Have you ever pushed yourself so hard in a workout that by the end, you feel like there’s no way you could have pushed for even one more second? Or, have you ever watched running events where participants literally collapse at the finish line, as though their legs are physically unable to hold them up any longer? These situations, where we push ourselves to the absolute limit and can go no further are explained by fatigue. This is defined as “any exercise- or non-exercise-induced loss in total performance due to various physiological factors, athlete-reported psychological factors, or a combination of the two.” In other words, it’s the decrease in ability to maintain a high level of exercise due to either physical or mental factors.
There are two types of fatigue, the first being peripheral. You’re probably familiar with the burn that comes when holding a squat or at the end of a rowing sprint – it makes you grit your teeth, as you try to push through an intense need to straighten your legs or slow down.
For a long time, this burn was attributed to the build up of lactic acid in our muscles. As exercise increases in intensity, the production of lactate (a byproduct of our anaerobic energy system) overtakes our body’s ability to clear it. It was thought that this, along with oxygen and glycogen depletion and raised body temperature, was key in explaining why performance declines over time. So, ultimately, it was thought that limits placed on performance were purely physical.
However, there are some flaws to this argument. It cannot explain how people sprint at the end of a marathon or why you’re suddenly able to push that much harder for the last minute of a workout. When Ben shouts, “20 seconds left!” during a 30-minute row, most of you will find the energy to dig deep and push harder to get as far as you can in those last seconds, right? Well, if fatigue really was purely physical, then you wouldn’t be able to find that “second wind”, because you’d be getting ever-closer to your physical limit.
What’s more, research has shown that skeletal muscle is never fully recruited (only 60% of muscle mass is ever used during maximal exercise). If fatigue were purely physical, then we would expect to utilise all muscle fibres until all become completely exhausted. The only explanation for this is that our brain stops us before we are able to recruit the rest of our muscle fibres.
Newer findings support the idea that fatigue cannot be explained by physical factors alone. The central governor theory goes as far as to argue that fatigue is a sensation completely manufactured by the brain – so it’s all psychological. According to this theory, fatigue symptoms exist to stop the body reaching any point of failure – essentially, your brain makes you feel that you can’t go on, to prevent you from doing any harm to yourself.
This would mean that symptoms associated with fatigue are not a result of physical reactions happening in your body, but are triggered by your brain. This model suggests that the best athletes in the world are not only the strongest and most skilled physically, but also have the best control of these illusory fatigue sensations.
Further evidence for the role of the brain in fatigue comes from the fact that there is usually an anticipatory element to exercise. For example, if you know you are only going to be working for a short time, you will begin exercise at a much faster pace (HIIT capitalises on this). In contrast, longer bouts of effort will cause athletes to begin exercising at a less intense pace. Exercise will always begin at a pace that the brain believes is sustainable for the duration of exercise. Furthermore, people are usually able to go harder in competition than in training – often, athletes who feel that they consistently push themselves to the max in training are able to go even further in competition and reach new personal bests. This is likely due either to a reduction in fatigue sensations created by the brain or an increased ability to override them within the competition setting.
In reality, it’s most likely that fatigue is explained by both physical and psychological factors, not purely one or the other, but it’s still important to note the crucial role that the mind has to play in pushing the limits of the body.
A new area of research is looking into the effects of mental fatigue on performance and studies have found that a tired brain affects performance as much as a tired muscle. During a study on football players, those that had been mentally fatigued before training (by completing a mentally
demanding task) reached the point of exhaustion faster than those who hadn’t. Moreover, although
both groups performed at the same level of physical exertion, the mentally fatigued group believed they were working harder.
This kind of mental fatigue can be brought about by sleep deprivation, which partly explains why you may struggle more than usual after after a bad night’s sleep. Athletes are now engaging in “brain training” where they perform mental exercises in between short bursts of intense exercises, to practice performing at a consistently high level despite mental fatigue.
So, if fatigue really is in part controlled by our brain and it is possible to overcome these sensations
to push even harder, how can we train ourselves to do this? According to Tim Noakes, the leading
researcher in this topic, self-confidence and positive reinforcement is key. Constant positive feedback from our trainers will infiltrate into our beliefs about our ability, so we are able to trick our brains into believing that we can actually push harder without reaching that harmful limit that our brain wants us to avoid. If you’ve been to a class at Grow (and if you haven’t, what are you waiting for? Book here!), you’ll know that our trainers top priority, after making sure your form is tip-top, is motivating you and encouraging you throughout your workout, helping to push you beyond what you ever thought you were capable of.
Another method of reducing time taken to fatigue is being used by many endurance athletes already. The concept of “carb-rinsing” involves mouth washing with a carbohydrate source (e.g. a sports drink). Although you are not actually ingesting any glucose, the glucose acts on receptors on your tongue which send signals to your brain to tell it that it’s receiving carbohydrates. Your brain will then potentially reduce fatigue sensations.
Lastly, crucial to performing at your best is to begin the workout with a positive mindset and high motivation. Once you acknowledge all the reasons why you may only be able to perform sub- maximally, you are setting yourself up for failure by allowing your brain to produce fatigue symptoms earlier than necessary. If you begin exercising with the belief that you are at your peak and able to push yourself, it is far more likely that you will indeed be able to exercise much more intensely.
As it turns out, the age old of saying of “mind over matter” really does have scientific basis and could be the key to achieving peak performance…