What you’re getting yourself into
8-12 minute read time
- Lifting heavy things is more metabolically taxing than most people realize.
- Most people think of weight training as a purely anaerobic enterprise, but the majority of the energy you use to train is produced by your aerobic energy system.
- Cardiovascular training can improve your recovery between sets and workouts, and won’t interfere with strength or muscle gains if you do it correctly.
- Low intensity cardio should be prioritized over interval training for the most part.
This article deals with how it can be used to enhance your training and actually help you get stronger, faster.
You’ll notice that I won’t be citing as much research in this article as usual. That’s because the bulk of this information comes from four main sources:
- My Exercise Physiology textbook. A lot of the ground covered in this article simply relates to basic aerobic physiology.
- The work of Joel Jamieson. He’s got a LOT of great resources that address this stuff. I’d highly recommend his book “Ultimate MMA Conditioning,” and if you’d like a brief primer on his work, you should check out this lecture.
- These two fantastic review articles (One, Two).
- Discussions with my friend Alex Viada, who specializes in improving peoples’ endurance while also making them jacked. If this subject interests you, I’d highly recommend his book The Hybrid Athlete.
First things first – a very brief overview of energy systems.
Your body’s No. 1 priority is staying alive. To do that, it has to produce energy at roughly the same rate you expend it. The metabolic currency of your body is ATP. There are two main ways your body regenerates ATP to produce energy: with oxygen (aerobic) or without oxygen (anaerobic).
Your body can produce energy much faster anaerobically. The fastest way is by using stored ATP, and replenishing ATP directly from phosphocreatine (PCr). However, this only lasts for 8-12 seconds. The next fastest way is by anaerobic glycolysis, which lasts for a few minutes, but which also causes acute muscular fatigue pretty quickly and doesn’t harvest very much ATP per molecule of glucose used.
Your body can produce energy aerobically for a very, very long time, getting every little bit of ATP out of each molecule of glucose or fat used. However, aerobic energy production is quite a bit slower than anaerobic energy production.
A one-rep max attempt relies almost exclusively on the anaerobic energy systems, particularly the anaerobic alactic (ATP/PCr) system. So, the thinking goes, since the aerobic energy system is almost entirely irrelevant when you’re on the platform, it must not matter very much for powerlifting.
This article explores why that’s shortsighted thinking. While your aerobic system isn’t doing much for you when you’re actually on the platform, it very strongly influences how hard you can train, which is ultimately what allows you to put up big numbers on the platform.
Lifting weight is metabolically taxing. Studies have found that doing 4 sets of 8 deadlifts with 175 kilograms burns about 100 calories. That’s roughly the amount of energy you’d burn running a mile if you weigh 130lbs, or running half a mile if you weigh 260lbs. Those numbers may not mean much to you right now, but I’ll show you why they’re important later.
An important thing to keep in mind is the “cost” of producing a given amount of energy aerobically versus anaerobically. We fatigue during exercise for a variety of reasons. I won’t even try to go through all of them here (and even if I did, all I could do is recount the best guesses we have right now. Because fatigue is so multifactorial and difficult to study, we really don’t know for sure what causes it, in all – or most – cases), but it’s pretty well-understood that burning through a ton of energy anaerobically in a short period of time is quite a bit more fatiguing than producing energy aerobically.
This is due to both local and central factors. Local factors have to do with substrate depletion (burning through PCr stores and, to a lesser degree, muscle glycogen), changes in ion concentrations that decrease the excitability of the muscle, and increases in metabolite concentrations and rather large decreases in muscle pH that can influence how hard the muscle can actually contract. Central factors mainly have to do with decreased oxygen availability, increases in certain inflammatory chemicals, a slight drop in blood pH, and other such factors that increase your brain’s perception of fatigue.
With aerobic energy production, you get a more modest drop in muscle pH and a much slower depletion of energy substrates. Central fatigue can certainly set in eventually, but it takes MUCH longer – usually accumulated fatigue after hours of continuous, strenuous activity or weeks of hard training.
Essentially, the more energy you can produce aerobically to meet a certain demand, the less you have to produce anaerobically, so the less fatiguing a given amount of training will be.
Reps and Fatigue Per Set
It’s important to keep in mind that even things we consider purely anaerobic still have an aerobic contribution, and it’s often larger than we think. For instance, this study showed that even for a 200m sprint (~20 seconds of all-out effort), about 30% of the energy produced was produced aerobically. For the 400m, 800m, and 1500m runs (considered heavily anaerobic events – especially the 400m and 800m), the aerobic energy system was already contributing more than half the energy produced by 15-30 seconds into the run. Even for relatively short efforts (like a heavy set of 5) the aerobic system is producing almost a third of the energy needed, and for higher rep sets, it’s producing more than half the energy.
The implication: The more powerful your aerobic energy system, the more reps you’ll be able to do with a given weight or percentage of your max, because every bit of energy you can produce aerobically is that much less that you have to produce anaerobically, which pushes off those factors that cause acute muscular fatigue. Also, if you do the same number of reps with a given amount of weight, less of the energetic contribution will come from your anaerobic energy systems, so the set will be less fatiguing. So you’re either looking at more work and the same fatigue, or the same amount of work with less fatigue; either way, you win.
This actually relates to a past article about sex differences: Women can generally do more reps with a given percentage of their 1rm because they generally have higher aerobic and lower anaerobic capacity per pound of lean body mass than men.
Recovery Between Sets
Although you’re obviously very reliant on your anaerobic system when you’re actually lifting the weights, what energy system do you think you use to recover between sets?
Your aerobic system is what produces the energy necessary to restore intracellular ATP and PCr levels, metabolize lactate, and generally get you headed back toward homeostasis so you can perform the next set. Better aerobic conditioning means you’ll recover faster between sets (and since you’ll be somewhat less reliant on your anaerobic system for each set, they’ll be less fatiguing in the first place) so you can handle higher total training volume.Lifting heavy things is more metabolically taxing than most people realize Click To Tweet
If You Plan on Getting Stronger
Let’s revisit the studies showing that you burn about 100 calories deadlifting 175kg for 4 sets of 8. We’re going to use those numbers as a yardstick for a bit.
They found that energy expenditure was directly (and quite strongly) correlated to the amount of work being done. Work scales directly with the amount of weight on the bar. Lifting 100kg is twice as much work as lifting 50kg.
So, if you deadlift 175kg for a set of 8, you burn ~25 calories. If you deadlift 87.5 for a set of 8, you’d only burn about 12.5 calories. If you deadlift 350kg for a set of 8, you’d burn about 50 calories.
This is why a new lifter may be able to bang out sets of 10 squats while barely breaking a sweat, whereas a tough set of 10 may floor a stronger lifter. If you’re lifting twice as much weight, you’re burning through twice as much energy in the same amount of time, probably with a larger proportion coming from anaerobic sources.
So, if you plan on getting stronger – especially if you plan on getting really strong – it would probably behoove you to improve your aerobic conditioning. If it’s not a limiting factor now, it very well may become one as your lifts increase.
As The Workout Wears On
As you move through a workout, you become even more reliant on your aerobic energy system. One study illustrated this beautifully using 30-second rounds of all-out cycling, interspersed with 4 minutes of rest. Total work dropped from 18.7kJ in the first round to 13.8kJ by the third, illustrating the effect of fatigue.
More importantly, however, this study showed how the participants were producing energy for each round. These charts show the difference between their first and third sprints.
In the first, ATP/PCr and anaerobic glycolysis carry most of the load for the first six seconds, ATP/PCr drops off between 6-15 seconds while the aerobic system picks up more of the load, and by the last 15 seconds the aerobic system is doing about 50-60% of the work.
Contrast that with the third sprint where anaerobic glycolysis is nowhere to be found, and the aerobic system is doing the vast majority of the work from 6 seconds onward. Basically, after the first sprint, ATP/PCr gives you a 6 second burst, but after that, it’s all up to the aerobic system.
You may be thinking, “But Greg, I’m lifting weights, not cycling. And besides, aren’t those all-out bike sprints supposed to be the most brutal thing in the world?”
Not quite. They’re the most brutal test that’s used consistently in research, but only because there aren’t enough 700-pound squatters for the “set of 10 squats with 500lbs” protocol to be very popular.
The brutal cycling sprints are known as the Wingate Test, and going off normative data I found, they don’t hold a candle to our set of 8 deadlifts with 175kg. The mean for average power in the Wingate Test (for men) is 562.7 Watts, and the highest value in the dataset was 711.0 Watts. Watts are Joules per second, so you multiply those numbers by 30 to get Joules (16,881 average and 21,330 for the highest value), divide by 1000 to get kilojoules (16.9 and 21.3, respectively) then divide by 4.184 to get kcals (4.04kcals and 5.09kcals). Since energetic efficiency for cycling is roughly 25% – meaning for every calorie burned, you only do about .25 calories worth of work on the bike – you end up looking at total caloric expenditure of 15-20kcals.
So a set of 8 deadlifts with 175kg burns roughly 25-60% more calories in roughly the same amount of time as the brutal Wingate Test. Similar values were obtained for the study referenced above – 18.7kJ on the first sprint is about 4.47kcals of work and 18kcals burned, and 13.8kJ on the third sprint is a scant 3.30kcals of work and 13kcals burned.Most think weight training is anaerobic, but the majority of the energy used is actually aerobic Click To Tweet
All of which means, the huge shift away from anaerobic reliance and toward aerobic reliance from sprint 1 to sprint 3 not only applies to picking up heavy things, but probably understates the degree of the shift since the energy demands per set are considerably higher, especially if you’re quite strong. Unless you’re only doing heavy singles or doubles (to fit within that short window where you can rely strongly on ATP/PCr), your training probably relies at least as much (and probably more) on your aerobic energy system as your anaerobic energy system.
Athletes become more susceptible to injury as they become fatigued. They lose a bit of coordination, and muscles themselves become less capable of absorbing force before a muscle strain occurs.
I’m not going to pretend like I have data to support this point, but I have seen my fair share of weight room injuries (and have had my own share of little muscle strains), and it’s pretty rare to see someone get injured on their first heavy set or two. It generally seems to happen later in the workout after fatigue has started to accumulate, which makes sense: more fatigue = more susceptible to injury. It doesn’t seem like too much of a stretch to assume that better aerobic fitness – meaning less fatigue per set and better recovery between sets – could reduce your injury risk in the gym.
Recovery Between Sessions
A central adaptation to aerobic exercise is increased parasympathetic nervous system (“rest and digest”) activity and decreased sympathetic nervous system (“fight or flight”) activity at rest. This means that between workouts, your body stays in a more robust recovery state.
Another adaptation to aerobic training is decreased carbohydrate usage and increased fat usage at any exercise intensity. This is probably more beneficial for a sport like CrossFit that has higher volume workouts, and whose competitions include multiple events per day over multiple days – sparing as much muscle glycogen as possible becomes a precious thing. But even in the case of powerlifting, a shift in substrate usage could make a small difference, especially in a calorie deficit if glycogen stores are already low since glycogen concentrations influence perceived exertion; low glycogen just makes everything feel harder, and improved aerobic capacity spares glycogen.
Now that I’ve made aerobic training sound like the best thing since sliced bread, it’s time to discuss the drawbacks. The most obvious is the “interference effect.”
A lot of the ways your body tries to adapt to aerobic training are in direct opposition to the ways your body tries to adapt to resistance training. Different metabolic pathways (AMPK vs. mTOR, though that’s not as problematic as most people think), using energy toward muscle protein synthesis vs. mitochondrial biogenesis, upregulation of aerobic vs. glycolytic enzymes, etc.
However, rumors of the interference effect, it seems, have been greatly exaggerated. At least, the meta-analysis on the subject found that it’s not aerobic exercise per se that causes the interference effect, but rather running in particular, probably related to the repeated eccentric stress of running. Cycling, on the other hand, did not hinder strength and muscle gains when combined with strength training.
Exactly zero track cyclists reading this article are at all surprised by that finding (refer to the picture at the top of the article).
The other drawback is simply the time commitment. Yes, it takes time. However, keep in mind that when talking about cardiovascular training for powerlifters, the goal isn’t to log 100 miles per week to qualify for the Boston marathon. It’s to attain a basic level of conditioning to fuel the energetic demands of training. For most people, you can accomplish that in 2 hours per week or less.
Can’t I Just Lift Weights?
Yes. Sort of. Actually, training to muscular failure has been shown to cause robust gains in aerobic capacity. However, most of the gains result from local tissue-level adaptations, not the global adaptations that come with dedicated cardiovascular training (increased cardiac stroke volume and increased oxygen carrying capacity being two biggies. They may be increased somewhat with strength training, but not to the same degree). These tissue-level adaptations shouldn’t be discounted, but if all you do is lift weights to failure, you’re still missing out on some of the potential benefits.
What About Intervals?
The answer for this is essentially the same as the previous one: Yes, interval training can improve aerobic capacity by itself, and yes, it’s much more time-effective than low-intensity cardio. Intervals also improve anaerobic capacity to a much greater degree than aerobic training does. However, while you get some of the benefits you’d get from low intensity cardio, you don’t get all of them.Low intensity cardio should be prioritized over interval training for the most part Click To Tweet
Furthermore, interval training is much more “costly” in terms of recovery, related to those central fatigue factors I briefly touched on earlier. Hopping on a stationary bike for 30 minutes with your HR at 130-135 won’t really affect your training very much tomorrow. Doing a few tough rounds of intervals (assuming you’re going hard enough to actually make them effective) can really put a dent in your ability to recover from your strength training, though. The idea of improving your conditioning in less time while doing fun movements sounds great on paper, but you pay for these advantages in how intervals can negatively impact the rest of your training.
Putting It All Together
The best conditioning plan for powerlifting will combine several different modalities (low intensity cardio, lifting to failure, and high intensity intervals) with an emphasis on minimizing the impact conditioning work will have on your heavy strength training.Cardio can improve recovery and, if done correctly, won't interfere with strength or muscle gains Click To Tweet
My general recommendations:
- Start slow. 2 sessions per week, both low intensity, and only 20-30 minutes per session with your HR around 130, or 60-70% of max heart rate. A bike is best, but incline treadmill walking is also a good alternative.
- Only increase aerobic training load when you need to. Track your resting heart rate (measured first thing in the morning) and the work rate you have to maintain to hit a HR of 130. As long as your resting heart rate is trending down and/or you can pedal faster/against more resistance or walk faster/at a greater incline week to week, then don’t make increases.
- Make increases slowly – 10 minutes more aerobic work per week. Evaluate your conditioning as you go. Your resting HR should end up somewhere in the 50s, and you shouldn’t have any issues recovering between sets. You should notice that the amount of training you can handle has increased quite noticeably as fatigue during training decreases, and recovery from training increases. Once you find your minimum effective dose for maintaining that level of conditioning, stay there – don’t do more for its own sake.
- Once you reach three weekly sessions of 40 minutes apiece (again, only making increases as needed), evaluate your level of conditioning again if you’re still not sufficiently conditioned (see the previous point).
- If your aerobic fitness plateaus at that level of low-intensity training, you may need to start including interval training. Start conservatively – 3-4 rounds of 1 minute intervals with 2-3 minutes of rest in between. Choose low-skill movements (NOT sprinting or weightlifting) like cycle sprints or kettlebell swings. Again, monitor improvements and only increase as necessary.
- Do 2-3 sets to failure per muscle group, per week. Save this for your accessory work – going to true failure on squats or deadlifts regularly probably isn’t the smartest idea. You can get the same local aerobic adaptations with safer exercises. This is perfect for isolation work, actually. If someone tries to hate on you for being a bro and doing pec flyes or leg extensions, you can say you just care about maximizing mitochondrial biogenesis, thank you very much.
Wrapping it up
Whether we’re talking about the Chinese weightlifting team’s morning jogs, Andre Malanichev’s 10km runs, or Chad Wesley Smith who does enough cardio that he’s only a couple seconds off the world record 500m row, a lot of the best lifters in the world already know how dedicated aerobic work can benefit their training. Especially if you’re finding yourself huffing and puffing between sets or having issues recovering between workouts, improving your cardiovascular conditioning may be exactly what you need to keep moving forward and getting stronger.