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Wednesday, 13 April 2011 00:00

The physiology of a pro cyclist

One of the benefits of streamlining my coaching work last autumn has been being able to pour the same working hours in to a smaller number of 1-2-1 athletes. I benefit by being receiving work satisfaction in probing deeper in to an athlete's physiology; and the athlete benefits because I begin to uncover more in their physiology and performance. It is like having a collective of "case studies", and it feels like I am better able to work on a project by project basis.

I have had a great example of that in the past week, with my athlete Nic making a visit to the UK. Nic lives in France, and rides for the Swiss UCI Continental Atlas Personal team. I've been working with him since the autumn of 2009, when he spotted 'Mobie' parked up at the Duo Normande, a race where he and his 2-up TT partner grabbed 10th place in the pro race. I've really enjoyed the journey so far with Nic - one where we have a shared aim to get a result at the French National TT champs, and to use this to secure a place on a Pro Tour team. No mean task, but Nic is not an ordinary human either - yes its a great experience to work with an athlete of Nic's ability and physiology; but its more his attitude to training and racing that I cherish. I may be biased, but I know he will be a great asset to any Pro Tour team willing to recruit him in 2012.

In order to prepare Nic for his attack on the 2011 French TT Champs in June, we have scheduled a few specific procedures this year: 1) he is spending more time on his TT bike 2) he has visited the wind tunnel in France 3) a couple of trips to the UK for specific testing, training and racing. It is the last of these that I would like to take you through in this week's blog post. I hope that sharing some real life data from a young pro will be of interest to you all, especially as it gives an insight as to what sport science can bring to the coaching process.

In the lab

Nic-in-the-lab

The first task when Nic arrived was to take a look at his physiology at race pace intensities. As with a lot of athletes these days, Nic trains using a powermeter - so I already have a good feel for what he can sustain at 'race pace'. This allowed me to set two power outputs for him to work at in the lab on a turbo: the first 10 minute trial was to be at ~380W (it actually turned out to be 390W) which was an approximation of the power he could sustain for 1 hour (or a 25 mile race); and the second 10 minute trial was to be 20W higher (the typical gap that most people have between 25 and 10 mile TT pace). Doing this in the lab allowed me to measure the physiological responses in each effort. I measured blood lactate, oxygen uptake and the oxygen saturation of his blood (using a small 'pulse oximeter' which Nic wore on his middle finger during the trials). We also had power, HR and cadence measured through his power measuring cranks.

To give you some background, Nic's first lactate threshold is 290W; his Maximum Minute Power is ~500W; and his maximal oxygen uptake ~6.5 L per minute (83 mL/min/kg). At rest (before the race pace trials) I measured both his haemoglobin (14.8) and haematocrit (44%) levels. These last two are probably on the low side for a young male - so he has gone home with a pack of Spatone and the promise of some training in the altitude chamber when he comes back in May. This will help boost his Hct levels in perfect time for his competition aims some 4 weeks after that trip. I will of course monitor his Hct levels during the May trip, as we know we cannot exceed the UCI's limit of 50%!

So, how did he fair in the trials themselves? Here are the data, presented in graph format (click on the graphs if you want a bigger view)

Lab-data-1Lab-data-2

The above graphs show data in the first trial. After 5 minutes of pedalling at the top of his zone 2 (290W or his LT power), you can see how oxygen uptake begins to rise and then achieves a 'steady state'. His HR is pretty flat too, although it kicks up a little as he gets hotter. The blood lactate is pretty steady too, and with the pattern of O2 saturation here (i.e. his blood stays very well saturated in the trial, between 95 and 97%) I can see Nic is 'in control' at this intensity. Indeed, at the end of the trial, he selected '13' on the Ratings of Perceived Exertion scale - RPE is how we ask someone as to how they felt in the exercise, and 13 is labelled as 'somewhat hard'. To see him comfortable at 390W (and 100rpm throughout) was really pleasing for me.

Lab-data-3Lab-data-4

About 30 minutes after trial 1, we repeated the exercise but this time using a higher power - the data is in the graphs above. You can see straight away that Nic is finally doing some work! His heart rate is climbing, his lactates too. The blood is also starting to desaturate - not catastrophic, but reducing to 92% would categorise Nic as suffering from hypoxemia (another good reason to get him on some iron, as this might help the oxygen carrying capacity of his blood). The observant readership will spot that oxygen uptake looks steady though - does this mean he is comfortable at this power too? Well, not quite - compare the values to the maximal oxygen uptake I mentioned we have seen in Nic previously - he is actually HITTING VO2max in this trial! This isn't that uncommon at these intensities, most 10 mile time trials would be performed at 90 to 95% in good level cyclists. And, Nic'sbeing able to hold this level for so long shows his ability as a rider.

However, I don't want to paint a picture that all is perfect here - it is my job to look at the data and try and find avenues for improvement - or I risk being made redundant! Nic can obviously hold a good percentage of his maximum oxygen uptake for this 10 minute trial, BUT we know performance is ultimately limited by the ability to developed power (as its power that makes the bike move forward). One of the best measures a physiologist has up their sleeves is 'efficiency' - or how effective Nic is at converting the oxygen he breathes in to make it work for him and produce power at the cranks. Using the oxygen uptake data alongside the carbon dioxide he produces (both measured by the mouthpiece and gas analyser he is hooked up to), I am able to estimate the energy he is using to produce the power. Humans are not very efficient: typically we are only ~25% efficient. We lose a lot of energy. If our fridge freezers were like that, we would be in trouble! In the research literature, cyclists at professional level may be measured at ~23%; the average club cyclist might be closer to 20%. If we were to class Nic according to his efficiency data, he would in fact be closer to a club level cyclist (at 20%). We have some work to do. If we can improve Nic's efficiency, we will 'win' some watts for the same oxygen uptake levels. For example, if could keep his sustainable oxygen uptake at ~5.4 L per min but improve his efficiency to 21%, we would gain ~20 more watts - worth having!

At the races

Nic-warming-up

Saturday morning, less than 24h after the lab tests, Dan and I took Nic up to Farnham for an Open 10 mile time trial - the first time Nic has raced in the UK, and the first time he has time trialled over this distance. A race on Saturday, a race on Sunday - having gone through the lab testing too, this was to be a tough weekend. However, the main aim of this racing weekend was to give him experience in racing time trials. As a pro, most of his riding is in road racing - he races where and when his director sportif wants him to. The enforced race programme has made it quite tricky in helping Nic towards his own personal goals; but we have to deal with it (as it pays the bills!). Thankfully, we have been able to carve out opportunities like this weekend for him - we weren't able to do this last season, but his results have meant his team management have given us slightly more leeway this year.

10_mile_time_trial

With performance itself as a second priority, it was really pleasing for Nic to get a win in this race - he rode to a 20:24 on a less than ideal day. How was the data from the powermeter? Take a look here (again, click on the graph for a bigger view):

Nic's average power for the 10 miles was 'only' ~390W, about the same level as the power we had him ride in trial 1 the day before in the lab - this is supposedly the power he should sustain for a 25 mile race. So what happened? Well, there might be many reasons - but one aspect we cannot ignore is his lack of familiarity of pacing a time trial effort. He actually goes off a little on the optimistic side of things - his average power being 450W for the first 5 minutes. With a more cautious start, he might have come back with a slightly higher power. We can work on this: he just needs more race efforts to 'calibrate' his perception of what he can sustain. I also believe if he paced it more evenly he would have come back with a faster time - he rode harder WITH the wind and was pretty tired when riding back in to the headwind - the slowest way to use available power (his average power on the way back was only 380W). Those of you that know about the 'normalised power' concept will understand that 396W for this effort is probably more indicative of where Nic is able to ride. So again, Coach is pretty satisfied with this outing. One down, one to go!

Late Saturday afternoon, I left Nic in the capable hands of another PBscience athlete, Mike. We performed a handover at the Starbucks on the M25/A23 junction. After my decaf, soya latte (Nic was highly amused by my coffee drinkiing this weekend - "at least you do not try to order alcohol free beer" he commented), Dan and I drove back to Eastbourne, while Mike and Nic drove back to the Mike's house: they both had the prospect of an early rise for the 25 mile effort ahead...what a curious world the UK time trial scene is!

25_mile_time_trialYou'll see from the graph of Nic's 25 mile race that relatively speaking, he under-performed (maybe he knew this and that's why he decided not to wear his HR monitor!) This is not atypical of a lot of riders in the early season, let alone for a rider who had been put through his paces by his evil Coach (I don't advise 3 back to back days of time trial efforts very often!). The normalised power of 348W is way below what we know he is capable of accessing. However, we need to get him up closer to 380W: if he were fresh, this might have been possible. But, we also need to develop his an ability to sustain a good race pace effort. The lab tests might tell me what he is capable of (over 10 minutes), but now we need to work on him holding that level over an hour long period - especially given this is the length of the lap in Boulogne he faces come late June. I believe this is where making Nic more efficient will come in to play. If we can do so, he is going to be more fatigue resistant - riding at 380W with less oxygen being consumed means he will be working at a lower % of his maximum - and therefore able to sustain that level for longer.

What next?

We have until the end of June to bolster Nic's time trial performance. The big priorities are to have him ride in his time trial position more often; and to ride a lot at race pace intensity. This twofold approach will see some shift in his race pace efficiency. He is hoping to return to the UK in a month's time - during which time we have a 4 week block of specific time trial training planned. After that visit, he then has another 4 weeks until the Champs in Boulogne. My plan for Nic is shaping up like this:

  • A 4 week block targeting his zone 5: we'll be looking to see Nic accessing higher powers than he currently can do - so we will targeting power of around 420W in some short, repeated efforts. He also has a big stage race (Tour de Bretagne) which makes total focus on time trial training tricky. We need to watch his state of "rested-ness" very closely.
  • Another week in the UK - more racing (over 10 mile and 25 miles) and also time in the altitude chamber at the University of Brighton. I'm hoping he can come over for 10d, as this will allow us to get him in the chamber just the amount we need for optimal dosing.
  • A final 4 week training block hitting his ability to sustain zone 4 (or 25 mile) pace. The aim will be to have Nic sustaining the higher powers we targeted in the first block above.
We'll also be spending time looking at the time trial course in Boulogne - one of the aspects of Nic's 25 mile TT performance on Sunday to be improved is the alteration of his power over varied terrain. He'll need this in Boulogne, as the course is run over a hilly profile. Nic has already ridden the course, and like last year his father recorded the ride on video. I plan to ride the lap with Nic too - but not at 380W!

What I gain from all this

even-pros-eat-cake

It has taken me nearly 6 hours to bring all this data together and write this blog post. I have really enjoyed doing so. Working on athlete data in this depth is one of the reasons I decided to leave the University and work more 'hands on'. As a researcher, I was always looking at spreadsheets of data - the difference now is that I get time to go deeper. As academics, we don't get chance to do what I have done in this post - the papers we publish show mean data of 10 'subjects', and we talk about trends across the group. In fact, its almost impossible to get case study data published, so we are not encouraged to explore very often.

'Depth' in my work is also about the relationship I have with my athletes. Having Nic come to stay in the UK gave us valuable "1-2-1" time. Whilst we speak on Skype a couple of times a week, face to face is best (especially if that means coffee and cake together!). I have no problem putting in a little extra time on people like Nic - I know it is appreciated, and I am happy to support a young guy like this as he attempts to hit the heights of his profession.

Bon courage Nic!

Published in Blog
Saturday, 13 September 2014 20:20

Training in Zone 6

PBscience_factsheet_logo

Training in zone 6 - VO2max intervals

Performance in endurance events is primarily limited by aerobic energy production i.e. energy being made available by the use of oxygen. Traditionally, the index of this ability is the maximal oxygen uptake, or VO2max. The VO2max is defined as the maximum rate that oxygen can be taken up from the ambient air and transported to and used by cells for respiration during physical activity. Check out our video of a VO2max ramp test to see how a sports scientist would measure this key parameter. It is the VO2max that describes the exercise intensity area of zone 6. This fact sheet explains why developing this ‘top end’ of your physiology can help your performance.

Why is ‘top end’ important?


For more information check out the following links

Training sessions for working in zone 6

VO2max test in the lab

Determinants of endurance performance

The physiological basis of the training zones

Setting your training zones

If you were to exercise at the intensity associated with your VO2max, you would typically last 4 to 8 minutes1. It would therefore make sense that in events lasting a similar duration (e.g. the 3 and 4km individual pursuit in cycling, or the 1500m in athletics), the VO2max would be the best predictor of performance. Indeed this is the case, with power outputs held in pursuits being very similar to ‘maximal minute power’ obtained in a ramp test. The time to exhaustion at maximum appears similar across different types of sports, but interestingly is inversely related to fitness2.

The relationship between VO2max and performance does extend down to less intense efforts too. Those events with durations of 30 minutes or less are still operating at high percentages of VO2max. Time trial cycling events (16km) and middle distance running events (10km) are run at ~ 90% of VO2max, and in fact, highly trained athletes appear to be quite stable at these high percentages of VO2max3,4. Some sport scientists argue that VO2max is the most important factor in dictating performance VO2, because it is the VO2max that sets the upper limit of VO2 at the race pace in events lasting one hour or so. Indeed, it is likely that a high fractional utilisation of VO2max is key because the higher you make your top end, the more likely that the rest of your profile is dragged up too. For example, consider a cyclist with a VO2max at 350W and a lactate threshold at 70% of this. If they worked specifically to improve VO2max power to 380W, they would likely also improve the LT by 20W (from 245 to 265. Furthermore, it is probable that there is some overlap in the mechanisms controlling both VO2max and high end race intensity. If a sport scientist observes an athlete with LT at a high % VO2max, they would likely suggest training to increase the ‘ceiling’.

What does limit VO2max?

Interest in the upper limit of aerobic fitness goes back to the work of Hill and Lupton in 1923, with research attempting to understand what controls VO2max ongoing ever since! Despite the amount of work performed, the exact mechanisms are still hotly debated by exercise physiologists. Essentially, the debate revolves around whether this upper limit is restricted by ‘peripheral’ or ‘central’ events in the body:

  • Peripheral: those aspects occurring at the muscle – number of capillaries, neuromuscular function, muscle fibre type, oxygen extraction capabilities. All these impact on the degree with which oxygen can be utilised by the muscle.
  • Central: factors within the central nervous system, and central circulation e.g. arousal, cardiac function, blood volume. All these impact on oxygen transport and the rate with which oxygen can be delivered to the muscle.

The figure below summarises these. It has been estimated that oxygen transport by the circulation controls 50% of the VO2max in exercise with large muscle groups5. As muscle mass decreases, peripheral factors such as the capillary blood flow and number of mitochondrial become more important as – so for the same person running and cycling, central factors might limit their running more than in cycling. It explains why cyclists often feel a VO2max test stops because of their legs!

Factors_determining_VO2max

How do we improve VO2max?

Like with any training aim, we must follow the principles of specificity. If, as the research suggests, VO2max is controlled by different mechanisms (e.g. central factors) to those in lower intensity exercise, it is important to stress the appropriate systems: in order to adapt, these systems must be stressed to a level to force re-modelling.

We know that VO2max is a product of the highest cardiac output (the amount of blood pumped around the body each minute) and the highest extraction of oxygen from this blood volume. Training to enhance either or both of these should lead to increases in VO2max. In a series of papers, Daussin and colleagues6, 7 looked at how these two products could be changed by training. In their first study, they found that interval training improved VO2max and cardiac output, more so than continuous, steady training of a similar total work. They concluded that interval training improves both central and peripheral components whereas continuous training was mainly associated with greater oxygen extraction. In their second study, they found the interval training more successful in changing the capacity of the muscle mitochondria to burn oxygen, yet capillary density was improved in interval work AND continuous training (in fact, to a greater extent in the latter mode).

Muscle fibre type changes do not appear to play a major role in VO2max enhancement in well trained individuals. This is mainly because the oxidative capacity of muscles far exceeds the cardiovascular systems’ ability to deliver the oxygen (i.e. increased rates of oxygen utilisation can always be instigated). However, working at VO2max intensities in training might recruit the fast twitch fibres preferentially. This would force them to become more oxidative, and add them to the muscle fibres usable in sustained, endurance events.

When would I choose to train the VO2max?

VO2max centred training is hard work, and will put great stress on the athlete’s system, so it is wise to consider when and how this training will be incorporated in the training year. You may use VO2max training in the following instances:

  • When looking to progressively increase VO2max to its maximum trainable limit over the many years of a runner’s competitive career. Several authors have suggested that athletes approaching their trainable limit for VO2max may even need to attain and maintain VO2max to elicit further increments8
  • After scheduled periods of low-intensity training and relatively low total training loads which have caused a transient decrease in VO2max (i.e. as part of a periodised training programme)
  • Peaking prior to competition when all physiological capacities are maximised to their trainable limit
  • After an absence from training due to a scheduled (holiday) or unscheduled lay-off (e.g. due to illness or injury). This training will lead to rapid improvements in form (if adequate base training has already been performed)
  • When decreasing the total amount of training time while still stimulating or maintaining a high level of cardiorespiratory fitness. Short bouts of training at and near VO2max may be effective in maintaining training during low training loads such as during tapering9

It is not recommended to start VO2max training without care and planning. Preparatory training should include several months of base training at intensities of 65–70% VO2max (zones 2 and 3) followed by transition training at 85% VO2max (zone 4)10.

What is the best training to do?

At the beginning of this factsheet, it was mentioned how the time to exhaustion (TTE) at VO2max is typically 4 to 8 minutes. This parameter has been used to optimise interval training sessions11, 12 – the idea being that athletes aim to increase the total time spent at VO2max in order to stress the appropriate systems as much as possible. When athletes perform high intensity intervals at the power associated with VO2max for 60% of the time to exhaustion, 40km TT performance and VO2peak increased (5% and 1% respectively)11. Using 60% of their own time to exhaustion gives an athlete enough time for the VO2 to ride to maximum in each interval – this is highly individual, as the speed of the oxygen uptake rise towards maximum levels may be longer or shorter than this: there is a need to decipher the time to reach VO2max for each athlete. Indeed, using a longer time to exhaustion (74%) is needed for some athletes to reach VO2max13.

So which is the best duration to use? Yes, using a higher % the TTE ensures VO2max is attained, BUT does it accumulate fatigue too rapidly? Perhaps it is better to extend the time spent at VO2max in the whole training session14 (i.e. the athlete can do more reps).

VO2max_training_example

Intermittent protocols have been found to be more effective than continuous protocols for maximising the time spent at VO2max – that’s pretty obvious, just try to as much work as you can at your maximal minute power in one go, compared to splitting the work into 3-minute blocks! Research points to the work interval intensity ideally being between 90% and 105% of the VO2max, enabling ~3 min. in each interval12. There has been a lot of interest generated in using smaller durations than this. Comparison of 15s on/15s off interval running and 4 x 4 min of interval running (at 90-95% HRmax) found similar increases in VO2max over 8 weeks, both being better than moderate intensities15.  Recent research has even begun to consider the use of more intense, short duration repetitions.

What about the recovery?

As soon as you mention interval training, we have to factor not only the intensity and the duration of the effort, but also the recovery. Intervals to boost VO2max require the emphasis of ‘aerobic’ functioning:

  • Recovery needs to be long enough to facilitate recovery and enable greater accumulation of time spent at VO2max
  • Recovery duration too long: yes, a higher intensity could be attained BUT, bigger contribution to energy supply from anaerobic energy metabolism.

Most research suggests an equal work rest ratio to be optimal. In a recent study by Rozenek and colleagues16 selected physiological responses to short-duration (< or = 60 seconds) interval work performed at velocities corresponding to 100% of VO2max were characterised. The researchers compared 15s on/15 s off (15/15); 30/15; 60/15; and a TTE trial at 100% of VO2max. They found high intensity, short-duration 2:1 W/R intervals to produce responses that may benefit both aerobic and anaerobic energy system development, and thus recommended these for training.

Again, in keeping with the fact that the recovery period is to facilitate recovery, you need to make sure the intensity of the recovery is kept low enough. Some continuation of exercise rather than purely passive rest is recommended though, as this keeps blood flow higher.

 

REFERENCES

1.   Billat & Koralsztein. Sports Med 1996, 22, 90-108.

2.   Billat et al. Ergonomics 1996, 39, 267-277.

3.   Perrey et al. Int J Sports Med 2003, 24, 138-143.

4.   Billat et al. Arch Physiol Biochem 1998, 106, 38-45.

5.   di Prampero. Eur J Appl Physiol 2003, 90, 420-429.

6.   Daussin et al. Am J Physiol Regul Integr Comp Physiol 2008, 295, R264-272.

7.   Daussin et al. Eur J Appl Physiol 2007, 101, 377-383.

8.   Billat. Sports Med 2001, 31, 75-90.

9.   Hickson et al. J Appl Physiol 1985, 58, 492-499.

10. Midgley et al. Sports Med 2006, 36, 117-132.

11. Laursen et al. Med Sci Sports Exerc 2002, 34, 1801-1807.

12. Billat et al. Eur J Appl Physiol 2000, 81, 188-196.

13. Laursen et al. Res Q Exerc Sport 2004, 75, 423-428.

14. Smith et al. Eur J Appl Physiol 2003, 89, 337-343.

15. Helgerud et al. Med Sci Sports Exerc 2007, 39, 665-671.

16. Rozenek et al. J Strength Cond Res 2007, 21, 188-192.

For more information check out the following links

Training sessions for working in zone 6

VO2max test in the lab

Determinants of endurance performance

The physiological basis of the training zones

Setting your training zones


 

 

Published in Free Factsheets