Endurance Training- Laying a Foundation

Over the next two chapters we are going to talk about how workout changes your Swimming Machine to make it better. We are going to separate out sprint and endurance training for each chapter, but we will start with endurance training since that is more important for our sport.

Before we start our journey, we should know where we are going. So, what is endurance? For us, endurance is the maximum speed we can hold for a long time (about 30 minutes). Sound familiar? That’s exactly what the lactate threshold is! We can always go faster, but the cost of acid will be too much and eventually cause us to slow down. That’s why we can’t sprint forever.

So how can we improve our endurance? There are two options: Get our ATP (energy) from somewhere more efficient that doesn’t create acid and/or get rid of the acid faster to keep it from building up in the muscles. This involves improving mitochondria size and number, increasing VO2max which is the delivery and consumption of oxygen, and increasing lactate transporters to the bloodstream and mitochondria. We can do this with two main training types: Aerobic Endurance training, and Aerobic Power training. When we talk about Sprint training, we will go through two more training types: Lactate Tolerance and Speed training.

Although we are going to separate endurance training into Aerobic Power and Endurance types, there is a lot of overlap in how and what they stimulate to adapt. The more elite the swimmer becomes, the less overlap there is, and the more important it is for them to separate out these two training types.

Aerobic Power: VO2max Training

Before we get into the nitty gritty of how Aerobic Training helps develop your Swimming Machine, let’s outline the typical sample set that defines this training type. Usually, these sets involve hitting a best average time with about a 1:1 ratio of swimming time to rest time. This is similar to 200 pace. A sample set would look like 20x100 @ 2:00 holding 60s. No more than 40 minutes of swimming time should be capable since your sugar stores will run out and pace times should fall off. If they don’t fall off…maybe you didn’t recover enough from the last workout, or you weren’t going fast enough in this workout.

Tangent: Other training names for Aerobic Power are: High Intensity Interval Training, USRPT and EN-3

So what’s happening to your body during the set? First off, heart rate should be around 80-90% of max (160-180 for most people), acid production is well above threshold levels during the swim, and then drop back down during the rest, and finally your body is maxing out it oxygen consumption ability. Because of the extra need for speed during this set, all of the slow twitch motor units and most of the fast twitch motor units are being activated during each rep (or 100 from our example), and so we are training most of the muscle mass we have.

Since VO2 is being maxed out in Aerobic Training, it is the most important target for this kind of training and will adapt maximally when you recover from the set. Let’s break it down and explore how the Swimming Machine adapts.

If you remember from our Cardio chapter, VO2 stands for volume of oxygen consumed by the body per minute. VO2max is the maximum oxygen consuming ability of the body. This is a measure how much ATP you are generating through the aerobic energy system (review in Energy Systems) by using oxygen. Remember that all combustion reactions require oxygen, and the more O2 you can supply, the better your aerobic engine will work.

VO2max is determined by three factors: Oxygen carrying capacity of the blood, delivery of that oxygen through the heart and capillaries, and extraction of that oxygen by the mitochondria by the muscles.

Overall, VO2max can increase by 10-25% with training, and of these three components, delivery of oxygen by the heart and capillaries will improve the most through Aerobic Power training. Again, remember that cardiac output is determined by stroke volume (the amount of blood squeezed out with each pump) and heart rate. Heart rate cannot improve, so only stroke volume changes with training. Essentially, Aerobic Power training increases the size of your heart.

Because Aerobic Power training will greatly increase Pre-load to the heart, it will force the heart to reach the limits of its capacity to stretch and hold blood inside it between each beat. And as the season continues and your body is operating at a higher than normal blood volume, this pre-load will continue to increase and improve.

Tangent: Stroke volume decreases in elite athletes at high exercise levels because their hearts are so big, there isn’t enough time in between beats to fully fill it up.

This signals the heart muscle to grow in length by adding sarcomeres and making each cardiac muscle fiber longer. When arranged in a sphere, this added length results in a larger heart that looks like a swollen balloon. The extra space inside allows the heart to increase the amount of blood that can be received by pre-load, and will increase the amount of blood squeezed out per beat… aka stroke volume.

Tangent: If this kind of change occurs because of certain diseases, we call it Dilated Cardiomyopathy…bad.

So how much change we talking about? A normal stroke volume for an average male is about 100ml of blood per beat. Training to an elite level can increase that to 170ml. Cardiac output as a whole can change from 20 liters (5 gallons) per minute to over 35 liters (almost 9 gallons) at maximum exercise levels. Also, the myosin heads will change in the cardiac muscle fibers to better handle the constant high level squeezing of training. Since the heart can pump more blood per beat, this decreases the heart rate when you are at rest and when doing sub-maximal exercise (easy swimming) because the heart can now deliver the same amount of blood with fewer beats per minute.

Tangent: Surrounding the heart is a stiff protective sac called the pericardium (peri=around, cardium=heart). Pigs had this sac removed surgically, and their cardiac output and VO2max jumped 30% because of all the extra room to expand! New doping strategy? Nope…bad idea.

Of course pumping the blood is great, but we also need to deliver it better. This is the job of capillaries. When you do an Aerobic Power set, your muscles burn right? That burning is caused by overloads of acid, and signals that the body is relying on glycolysis and not the aerobic system. The body assumes this is because not enough oxygen is getting to the muscle, so it sends out a signal molecule VEGF, or Vascular Endothelial Growth Factor. This stimulates capillaries to grow and spread in between the muscle cells and increases the surface area for red blood cells (and their hemoglobin) to interact with muscle cells to improve deliver of oxygen to the mitochondria.

In addition, the increased piping in the body slows down the blood’s speed as it travels by the muscles, and increases the time the blood and muscle are interacting. Because oxygen is delivered by diffusion (simply “seeping” into the muscle), the added time allows for greater delivery of oxygen and pickup of CO2. Yay VEGF!

Capillary networks can increase by 5-10% over 6-8 weeks of consistent training. The key is to provide plenty of opportunities to stimulate these adaptations… that means Aerobic Power sets, no matter how much they hurt.

Mitochondria make up a big part of improving VO2max, and they are definitely improved by Aerobic Power training, but they are more better (you heard me) improved by Aerobic Endurance training, so we will defer our discussion on their changes until later.

For now, let’s go back to the acid issue. Because we have repeating bouts of super-threshold levels of acid build up in the muscle cell, this signals the cell to increase its ability to get rid of that acid. There are two ways to do this: ship the lactate out of the cell and into the blood, or ship it into the mitochondria to be metabolized. Both solutions require “shipping” the lactate across the membrane because the lactate molecule can’t cross the membrane on its own, it needs the help of a transporter. We spoke of this in our Lactate Threshold chapter, here’s a picture to help you remember.

Tangent: These lactate membrane transporters are called monocarboxylate (MCT) transporters.

Again, we will talk about mitochondria soon, but during Aerobic Power training the overload of acid provides the signal for the muscle cell to create more of these transporters to increase the rate of lactate removal and metabolism. This has the great result of improving the lactate threshold and lower lactate levels during sub-maximal speeds, which means less pain for you!

We said earlier that the speed of Aerobic Power training requires us to kick in our higher order motor units, which are usually made up of fast twitch fibers (or higher order slow twitch fibers if that’s all you have). This is great because a muscle fiber that doesn’t activate is a muscle fiber that doesn’t adapt. On the other hand, intense endurance training will decrease the size of fast twitch fibers and will also decrease their contraction velocity because of an increased signal to build slow myosin heads. This is ok. We want the endurance ability of those fast fibers to get better too. Studies have shown that even if weightlifting is continued during this period, endurance training “interferes” with achieving maximal strength gains. For most swimmers, this is not a big issue since we plan on racing 400IMs and not benching 300 pounds. In addition, the reversal of this training adaptation may explain what happens during taper. 

Aerobic Endurance: Mitochondrial Training

Again, let’s start with what kind of set this training looks like. The simplest version of an Aerobic Endurance set is 3000 yards for time. Basically swimming at your lactate threshold pace. Otherwise, anything with long swimming reps (300s) and short intervals (10-30s rest) will hit the target. These sets should last for a while, about 20-60 minutes.

Tangent: Other training names for Aerobic Endurance are: Threshold Training, Volume Training and EN-1/2

During these sets heart rate is around 70-80% (140-160), VO2 is about 75% of max, lactate levels are at or almost at their maximal steady state and mostly the slow twitch motor units are being used since swimming speeds here are not that fast. Technically, nothing is being maxed out here. But this is the maximum speed you can hold without taking breaks to let the acids levels drop back down.

Because of the constant uninterrupted swimming that sits right on the threshold, these sets maximally stimulate improvements in lactate threshold through development of big awesome mitochondria. You could say Aerobic Endurance training provides the maximum “in swimming” oxygen consumption per minute. Even though we are not training at VO2max, we are still consuming more oxygen molecules per minute during the swim because our swimming is un-interrupted, unlike Aerobic Power sets. This stimulates the mitochondria to work, and the body to improve those energy factories. 

Mitochondria can improve 50-300% with this kind of training! But how does this happen exactly. We have mentioned before that mitochondria can improve by growing in size and number. This is not easy. Mitochondria are basically their own little cell inside a cell. In fact, one of the theories in biology is that since mitochondria contain their own DNA, they were once free living bacteria that got caught inside a bigger cell, and the symbiotic relationship kept them together from then on. Constructing these monster factories from scratch is tough. But it is relatively easy to increase their size.

Mitochondria have two membranes, and better mitochondria have more surface area on the inner membrane to make room for all those ATP generating molecular machinery. In fact, we measure these enzymes to figure out how good of mitochondria we have. With training, most of these enzymes will double in number. This has two effects. First, it doubles the metabolizing ability of the mitochondria for all fuels that is burns: pyruvate (sugar), lactate and fat. And secondly, mitochondria are activated by a decrease in the cell’s ATP pool. Because of all these extra machines, the mitochondria are more sensitive to changes in ATP and will activate sooner when there is a drop, which takes a load off of the glycolytic system and decreases acid production right from the get go. Better mitochondria can also reach their maximum ATP producing power sooner, especially when it comes to burning fat. That’s nice in a 500.

Tangent: Track athletes at the end of a race perform a “kick,” which is speeding up their pace. The one with the strongest “kick” is the one who is freshest, which means has the best oxidative capacity throughout the race, not the best sprinting.

Tangent: Recovery is an aerobic process! Bursts of sprints need good aerobics to recover from. Active recovery maintains blood flow to those muscles and maintains mitochondrial metabolism of lactate.

Even though Aerobic Endurance and mitochondrial ability correlate better with endurance ability when compared to Aerobic Power and VO2max, there are some limitations to Aerobic Endurance training. Firstly, Aerobic Endurance is not race pace training. Even Aerobic Power, while an endurance training type, still replicates the speed and technique used in a 200 or 500. But with Aerobic Endurance, we never hit race pace, and so we are not training as specifically as we can.

On top of that, genetics play a much bigger role in determining Aerobic Endurance than Aerobic Power. Because Aerobic Endurance depends on mitochondria so much, a swimmer’s baseline and maximum ability is really determined by the amount of slow twitch fibers they have, which is 100% genetically determined. Here are some numbers to give you an idea of how big a difference this can make:

Aerobic Power on the other hand is about adapting the size and scale of the heart and capillaries, so it is more amenable to training and the adaptations last longer.

Before we move on to talking about sprint training, let’s talk about structuring training throughout the season. Both Aerobic Power and Endurance training can take a very heavy toll on body, especially with swimmers. We will talk more about the hormonal changes that happen with overtraining later, but one thing you can do to avoid that outcome is by Zig Zagging your overload training. As your Swimming Machine adapts and improves over the weeks of the season, you and your coach will naturally do more and more each day in terms of yards and intensity. Rather than continuing on a straight line trajectory, create mini-cycles of 3-6 weeks that increases yards/intensity over those weeks, then drops back down and repeats the cycle.

This is called periodization of training and can be done with endurance, sprint and dryland training. Speaking of sprint training… time to talk about speeeeeeed (the motion, not the drug)!

Karl Hamouche- Swim Smart founder

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