Alice has Three Pizzas
I’ve always been a swimmer, but I got more serious in 5th grade when I joined a USA Swimming club that trained year-round. Swimming became my main sport. Ballet was out (I was way too clumsy for it anyway) and softball took a backseat. Instead, I swam for about an hour and a half six days a week under the watchful eye of coach Steve at Voyagers who always wore socks on the deck. (I never did find out why, but always thought it was a bit odd.)
Despite his quirks, Steve was a great coach who not only pushed us in the pool, but introduced us to the basics of sports nutrition, mental training, and the physiology of peak performance. And I’ll never forget the way he described how the body creates energy via the three different energy production systems: ATP-CP, anaerobic glycolysis, and aerobic (oxidative phosphorylation).
Steve began by explaining our sprinting system (ATP-CP) by drawing the letters ATP (which stands for adenosine triphosphate) and CP (creatine phosphate) on the giant whiteboard that typically foretold workout doom. He pointed to the ATP and said, “Alice has three pizzas. The A is for Alice, and the TP are her three pizzas.” As a 12-year-old swimmer, I’m wondering what the heck pizza has to do with the molecular process of human metabolism, but we knew to trust that Steve was going somewhere with his unconventional explanation.
Alice has three pizzas. The A is for Alice, and the TP are her three pizzas.”
He then pointed to the CP. “The problem is, Charlie only has one pizza. He doesn’t like that, so he steals one of Alice’s pizzas. He grabs one of her phosphate molecules and adds it to his phosphate pizza.” Nothing like a mixed metaphor, but we were enthralled by the concept of anyone stealing a pizza. “Well, now of course Alice isn’t happy that Charlie just stole one of her pizzas, so she screams at him.” Steve let loose one of his rafter-rattling yells, waking anyone who wasn’t paying rapt attention. “This yell is a burst of energy. And that’s how you move forward.”
In those simple, memorable terms, Steve explained more-or-less how the body generates motion on a cellular level. Although the actual science is more complicated, Steve’s explanation summed up the first of three types of energy generation in humans: anaerobic glycolysis, or the first 12 seconds or so of high-intensity movement. This system powers the intense leg churning of a 100-meter dasher, a homerun slugger’s smooth and lightning-fast swing, or a powerlifter's explosive press upward. The other two systems kick in afterward, once oxygen has gotten into the mix, and these days I rely a whole lot more on the aerobic or oxidative system, the third and longest-lasting energy production system that allows us to swim, run, row, bike, and do everything else we do for hours on end.
Food to Fuel
ATP gets the ball rolling when it comes to motion on land and in the water, and it’s not something we have an unlimited supply of. ATP must be replenished. Our bodies convert food to fuel—elements of the actual pizzas we eat eventually get broken down and converted into phosphate molecules. And when the duration of exercise extends past the 2-minute mark, we slip into the oxidative or aerobic system, which relies on the Krebs Cycle for energy generation. This stage can last indefinitely, depending on the athlete’s training, and uses the body’s fat stores, blood glucose levels, water, and oxygen to provide the energy to continue running, swimming, biking, or sleeping, mowing the lawn, and all the other things we do with our bodies in an aerobic capacity.
Endurance athletes train the body to become more efficient in using this system, but we also deplete our stores of electrolytes and other nutrients that can help it run more smoothly. Electrolytes are the ion regulators that facilitate the molecular actions in the muscles. Without them, we simply couldn’t move. Electrolytes help cell walls regulate how much water can pass in and out of cells as needed. As water molecules move in and out of cells, an ionic concentration difference, an electrochemical gradient, arises between the inside and outside of the cell. These gradients allow nerve cells to transmit impulses; small molecules, like sugar, to pass into the cells; and most importantly for our discussion here, allow mitochondria to generate energy.
Electrolytes help cell walls regulate how much water can pass in and out of cells as needed.
Mitochondria, typically referred to as cellular powerhouses, are organelles residing inside each cell that regulate respiration and energy production for the cell. Mitochondria rely on calcium, magnesium, and potassium to do their jobs, so in addition to staying well hydrated (the Krebs Cycle is wholly dependent on the body having enough water to enter and exit cells as needed and to facilitate that transfer of phosphate molecules), supplementing with a complete electrolyte product like Ultima Replenisher can help ensure these organelles have the resources they need to perform.
Top triathlete and sports nutritionist Molly Breslin does a great job of explaining why endurance athletes need to worry about our mitochondria in this post on Training Peaks. So while pizzas are fun and tasty, and your body can use them to make the energy you need, both literally and figuratively, the science behind energy metabolism in the body says that making sure you’re hydrated and have adequate levels of electrolytes in your system may be even more valuable in helping Alice scream explosively and your mighty mitochondria move you forward. For more information about how the body produces energy, this simple graph representation can help explain it. Another good plain-English explanation can be found here: http://breakingmuscle.com/health-medicine/understanding-energy-systems-atp-pc-glycolytic-and-oxidative
Elaine Howley is an accomplished ultra-marathon ice swimmer, science writer and co-directs the 8-mileBoston Light Swim. Since catching the marathon swimming bug, she's been lucky to have had the opportunity to tackle some of the most beautiful and challenging cold waterways in the world, from the English Channel and Loch Ness to Lake Tahoe, Lake Memphremagog, the Catalina Channel, around Manhattan Island and aroundAbsecon Island in New Jersey.
Cover Photo by Taylor Simpson