EPOC At Millcreek
Last Wednesday night I taught All Terrain at Millcreek. I really like the cycling room there because it’s enclosed, kind of dark and has such poor circulation that they have two industrial fans to move around the air; it reminds me of a rave environment. On Wednesday, as luck would have it, the mic wasn’t there meaning I had to cue with my hands and using verbal commands only as loud as I can shout. But by track 3 it was evident that I wasn’t loud enough and that my attempts to communicate were leaving me out of breath and not helping anyone. It was a little stressful so I did what I always do when I’m stressed, I worked as hard as I could. I was hoping that if they were able to copy what I was doing on the bike, they were going to get a heck of a workout.
The class went like most classes, really quickly and I was soaked by the end of it. I locked the studio door and changed. As I was leaving, I noticed that I was still pretty hot. My body temperature was still a little high and my breathing hadn’t returned to normal either. This was about 10 minutes after class ended and about 20 since the last working track. I seemed to float to my car and then sat in silence for about 10 minutes before I started it to drive away.
The drive was blissful. It was a sunny spring evening so I had the car windows open. There was a nice breeze and it was still bright out. Everything about it said that the winter was over and that spring was here. It was peaceful because I didn’t care about anything. “Stop at red lights and don’t hit any cars” was my only mandate. No speeding, no weaving, just mindless driving with plenty of time to get to where I was going. A quick stop to get some groceries and then to my brother and sister inlaw’s place to make dinner and go to bed - I had to be up for 5:15 the next morning.
The thing was, I didn’t feel any different from how I did when I floated across the parking lot. In fact, I hadn’t seemed to come down at all from the workout. I still had the narrowed spacey focus I get when I race and I felt nothing. Whatever was coursing through my veins was coating my insides numb and leaving my brain not much better. Shopping took a while and they I went to Des and Sarah’s to watch American Idol. I feel asleep around 10:30 and slept well until the alarm woke me up.
I get that feeling a fair bit. It seems to come on after every lap or race I complete, after a really really intense weight workout or when I get my heart rate up above 170 for longer than a minute 3 or 4 times in a cardio session. It doesn’t come on with steady state cardio or short duration resistance workout, only after very hard work; work that could be viewed as fight or flight because it taxes the body so severely. While not the result of the acute stress response initiated by sympathetic nervous system arousal, the physical symptoms / reactions are exactly the same - increased blood flow to the muscles, increased heart rate, a deadening of your ability to think clearly about abstract things.
I believe that this is the cause of EPOC (excessive post-exercise oxygen consumption). EPOC is the tendency for the body to continue to burn energy at an elevated rate after a workout; we know it exists because there is an increase in O2 consumption above baseline levels following certain types of workouts. Most of the evidence comes from studies addressing resistance training workouts which show a sustained increase in O2 consumption following intense exercise because adaptive change requires energy and intense exercise forces adaptive change.
While the amount of evidence on EPOC with high intensity interval training (HIIT) isn’t nearly as robust, anecdote and interpretation of the results of these type of studies indicate greater fat loss for HIIT vs. steady state cardio exercise. I believe that HIIT does one that that steady state does not, it forces the body to adapt to a variety of different intensities vs. just one, which I believe causes more EPOC than steady state cardio.
All things being equal I’d rather connect with the participants of the classes I’m teaching. But when the mic is broken and I can’t yell as loud as I need to, I’ll take EPOC.
April 26th, 2007 18:23
Some follow-up from an email:
Just three years ago EPOC was thought to have two components, fast and slow. Fast component represented the oxygen debt required to rebuild ATP and PCr used during ex (exercise). Without sufficient O2, phosphate bonds are broken to supply energy. During recovery, bonds need to be reformed via oxidative process to repay the debt. The slow component was thought to be the removal of lactate from the tissue either by conversion to glycogen or oxidation to CO2 and H2O, therefore providing energy to restore glycogen. Based on this theory people thought that by examining post oxygen consumption, they could guess the amount of anaerobic activity that had occurred. Studies were way off.
But a study done a Queens U and AZ State, about two years ago found that infact that was too simplistic! During the initial phase of ex O2 is borrowed from oxygen store, myglobin and hemoglobin, therefore it must be replenished during recovery. Respiration remains temporarily elevated following exercise partly to clear CO2, that is in the tissue from metabolic waste. Body temp is also elevated that keeps metabolic and respiration rates high, therefore needing more O2. Elevated levels norepinephrine and epinephrine are elevated during ex and also have similar effects.