How Different Workouts Affect Your Body
How you train will affect how your body adapts. So today, we’ll look into that a bit. I’ll start by talking about muscle fiber types and how to recruit different types of fibers, then I’ll talk about load to muscles, and lastly, I’ll tie it all together by talking about how different workouts like Pilates, barre, lifting, yoga, and running, will affect your muscles and body composition.
So let’s start by talking about fiber types. This is important, because your muscles are made up of different types of fibers that are stimulated differently, recover differently, and are of different sizes. You have two primary types within a single muscle: type 1 fibers and type 2 fibers. Within your type 2 fibers, you have several sub-classifications. But for the sake of today’s podcast, we’re going to talk about type 1 fibers or the slow-twitch, type 2a and 2ab, which I’ll lump together to call the intermediate fibers, and type 2b which I’ll call the fast-twitch fibers.
Every muscle has a certain distribution of both type 1 and type 2 fibers, and this distribution will vary among individuals. Some people will have more type 1 fibers and make them better at endurance activities, and some will have more type 2 fibers which will make them have generally bigger muscles and be able to produce more power. Anyone can stimulate and grow their type 1 and type 2 fibers by how they are training. But some people will be genetically predisposed to lean a certain way.
Let me start by saying that we don’t want to only stimulate type one fibers or only stimulate type 2 fibers. We want to stress all as many fibers within a muscle as possible. When I talk about load, I’ll talk about how to engage as many fibers as possible within your workouts so you know you’re getting the most benefit from the time you’re spending in your workouts. Your type 1 muscle fibers are also called slow-twitch. But I don’t like to use fast or slow-twitch, because it’s a little misleading. It’s less about the speed of the contractions and more about the force they produce.
In fact, they are called “slow-twitch” because they are slow to fatigue, not because they produce slower movements. And fast twitch is the opposite – they are called “fast-twitch” because they are quick to fatigue. They are built to contract with lower power but are able to sustain your movements for a long period of time. These fibers are activated first because they don’t take much energy for the body to engage. They are relatively easy to engage and don’t fatigue easily.
These fibers are also very quick to recover, about 90 seconds. Recovery, in this context, means the physical and electrical capability of the muscle to be contracted again, not the recovery of the energy depleted during the workout. You could do a workout where you only recruit type 1 fibers, and although your type 1 fibers will be capable of producing force again almost right after your workout, your system may have been stressed and in need of recovery.
These fibers are smaller and don’t account for much mass in the muscle tissue itself. This means that stimulating your type 1 fibers only won’t account for as much muscle growth as also stimulating your type 2 fibers. Type 1 fibers also don’t burn through as much glycogen as type 2 fibers do, which is one of the reasons your body prefers to use these fibers. And this is important in body composition.
Let’s quickly talk about glycogen, and how muscle fiber types can affect body composition. When we eat, the carbs in our food are converted to glucose. This glucose is what your body uses as fuel to operate different processes in your body and keep you alive. When your cells have enough fuel from glucose, the extra glucose is converted into glycogen and stored in the liver and in the muscle cells. This glycogen is used by the liver to power processes like digestion and your heart. The glycogen in the muscles is used to produce strong muscular contractions. When there is too much glycogen in your liver and muscle cells, the leftover glycogen is stored as fat.
This is where exercise comes in. Utilizing intense muscular contractions, we empty the glycogen in the muscles, empty its stores, and allow for more glycogen to flow in the next time we eat. If we repeat this process regularly, emptying the stores of glycogen in the muscles with strength training, our bodies utilize the food we are eating as fuel rather than converting it to fat. So this is why doing endurance-only activities like pilates, walking, biking, etc. may not move the needle on your body composition. Remember that nutrition is FAR more important than exercise, so please don’t blame your workouts entirely on body composition, but how you’re working your muscles will have an effect.
The next type of fibers we’ll discuss are type 2a and type 2ab, or collectively, the intermediate fibers. These fibers have less endurance than the type 1 or slow-twitch fibers and also take longer to recover. When these fibers are used and fatigued, they can sometimes take days to recover. I recently had some of the Evlo members talking about biceps and how a week ago they were able to bicep curl a heavy weight, and this week they can’t. That could be because they tapped into their intermediate muscle fibers on week one and maybe need a bit longer to recover. And because their fibers hadn’t fully recovered before they worked them again, they weren’t able to lift as heavy as they could the week before. This is no big deal and happens sometimes, but just illustrates the importance of recovery. This happens in all muscles but tends to be more easily identifiable in a bicep curl, probably because it’s more difficult to compensate in a bicep curl than something more complex like a step-up or lunge.
Lastly, we have the type 2b fibers or the fast-twitch fibers. These fibers are only called into action in emergency situations and will engage in the last few seconds of your set when you are very near to fatigue. These fibers can sometimes take days to weeks to recover. What happens with muscle fibers is that they are recruited based on the perception of effort. If your nervous system perceives the load is too heavy for your type 1 fibers, it will instead engage your type 2 fibers. This happens in power lifting when you are using very heavy resistance, but only doing 2-3 reps.
A second way your fibers are recruited is based on time. So if the load is moderate and you can do the exercise for about 60 seconds, 90 seconds max, you can actually recruit the slow, intermediate, and fast-twitch fibers.
First, your type 1 fibers will engage and fatigue, your intermediate will kick in when the load is too high, and your fast twitch will kick in at the very last second when your muscles are close to failure. If the exercise is too light and going on for too long, your type 1 fibers will be the only ones recruited. This is basically a recycling effect of your type 1 fibers – because they recover so quickly, your type 1 fibers turn over and you can continue to use them to power the movement.
By the time your intermediate fibers are called into action, some of the type 1 fibers have had the opportunity to recover and can be used again. Remember that your body will be reluctant to use your type 2 fibers, so if it can keep using type 1, it will.
For the greatest benefit, we want to stimulate as many muscle fibers as we can during our strength training workouts. We can do this by applying the right amount of load to our tissues, so the fibers are recruited from slow to intermediate, to fast, but not too long to where the slow-twitch fibers have a chance to recover and be recruited instead of the intermediate or fast-twitch. The way to do that is with a moderate load, moving SLOW for 60-90 seconds. Towards the end of the set, you should feel close to failure – with maybe 3-4 reps left.
If your resistance is too light, you will only get through the slow-twitch fibers. By the time you start to recruit the intermediate fibers, some of the slow-twitch fibers will have recovered and your body will use those (because it prefers to use slow twitch). If your resistance is too heavy: you will only be able to do a few reps and only recruit the fastest twitch fibers and miss the slower and intermediate fibers. Moderate weight when you are fully fatigued after about 90 seconds is the right dosage: you will be able to fatigue and stimulate all the fiber types.
Now, resistance and load don’t necessarily have to be heavy weight, it just has to use an efficient lever. For example, a body-weight step-up loads the glutes with more force than a sumo deadlift holding 60lb. This is because of the physics of the exercise that I’m not going to get into today. But just remember that weight can be helpful but isn’t always necessary if you choose exercises that are fatiguing your muscles within that 60-90 seconds-ish time frame.
Also, although acceleration and speed will add more force, you don’t have to move fast in order to stimulate the faster twitch muscles. Because the faster twitch fibers are recruited based on perceived need, which means that heavy resistance and slow movement can also recruit them. This may be a little kinder on your joints than something like a plyometric. So don’t feel like you need heavy weight or speed to recruit the fibers – just go by how fatigued your muscles feel after about 60 seconds. If the 60 second-ish mark hits and you feel like you could easily go longer, go up in resistance on the next set.
Let’s quickly talk about sets, then we’ll get into specifics of different types of workouts. If your first set is moderate weight and let’s say you fatigue through your type 1 and type 2a fibers. Your type 1 fibers will reset by the time you get to your second set, but maybe your type 2a hasn’t. This means on set two, maybe you fatigue your type 1 fibers a second time, and you recruit your type 2ab fibers since the 2a wasn’t recovered. And so on for another set or two, which means you could potentially get to the fastest twitch fibers by the end of your workout. You can do this in fewer sets for sure – just go by how fatigued you feel after each set.
Let’s get into different types of workouts. Please remember that there are tons of methods, so I’m making lots of generalizations with these statements. There are so many different types of yoga, pilates, lifting, etc. But we’ll briefly talk about each. We’ll start with just traditional weight lifting where your sets are lasting about 60-90 seconds, and you rest in between sets and complete several sets. To me, this is the most effective at stimulating muscle growth because you’re recruiting as many fibers as you can.
Now remember that exercise selection is everything – it’s less about how much weight you’re pushing and more about the exercises and how they are targeting muscles. I’ll give you another example – a matrix move with body weight targets the quads with double the amount of force as a squat using weight. And this has to do with the lever to the knee and how your body weight is distributed to target the quads. Another recommendation I have – and this goes for any resistance training – is to target muscles one by one, whenever possible.
So instead of choosing an exercise that works glutes AND core AND shoulders AND quads, just do one at a time. It seems like it would save time to do more at once, but it actually doesn’t. Because if you aren’t getting optimal work to any of those muscle groups, you’ll have to do more exercises to fully fatigue each one. Whereas you could just tease out each muscle, target it using an exercise that effectively loads it, and then move on to the next muscle group. And also, your nervous system can produce better output to muscles when it has less to focus on and stabilize. Maybe I’ll do an entire podcast about this soon, but for now, just remember that less is more. Try to target one muscle or muscle group at a time.
How does weight lifting affect your body composition? Well first, it’s important to remember that body composition will not significantly change if your nutrition is not right. You cannot lean on your workouts to burn off what you ate – that’s when people get into over-exercise and back-track. But more muscle improves insulin sensitivity, which improves your body’s ability to use your food as fuel rather than storing it as fat. There’s also a new study that I’ve discussed before how adding muscle can actually break down fat. I’ll link that study in the show notes. More muscle can also improve your resting metabolism since muscle is very metabolically active. So over time, adding muscle can absolutely improve body composition.
Next, let’s talk about Pilates and barre. Pilates and barre – depending on the exercise, is often more of an endurance-type modality. Most Pilates and barre exercises are longer holds and stimulate type 1 fibers, recycling them over and over. Now, this is not a bad thing – improving the strength of your type one fibers is great for stability and strength. But it may not move the needle for your body composition as much as weight lifting since you probably aren’t tapping into those type 2 fibers at all.
This isn’t true for every barre or pilates type exercise. I think a lot of slow abdominal work gets classified as barre or pilates that still can stimulate the type 2 fibers. For example, the ball crunches that we do in my Burn class – which is like pilates – are HARD. You will be cooked and near fatigued by the end of 90 seconds if you’re doing them right. There are other examples too, like the skiers in barre. So just because they are slower and sometimes smaller movements, doesn’t mean that they can’t tap into the type 2 fibers. But some more endurance-type movements like donkey kicks, hip circles, bridges, arm circles, etc. where you are sustaining a muscle contraction for sometimes minutes, are probably more likely to recycle those type 1 fibers. Again, not bad, but just not going to be AS effective for building muscle and changing body composition.
Next, we’ll talk about running. Two types of running: jogging and sprinting. Jogging stimulates type 1 fibers almost exclusively, where sprinting stimulates type 2 fibers almost exclusively. That’s why sprinters will look JACKED and long-distance runners may have less muscle mass.
And finally, let’s talk about yoga. There are many types of yoga, but let’s talk about vinyasa style, which is very popular in the US. This is where you’re flowing between postures, maybe with some brief posture holds. Again, this is probably more of a type 1 fiber recruitment, since you aren’t really targeting muscles with repetition. Yoga can build type 1 strength and body control/awareness, which can absolutely improve the results from your lifting sessions. It can also aid in balancing your nervous system which is an important aspect of your body’s ability to heal and get stronger from any resistance training program.
So given all this information, what’s the best way to work out? Of course, there is no best way – whatever will keep you consistent, and one that you enjoy doing, and one that is healthy on your joints is great. But I have my bias of what’s “best”, of course. I believe a focus mostly on resistance training/weight lifting is great. But not working muscles too frequently, so those type 2 fibers have time to recover and get stronger. I did a podcast about how to know when to take a reset week a couple of weeks ago, so if you feel like you aren’t recovering between your workouts, go listen to that episode. It could help move you forward if you feel like you’re stuck in a plateau. Then everything else sprinkled in is great. So we do 3 heavier lifting classes/week, then I teach a Pilates class – where we are still working type 2 fibers in the core.
Then if you want a 5th workout, you can choose between a yoga class – if you feel like your nervous system needs some extra recovery, a barre class, which is more type 1 endurance training, and a F+S class, which is also type 1 endurance training, but also with some cardio bursts and yoga flows. I always say that Thursday’s class is a bonus, and not necessary for results. It’s only there if you want it. BUT – can you do two or three focused strength-training workouts/week and see great results? Of course. It just depends on what’s inside of those workouts and how you are fatiguing your muscles. We have a three-day track where you are lifting Monday and Friday and doing a barre/Pilates class focused on trunk/core on Wednesdays. And that can be super effective as well.
We probably want to move every day, so I do recommend trying to go for a short walk or even walk around your house pretty much every day. Hopefully this was helpful! If you’d like to join us in Evlo where we progressively load all our muscle fibers with less wear and tear through the joints, you can try our classes for free. I put a link for 7 free classes in the show notes. We also just brought back the free trial.