Find out how scientists are questioning what really causes fatigue, limits human performance and how you can trick yourself into beating PBs!

Port de Pailhères, Summer 2004

I arrived at the base of the Port de Pailhères, a ‘hors catégorie’ (beyond categorisation) mountain in the Ariège department of the French Pyrénées. The road wound and zig-zagged up the terrain ahead of me; 15.5km, 871m of elevation, an 8.2% average gradient reaching a maximum of 10.2% in places. It was a hot day, over 30 degrees centigrade, but I felt good; warmed up from the spin along the relatively flat road from my home in Limoux to Mijanes, the town near the start of the climb.

It All Started So Well…

In 2004, my statistics were as follows: 

  • Rider weight: 63kg
  • Bike weight: 7kg
  • 60 min power: 320 watts
  • Power-weight ratio for 60 min power: 5.08 w/kg

Strava was still a twinkle in Michael Horvath’s eye so the plan was to test myself against myself; a sustained threshold effort over the entire climb, reaching the 2009 meter summit in around an hour. I was planning on a ‘negative split’ pace, using power to gauge the effort, holding back slightly at the beginning so I could produce a higher average power for the final section of the climb which features a series of demanding switchbacks. Based on previous performance, I should have produced a 320 watt average over the climb as a whole.

I was well hydrated and fueled, with carbohydrate stores replenished from a few days of rest and easy riding prior to this test. The 60 minute effort should have expended around 1200 Calories. It’s estimated that an average 70 kg male has 1500-1600 kcal of stored carbohydrate in the liver, muscles and circulating blood glucose., so I should have had enough high-energy fuel on-board to supply the requirements of the effort.

Read more about how understanding fuel energy metabolism may help to improve your cycling performance, here

Hill climb

Pacing As A ‘Budgeting Decision’

The preview summary for Ross Tucker’s presentation at the 2014 World Congress of Cycling Science, described pacing strategy as:

“a budgeting decision, by means of which an exercising athlete makes decisions about how best to ‘spend’ physiological capital while accumulating the ‘costs’ of the exercise exertions.” 

This is consistent with Foster et al (1993) who suggested that a pacing strategy could be defined as the “allocation of physiological resources during self-paced exercise”.

What Is The Optimal Pacing Strategy

There are many approaches to pacing, with the principle influence on the optimal strategy being the type of exercise and duration.

Short Duration Pacing

Research and anecdote suggest that for efforts less than or equal to 30 seconds an ‘all-out’ positive strategy works best i.e. go as hard as you can then hold on for dear life.

Longer Duration Pacing

For longer durations (greater than 30 seconds), even pacing, negative splits (becoming progressively faster) or ‘endspurt’ strategies (think of a ‘final sprint’) appear to be the most effective (Tucker & Noakes, 2009)

Performance Testing Up Pailhères

Alpine Road2

It was warm at the base of the climb. I was already sweating but started with a strong, controlled 305 Watts, dosing my effort carefully and selecting a gear resulting in a cadence of around 90 RPM. My breathing was even, the effort aerobic and my sensations suggested it was a sustainable pace, a manageable accumulation of lactate smoldering in my quadriceps.

20 minutes in, all vital signs are still within acceptable range.

30 minutes in, breathing is becoming more labored, I’m getting hot, but I push on, focussing on the metronomic pulsing of my pedal stroke.

35 minutes in…. has it only been 5 minutes? I pour a bottle of water over my head. It’s all in the head. Isn’t it? My power is dropping off…

38 minutes… bloody hell, how can there be 22 minutes left. Must hold at least 300 watts…

40 minutes in… 290 watts. I’m really hot now.

41 minutes in… BOOOOOOM!

The Man With The Hammer

In case you didn’t guess, at 41 minutes in my performance test ground to an unspectacular halt. In truth, less ‘BOOM!’, more of a deflation, like a faulty blow-up mattress. So what went wrong? My pacing strategy was rock solid based on previous performance. I already mentioned that I was well fueled and hydrated.

What Factors Influence Pacing & Limit Performance?

Afferent Feedback: ‘Information’ from the peripheral nerves of the body to the brain.

Efferent: ‘Information from the central nervous system to the body. 

Since 1923, when Nobel Laureate A.V. Hill suggested that maximal exercise performance was limited as a result of the metabolism of exercising muscle becoming anaerobic, models of human performance have often described a ‘brainless’ system. These approaches focussed on physiological and metabolic factors that could be related to fatigue: depletion of energy reserves, accumulation and storage of heat, accumulation of metabolites and resultant afferent feedback (‘signals’ from the peripheral nerves of the body to the brain or spinal cord) and even cerebral oxygen delivery. 

This perception is still prevalent in some circles and probably most visible amongst sports commentators who delight in describing how ‘lactic acid’ is building up and creating all manner of complaints from reduced running speed to cramp. However, it’s become clear that the limits to human performance are more complex (and lactic acid is not the ‘baddie’ we once believed, but I’ll save that for another blog).

Take my n=1 ‘study’, for example. At the time, I was convinced that my performance was limited by getting too hot – the accumulation and storage of heat – but is it as simple as that? Perhaps I just thought I was too hot…

Factors In Fatigue

Physiological & Metabolic 

  • Depletion of energy reserves
  • Accumulation and storage of heat
  • Accumulation of metabolites and resultant afferent feedback
  • Cerebral O2 delivery


  • Perception of pain
  • Prior-experience
  • Anticipation of exercise duration
  • Motivation
  • Cost-benefit decisions


Understanding The Mechanisms Underpinning Fatigue

By manipulating variables in an athlete’s environment (both internal and external) and monitoring the rider through multiple channels – time to exhaustion, power output, time to complete a task, arterial oxygen content and even electromyography to explore muscle activity – we can use pacing as a tool to understand the mechanisms underpinning fatigue.

Is Fatigue All In The Mind? Pain Killers & Performance

At the end of a challenging interval or race winning effort, you may feel like you’ve given your all, exhausting your muscles, but in reality, this is not the case. Your brain stopped you ‘getting it all out’.

Fentanyl is pain-killing drug which blocks afferent feedback – the signals from your muscles to your brain. Studies have demonstrated that Fentanyl will allow athletes to work harder than is normally possible. When the brain doesn’t know what’s going on in the muscles, it allows them to become more fatigued than it usually would, potentially improving performance. This finding illustrates the powerful influence of the brain as a ‘Central Governor’. Could it also explain the popularity of Tramadol in the peloton?

Ultimately, in most situations the brain is conservative. It would prefer that we didn’t try to race up mountains as fast as possible!

Hot Sportive

Heat Experiments: Improving Comfort Enhances Capacity To Maintain Intensity

Non pharmaceutical interventions have also illustrated the power of perception. In 2011, Zachary et al. used a menthol solution to independently alter athlete’s thermal perception and skin temperature during exercise.

Intensity was regulated by the athlete, using a fixed rating of perceived exertion (RPE).  The results of the study demonstrated that using the menthol to improve the rider’s ‘thermal comfort’ and reducing sensations of warmth enhanced the rider’s capacity to maintain exercise intensity, even though skin temperature did not change.

Just Tell Yourself It’s Cooler Than It Is!

So what do you do if you don’t want to take pain-killers or spray yourself with menthol? Just tell yourself it’s cooler than it is! In 2011, Castel et al. conducted a study which involved deceiving athletes. The researchers asked the subjects to carry out a 30 minute cycling time-trial at different temperatures and humidities, but provided incorrect visual feedback of their ambient and core temperatures, suggesting that the room and their temperature were lower than it actually was.

The findings were compelling:

“Deception improved performance in the heat by creating a lower RPE, evidence of a subtle mismatch between the subconscious expectation and conscious perception of the task demands.” 

In the hot-humid test, the ambient temperature was 31.6°C with a relative humidity of 65.4%. In the ‘deception’ test, despite the conditions in the room being the same, the participants believed that the ambient temperature was 26.0°C, the relative humidity was 60.0% and they were also told that their core temperature was 0.3°C lower than it actually was. Control conditions were 21.8°C at 4.3% humidity. The results were as follows:

Distance Covered

  • Control: 16.63 ± 2.43 km
  • Hot: 15.88 ± 2.75 km
  • Deception: 16.74 ± 2.87 km

Mean Power Output

  • Control: No different with Deception test
  • Hot: 168.1 ± 54.1 W
  • Deception: 184.4 ± 60.4 W

So if you want to improve your performance in the heat, convince yourself it’s 5°C cooler than it actually is!

Micro Goal-Setting To Improve Performance

Micro-goal setting is a technique I’ve applied since early in my cycling career. I found it almost by chance when I discovered that I could significantly improve my climbing performance (measured of course) by tricking myself into believing that I only had to get to the next imaginary ‘check-point’, then I could climb off. However, as soon as I arrived, I immediately selected a new point, often as arbitrary as a pot-hole or plant, and convinced myself that I only needed to get to this before enjoying the blissful break. I’m perhaps not a particularly sophisticated mind, as I was able to effectively convince myself to endure inordinate amounts of pain for extended periods using this simple game.

You can find a good piece related to this subject here. You may need to skip over the unhelpful commentary on lactic acid and the fact that the author suggests that Ivan Basso is a “mountain bike rider”, but the psychology is compelling.

In summary, there are a number of ways to approach this technique, but a practical application is to set a series of targets for a particular segment that you’re riding. Each target should be within sight. One at a time, focus on finishing the section leading up to this target, checking it off before quickly setting a new one further up the road. Breaking a task into sub-goals should improve your performance.

A Warning Against Polarizing The Debate

Like many areas in science, the debate between peripheral and central governors of fatigue runs the risk of becoming unnecessarily polarised. Whilst peripheral/metabolic (what’s going on in the tissues) factors are important, they cannot explain fatigue in entirety. Similarly, central (neural) models based on the nervous system can’t describe everything that we encounter during sport and exercise.

Fatigue and the regulation of pacing strategy are a complex combination of central, peripheral and psychological factors.

Practical Advice To Optimize Your Pacing Strategy

If I was to do my Port de Pailhères performance test today, the following list represents the steps would take to ensure optimal performance:

Take steps to prepare myself physically: rest, fuel and hydrate appropriate

  • Choose a pacing strategy appropriate to the duration of the climb by modelling various approaches at CyclingPowerLab.
  • Use a power-meter to pace your event.
  • Convince myself it was cooler than it actually was!
  • Break the climb down into sub-goals, perhaps as simple as the stretch of road leading up to the next tree I could see, or even a mark on the road.

Feel free to try these on your next ride and let me know how you get on! If you’d like to receive more insights and advice from the world of cycling science, you may want to sign up for the James Hewitt Cycling Performance Newsletter.