Michael Guilford, level 2 MTB and Level 3 Road/TT British Cycling coach, ABCC coach and XC mountain biker.
Emma Neupert, Sport Department, Winchester University
The article covers:
- Background into XC racing
- Literature review of current scientific research into XC racing
- Analysing power data
- Training for XC racing
This article is not intended to be a complete training guide.
Background to Cross Country Mountain Biking
Cross country (XC) mountain biking is a unique cycling sport. XC has similar technical demands to downhill, enduro and four cross, but it is an endurance sport so the physiological, psychological and tactical demands are different. Cyclocross has the most in common with XC mountain biking.
XCO MTB refers to Cross Country ‘Olympic’ format, as it is the only Olympic MTB event.
Summary of cycling disciplines- Table 1
|XCO||<2hrs||Off-road, hilly, obstacles, singletrack, dual track||Mass start|
|XC Endurance||<2-24hrs||Mass start||Bike handling/coordination, MTB techniques|
|DH, 4x||<5mins||Downhill, obstacles, single/dual track||Individual (DH), 4x (4x)|
|Road Crit||<1hr||Tarmac, (sometimes cobbles||Mass start||Group riding, cornering, other road techniques|
|Cyclo-X||<1hr||grass, mud, hurdles||mass start||Bike handling coordination, cyclo-x techniques|
Event Profile- XCO
XCO races typically last <2hrs for elite races, with up to 8 laps per race. Riders are gridded and are started onto an open (dual track) section of course and often reach 20-25km/h, due to the technical singletrack nature of some of the course overtaking is often difficult and tactical.
Course Profile- XCO
XCO race courses are around 4 miles long and can have up to 200m of climbing per lap.
XC racing takes place on a mixture of terrain:
- Fields (grass)
- Soil: cohesive (clay), granular (sand/silt), mixed (loam)
- Rock (sandstone, granite, limestone, chalk etc)
- Compacted granular materials
- Imported rock (usually a hard grippy rock such as sandstone)
Obstacles and technical features
XC races feature similar obstacles to downhill courses:
- Corners- flat, off-camber, bermed, switchbacks
- Climbing- technical, power, rhythm
- Jumps- doubles, table tops
- Log-jumps, stream crossings
- Rock-gardens, steps
Cross Country Rider profile
Here is an example of physiological characteristics for world class riders, taken from the British Cycling Level 3 coaching handbook. The max minute numbers for road and XC racers are fairly typical according to other literature.
Cross Country Rider Profile -Table 2
|Event||Body Weight (kg)||Peak Power (W)||Max Minute Power (W)||P/W (W/kg)|
Road and XC racers are similar in terms of power abilities, however XC racers are generally lighter than road racers.
Key observation: This data gives little indication of a rider’s endurance capabilities for a given interval, i.e. the number of times their Max Minute Power effort can be repeated in one race. The research below suggests that a rider’s ability to repeatably exert 30s efforts is particularly significant to performance.
Andrew Coggan created a more in depth table for road and track riders, which gives suggested performance bands for certain power outputs at certain durations. You can read more about it here. These tables can be useful for an XC racer by highlighting major discrepancies in your ability between long and short duration efforts, but they are unlikely correlate with performance in an XC race.
Components of fitness and energy systems
Coaches use ‘components of fitness’ to help understand the physical demands of a sport and to analyse performance. It is also useful to understand the general energy systems, represented by the following diagram, the x axis is logarythmic
Terminology differs, but the concepts covered are very similar:
- Aerobic endurance- the ability to sustain a continuous effort for a long period of time
- Short term muscular endurance (STME)- the ability to sustain anaerobic efforts
- Muscle Power- the ability to produce instantaneous power
- Force- the amount of force that can be applied on the pedals
- Speed – the ability to accelerate cadence or to achieve a maximum cadence
- Flexibility- the range of movement of joints/limbs
What makes a good XC racer?
A scientific perspective…
Here is a summary of the investigation methods used in the articles I reviewed:
- three of the six articles correlated lab test data with performance in XCO races (FM Impellizeri et al. 2005 , FM Impellizeri et al. 2005, A Inoue et al.)
- one of these correlated anaerobic lab tests with XCO race time (A Inoue et al.)
- four out of six of the articles used international level subjects, with the other two using national/regional level subjects
Note: I have included a reference list at the end of this article.
What does the research tell us?
Maximal aerobic power (Wmax) normalised to weight does correlate with cycling performance, with international standard riders achieving upwards of 350 W or 5.5 W/kg in incremental maximal aerobic tests. This means that riders at an international standard require a level of aerobic power similar to a domestic level Elite road racer.
The one study that correlated anaerobic Wingate tests (30s test) with XCO race time found that there was a good correlation between anaerobic power (normalised to weight) and XCO race time. The same study also used a Wingate test repeated 5 times with 30s rest periods and the results from this were correlated more strongly with XCO race time. Coggan’s normalized power function selects intervals of 30s as being significant to represent the physiological demand of a ride. (see below for an explanation of normalized power)
The studies confirm that international level road and XCO racers are similar in terms of Wmax and VO2 max variables, but there is still a lack of data comparing anaerobic performance variables.
The studies did not collect much useful data to help analyse race performance. An analysis of riders’ times over climbs, flat sections and descents would be fairly straightforward, and would give more opportunity to find correlations to lab test data.
The lab tests suggest that standard lab test procedures (i.e Wmax test) is unsuitable for benchmarking XC race performance and that a test using repeated intervals should be more widely used. Moreover lab tests should be specific to the event that a rider is training for.
Power Metering for XCO racers
Why is power metering so useful?
Power gives us an estimation of the kinetic energy output of a rider
Power provides a measure of intensity that is more independent from the rider or external surroundings, than other variables such as speed, heart rate, RPE (rating of perceived exertion) or VAM (mean ascent velocity).
Power helps to isolate changes in heart rate, and RPE in order to interpret how the rider is responding physiologically to the training.
Power is practically useful to training in two ways:
- It gives us insight into how we can train more specifically for an event- through analysis of race data.
- It helps us to measure progression in training- through monitoring training data.
Why is Power Useful for XC Racing?
In cross country racing the rider will optimise their pace in order to complete the course in the shortest time.
In order to complete a cross country race in the optimum time a rider needs to choose how to expend their energy on parts of the course:
- On technical sections a rider will optimise their speed in order to limit energy loss through braking.
- On uphill and flat sections a rider will increase their power output in order to maximise their average speed, power helps us to see the exact kinetic energy output of these efforts
Power doesn’t show the whole picture
Power metering is popular for road and track cycling, because power output correlates closely with a rider’s velocity. In BMX racing we can see that the rider’s velocity depends on some power output that cannot be measured such as ‘pumping’ with the arms and legs. Similarly, in cross country there is power output that cannot be measured with a power meter due to non-pedalling movements.
- Short ~1s movements for individual obstacles, corners, drops, log jumps etc. These movements could have little affect on average speed but may be necessary in order to complete the course.
- Involuntary movement and stability e.g effort expended while riding on rough ground. Similarly, these movements may be unrelated to average speed.
- Repeated movements, short 1s repeated movements over periods >20s which result in increased blood lactate and heart rate, e.g technical steep descent, slalom, stepped causeway, BMX pump track etc.
- Short 1s repeated pedal strokes, e.g pedalling between two corners in singletrack
- Short 5-20s efforts, e.g short explosive climbs, or longer sections in singletrack
- Extended efforts>20s
- Long efforts >3mins
Analysing power data
There are various metrics that can provide quick, helpful insight into power data.
Normalized Power (NP) Explained:
The selection of a 30s interval used in the study above is particularly interesting as Coggan’s normalized power averaging method also uses a 30s time period. NP is calculated as follows
A 30s moving average is taken for 1s measuring intervals this would the average of 30 measurements, so at 15s into the ride:
(W1 + W2 + W3…+W30)/30= AW15 (average power at 15s)
This is carried out for every 1s intervals and each average raised to the 4th power, these values are then averaged over the ride duration
The fourth root of this is then taken.
The important thing to note is that the interval used is 30s and it is the fourth power that is used to weight these intervals. The power vs lactate curve is roughly a fourth power curve which represents the physiological cost of a range of power outputs of the same duration. Going back to the energy systems diagram you can see that interval durations longer than 1 minute are more reliant on the aerobic system than the anaerobic system. When you consider the context to which NP applies (endurance cycling), weighting shorter intervals of 30s is more appropriate than say 1-2min, as the 30s interval will often take place within sustained exercise where there is already an enrgy demand on the body.
Critical Power profiles- assist in highlighting major discrepancies in a rider’s power ability over a range of interval durations. As a coach I would start by assessing FTP, 5min and 1s peak power and compare these figures with data available from scientific research for XC riders and road riders. You can use Andrew Coggan’s Rider Abilities Profile, but bear in mind that the data used for his profile includes track sprint riders.
For this 58kg rider below we can see that they are able to produce >17W/kg 1s peak power, ~4.8W/kg FTP and ~5.2W/kg 5min power. Elite XC/road riders can produce >18W/kg 1s peak power, >5.5W/kg FTP and >7.5W/kg 5min. This suggests this rider’s main focus should be 5min power followed by FTP power.
Histogram analysis is useful for finding out how the workload is distributed across certain power ouputs. This does not give any indication of the length of interval that contributes to each power-bin-range.
The histogram in figure 2 has a near t typical bell curve shape (normally distributed), whereas the histogram in figure 3 is heavily weighted to the lower power outputs. From my experience of seeing road race and XC power data, I would say that histograms from road races are much more irregular, I believe that this due to the tactical element of road racing.
This is a flat cross country race in February, 45 mins is below Z3 and 53.5 mins is above Z3.
In the next step I analysed some of my race data to assess the demands of racing. I have carried this out in more a detailed way than I would for every race.
I carried out an analysis of the intervals that made up a lap of a cross country race.
I selected intervals on the basis that each interval was a pedalling effort split up by a zero cadence and zero power interval. I also worked out where these intervals occurred in respect to technical course features. Figure 4 shows alternate intervals, marked by the blue and grey line colours. Generally non pedalling sections occurred at corners, but the other non-pedalling sections were due to technical features
NOTE I: Bear in mind that your race data does not indicate ideal performance.
NOTE II: The reliability of this analysis is limited by the accuracy of the power measuring device. I was using a Stages (non-driveside) crank arm. The device only gives a power reading when there is a cadence and a force registered in the non-driveside crank. It can produce a positive cadence reading with a zero power reading but will not give a positive power reading when there is a zero cadence reading. Very short/slow pedal turns, like swapping feet may not be picked up.
I am using Golden Cheetah V3 and WKO + v3 for this. The programs use slightly different computation for metrics such as normalized power (NP) and Training Stress Scores (TSS).
Metrics for each 4.4km lap- Table 3
|Interval Name||Duration||Average Power (watts)||xPower (watts)||Average Heart Rate (bpm)||Average Speed (km/h)|
You can see there is a large drop off in power after the first lap of about 10%.
Analysis of Lap Splits – Table 4
|HR (BPM)||Speed (Km/h)|
Note: For every lap there are two lap splits
The second half of each lap (split 2,4,6, 8 & 10), has a higher average HR and Power output. This is due to the technical nature of the first half of the course which made it more difficult to pedal. The ratio of average power to heart rate for splits 2,4,6,8 and 10 was 1.63 whereas for splits 1,3,5,7 and 9 it was 1.79. This suggests that riding the first half of the course results in a lower aerobic efficiency. This could be due to non-pedalling movements, or it could be recovery from high lactate levels produced during the second half of the course.
I analysed the intervals for laps 1 and 5 and there were between 46 and 50 intervals per lap respectively.
The table below shows that about 1/4 of a lap was zero cadence, and that the average power for the remaining pedalling time was ~360W.
|Lap||Zero Power Time %||Average interval duration (s)||Average Power for individual intervals (W)|
The intervals for lap 1 are plotted on Figure 5 to help understand the technical features involved in the zero cadence elements.
Figure 5 shows that around 80% of the work periods are made up of intervals between 3 and 12 s.
Figure 6 shows that for longer intervals the average power becomes more consistent. Logically if the data on figure 6 was extrapolated for longer durations it would tend towards threshold power.
Figure 7 and 8 show that for Lap 1 and Lap 5 a large proportion of the work was carried out in Quadrants I and II. The drop in power between Lap 1 and Lap 5 can account for a loss of 2.8% in Q II, 1.5% in QI and 1.3% in Q IV. This suggest that high force, low cadence power is the key muscular endurance demand for this race.
What do individual intervals look like in terms of accelerations?
Unfortunately, I didn’t have a speed sensor fitted when I did the XC race so I have used some data from a road ride. Figure 9 shows an acceleration from zero cadence (road), whereas figure 10 is offroad.
The speed increases during the 10s period (blue line). There is a rapid increase in power, speed and cadence in the first 1.5s, as cadence levels out, power (and torque) decrease rapidly), because the bike is moving faster. There is no change of gear during this interval.
What about uphill intervals?
When you accelerate on the flat you produce kinetic energy, which results in a change of momentum. When you climb a constant gradient at constant velocity, you produce kinetic energy which increases your potential energy but your momentum stays constant. Whilst climbing a constant torque can be applied to the pedals with no change in velocity or cadence.
What about other resistive forces? Aerodynamics? Rolling Resistance?
Most cross country racers average around 15mph, although there are often faster sections ~20mph, aerodynamic affects are fairly negligible. However, roller resistance does create a large resistive force. Similar to climbing uphill, aerodynamics and rolling resistance create a constant resistive force at a constant velocity. This means once you have accelerated to a certain speed a constant torque must be applied to keep a constant velocity.
How to train for XCO racing?
Racing for fun
If you are racing just for fun, i.e. you are racing to finish, then gruelling interval sessions are unnecessary unless you particularly enjoy them. Instead, focus on acquiring technical skills which will lead to much greater enjoyment in XC racing, riding with friends and on your own.
A mountain bike skills training course is a very effective way of learning the correct techniques and building confidence. A coach can help you progress much more quickly, and will help you to avoid picking up bad habits.
Racing for results
If you are racing for results, you should train and prepare for results.
Hopefully the information in this article will help you to hone your training method and bring some fresh inspiration.
Training for results
There is a lack of scientific research into what physiological characteristics lead to performance in XCO racing. There is also a shortage of guidance on specific XCO training. This means you are likely to be exposed to a lot of training guidance geared towards road racing.
Set your goals
Every athlete has different expectations and levels of commitment towards racing. Athletes need to be honest about their level of commitment and realistic about their goals.
To maximise results from training there are three predominant approaches:
DIY Self-Coach – basing your training plan on your own understanding and experience.
Informed Self-Coach– seeking external input from an experienced coach and/or consulting manuals and research to inform your training, including how to produce a periodized plan.
Externally coached- employing a coach to set the training plan for you. They will have an outsider’s perspective on you as an athlete, as well as additional insight into your event.
As both a rider and a coach, I have observed a number of racers who have a narrow perspective of what is involved in training. It is a complex process which requires individualisation to the rider /event and a periodized plan which progresses training.
Take your preparation as seriously as your goals. However, in racing nothing is clear-cut- good preparation doesn’t guarantee success, nor does poor preparation guarantee failure.
Apply up-to-date training principles
The process of coaching an athlete, is in an depth one. Coaches will help to decide goals, analyse the event demands and the athlete’s profile in order to produce training objectives. As training progresses the coach will evaluate the progress of the athlete with respect to their goals and objectives. From my own experience this is a difficult process to apply as a self-coached athlete.
The next step is to produce your training plan. From your objectives you will draw up an annual, monthly and weekly/daily training plan. This is the process of periodizing your training. There are excellent guides to this process in books such as Joe Friel’s Training Bible. Here is a summary of periodization terminology:
- Base Periods 1, 2 and 3 (Preparation Period)
- Build Periods 1 and 2 (Pre-competition Period)
- Peak and Race Periods (Competition)
These periods tend to be in chronological order but may be repeated or re-ordered throughout the season.
Training should be specific to an athlete, in order to meet their goals and objectives. There is no point a coach providing a rider with generic training plans, apart from being boring they are unlikely to be effective.
I am going to give some key event specific components to help design your training, for each of these compnents you should define a process goal which you will progress towards.
Event Specific Components for Cross Country Racing
- Average Race Speed
- Aerobic Endurance at a VO2 Max Intensity
- Muscular Endurance at High Force Low Cadence
- Average Power Output for Intervals
- Efficiency of Shorter Accelerations
- Technical Abilities
Average Race Speed
This may sound obvious, but it is the key objective in your training and it encompasses most of the other objectives. You can measure this in various ways, but you need to consider all the other variables that might affect your measurements. Be wary of using comparisons with other riders as a measure (i.e. strava).
Part of the training of all endurance cycling athletes is to improve aerobic endurance. The event specific part here is the VO2 max intensity. In cross country racing your lactate levels are likely to be above threshold levels for the entire race, this results in your aerobic system working hard in order to process the by-products of anaerobic respiration. You are likely to be building this area of fitness in periods Base 1, 2, and 3. It might also be necessary to focus on this area later in the year, in order to boost your aerobic endurance.
Muscular Endurance at High Force Low Cadence
This objective is likely to be worked on also in periods Base 1, 2 and 3 but also Build 1. I would look at the ranges of torque a rider needs to produce throughout a race and aim to build endurance to this muscular workload, starting first at low power outputs (i.e. high force, low cadence) and gradually building cadence, close to power outputs required in a race. For example, my average torque throughout 15s intervals in race was 400 lb.in with a power output of 380W. I would start by working at similar intervals at ~400 lb.in but at a lower power output (and therefore cadence), gradually increasing the power to ~400W for 15s intervals. The key thing is to first build muscular endurance at a lower power, but for a total duration close to that required in the race. For a 1.5hr race, this is about 1hr worth of muscular endurance intervals. You will need to decide on the duration of individual intervals.
Average Power Output for Intervals
Logically, to increase power output either or both cadence/force must be increased. I am an advocate of strength training, particularly maximal strength training. If you do weight training you will probably have to transfer these gains onto the bike. This training is likely to be done before you work on muscular endurance, in periods Base 1 and 2. You are looking particularly to improve muscle fibre density and neuromuscular efficiency. This is best done at very low aerobic workloads, in order to do this, a low number of reps (2-5) with lots of recovery time used when weight training. On the bike use intervals with a low number of pedal strokes (2-6) with lots of recovery time. In order to get a high resistive force on the bike, a large gear on an increased gradient can be used (hill starts).
This part of building power is likely to feature in period Base 3 and onwards throughout the season. During the race the interval time/power is likely to tailored to the event you are training for.
Efficiency of Shorter Accelerations
As figure 7 & 8 show, cross country racing is dependent on muscular endurance for high force, low cadence pedalling. Figures 9 & 10 suggest a proportion of the high force low cadence workload can be accounted for in the first few seconds of an acceleration. We can reduce muscular damage of this workload by reducing the peak force (or torque) of the accelerations. For a short 10s interval, you can start the acceleration in a harder gear and increase the cadence more gradually so that it reaches a peak closer to the end of the interval.
Figure 11 shows a ~30s interval with a fairly constant torque output.
Figure 12 shows the same section of course with a less constant torque output
NOTE: Don’t try to get this right by looking at the power/torque numbers on your screen during training. Instead observe how much your cadence is varying and how often you are changing gear during an interval.
Track cyclists are known for having exceptional pedalling technique, this is due to the high speed (cadence) involved in track cycling due to the fixed gear. Good pedalling technique will mean that power is transferred through the pedal stroke more smoothly. This is important for XC racing as it will help to keep the power output more consistent (and therefore efficient during intervals). It will also allow the rider to ride more efficiently at a wider range of cadence, requiring less gear changes during intervals. High speed intervals on rollers is my preferred way of improving pedalling technique, but it can also be done on the road during recovery/endurance rides.
Speed in Technical Sections
This race data highlights that I would benefit from increasing my speed in technical sections. The data shows that I am deccelerating (braking) into corners / technical features, if I could ride these features faster less braking would be required which would increase my overall speed.
Technical skill needs to be assessed during racing and not just riding, the pressure and fatigue of racing highlights where a rider is technically weak.
pacing of intervals
It’s important to optimise the pacing of efforts, particularly in technical sections. For this race I need to try and increase the length of pedalling intervals, I could do this by using a harder gear and pedalling sooner out of technical features, particularly corners.
pacing of laps
If you look at international level rider’s lap times, you will often see that lap times are all within the same minute. It is less important to keep the first lap within the same minute as position is important. However, a good aim is to keep all other lap times within the same minute or faster than the 2nd lap.
XCO racers have to maintain intense focus for up to 2hrs, they also need to be confident in their abilities. Techniques and skills need to be planned for and completed very consistently during a race. If you are serious about improving your racing I recommend you hire a sports psychologist for around 1 day’s worth of time to help you develop a psychological strategy. You can also read the book ‘The Chimp Paradox’ by Prof. Steve Peters of Team Sky.
This exercise highlights how XCO racing is characterised by a large number of short intervals. This observation was only possible due to the analysis of power data.There is a lot left to be discovered through this sort of analysis.
Riders who base their training on feelings and widely held ideas would benefit from undertaking a detailed analysis. However, this needs to be used in conjunction with a progressive, periodised training plan. If you are a self-coached athlete, you would almost certainty benefit from some outside coaching to ensure that your training plan is specific to you and your event.
Coaches and self-coached athletes should ensure their training method is justified. I aspire to adopt an innovative approach similar to that used by Team Sky, exploiting all the information available about the event and the rider. This philosophy adopts a process of continually analysing information and evaluating the training method.
Please reply with any thoughts, queries or responses on this article.
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