Do Time Domains Matter?
by Erik Castiglione

For those that missed my review on the Open this year, I thought it was one of the most well-rounded Opens we’ve had yet. My ONLY gripe was that all the times, when taken to the time cap, were fairly long (15+ minutes), which made class logistics difficult. Traditionally, the Open has included more range with its time domains. Of course, by time domain, we mean the work time in a particular workout. According to the CrossFit Level 2 programming review guide, a balanced program will have short workouts (<5 mins), medium short workouts (5-10 minutes), medium workouts (10-15 minutes), medium long workouts (15-20 minutes), and long workouts (>20 minutes). Are these numbers just arbitrary, or do time domains actually matter?

The answer to both parts of that question is yes. Yes, there are instances when the time domain matters. I’ve previously written about the body’s energy systems and how they pertain to conditioning. As a quick review – the phosphagen system is sometimes known as “the immediate energy system,” and it allows us to perform max effort work for up to 10-15 seconds. If we push as hard as we can and extend beyond the 15 second mark, we end up using the glycogen energy system, which can sustain hard effort until roughly 2 minutes. Hard effort beyond that requires the use of the oxidative system, which will kick in when you feel like you’ve “hit a wall.” The phosphagen and glycolytic systems are anaerobic (don’t require oxygen), while the oxidative system is aerobic (it does require oxygen).

At the opposite end of the spectrum we have low intensity steady state cardio (LISS). Our goal with this is to increase the pumping power of our left ventricles – the part of the heart responsible for pumping blood to the entire body. The MINIMUM amount of time to achieve this result is 30 minutes, while keeping a conversational pace (~40% effort). And, over time, as athletes develop this pathway, their duration can increase.

Other than work within those specific time ranges, time domain doesn’t really matter. And, nowhere did we see the “time domains” laid out by CrossFit HQ, which is why they are arbitrary. But, digging a bit deeper into their listed time domains, you may notice that they all fall between the 2 minute and 30 minute mark. What happens in this large range of time?

Well, depending on the workout, you may see a shift from energy system to energy system. The idea that we use the phosphagen first, and then the glycolytic, and then the oxidative, based soley on the duration of exercise is erroneous. In describing the phosphagen system, the first thing I mentioned was “max effort work.” Effort, aka INTENSITY, is the key here. All of our energy systems are always working simultaneously, but our effort will determine which one is dominant, assuming that it is still available to use. For example, if you go for a leisurely 400m jog, and then sprint the last 100m, you’ll likely go from oxidative to phosphagen. Similarly, if you start a big set of wallballs, and you feel good for 10 reps because you’re pacing yourself, but then you find yourself fatiguing more as you progress through 30 reps, and then 40, and 50, it’s likely because your body was forced to shift from the oxidative system to the glycolytic because it burned oxygen more quickly than your lungs could exchange it. In other words, you went anaerobic.

So, the important thing to remember here is that effort should dictate the time domain, not the other way around. If we’re performing short sprints (~1-2 mins), it’s because we’re purposely trying to develop our glycogen energy system. You’ll see us do this by performing short intervals with specified rest periods. If we’re performing longer intervals, we expect to shift into the oxidative system, but while working at a high enough intensity that you probably can’t sustain it flat-out for 10 minutes. Our coaching staff will convey this intent to you by telling you the goal of the workout. For example: “the row should be fast but manageable, at about 85% effort, and then your wallballs should be unbroken.” Or something similar to that.

Now, notice that I gave no context for the workout I just described – is it a 250m row, a 500m row, or a 1k? If we have two athletes and one is significantly faster at rowing than the other, we’re going to see a time discrepancy between the two. The longer the row, the greater this discrepancy will be. So, let’s say the above workout was a 500m row followed by 30 wallballs. Athlete A might finish a round in 2:58, while athlete B takes longer than 4 minutes for a round. Does this mean that Athlete B is not meeting the stimulus of the workout? Not necessarily. Again, it depends on their effort – their 85% may just be a slower pace than Athlete A’s, and that’s perfectly okay.

Similarly, and we’ve run into this in the past, let’s say it’s benchmark time! You’re performing “Diane” (21-15-9 of deadlifts at 225/155 and handstand push-ups) and it’s your first time going Rx’d. Your coach says that the goal is to finish in under 10 minutes, but you didn’t break up your 21 HSPU into small enough sets, and so you’re down to singles by the end of the round of 15. Your workout takes 14 minutes instead of 10. Does this mean you messed up the workout? Well, maybe from a strategy perspective. As far as the goal of the workout is concerned, your goal was to finish Rx’d, and you did!

Once again, time domain within a workout only matters if we are specifically training the phosphagen or glycolytic energy systems. Otherwise, intent and effort are the point. Focus on you and strive to hit YOUR goal for the workout, as discussed between you and your coach. What other people do doesn’t matter.

Lastly, I would be remiss to not mention that your total training time matters as well. The ideal training session for most people is 45-60 minutes. Advanced athletes can push this to 90 minutes. This total work time includes warm-up, strength, conditioning, and cool down. If you’re lollygagging around 10 minutes between exercises, that doesn’t count. But, the way we run our classes, including built-in rest periods, is all part of training time. Why 45-60 minutes? Because that’s about as much as your central nervous system can handle and still recover. There is a common misconception that elite athletes have super long training sessions. The best ones still keep their training sessions to <90 minutes, but they might have multiple sessions in a day. And, when your full-time job is to exercise and recover, you can get away with that. For the rest of us, life gets in the way, and recovery is harder. So, we want to limit our sessions and recover so we can come back from more. Louie Simmons said it best: “Don’t train maximally, NEVER train minimally, always train OPTIMALLY.” See you in the gym.