You’re on the floor of the gym. You’ve done your warm ups, drills and skills training and you are part way through your workout. You come to an exercise that you know and respect, it’s a big movement and the load is something you have done before several times. Still, you focus, prepare yourself for the next 4 min of pure solid output and go to take the first rep. You fail. You can’t seem to get into even the first position of the movement. You shake it off, walk away, take a couple of breaths and return to the mat to try again. Again you go, again your body just seems unable to summon up the co-ordination to perform the movement.
You’ve done this routine before, your muscles know what this is, you may be a little tired but physically you’re not spent – you’re half way through a workout routine that you know and have completed before. Still you can’t get past this first movement. Eventually you have to walk away from the mat and submit to defeat. You feel like you could still keep going but mentally you’re broken. There’s no preparation that can get you back onto the mat, back in the groove, back into form.
This can be more than just lack of physical ability. Neuromuscular Fatigue (NF) is something that effects every athlete, every body, every person. It’s a very unique line in each individual’s health and fitness that can not be negotiated with. It’s a block to being able to perform movements and it comes from the central nervous system, not from muscular ability.
NF is primarily a “change in the synaptic concentration of neurotransmitters with the Central Nervous System”. It’s the nervous system shutting down muscular function and control to prevent potentially damaging situations from causing harm to the system. The synapses (spaces between neural connections – think spark plugs in a car) can increase in particular neurotransmitters such as serotonin and noradrenalin to downgrade nervous function and prevent the body from being able to perform a co-ordinated or muscular action. The other element of note is that Seratonin in the brain itself can rise to levels that affect the brain’s perception of effort and peripheral muscular fatigue. It is this perception of fatigue in the brain that can trigger a brain to downgrade muscular activity to prevent damage.
Many elements contribute to these brain perceptions on a chemical level with the presence of certain elements in the brain and synapses all making a difference to the amount of perceived effort that the brain senses in it’s osmoreceptors. Hence dietary influence can have a huge impact on how much your brain allows your body to perform. Consider the following:
1. Caffeine delays the onset of fatigue in exercise
2. Carbohydrates by way of higher plasma glucose concentration can effect the perceived effort of exercise in the body.
3. Amphetamines block the reuptake of dopamine and norepinephrine in the brain that delays the onset of fatigue in exercise.
Essentially the brain is getting feedback from it’s osmoreceptors (nerve cells that measure dehydration, nutrition, body temperature etc) and armed with that information it can limit the amount of motor control mechanisms that the brain sends to the body. This is done to prevent peripheral muscular injury and prevent you from performing actions that will be dangerous to the homeostasis (balance) of the body’s system.
Central Nervous fatigue alerts the athlete when physiological conditions are not optimal so either rest or refueling can occur.
Many endurance athletes learn that the brain is key to performance and if it senses dangerously high levels of heat or chemical imbalances, it will try to prevent you from continuing an action. Some of us may remember the image of the Swiss marathon runner in the 1984 Olympics in LA where she was literally hobbling across the line. This is the perfect example of the body fighting against the will of the participant to complete the action. Gabriella Anderson’s body was shutting her down – saying YOU ARE AT RISK OF DAMAGING YOURSELF and trying everything to prevent her from taking another step.
Now this extreme case doesn’t have to be the example of reference, but another example is a CrossFit competitor who was an accomplished athlete in the middle of a performance WOD. This guy was a powerhouse – he didn’t even have to train squats – it was his go to element. A hard WOD was on the cards and he had to perform sets of muscle ups and handstand push ups before progressing to the Thruster set. He went out hard and fast in the first part of the WOD, feeling strong and powerful in the muscle ups. Perhaps faster than he had anticipated. He got to the barbell, set his grip and went to lift – NOTHING. He couldn’t do it. The weight was well below his 1RM and he had bashed this weight out plenty of times in much harder workouts. Due to his performance of going too hard and too fast initially, he was unable to muster the neural co-ordination to endure a relatively simple and achievable lift in the next round.
Much research exists on neural performance and fatigue in high intensity and endurance athletes. In a nutshell, the consensus of articles tends to value that the nervous system needs more time to recover from intense exercise than does the muscular and cardiovascular systems. Pushing into fatigue on hard days in a training regimen is beneficial, only if you also have your ‘easier’ or ‘off’ days. This allows all the systems in the body the time to recover and reset before optimal output is once again attempted. Endurance and strength actions are different in nature and each differs in terms of susceptibility to neural fatigue (strength athletes usually can train into fatigue more efficiently than endurance athletes due to the nature of how they train). Both types of athletes however are at risk of neural fatigue if they don’t consider the value of the restive in their training and performance schedules. This is why so many running programs have the deload or tapering phase in their build up to a long distance event.
With so many elements acting on neural fatigue, the lay person exercise athlete may not be as aware or cognitive of elements involved in their ability to keep training. The body doesn’t differentiate ‘type of stress’ it just perceives that it is stressed. This leads to an increase in cortisol and all manner of elements that effect our performance which can effect our levels of fatigue. It can also be a slip in missing a meal on that day, or recovering from a particularly complex workout from the day before that had an element of dexterity to it that wasn’t present before. This can be particularly indicated when you are involved in learning new movements or skills. These perceptions make a difference on our ability to recover. So if you find yourself being unable to perform something that you have been able to achieve before, don’t berate yourself too much and definelty don’t sit on the floor of the gym slapping your legs with tears in your eyes thinking ‘come on body – you can do this’. Sometimes it’s best to know that you are not able to today and that tomorrow you will!