses, starting with power or wattage:
Power Output
When viewing race data through the lens of a power meter, it clearly shows that there are many surges in power output throughout the race which often reach over the typical “VO2max” intensity range and into the anaerobic and neuromuscular intensity levels.
These large spikes are then followed either by:
(i) sustained periods of either pedalling at or slightly below the lactate threshold (on a sustained climb or flatter part of the track for example)
or…
(ii) little/no pedalling at all and a correspondingly low wattage reading when descending.
Normalised power for the entirety of 90 minute MTB XC races is typically 90-95% of threshold power and the actual time spent in each of the training intensity zones ( when using a common 6 or 7 zone scale) are something similar to the following:
You can clearly see the large contribution of short-duration, high wattage efforts at or above aerobic capacity (i.e. VO2max) which add up throughout the course of the race, in addition to a significant time spent at low intensities too.
Overall, MTB XC race files often show a relatively equal spread across all power training zones, with a slight polarisation of low and very high intensity.
VO2max
The VO2Max, i.e. the maximum amount of oxygen that can be taken in, delivered to the working muscles and used for energy production, is one of the key determinants of performance in MTB XC competition and the aerobic capacity is taxed tremendously throughout a race.
By using HR data from a race as a proxy for VO2 or through the use of wearable and mobile VO2max monitoring units like the VO2Master, it’s possible to get an even greater understanding of the demands of MTB competition.
In contrast to the data from a power meter, where pedalling force is often low to non-existent on descents, the VO2 remains elevated during short downhills, again strengthening the position that MTB XC athletes must try to recover as quickly as possible even though this is only ever a partial at best.
During climbing portions, which are obviously a huge part of MTB XC and XCM racing and often where the decisive moves are made, the percentage of the VO2max being utilised gradually increases. The reason it stays elevated on the descents is mainly because both the upper body and lower body are being used for balance, stability and steering.
This means the fractional utilisation of the VO2max is consistently high throughout a race, placing a huge demand on the athlete’s aerobic system.
Heart Rate
Using heart rate (HR) data to assess the demands of MTB XC again presents somewhat of a different picture to power output…
Here’s a time in zone chart from that same Slovenian UCI C1 race, so you can see those marked differences from the corresponding power chart:
With MTBing being so stochastic or “choppy” as mentioned before, there’s an inherent limitation in precisely analysing a file like this due to HR lag. However, what is clear is this HR rises very quickly after the fast mass start of a race, rises almost to Max HR, and then stays elevated throughout the entire race, never dropping below 85% of HRMax at any point from start to finish:
Average HR for a 90 minute race usually falls somewhere around the threshold HR of the athlete, or about 85-90% of HRMax.
This is of course a very individual thing and does depend on variables like how well the race was paced, the current fitness of the rider, their fatigue levels going into a race etc.
Interval Training For MTB XCO
When we talk about interval training, this is a broad term that refers to any type of training that is intermittent…
i.e. has a work or “on” part, and a rest or “off” part to the workout, where the term “interval” actually refers to the inclusion of the rest part specifically (as in the ‘interval’ part way through a theatre show, for instance) – who knew?
So, in preparation for MTB XC events and to develop the greatest amount of race-specific fitness possible, why is interval training such an effective method?
Well, interval training’s primary benefit is this:
It allows you to spend greater amounts of time at a given intensity than would be otherwise achievable if this intensity was ridden continuously without any rest periods. It’s these “rest” intervals in between the “work” intervals that allow for higher training loads and greater time within the target zone on a per-workout basis.
This results in greater adaptations and a larger supercompensatory response provided that adequate recovery time is allowed.
Here’s how supercompensation works (this model is a simplification, but is useful for conveying the basic principles):
The “intermittent” nature of interval training also has benefits in its specificity to the MTB XC discipline, where it helps to train and develop abilities like:
high power repeatability (i.e. the ability to surge and sprint over and over without fatiguing)
force production, going from slower to faster speeds over and over again
ability to handle sudden and random changes in rhythm.
What’s more, interval training, especially HIIT (High Intensity Interval Training) can be very time efficient compared to the steadier endurance training elsewhere in the training plan.
Physiologically, interval training can be applied in a number of different ways and for different purposes, so let’s take a good look over what areas of your fitness can be most improved…
Interval Training Benefits
So, now that we have a greater understanding of the demands of MTB XC racing, as well as the potential of interval training to help you prepare for these demands, let’s get into the more nuanced discussion of exactly how and where interval training can be applied in your plan…
Endurance
Your aerobic endurance provides the foundation that supports all of your high intensity fitness and is incredibly important in a sport lasting for ~90 minutes in the XC format, and up to 6 hours in marathon events.
It ensures that:
(i) you can ride at higher power outputs for longer
(ii) you’re able to use a lower fraction of your lactate threshold and VO2max for a given power, which influences how your body is able to use different fuel and its economy.
Although typical endurance training (also known as base training) seems quite removed from the high intensity demands of racing, the fallacy of specificity (by which I’m referring to the mistaken belief that the best training for a sport is ALWAYS that which most closely reflects its demands) should be considered.
To train your endurance and improve the systems and mechanisms associated with greater endurance, you can use very long intervals to:
develop the strength of slow twitch muscles
raise maximum power output where fat is primary fuel source (FatMax)
build greater mitochondrial density (the power houses of the cell which convert glycogen into ATP – the body’s energy currency)
increase in amount of capillaries in the muscle (which allows for greater blood flow to the muscle)
Lactate Threshold
Perhaps one of the aspects of fitness that can be improved the most through correct application of interval training is the lactate threshold (LT).
As it’s such an important component of performance, I’ve written an entirely separate guide on the lactate threshold and how to improve it here.
The LT is sometimes used interchangeably with the terms:
the anaerobic threshold
maximum lactate steady state (MLSS)
the lactate turnpoint
These terms have slightly different meanings, but for the purposes of this article, we’re defining the LT as the highest power at which lactate production rates equal lactate clearance rates.
When this threshold is crossed, you’re essentially on borrowed time.
This is where lactate levels will continue to rise (albeit at different rates depending on what % over threshold you’re riding at) until you’re forced to slow down.
The bottom line:
The higher power output you can generate whilst staying at or below the LT, the better.
It’s worth highlighting that lactate itself is not bad. But its presence in the blood is highly correlated with other metabolic products (aka ‘metabolites’) that have been associated with fatigue.
Interval training to improve LT power is typically performed either at or ideally just above LT for long periods, which will provide greater training stress, but keep accumulation of lactate (and associated fatiguing metabolites) to a level where you can still perform intervals of relatively long duration at elevated HR and VO2 for sustained periods.
It’s best performed above LT because of the demands that higher-level athletes need to place on themselves to cause meaningful adaptations and to achieve the minimum effective dose.
Training right at this LT and the pain associated with it is very manageable for those with high training volumes or long training history, but the stress on the aerobic system can be risky and under appreciated, leading sometimes to both physical and mental burnout.
So, so-called ‘supra-threshold intervals‘ work particularly well for the purpose of raising LT, and are usually performed as intervals of 5-10 minutes in duration and at about 103-108% of Functional Threshold Power (FTP).
You want to use these kinds of intervals in what I call the “Push-Pull Technique”.
The “Push-Pull Technique” is all about improving your LT by “pushing” it up from the bottom (with low intensity endurance training volume) and “pulling” it up from above (using intervals above LT like those mentioned above).
VO2max
Alongside LT, your VO2max and ability to use as much of your aerobic capacity as possible in a race situation will have the highest leverage from a training point of view with regard to your fitness and performance.
Like improving LT, you can develop your VO2max with longer, lower intensity intervals at the same time as improving your endurance (though these changes will take a lot longer to come to fruition) and by intervals that elicit close to maximum HR.
What do pure VO2max intervals look like?
Well, they’ll be relatively short in duration (typically from 2 minutes up to about 8 minutes at the very top end) or as a longer interval block of “micro-intervals” which feature short bursts of power and even shorter recoveries, typically at a 2:1 work-recovery ratio:
Relative to FTP, VO2max work is usually in the region of 115-125% of FTP, but this differs greatly from rider to rider, so either direct measurement of the VO2max and LT or a lot of precise and varied training is needed to discover what your true capabilities are when riding over LT or FTP.
Anaerobic Power & Capacity
Your ability to produce huge spikes in power is determined by your ‘anaerobic power’ (which is the maximum rate at which you can produce energy via anaerobic energy pathways (i.e. ones that do not require oxygen).
However, it’s also dependent upon your ‘anaerobic capacity’, which factors in both your anaerobic power and your ability to sustain energy production via these anaerobic pathways before you hit fatigue.
In other words, your anaerobic capacity is the total amount of energy that can be produced via the anaerobic energy systems, and isn’t associated with a single wattage.
Think of your anaerobic capacity like this:
It’s a battery that has a finite amount of charge, where each time you produce a high power effort, you use up some of this energy reserve.
How much of this charge you use depends on the intensity of the effort and how long the effort lasts, and similarly, how fast you recharge this battery will depend on your fitness level, but once you’re out of charge, you’ll be cooked:
How big your battery is is limited and naturally bigger in some athletes than others. It depends both on VO2max and on anaerobic power. While VO2max can take a long time to develop, anaerobic power can be developed relatively quickly, over a matter of weeks.
As a MTBer, spending some time on your anaerobic power in the few weeks before you target events is important for most athletes to make sure it is adequate for demands of the race. Remember though, this should not be at the expense of developing your aerobic capacity, since improving your anaerobic power will mean higher lactate production…
…and even though you’ll see plenty of short, high-intensity efforts throughout a MTB XC race, you’ll always want your anaerobic power to be appropriately balanced with your aerobic capacity (for more on this, check out this article).
You can try to deduce from your training whether you’re more of an aerobic or anaerobically-gifted athlete naturally, and tailor your training in the build up to a race accordingly. We cover methods for assessing your physiological profile in detail in our Cycling Physiology and Training Science Guide.
Typical anaerobic power training will usually be done at between 130-150% FTP, again with large individual differences possible.
Sprint & Neuromuscular Power
Interval training can also be used to improve your sprinting and neuromuscular power for MTB XC racing.
Being strong in this area is particularly useful for:
the start of a race, which is usually a hard sprint off the line and multiple other sprints in the moments after the start, e.g. trying to get around a slower rider or to be as well positioned leading into the first narrow section of single track
attacks like those mentioned above, but also during the race to bridge up to another rider or group, or to get away from others on a climb or flatter section
fast finishes, where you’ll need to sprint for the line or make a late attack stick
This kind of training will help your overall fitness by developing your ability to produce greater muscle tension and neuromuscular recruitment for higher force production.
In addition, specifically working on sprinting and neuromuscular efforts will usually bring about better muscle coordination, which can result in benefits like less cramp and higher strength overall.
These efforts typically last from a few seconds up to around 20 seconds at the very longest and are all-out, with no real associated power output or pacing other than close to your max.
MTB Interval Workouts
In addition to the multiple areas of your fitness that can be improved with interval training, there are various ways of designing effective mountain bike workouts that can further help you gain more pronounced adaptations.
Let’s take a look at these interval workout designs, and the advantages/disadvantages of each:
Short Intervals
When we think of short intervals, what springs to mind is usually those very intense efforts lasting somewhere from 30-90 seconds in duration.
Short intervals often jump out as the most specific effort for MTB XC racing too…
…but, sometimes all isn’t what it seems.
Because of the fact there’s very little recovery time in a race after a short burst of power and almost never the opportunity for full recovery, the efforts in a race can actually be quite different to what you’d typically do in training, being shorter in duration and at lower power outputs.
In contrast, traditional short intervals are often much longer and higher intensity and feature longer recoveries.
Now as alluded to above, workouts do not at all have to be specific to MTB XC racing to be incredibly effective as training for competition, but it’s key to know how they fit into a training plan.
It’s important also, especially given the developments in understanding of things like maximal glycolytic rate mentioned before to ensure that you’re not focused too greatly on short, high-power intervals and training the body to produce higher amounts of lactate.
Why?
Given the fact that MTB XC is an endurance sport with racing lasting ~1.5H (and plenty longer in the Marathon discipline), a lower maximal glycolytic rate and a higher lactate threshold is desired, even though the contribution made by anaerobic energy pathways is no doubt higher than other cycling disciplines.
That’s again what makes the sport so unique!
Micro-Burst Interval Blocks
This workout design uses short work intervals combined with short recoveries within a longer block:
These blocks of micro-intervals and micro-recoveries typically use a 2:1 work-rest ratio and the aim is to be able to spend as long as possible in the target zone, both from a power and a HR perspective.
This kind of design allows for just enough recovery that many micro work-intervals can be accumulated, but the recoveries are short enough so as not to allow the HR to drop significantly at any stage through a block:
This ultimately leads to a high average HR for the interval block, which means a strong adaptive signal to the body to develop VO2max. Secondarily, they also help to develop your ability to handle changes in rhythm and overcome high amounts of torque as you constantly re-accelerate.
If this isn’t 100% clear, you’ll find an example of this style of interval workout below.
Long Sustained Intervals
Longer intervals are more useful than they’re given credit for in MTB XC…
In contrast to the short intervals mentioned below, longer intervals don’t immediately seem specific to MTB XC racing, but in actual fact they are!
Let me explain…
Long sustained intervals train the ability to tolerate elevated levels of blood lactate, high heart rates and sustained high intensity muscle load for long periods of time, which during the course of a lap and race overall is EXACTLY what you experience.
In fact, you’ll see that the pros do exactly this and see great success, whereas a lot of the TrainerRoad warriors with they’re super-short HIT training often flounder.
Long intervals are there to build a foundation of very high fitness and fatigue resistance, where once this is built, it then make sense to put those anaerobic finishing touches on top.
These types of intervals can be done on-road on a long climb, off-road where a dirt road works well, on the flat to train flat speed, and they typically look like this:
This last one is often ignored by MTB racers!
Indoors on a turbo trainer works well too, where the key benefit is the consistency and lack of interruptions, where intervals can be made as long as needed and ERG mode can be used on smart trainers to stay within the correct intensity zone.
Long Intervals With Surges
In addition to the standard long intervals laid out above, adding in some high-power bursts or surges throughout will help in several ways:
It’ll keep the HR elevated
Cause spikes in blood lactate as you go over threshold for a more pronounced training stress
It mimics the burst of power you might need to produce in a race to ascend punchy climbs, get through a technical uphill section or move past another rider on a climb.
The surges can be done throughout a long interval, placed at the start of an interval, or left until then end, where each approach has its own benefits and drawbacks.
Experiment with some different designs to see what provide the greatest adaptations for you specifically.
Fatigue Resistance Intervals
So-called “fatigue resistance” intervals are designed to do just that; help you stave off tiredness in a competitive situation, whether that fatigue is caused by going hard from the off, or having to protect your position or make late attacks at the end of a race.
In training, these look like long rides with a series of moderately high intensity intervals placed either at the very start or very end of the ride:
The purpose with those intervals placed early on is to load the legs up with some level of fatigue early on, which is then present throughout the rest of the ride. This is quite similar to a MTB marathon race, where there’s often a fast start followed by a quick settling into a sustainable pace, given the duration of such events can be up to 6 hours.
The intervals placed at the end of the ride on the other hand train your ability to still produce meaningful power repeatedly, even when the legs have a significant amount of fatigue in them already.
These can be used to specifically prepare for the demands of a particular race, or as a bridge from endurance workouts of about 3 hours progressing to 4 hours plus.
Fartlek Intervals
To borrow a term from running, fartlek is a Swedish word that translates as “speed play”, and in practical terms refers to workouts with unstructured intervals, that are performed in a much more random way.
These types of workouts are excellent when you still want to get a quality workout done, but need break from otherwise structured sessions.
They’re also much more like a race in the sense that one interval is different from the next and the amount of recovery between the intervals constantly changes.
Fartlek intervals work very well if you’re riding with others, where each rider takes a turn dictating when these random intervals happen for the others.
Key Workouts
Using interval training to prepare for your target MTB racing doesn’t require creating never-before-seen, complicated sessions that are hard to apply out on the road or trail.
Here’s a selection of five of the most effective interval workouts we’ve found to improve the key determinants of MTB success and the aspects of fitness discussed above.
If you have any questions or queries about the workouts as you read through, please don’t hesitate to leave a comment below or get in touch.
Equally, if you have a TrainingPeaks account, and want these workouts in your account, along with a wide variety of other effective training sessions that can be used both for XC training and for other cycling disciplines, check out our Workout Library.
Alright, so let’s get into the first workout, which is designed to improve your anaerobic threshold/lactate threshold power…
Supra-Threshold: 4x8-Mins
This workout is a supra-threshold session of 4x 8 minutes at just above your anaerobic threshold power, threshold heart rate or roughly your Functional Threshold Power (FTP).
This workout specifically targets improvements in your aerobic capacity, threshold power, and muscular endurance.
An example workout could use around 20-30 minutes of steady riding, gradually increasing from a very easy to a moderate effort before the intervals begin.
Then, on a hill of either tarmac or dirt road, or indoors on a turbo trainer, you’ll then do 4 lots of around 8 minutes, aiming to be in that just-above-threshold intensity range for as much of the 8 minutes as possible.
In between the intervals, you’ll coast back down the hill, lightly pedalling if possible for active recovery.
This workout can be done on your MTB, but equally works well on a road bike or indoor trainer, especially if the the weather is bad or you don’t have access to a climb with a relatively consistent gradient for 8 minutes.
You’ll find that at this intensity, you’ll be pushing yourself hard and feeling the burn of the accumulating lactate, but will still be riding at a low enough % over your threshold that you don’t reach complete fatigue too quickly.
After the intervals are done, riding nice and easily for the remaining time will help you to cool down, decompress after the session and also help the body start the recovery process.
Threshold: 10M Hard Starts
The next workout is another session focussed on aerobic capacity, threshold power and muscular endurance. However, we add an element of specificity, meaning the session more closely reflects the demands you’ll face in a cross country race.
The main set of intervals in this workouts are 3-4x 10 minutes at your threshold power or heart rate, or rating of perceived exertion of around 7 out of 10.
The specific element comes from a hard start or surge at the beginning of each interval, which serves a number of purposes…
The first of these is this initial surge quickly raises the heart rate, increases oxygen consumption, and elevates lactate levels, meaning that when you then settle back down to threshold, you score more time at an intensity that’s good for improving both aerobic capacity and potentially also lactate transport.
Second, it mimics a few key elements of a MTB XC race, be it the start, where there’s a big spike of power followed by a sustained high intensity, or a small surge in power to get up a punchy climb before settling back into a sustainable race pace:
By starting in a large gear, you can also work on your force production, which is always helpful in a high torque discipline like mountain biking.
In between the intervals, try to aim for about a 2:1 work-recovery ratio, typically of 4-5 minutes, using active recovery, i.e. light pedalling where possible.
This interval set can be used in a shorter ride where it’s sandwiched between a 20-25 minute warm up or cool down, or within a longer ride when your fitness is higher or time allows for both longer sessions and enough recovery.
Feel free as always to do these on the MTB, road bike or CX/gravel bike, either on the road or off.
VO2max: 30’ On, 15’ Off
The third essential workout for MTB XC riders is aimed largely at improving your VO2Max, but does a great job of pulling your threshold up from above too.
This session comprises of longer blocks of micro-intervals:
More specifically, you’ll perform 3-4 sets of these blocks, which each last anywhere from 8-12 minutes each, and are made up of 30 seconds at between 115-125% of FTP and a meagre 15 seconds of partial recovery usually at around 50% of FTP.
Exact intensity ranges for each will differ from person to person because of the limitations of FTP, where the on micro-intervals should feel about a 8.5/10 effort, and recovery about a 5.
Use these blocks within a medium length ride or as a compressed turbo session, being sure that you adequately warm up and cool down before kicking them off.
Start off conservatively and be sure to hold back slightly in the first few 30 second micro-intervals, since it’s very easy to go out too hard when fresh and then find yourself struggling to complete the entire workout later on into the blocks.
Between each of the blocks, you want to give yourself adequate recovery to be able to perform the proceeding block to the necessary quality, where anything over 3 minutes will usually suffice.
Once more, feel free to do these on the road or trail, but ideally try to perform them on your mountain bike regardless, since the constant need to reaccelerate for each 30 second micro-intervals will be best done in a way that uses your MTB riding position.
Anaerobic: 50-90-sec Repeats
The final workout is intended to ensure your anaerobic power and capacity are developed enough beforehand to meet the demands of your higher priority races. This specific session helps increase your anaerobic power, which is the maximal rate at which you can generate energy anaerobically.
As mentioned, for the requirements of XC racing, your anaerobic power can be elevated to a suitable level in a short space of time with a focused approach in training. So these are workouts that you’d primarily want to add in with just a few weeks to go until your most important competitions.
The intervals themselves work well when done on the MTB and off-road, and will be anywhere from about 45-90 seconds in length.
Whilst they’re certainly done at a very high intensity, they aren’t completely all out efforts and should be paced to some degree. If not, then you can find it tough to get through more than 2 or 3 with any real quality.
Take a decent amount of recovery between each effort, to make sure you can nail each interval at the required intensity.
By the end of the workout, you’ll likely feel that the legs are pretty stiff and on the final 1-2 intervals that you’re starting to experience some neuromuscular breakdown.
Sandwich these intervals between a solid warm up and cool down, keeping the intensity in both relatively low.
This is so you can apply your energy to the intervals themselves, though adding in a few bursts of power before starting the main set will help wake up the legs.
Additional Tips
Finally, let’s look at a few quick-fire tips for performing better interval training for MTB XC racing.
1: Stop Before Task Failure
Call it a day when you could just about squeeze out one or two more out of yourself if your life depended on it, as the additional fitness you might gain from that final repeat simply doesn’t outweigh the risk of overtraining and burnout.
2: Seated And Standing
Next, try some of the intervals using both a seated and a standing style, so that you’re not becoming too reliant on one position or another. Being able to apply power both sat in the saddle and standing up on the pedals will help you in different situations and different parts of a XC course, so being strong in both domains can be a great advantage.
3: Train On Both Flat And Climbs
Similarly, try some of your intervals on the flat as oppose to a climb, so that you’re again not unbalanced in how strong you are in one domain relative to another.
4: Set Up Your Head Unit
Next, make sure to set up a dedicated interval page on your head unit so that it’s easy to see all of your important metrics at a glance. Here is the recommended setup we advise our athletes to use:
5: Start Conservatively
The final tip for better interval training would be to start off conservatively and settle into your workout.
It’s so easy with all of the workouts laid out here to do too much intensity early on and suffer for it in the end.
It will always be better to be at the right intensity at the end of a workout and have gone a bit easier initially, than starting out really hard and hanging on for dear life.
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We hope this specific post using interval training to prepare for MTB XC competition has been helpful in providing a greater understanding of the demands of the sport and where you can best direct your training time and energy to see the greatest improvements.
If you’re interested in leveraging our unique understanding of training for MTB racing, please take a look at the services we offer and get in touch to discuss how we might be able to best work with you on an individual basis:
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