Can you dig deeper?

What is it that prevents you from knocking 1 minute off your marathon time, curtails a 3 hour ride early or has you exiting the Ironman swim and transitioning straight to your car?

Fatigue was one of the key areas of discussion at the Science and Cycling Conference in Nantes, France. Here, I’ll attempt to clarify exactly what fatigue is and, thanks to former pro cyclist Lieselot Decroix, reveal how your nutrition strategy might be able to manipulate your brain into helping you perform at your best.

What is fatigue?

Historically, fatigue was typically viewed as a mechanical breakdown. You reach a limit in your ability to pump oxygen to your muscles, lactic acid accumulates in the blood, raising pH levels and, as a result, you slow down or stop.

But, over the past 20 years we’ve come to realise that, to a greater extent than previously imagined, those limits are determined by our brains.

In the late 90s, Prof. Tim Noakes suggested that the brain holds the levers of a subconscious safety mechanism that kicks in to prevent serious damage to our vital organs.

This self-preservation mechanism - known as the “central governor” - seemed to explain why athletes running on hot days tended to start slower than they would on cooler days.

If the subconscious brain perceives a threat to the body’s homeostasis, it reduces muscle recruitment and slows you down to prevent your core temperature rising to dangerous levels.

Then there’s the more recent work of Prof. Samuele Marcora, an exercise physiologist at the University of Kent. He agrees that the brain controls the body’s brakes, but he argues that fatigue and endurance performance depend primarily on the conscious brain, and specifically on how we perceive effort.

He insists that even the greatest athletes quit or ease off not because their bodies can no longer go on, or even because the subconscious brain steps in, but because they think they've reached some maximum effort level. At that point they make a conscious choice to stop.

In addition to Marcora and Noakes' work, there’s the energy-depletion model, neuromuscular fatigue model, muscle-trauma model, the biomechanical model, etc etc...

“Certainly the Marcora and Noakes’ models have led to huge debate on Twitter,” fatigue expert Prof. Dominic Micklewright of the University of Essex tells me in France, “but recent work suggests it’s content-specific. In other words, sometimes fatigue’s down to the physical, sometimes the mental.”

This is known as the ‘complex systems model of fatigue’ that, broadly speaking, brings together several theories, stating that at different stages of effort, different fatigue factors kick in.

Take the fatigue that you might experience during a prolonged period of cycling at a relatively constant cadence and power output.

Local ‘fatigue’ (pain!) is felt in your quadriceps that ultimately ends with plummeting power, or you stepping off and chomping down some cake. 

That is, of course, unless you stand out of the saddle. Even for just a few revolutions, this can relieve the local sensation of fatigue and, when settled, you resume back in the saddle at your previous power output.

Then there’s the fatigue that kicks in after six hours in the saddle, which is arguably simply down to boredom and a lack of motivation.

“Ultimately, the translation between sensory stimulus and how that’s experienced (perception) has an enormous influence on your performance,” Micklewright explains.

“I’ll give you a further example. We placed time-trialists in front of a video screen that simulated a ride, but over two trials we altered the optic flow. In other words, we placed on them the same amount of work but changed the screen speed so it reflected faster or slower speeds.

“We then measured their rate of perceived exertion (RPE) throughout. Interestingly, the slower optic speed resulted in a lower RPE for the same amount of work and cadence. You might think that per unit of work you’re progressing less, so surely perceived exertion would go up? But no, it worked the other way around. The fact that the optic speed was slower suggested to the rider a lower work rate and lower exertion.”

Intensity and deception

Micklewright’s work highlights just what a subjective thing fatigue is.

But what does this mean for your performance?

One thing that comes up time and time again is intensity of training.

“Interval training is fantastic as it stretches the body and the mind,” Andreas Venhorst, a graduate student at the University of Cape Town and a former elite Ironman competitor, once told me.

“Studies have shown that interval training can make someone quicker after just four sessions. That’s too soon for physiological changes, so it reveals that you’re training your mind to tolerate harder work.”

You can also seek out deception.

In 2011, Kevin Thompson, now at the University of Canberra, had a group of cyclists undertake a 4km time-trial against an on-screen avatar that the riders thought was going at their best pace. In actual fact, it was 1% faster.

Despite Thompson’s deception, riders kept up with their virtual rival, cycling faster than they ever had before. “That showed us that the body has an energy reserve of 2-5%,” Thompson told me.

The method seems to work even when the riders know they’ve been duped. A team at the Indiana University worked with Thompson to replicate his earlier study and, again, the majority of riders beat their best by 2% when racing the avatar.

Then the researchers told the athletes they had been deceived and asked them to race the competition one more time, again at a 2% faster pace than their personal best. “So they knew it was higher than their original best but they still managed to beat it,” says Thompson. “They’d shifted their pacing template.”

Clearly it’s hard to deceive yourself, so this is arguably more one for coaches, but it should tell all of us we’re all capable of digging deeper.

Which is where those intervals come in.

You can also encourage better brain – and, subsequently, sporting – performance. In Prof. Chris Cooper’s excellent book ‘Run, Swim, Throw, Cheat: The Science Behind Drugs in Sport’, Cooper identifies the brain as a neglected area of both legal and illegal performance enhancement. 

Nutrition hacks for your brain

This is a subject former professional cyclist and sports-scientist Lieselot Decroix picked up on at the conference in Nantes. “Whichever model of fatigue you believe in, neurotransmitters play a key role,” she explained. And this is the key to supplement intervention, specifically dopamine. “Dopamine is a neurotransmitter and impacts motor behaviour, especially in the heat.”

Dopamine plays an integral role in the thermoregulatory centre of your brain, which is why changes in dopamine concentrations have been shown to affect core temperature regulation during exercise.

This is key because, although studies into endurance exercise in normal temperatures show no significant change over a placebo, at 25°C (77°F) or above performance is improved with a dopamine hit.

Dopamine is synthesised in the body, so you can’t simply consume dopamine. But, there are foods and supplements that’ll ultimately boost your dopamine levels, including the amino acids L-theanine and tyrosine, fish oil and the phospholipid ‘phoshatidylserine’.

Interestingly, Decroix also focused on concussion in sport and the effect of dopamine. “Similarly to fatigue, the exact mechanisms behind concussion aren’t fully understood, but it’s pretty much accepted that damage to the plasma membrane of the neurons impairs the regulation of metabolism, which increases oxygen distress, heightens inflammation and decreases cerebral bloodflow. The area needs research but dopamine could help all three.”

Decroix’s shortlisted the following supplements as ones worth trying… 


“We’ve looked at scientific evidence in humans and know that an acute intake of caffeine of 3-6mg/kg bodyweight improves cognitive and physical performance. It also decreases perception of effort."


“Studies show creatine supplementation raises ‘brain creatine’ levels by 10%, which then increases phosphocreatine synthesis and leads to more brain energy. Scientific evidence in humans shows that this can improve cognitive performance, albeit with the risk of weight gain."


“There’s some evidence that suggests ketosis (when the body’s almost entirely fuelled by fat) rather than exogenous ketones (which come in drink form and are prohibitively expensive) reduces neurological inflammation and improves cognitive function. However, there’s no firm evidence – yet – that suggests it improves physical performance."


“These antioxidants increase cerebral bloodflow, which might improve both cognitive and athletic performance. There are also flavanols, which are mainly found in cocoa. Again, these increase cerebral bloodflow.

In theory, this could improve decision-making. This was the subject of my PhD but the results were inconclusive. More proven are the effects of beetroot. Beetroot’s a rich source of nitrates, resulting in higher cerebral bloodflow and better cognitive performance.”

Your brain is clearly central to your physical output (and that’s without touching upon psychological constricts like motivation) and with a bit of experimentation you might just be able to encourage your brain to help you dig that little bit deeper when it counts...

Further reading