A Fireside Chat on CNS Fatigue

More is better. This methodology is predominant not just in the field of strength and conditioning, but also in general lifestyle of the average American. More stuff, more food, more money, more Starbucks. As coaches often time we want more effort from an athlete and it just isn’t there. More can be worse when it comes to working with higher level athletes. One of many reasons why more isn’t necessarily better is “Central Nervous System” fatigue.

CNS fatigue is the blanket term used by many professionals in athletics that usually encompasses two things: Peripheral Nervous System (PNS) fatigue and (CNS) Central Nervous System fatigue. PNS fatigue involves a breakdown in the interaction between the Nervous system and the Muscle cells. CNS involves a breakdown in the function of the brain and spinal cord’s ability to execute movements and motor programs. For all intents and purposes let’s call both terms CNS fatigue.

So how can you fatigue the CNS? Think shortest duration, highest intensity. For sprints the closer you get to 100% effort the more taxing on the CNS the activity is. Sprint starts, 100 yard sprints, high intensity (heavy) sled pulls, high volumes of max effort med-ball tosses are all CNS intensive. In the weight room doing heavy strength work on bigger movements (Deadlift, Squat, Clean) to failure also taxes the CNS. If athletes are moving weight heavy enough to keep their repetitions down to 5 or less, then the CNS is producing the lion’s share of the force. When intensity decreases to allow for more reps (6-12+) the muscle organ itself is mostly affected. Pretty basic stuff so far, right? What people tend to overlook is that there is a finite store of energy (for lack of a better term) that athletes can pull out of their CNS. Many coaches tend to overestimate this amount of energy and underestimate the amount of recovery time necessary to refill this “gas tank”.

If athletes “don’t have it today” in the weight room or aren’t hitting weights simply because they “don’t have it” many times it is due to their CNS being fatigued. If a high level sprinter has been hitting several 100% sprints at 100m and does a personal best that day in practice and then goes and tries to lift heavy on squat and is having trouble and the coach wonders “hey, what’s going on here?” then that coach needs to drop everything and go read Charlie Francis’ Training Systems and if that doesn’t work… well the world needs plenty of bartenders, my friend. Higher level athletes (college and above) should be treated like a high end sports car as opposed to a snow plow that you can work into the ground. Athletes should be fresh and be able to produce the highest quality in order to produce the best gains. The proper rest time to allow for full CNS recovery can be 48 hours to 10 full days depending on the athlete. An Olympic level athlete that completely drains their CNS will need 10 days. The lower the athletes level of skill and proficiency at the exercise the less time is needed for this recovery. A junior varsity sprinter at high school level won’t need 10 days for their CNS to recover from doing full sprints; they might need 2-3 days at the most. Again, much of this is dependant on the individual needs of the athlete.

So, how does a coach adjust their programming accordingly? First of all, coaches need to look at what athletes are doing before they come in to workout. Does the athlete have practice before they come in? If so, what are they doing in practice? Have they been sleeping well? Are they stressed (can anyone say Cortisol)? These are all things a coach should consider. Many coaches aren’t in a position to know all the details of their athletes’ personal life, however there are things that even coaches with multiple large teams can consider. Just one example is trying to Max cleans or squat during finals week. How much effort will a sleep deprived, stressed athlete coming down off of a week-long Caffeine high?

The coach should always be aware of the athlete’s CNS state. If an athlete is in a state where their CNS is fatigued it will many times look like a general state of malaise. Sleeplessness, lack of concentration, and even trembling post-workout are all signs CNS fatigue. Grip strength is a simple indicator of CNS readiness. Remember the homunculus model learned in college A&P? A huge area of the brain is dedicated to the hands. Using a grip dynamometer to measure baseline strength level and then testing where athletes measure up too can be a great indicator of how ready their CNS is for heavy work. A cheaper option would be to get some Captains of Crush grip trainers from Iron Mind (as recommended by Gray Cook and Brett Jones) and test how times the athletes can completely touch the ends.

According to Charlie Francis, “All CNS work should be very high quality work in terms of effort and technique.” If a player is lagging, sometimes it isn’t just because they’re lazy (sometimes they are just lazy) it could be because their CNS is fried. Not everything can be fixed by heavy back squats and power cleans. Rest needs to be thought of as a training element like any other.