When to Rest

Tuesday October 4, 2011

A. Back Squat


B. 15 Minute AMRAP

6 Back Squat (185/105)

9 Ring Dips

12 Knees-Elbows

Strength Rest vs. I'm Tired Rest

You're at the pullup bar.  You're pushing as hard as you can, taking as little rest as possible, but the pullups just aren't coming easy.  No matter what you do, how hard you push, the muscles just won't respond. You're doing burpees.  It's you're last round and these last 15 feel like slow motion.  You hunch over, the only position that seems to give you some solace from the burn.  You are resting, because that is what your body is telling you to do.

These two scenarios show up in the gym everyday. The first scenario A, is a perfect example of muscle fatigue. Exercise physiologists have a few theories on why these muscle failures happen and I'll go into some detail about this.  When our muscles contract to produce force, it is the nervous system that tells them too.  The nervous system is governed by the brain.  As the brain becomes aware that we tired, it slows sending those contracting signals to the muscles. This is not a conscious process, in other words, will and fight may not overcome the obstacle at hand. With rest, however, the nervous system recovers and that pesky handstand pushup or pullup is completed. A recent Colombia University study found that furing intense exercise, calcium begins to leak from channels within a muscle. This is important because we know that calcium is one of the main minerals that sends the electrical signal for muscles to contract. When calcium is depleted, muscles will have weaker contractions.

Scenario B is a bit different. The muscles are not necessarily failing here but the perceived exertion by the brain is what is holding you back. This type of fatigue known as central fatigue, can be brought on by a variety of factors, especially psychologic ones. We've all had moments in workouts where we think, "There is no way I can do this", but somehow finish the task more easily than originally thought.  This mind over matter phenomenon can be seen in a variety of settings, but I feel CrossFit is one of the best examples of all. Every day we push our bodies to the brink of exhaustion, and always come out of it to tell the tale.

Back to some physiology. Our brains are adapted for survival. It would not be beneficial to use up all your energy hunting for prey and then have zero gas left in the tank when the saber toothed tiger comes along and makes you the prey. Our brains tell us, "Whoa, don't pick up that barbell just yet in case something serious goes down and you have to sprint your ass out of this building because of... (insert threat here.)" The point is, we are are both consciously and subconsciously saving energy.  Ever look back on workouts and think, "If I just pushed a little more on blank, or if I rested less there, etc."

Okay so what's the difference between scenarios A and B?  First of all, I would argue that there are a lot more physiological limitations in A. Your nervous system and muscles are either going to work or they aren't.  There are definitely exceptions, but simply willing yourself over the bar won't always work.

How do you apply this in the gym? REST! Yes I am actually telling you to take rest on strength exercises. These include HSPU's, Pullups, Barbell lifts, and anything else where outright failure occurs. Take some deep breaths, let that calcium flood back in and get after it.

Scenario B is a bit trickier.  Because there are more mental factors at play here, each person will be quite different with variables like diet, prior training, sleep, perceived exertion, and motivation determining rest periods. Running, rowing, burpees, jump rope, KB Swings, box jumps, body weight squats and other more "cardio" type movements come to mind. These exercises will probably not induce outright failure, but just make you tired and want to stop doing them. The advice here is rest less, think less, and surprise yourself. Remember, our brains are telling us to be cautious in case of an emergency. Trying shutting that off and see what happens. These mini breakthroughs breed confidence and increased capacity, which is what we are constantly chasing. "You can always do one more burpee" is a common CrossFit saying and it holds true here. One more rep, one more set, one more round, you got this.