#PTonICE Daily Show – Friday, December 22nd, 2023 – Interval training: science, not magic

In today’s episode of the PT on ICE Daily Show, Fitness Athlete division leader Alan Fredendall discusses why & how interval-based training causes positive adaptations, how to assess & program intervals for patients and athletes, and how to help them approach interval-based training.

Take a listen to the episode or check out the show notes at www.ptonice.com/blog

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Hey everyone, this is Alan. Chief Operating Officer here at ICE. Before we get started with today’s episode, I want to talk to you about VersaLifts. Today’s episode is brought to you by VersaLifts. Best known for their heel lift shoe inserts, VersaLifts has been a leading innovator in bringing simple but highly effective rehab tools to the market. If you have clients with stiff ankles, Achilles tendinopathy, or basic skeletal structure limitations keeping them from squatting with proper form and good depth, a little heel lift can make a huge difference. VersaLifts heel lifts are available in three different sizes and all of them add an additional half inch of h drop to any training shoe, helping athletes squat deeper with better form. Visit www.vlifts.com/icephysio or click the link in today’s show notes to get your VersaLifts today.

Good morning, PT on ICE Daily Show. Happy Friday morning. I hope your day is off to a great start. My name is Alan. I’m happy to be your host today here on Fitness Athlete Friday. Currently I have the pleasure of serving as Chief Operating Officer here at Ice and the Division Leader in our Fitness Athlete Division. Fitness Athlete Friday, if you’re working with that person that is recreationally active, the CrossFitter, Olympic Weightlifter, Powerlifter, the Endurance Athlete, whatever, Fitness Athlete Friday is for you. Today we’re going to talk about intervals. I think this is a great topic because what we’re going to talk about today can really apply to all of these athletes. Runners, cyclists, swimmers can obviously benefit from interval work, but so can crossfitters and powerlifters and Olympic weightlifters. And we’re going to talk about types of intervals, why do intervals work, how do we program these intervals more specifically. to the weaknesses that these athletes need to work on. And then we’re going to talk about how to actually approach these intervals as if we were in the driver’s seat. Being that athlete, how should we approach interval based training? I’m going to reference a paper today that is just basically a review of a whole bunch of different research articles on interval based training. It’s by Oticon and colleagues from 2021. It’s the International Journal of Environmental Research and Public Health. and the title is Evidence-Based Effects of High-Intensity Interval Training on Exercise Capacity and Health, a Review. And this is just a paper that consolidates a lot of different research on what is actually happening to the body physiologically when we do intervals, what is the benefit of interval-based training, and then a little bit about adherence and enjoyment as well as we talk about compliance with interval-based training versus other types of training.

So let’s discuss the first part that a lot of us maybe have questions on, especially if we’re explaining to patients or athletes why we might be doing interval-based work, even in the course of their rehab. If they’re doing remoms, if they’re doing AMRAPs or something with rest, when you have folks doing interval-based exercise in the clinic or in the gym, why do intervals work? The first thing I want to speak to is the concept of excess post-exercise oxygen consumption, often abbreviated as EPOC. For a long time, this was thought to be the main benefit to higher intensity interval training, that somehow, because we were working so close to our max threshold, that as we did interval-based training, our body could somehow not supply enough oxygen to itself during the training, had to pull oxygen from other sources, and otherwise created a large deficit that throughout the day would need to pay down that deficit, would lead to a huge consumption and calorie burn, would lead to otherwise a lot of increased metabolic effects throughout the day after interval training had completed. We know now that has been thoroughly trounced in the literature, The most effective thing you can do for EPOC is actually resistance training, right? To accrue more muscular mass that is more metabolically active, that’s going to result in an increased metabolism throughout the day, and actually every day, the more and more mass you accumulate, right? Very large muscular people have very large base metabolisms, and that’s related to resistance training, not related to high intensity interval balance, of aerobic exercise. So know that EPOC is really not what we’re after. What we’re actually after, depending on the type of interval and training we do, is looking at central versus peripheral cardiovascular adaptations. So with central cardiovascular adaptations, we are mainly targeting the heart. We have improvements in ventricular hypertrophy, we have improvements in maximal stroke volume, the amount of blood that gets sent out every beat of our heart, and an overall increase in red blood cell volume. Now, when we do moderate intensity steady state exercises or longer, slower intervals, we primarily get peripheral cardiovascular adaptations. We get increased mitochondria, we get increased capillary density, we see improvements in lactate buffering and transport, converting pyruvate that’s broken down during exercise back into lactate to be reused for energy. And the key there is that when you do really long, slow aerobic training, or you do very, very long intervals, you are only really becoming better at doing long, slow aerobic training or really long, low intensity intervals. That really long aerobic training or long aerobic intervals only make you better at long aerobic training as a whole. So when we discuss intervals, especially when we’re talking about how to program intervals for maybe crossfitters, powerlifters, or Olympic weightlifters, we need to understand that the kind of craze right now in training for them of 40 minute EMOMs and 60 to 90 minute zone two training sessions has really a minimal benefit for those folks. Those folks need to be doing shorter, higher intensity intervals to get those central adaptations. Literally increasing the size of their heart, their stroke volume, their red blood cell volume, giving them more power and energy for those shorter bouts of exercise that they’re conducting, Olympic weightlifter or powerlifter, you know, maybe one heavy lift, maybe a double or triple crossfitters, maybe exercising in the 8 to 12 minute time domain. Those folks are really not going to benefit from those peripheral adaptations from really long aerobic training. So we really don’t want to see those people doing a lot of long aerobic training, especially if it’s competing with their weightlifting or natural crossfit training. And then translating out of the gym, most human functional tasks and sports exist in a relatively short time domain that’s also going to benefit from those central adaptation improvements. So we need to understand that if I do 90 minutes of zone two a day, that’s probably not going to help me in a sport like football, in a sport like basketball, which is much quicker, much shorter, short bouts, When you look at a game of like basketball or football, it almost looks like interval training, right? Play for 30 seconds or a minute and then there’s rest, right? There’s timeouts, that sort of thing. Very different than going for a five mile run or a 10 mile run or a marathon. So if you’re not doing long aerobic events, you should steer away from long aerobic training or long aerobic intervals. And then the final benefit of why do intervals seem to work? They seem to work because people really seem to enjoy them. When we look at research around high intensity interval training, we see that exercise adherence and enjoyment is very, very high. And I think we’ve talked about this before. It’s often overlooked, right? Of what do you like to do? We should probably program that stuff because it’s going to be stuff that you’re going to do more often. And if your adherence, your compliance, your enjoyment is high, you’re much more likely to come to the gym or go to the track or whatever and do it. and that consistency is what is going to increase your health and fitness over time. So that’s why intervals work. They may benefit central versus peripheral adaptations, and that’s going to depend on the athlete in front of you of what adaptations they may be seeking.

Now, when we’re programming intervals, whether it’s a patient in the clinic, whether Darlene’s in the clinic, or we have Frank the CrossFitter, whatever, how do we program these? Remember, with intervals, intensity is the goal. We’re looking for most interval sessions, especially if we really want to produce a lot of those adaptations, to be around 90% of our VO2 max. If you’ve never done a max effort Bruce treadmill test, looking to find your true 100% VO2 max, it’s quite the experience, right? You’re running on a treadmill, you have the metabolic heart, you have the oxygen mask on, you’re running on an ever-increasing speed and grade until failure. With a true VO2 max test, Failure is when you pass out, right? There are people behind the treadmill to catch you as you pass out. You reach the point at which you can no longer pump enough blood to all of your body and you pass out. That is the true test. So we’re not going for that with our intervals, we’re not going for 100% blackout, but we are looking for 90% or maybe 80%. So we’re looking for very, very, very hard efforts. The type and amount of those intervals is going to be key to facilitate that intensity. That’s going to be a combination of work and rest, hopefully working on things that that athlete or patient needs to improve related to time domain and functional tasks. So if intensity is the goal, how do we notify that intensity? If we’re not having folks do a treadmill test to failure, well, we do need to do some testing. We do need to have some sort of baseline measures in place to know what sort of paces are we looking for. We can get a metabolic heart in the clinic. We can measure heart rate. But the easiest, most practical thing for a lot of us is just going to be to have somebody do something like a 500 meter row one day and then a couple days later do a 2000 meter row or a run or a bike or whatever. Get some sort of short time domain effort and some sort of longer aerobic time domain effort. And the key there is we’re looking to establish fatigue fall off factor. So we know does this individual need to work on speed or do they need to work on endurance? Now, with some of our patients, especially more of our deconditioned patients, we don’t need to do a lot of testing to know what they need to work on, right? That patient that barely makes it into the clinic from the parking lot, the 20 second walk from their car to the chair in the lobby was max effort for them. You know where you need to start with that person, right? That person needs to work on shorter intervals. They have no aerobic capacity. Certainly, they’re not gonna do well on something like a six minute walk test. Shorter intervals for that person, build them up. But with somebody who’s already active, how do we know their weaknesses? We need to calculate that fatigue fall-off factor. How do we do that? I’ve got it written out on the whiteboard here. I hope you all can see it. I hope it’s not backwards, but I’ll read it out loud nonetheless. So, I happened to just do a 500 meter row yesterday and find a new PR. It was 133. That’s 93 seconds. I already know my 2,000 meter row time. 2,000 meter row is gonna feel a lot like a mile run. it’s 648, which is 408 seconds. So what is the time difference? If I think about, if I could hold that 500 meter row four times, I could theoretically get that 2000 meter row done in 372 seconds. However, that’s not realistic. Why? Fatigue falloff factor. As exercise bouts get longer, There’s some natural fatigue accrual that’s going to slow me down more than just thinking I could rock my PR 500 four times in a row. If that PR short distance effort is truly max effort, there is no way you could sustain that for four times as long, right? And that time difference is called fatigue falloff factor. So 372 seconds over 408 seconds is about a 91% Integer there, that means I have about a 9% fatigue fall-off factor. Now, how does this let me program? If folks have less than a 10% fatigue fall-off factor, they need to be working on power and speed. Folks that have more than a 10% fatigue fallout factor, they need to work on endurance. So that kind of tells you right away, does this person need to be working on shorter intervals, more power and speed? Or does this person need to be working on longer aerobic intervals to build up their endurance? And then again, the final key there is, what is this person actually doing in the gym? Because at the end of the day, if they’re not doing long aerobic work for training, even though it may seem like they need to train endurance, again, does not make sense for them to train a lot of endurance and vice versa. So make sure we’re training the right energy system. I love testing this stuff with patients. I’ve watched a lot of people row a very slow 2K row just to get that data. Data might not change behavior, but it certainly does inform our decisions when we’re gonna start creating some exercise programming. Now, establishing that baseline, knowing intensity is the goal. How do we implement this in the gym and the clinic? For a lot of folks, that’s going to look like running or using a machine. Why? Because our bodies are very, very efficient at using cardio machines or running, we get to use our full body, which means we get to get a lot of blood pumping, which means we get to buffer a lot of things like lactate, much more so than if we decided to do intervals of something like strict pull-ups, right? Where muscular fatigue, the lack of muscular endurance or indoor strength is going to affect our ability to do work. Not many people have gone to the point of failure on a bicycle and collapse on their bicycle due to a lack of leg strength pedaling that bike, right? It’s always usually at the end of the day an endurance thing. So when we’re having folks do intervals, yes, in CrossFit, we can do intervals, but we often do intervals, we mix things up, right? We have biking, pull-ups, and kettlebell swings or something, right? We have enough work where just as we get tired, we move to the next thing, and then we get some rest. We don’t just do big rounds of one movement unless we happen to be on cardio machines or running. So make sure in the clinic or the gym, you have a rower, you have a bike, you have a ski machine, whatever, or you have a treadmill or otherwise ability for the athlete to run. So that’s how we program intervals.

I want to show you an example now of how I would program for myself based on the data I just shared. So same whiteboard, right? We know that we want to be ideally 90% intensity of whatever we just did. I know my max effort 500 is 133. So that means that if I’m going to be doing rowing, again, my fatigue fall off factor was 9%. I need to be working on power and speed. I’m going to program myself 500 meter row repeats with some rest. Why? Because I need to work on that power and speed. How do I know my pace? Well, I know my PR and I know my intensity thresholds. So I know if I want to be doing these 500 meter rows at 90% I need to be rowing at at least a 143 per 500 pace. If I wanted to work at 80%, I could be rowing at a 151 per 500 pace. And now I can give myself a range. Hey, I’m going to do five sets of a 500 meter row. My range is a 143 on the fast end and a 151 on the slow end per 500 meter row pace. And I’m going to rest three minutes after every round. Why? Because I want to be resting at least as long as I’m working. Now, how do we approach this? How do we help patients? and athletes approach this interval work. Now that we know why we’re doing it, now that we know how we program it, first things first, what is the goal? For a lot of our patients in the clinic, statistically 90% of them are completely sedentary, so anything goes, right? They can benefit from both short time domain and longer time domain intervals. They can benefit from doing it on any of the machines. They have room to grow on running, biking, and rowing. With those folks who maybe, again, They clearly do not appear to have any long aerobic system left. You’re probably going to be stuck with short intervals in the short term until they start to build that aerobic base up. If we want to improve power or speed with these folks, we want to keep the time domain two minutes or less, right? We want to keep it in that anaerobic time domain window. So if we’re thinking rowing, if we’re thinking running somewhere between 100 and 400 meters and we want to have relatively short bounce, with longer rest at least one to one rest to really facilitate our ability to repeat those efforts to hit those paces with power and speed. Now on the opposite end, what if we want to improve longer endurance? Well, we’re probably looking at running 800 meters or longer, we’re probably looking at rowing 1000 meter repeats or longer. We’re otherwise looking at exercising longer than the two minute time domain. Here, the bouts are going to be longer, the rest is going to be a little bit shorter, because again, longer effort, lower intensity, we don’t need as much rest, so here you could get away with maybe one to two rest. If it took you four minutes to run an 800, you could rest two minutes and then run that 800 again, hopefully in another four minutes or whatever your pace may be. I cannot stress enough that you should match the modality of what the patient wants or needs to get better at, right? If you want to get better at running, you should probably do most or all of your interval-based training running. I hope I don’t have to explain why being specific there is really important. But most of your intervals should be on the modality that you want to get better at, especially if we’re talking about doing this for performance. Yes, there will be some carryover from the rower or the bike to running and in between. But if you want to become a better biker, you should do a lot of biking. If you want to become a better runner, you should do a lot of running.

And then the final thing I’ll say is make sure that you’re actually getting the stimulus. Remember, these efforts should ideally be around 90%. They are higher intensity because they are intervals, because you are eventually going to get some rest. You should not be shooting to get a PR during your training, right? If it’s a test day, it’s a test day. If it’s not, we should not be shooting for 100%. We see this a lot in the CrossFit gym. We will have 400 meter repeats. or 500 meter repeats. And our guidance is these should be at 80 to 90% of your max PR of whatever, whatever distance we’re going. And what do we see a lot, we see a lot of people swing for the fences on the first round, and PR their runner row, maybe they puke in the bushes, and then some of them are not able to complete the rest of the training, right? So some folks may even fall short of a PR, they try to get it, they miss it, and then they’re not able to complete the rest of the training. Completing the volume of the training at the intended intensity is getting the stimulus and making sure that we’re actually trying to get max effort, but we’re not going for 100% every time it’s time to run a row. On the other side, we make sure we don’t under dose ourselves, right? If we’re aiming for 80 to 90% of our max, we should not see a slow warm up in those intervals where maybe only the last couple rounds are actually at 80 to 90% of our max capacity. Again, intensity is the key here. All of those benefits central or peripheral come from getting close to those intensities. If we miss those, I don’t want to say you’re wasting your time, but you’re not getting the same benefit you could as if you were really pushing yourself. Interval based training should be very, very, very uncomfortable. You should feel like you need that rest break. You should feel like, geez, I wish I had more of that rest break. If that’s the subjective feeling you have with interval training, you are doing it correctly. So interval training, why does it work? Central versus peripheral adaptations, different needs for different patients and athletes. How do we program it? We program it by making sure we establish some baseline testing, find out what our person needs to look at. How do we approach it? We understand if that person needs power or speed, they should be doing shorter time domain, longer rest. If they need endurance, they should be doing longer time domain, shorter rest. And whenever possible, we should be matching the modality. If you wanna get better at running, you should do your intervals as running. Make sure we’re getting the stimulus, hitting that 90% mark, and actually getting good effect from our training in the clinic or in the gym. So that’s interval based training. Very quickly, some courses coming your way. Your next chance to join the fitness athlete division online will be our level one course that starts January 29th. And then our level two course starts February 4th. Live courses coming your way in January, Portland, Oregon with Zach Long, January 27th and 28th, February 10th and 11th of 2024. Mitch will be in Richmond, Virginia. and then February 24th and 25th, Zach Long will be at home base in Charlotte, North Carolina. So check us out, ptownice.com, click on our courses, see where we’re coming your way. I hope this was helpful, hope you have a fantastic Friday, have a wonderful weekend, have a great Christmas, we’ll see you next week, bye everybody.

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