Central nervous system (CNS) fatigue is a concern mentioned by powerlifters and other athletes. They fear lifting heavy weights too often near their one-rep max (1 RM) in the big compound exercises. Dead-lifts especially are shunned with many lifters that include them will do so only once every couple weeks.
Some use the concept to criticize training to failure. They argue it overburdens the nervous system and is unnatural.
They use more isolation to stimulate their target muscles without activating too many others.
They may cycle intensity and exercises to avoid CNS burnout.
Others use nutrition and drugs to overcome it.
The main idea behind CNS fatigue is that activating many motor units at once seems to drain the body specifically. This form of fatigue also tends to accumulate slowly.
Delayed onset muscle soreness (DOMS), on the other hand, appears within a couple of days.
Perhaps due to its less than clear-cut nature, some question if it is even real. They have suggested it may involve hormones instead. Some feel it may be psychological.
The limited research into the phenomenon does suggest real changes. An increase in serotonin activity within the brain along with a drop in dopamine seems to take place when trainees have it. For the peripheral nervous system, lower levels of acetylcholine may limit muscle contraction strength.
Trainees describe that it harms their mood and sleep. They may feel anxious or even depressed. It may slow the speed of excitation for the fast-twitch muscle fibers, which would explain why the effect seems greatest at weights close to the 1 RM.
They feel a lack of focus and motivation along with a delayed reaction time. Everything feels tougher than it should.
Some Conclusions on CNS Burnout
I’m not one of those complicated, mixed-up cats. I’m not looking for the secret to life… I just go on from day to day, taking what comes.
– Frank Sinatra
There definitely exists fatigue beyond what affects the muscles locally after a workout. CNS fatigue likely can and does occur. Overanalyzing it though will lead you down the endless paths to nowhere.
You do not have to understand all the details of the training and recovery processes to make sound choices. If anything, dwelling on them will tantalize you.
Eat enough food, sleep long and well enough, and lift heavier weights with as much rest as needed between sessions. This will build muscular strength and size. Focus on these broad categories, and you will get just about the best results you can achieve. CNS issues should not limit you.
Periodization is a valiant if flawed attempt to surpass our limits. It aims to manage the many forms of fatigue. These complicated, long-term programs cycle the emphasis on various fitness goals, overreaching for some while backing off on others.
CNS fatigue seems more likely to occur with split routines, especially the ones that have you train most days of the week. It matters not that this may balance for the local effect by dividing up the muscles properly. Though this may work for some, average trainees are more likely to fail versus the drugged and those with elite genetics.
Lifters will avoid the top compound exercises to protect the CNS. They then replace the best and safest options with isolation exercises. They may rotate between many bad exercises to avoid burnout and for the sake of variety as well.
Consider that training to failure only means that you will fail with a given weight. If you could reduce this weight slightly and immediately after the hardest rep of the set, you could continue. This along with other advanced techniques though is unnecessary.
Feeling the burn and getting sore are not the main stimuli for more strength and size. Tension, or the squeezing of the muscles, stimulates growth foremost. This is achieved by training hard with heavy enough weights.
Avoid Overanalyzing Central Nervous System Fatigue
Many forms of fatigue affect the body. They are complex. Gaining a complete picture is futile.
The journey to do so may paralyze you. Those that venture down this road come to reach rather bizarre, narrow-minded conclusions. They avoid focusing on the right things and sift through countless grains of sand to find diamonds.
They may very well come to understand a piece of the puzzle but then overemphasize its role and ignore its relationship with the whole.
Balance your training, rest, and nutrition variables. Avoid overtraining that comes from exercising too much, too long, and too often. Get enough sleep, rest, and food.
This is all rather simple and easy to figure out. What people lack though is self-discipline. They seek quick and easy fixes.
If you train ideally to positive failure within any reasonable rep range, perhaps with an upper limit of 30 reps due to energy systems, you will recruit the fast-twitch fibers most responsible for the changes you want.
I suggest moderate reps not so much due to any dread of CNS burnout but because lifting too closely to your 1 RM can be dangerous. The idea that you can train close to your 1 RM to focus on strength and limit muscle growth is false as well. You do not need to lift close to your 1 RM to gain strength and size at the fastest rate. Powerlifters and Olympic lifters need to work close to this limit only for their sport.
Beginners can thrive with 2-3 bouts of an exercise per week. They may need to eventually consider once a week though. They can determine when they need to change because they hit an insurmountable plateau.
Progress embodies everything. Judge your results by progress alone, by improving a tad in weight or reps from session to session. This will summarize any complexity with a simple measurement.
If you experience CNS fatigue, it reveals a problem. This fatigue is real, but avoid dwelling on it alone. Consider the advice here as a way to perceive it correctly.