Coach’s Corner: Why CrossFit?
“You just don’t understand.” Will Smith said this about parents. I’m directing this to the weightlifters, power lifters, runners, and all athletes, grandparents, housewives, and toddlers. Everyone on the face of the planet should CrossFit and I’m going to tell you why. Cause I freaking said SO! Well that isn’t very enlightening, but I digress. CrossFit improves performance. CrossFitters stretch, flex, analyze, and diagnose to improve movement and overall awesomeness. CrossFit also confuses almost everyone except those directly involved.
Matt Fraser recently hit a lifetime PR snatch of 315lbs, with his shoes untied, yet also place 2nd at the Games. This might not seem that big a deal coming from the second fittest man in the world until you realize he used to be an Olympic hopeful that trained in Colorado at the Olympic Training facility for years until sustaining a traumatic back injury. How did he do it? Here is the answer: physics and kinesiology.
However, we will have to expound on the idea of physics and kinesiology to understand their application to CrossFit. Let’s focus on energy (think force/power/work) as it relates to kinetic energy and potential energy. Kinetic energy is the energy of motion and potential energy, also known as stored energy, is related to the amount of force or gravity on a mass in relation to its height. So as not to reinvent the wheel here is an excerpt from Teach Astronomy:
Examples of kinetic energy are all around us. We might imagine that a fast moving object has more kinetic energy that a similar object moving slowly. In fact, the kinetic energy is proportional to the square of the velocity. If we double the speed of a moving object, we increase the kinetic energy by a factor of four. We might also imagine that heavy or massive objects have more kinetic energy than light objects. In fact, kinetic energy is proportional to mass. These two relationships get combined in the simple equation for kinetic energy
Kinetic Energy = ½ mv2. In this equation, m is mass and v is velocity. If we insert velocity in meters per second and mass in kilograms, the kinetic energy comes out in units of Joules.
How about a human compared to a speeding bullet? A fast sprinter weighing 70 kilograms can run 100 meters in 10 seconds or a speed of 10 meters per second. This is a kinetic energy of ½ × 70 × (10 × 10) = 3500 Joules. A bullet has a mass of about 50 grams or 0.05 kilograms and travels with a typical velocity of about 400 meters per second or 900 mph. The bullet has a kinetic energy of ½ × 0.05 × (400 × 400) = 4000 Joules. A human really is nearly as “powerful” as a speeding bullet!
Any object that is subject to the force of gravity will have an amount of gravitational potential energy. Here are some examples of gravitational potential energy — a barbell held over your head, a boulder balancing precariously on top of a hill, a roller coaster at the highest point in its path, a lake held above a valley by a dam. In each case something with mass has the potential to move under gravity. In each case the motion will be towards the source of that gravity, which is effectively the center of the Earth.
The gravitational potential energy is given by the weight or force of gravity exerted by an object multiplied by its height above the ground. Newton’s second law of motion says that gravity force is equal to mass times acceleration. Combining these relationships we see that: Gravitational Potential Energy = m g h. In this equation, m is mass, g is the Earth’s gravitational acceleration, and h is the height above the ground. We have already seen that acceleration at the Earth’s surface, denoted g, is 9.8 meters per second per second. A top weightlifter can lift 300 kilograms over his head. The potential energy of this weight lifted 2 meters off the ground is 300 × 9.8 × 2 = 5880 Joules. This is the amount of energy a human must provide to lift such a weight. When the weight is released, the gravitational potential energy is converted into kinetic energy as the weight falls.
Consider the example of weightlifting. It takes only 2 seconds to raise the weight from the hanging position to the arms-raised position, a vertical distance of 1.5 meters. So in that second (1.5 / 2) × 5880 = 4410 Joules is generated, or a power of 4410 / 2 = 2205 Watts. This is enough to light up 20 light bulbs!
So, what did all of that have to do with CrossFit? We lift weights and we move our bodies QUICKLY. Mass times velocity squared. Part of CrossFit’s prescription is to move large loads long distances through different time and modal domains (quickly). Think about the human, the bullet, and the weightlifter as we approach the next subject of eccentrics and concentrics.
Eccentric contractions and concentric contractions explain the lengthening and shortening phases of muscular movement. The concentric contraction is the raising of the weight as in flexing the muscle and is when the muscle is its shortest. The eccentric contraction is the lowering of the weight and is when the muscle is its longest. An important part of this process is the amortization phase which is the reversal of movement in between contractions. Many athletes understand these contractions and how best to apply them to their individual performance goals.
Bodybuilders focus on a heavy concentric contraction followed by a slow eccentric contraction squeezing hard as the weight is lowered. This is known as the negative phase and blasts the individual muscle fibers as well as increases the sarcoplasm (fluid) around the cells. This coupled with relatively high repetitions accounts for their muscular density and growth however affecting their actual force production capabilities. Mass with limited speed. Powerlifters and Weightlifters (Olympic) are less concerned with muscular density and more concerned with force production. Thus, they apply more speed to the eccentric contraction by exploding out of the amortization phase. This is where you get the “bounce” out of the lift and hit the stretch reflex where the muscle, somewhat, operates like a rubber band. Cool anatomical things like Golgi tendons and neurotransmitters scream at the body and take it from the stretched eccentric position and power it back to a more normalized less stretched concentric contraction. You’ve heard me say “Speed down equals Speed up.” This is a Louise Simmons quote. Watch the quick change of direction that a weightlifter makes out of the bottom of a squat or a powerlifter out of the bottom of a bench press. Now think back to the first part of the discussion. This creates a massive amount of kinetic energy that transfers to potential energy creating excessive amounts of power and wattage. Now how does all of this apply to a CrossFitter like you and Matt Fraser?
Greg Glassman and Uncle Rhabdo have combined to make the perfect programming monster. Greg Glassman provided a simple prescription in constantly varied functional movement performed at high intensity moving large loads long distances over different time and modal domains. Uncle Rhabdo was there to remind us not to kill anybody through foolishness. One of the known culprits of Rhabdomyolysis is the negative phase or eccentric contraction in a lift when performed with extremely high repetition especially on deconditioned athletes. Thus, we tend to avoid it in high volume work. Now think about your typical CrossFit movements and how they are performed in a workout. The eccentric contraction is performed with as much speed as possible. Think about kipping pullups, butterfly pullups, air squats, and wallballs. These are performed with as much downward force as possible. Imagine performing a push press, thruster, or pushup. The eccentric contraction is done quickly and with as much “bounce” or quick reversal as possible. Now add in the aspect of weightlifting and its vast amount of energy production mashed in with countless touch and go repetitions. On a daily basis CrossFitters are not only challenging their bodies to increase its lactic threshold, aerobic capacity, and VO2 max but they are putting in multiple repetitions designed to do one thing: increase force production.
Every single day the nervous system, ligaments, tendons, and muscle fibers are being trained to be as explosive as possible. Look back at the kinetic energy equation. Velocity is squared. Speed is important. I believe the speed of the lifts performed and the intensity at which most CrossFit workouts are performed turns into what most would conceive as aggression. A controlled bit of powerful aggression. Matt Fraser has increased and improved every facet of performance. He has trained through multiple planes of movement (balanced) with speed and power. The outcome speaks for itself. A human that can out lift his former Olympic caliper self yet outrun, climb, swim, and jump that same lifter. Take just a few of these ideas and truly sit and think about what CrossFit genuinely does to the body. It’s amazing. It will continue to get better and amaze those that perform it and drive crazy those that don’t.