5 Surprising new studies on how to build muscle in 2025

Chapters:

00:00 1. Pre-workout carbs

02:42 2. Is fasted training ok?

05:20 3. Cold plunges impair recovery

05:30 My Online PT Course

06:25 3. Cold plunges impair recovery

09:10 4. Post-failure lengthened partials are suboptimal

10:31 5. Muscle Memory

12:33 Outro

Transcript:

First up, we have a study finding that pre-workout carbohydrates are overrated for lifters. This was a very well designed study in which a group of trained lifters performed a workout with either no carbs, low carbs, which was 0.3g/kg, or high carbs, which was 1.2g/kg as a breakfast 2 hours before the workout. The meals were taste and texture matched so that the participants could not know how many calories or carbs they were consuming and the workout consisted of three all-out sets of squats, overhead presses, bench presses, and rows at 80% of 1RM. So a conventional full body workout.

The groups with varying carbohydrate intakes did not differ significantly in how many reps they could do for any of the exercises, or the total repetitions in the complete workout. Our own recent systematic literature review of all studies published up until that point also found no significant effects of pre-workout carbohydrates on performance if people were not training fasted or doing extremely high training volumes. In many of the studies in which pre-workout carbs improve performance the control group was fasted and was not consuming a proper placebo. Some of the studies find that if you do give them a placebo the effect is gone, meaning that the effect of pre-workout carbs in large part may be placebo. The idea that you consume something, and in particular the idea that if you think you need carbs but you don’t get them, then your performance might suffer. But if you don’t believe that, or you did believe that you had a breakfast and you didn’t know that it didn’t actually have any carbs, you were fine. We also found no significant effect of carbohydrate intake on long term strength gains.

Pre-workout carbohydrates are much less necessary than many people think for multiple reasons. First, you don’t rely on the carbs that you just consumed for performance. Your muscles mostly rely on the stored glycogen, which is glucose that’s stored in muscle and it’s only available for that muscle. So the pre-workout carbohydrates are essentially already too late. And after the workout, your body is very good at resynthesizing glycogen stores, even with very low carbohydrate intakes. For one, it uses the Cori cycle to essentially recycle the lactate back to glucose and store it back as glycogen. Moreover, a very underrated part of the energy production from strength training is fueled by the creatine phosphate system and the aerobic system. You only need glycogen and carbohydrates in general when you’re in that medium range where the intensity is not super high, because if you’re only doing, say, 15 seconds of exercise it’s mostly the creatine phosphate system that’s fueling performance, and it’s also not so long that the body can fuel performance by burning fat, so the aerobic system. Meaning it’s mostly at intermediate range where the body actually relies heavily on carbs, but for a total workout for strength trainees, especially given that rest intervals are quite long, the total carbohydrate intake is not that shockingly high. You’re talking about fewer than 100g of carbs, even for pretty extreme workouts.

The second new study I have for you today took things one step further. What if you don’t just skip the pre-workout carbs, or a placebo at least, and you just eat nothing at all? How is that going to affect your long term gains? For 12 weeks the participants trained either after an overnight fast or 1 or 2 hours after a high carb breakfast. Total daily macronutrient intakes did not significantly differ between the groups. By the end of the study there were no significant differences in their best measures of muscle growth and strength development. For muscle growth the researchers measured quadriceps muscle thickness using ultrasound and for strength development the researchers looked at 1RM and various measures of power. There were also no significant differences in total workloads during the training program indicating that the fasted training did not significantly hinder their performance. Neither group experienced the change in fat mass. In terms of total fat free mass as measured by DEXA scans, the fasted training group actually gained significantly more fat free mass than the fed training group.

This finding is quite hard to believe, given that prior research has found that fasted training is at best neutral and in at least one other study, significantly worse for muscle growth than training fed. It should reduce muscle protein synthesis, increase muscle protein breakdown, and it might hamper performance. It’s also not the case that the fasted training group made miraculously great gains. It was the case that the fed training group didn’t experience a significant increase in fat free mass at all. The difference in effect size was trivial so by and large we should interpret this as a no difference between the groups. However, it does make me skeptical of the relevance of the findings for serious lifters because this was a study on untrained, overweight individuals. A multiple of the participants also complained of feeling lightheaded and nausea, which are typical complaints that you see in people that don’t really like to exercise. Indeed, 25% of the subjects dropped out despite only being required to go to the gym two times per week.

We recently conducted our own study on fasted versus fed training in seriously trained lifters and we also found no significant difference in muscle growth, but we did found significantly impaired strength gains on the squat and also lower performance in the group that was training in a fasted state. They also reported lower energy levels. Importantly, this gap in performance widened over time, so it’s possible that over the very long term this difference in performance would also start affecting muscle growth. In the end muscle growth is driven by the total mechanical tension exposed on the muscles, so if your performance is lower for a long period of time that reduces your training volume, which in turn should reduce muscle growth. However, clearly based on both of these new studies fasted training is not such a big deal. If you’re not a competitive athlete doing very high training volumes or you simply strongly prefer to train fasted, that is absolutely viable.

So that’s two studies showing it doesn’t seem to matter that much what we do before a workout. However, the third new study I have for you today shows that there’s something you shouldn’t do after your workout, which is, ironically, something that a lot of people are doing to improve recovery – Cold plunges.

Cold plunges and ice baths have recently skyrocketed in popularity. However, research is very clear that they’re not a good idea to do post workout if you’re interested in maximum gains. The researchers concluded that cold “…greatly reduces microvascular blood volume, which is strongly related to a lower post-prandial amino acid incorporation in skeletal muscle protein in recreationally active males. Cold-water immersion should be avoided during post-exercise recovery.” This finding explains why previous research has found that post-exercise cold exposure can reduce muscle protein synthesis and long term muscle growth and strength development. Mechanistically, there’s just no way cold is beneficial for recovery.

The only possible benefit it has is that it reduces swelling, and it essentially puts the recovery process on hold. If you’re an Olympic athlete, train twice a day at the Olympics, cold can be beneficial because what’s cold essentially does is delay swelling and inflammation, which is bad long term for recovery, but is good to sustain short term performance because part of the recovery process actually further reduces your performance. Swelling and inflammation are good for the recovery process. Inflammation is a signal for the immune system to pay attention to this area and start healing. However, it further reduces performance acutely. So ironically, something that is good if you have to perform again and say 4 hours is bad if you want to perform again during your next workout. So for most recreational lifters, cold exposure post-workout is no bueno.

And that’s not the end of the bad news for my cold plunging friends. Another new scientific review concluded that cold exposure does not improve most health outcomes. Cold water immersion actually caused significant acute inflammation without affecting overall immune functioning. One famous study did find that people call in sick for work less when they do cold showers. This study became extremely famous but is highly misquoted because there was no objective difference in their actual number of illness days. This suggests a potential mental resilience type benefits where people do go to work even if they are slightly sick, or they simply lie less about being sick when they weren’t sick and they just didn’t want to go to work. But objectively, there was no difference in how often they actually got sick. The review also found no significant effects on most measures of mood and stress.

One study reported better sleep quality after cold exposure, but this was after heat training, so it’s probably not very relevant for most conventional purposes. And one study found an improvement in self-reported quality of life after one month, but this was not sustained over three months. Overall, I think it’s fair to say that cold exposure has become overhyped. However, cold exposure is not completely useless. In my book I also recommend cold showers as the equivalent of a shot of adrenaline. If you’re very fatigued or if you feel like after a warm shower you’re kind of drugged and drowsy, then a cold shower can significantly energize you. It’s very much like just getting a shot of adrenaline. Beyond that, though, I wouldn’t expect any miracles from it.

Shifting gears to training, new research finding #4 is that post-failure lengthened partials are probably suboptimal. Technically, this is research finding #5, because the previous one was a double. You got a bonus! The researchers had a group of strength trained lifters perform calf raises doing either only lengthened partials, only doing the bottom part, or doing full ROM reps to failure and then doing partial reps to failure at the end. Many people like doing lengthened partials because they have gotten quite popular and they do them after a set with full range of motion. The idea is that you get the benefits of full range of motion training and then after you get the benefits of lengthened partials. However, you do hit failure twice and you get less total exposure to the bottom range of motion. Indeed, the new study found that just doing lengthened partials as opposed to doing full range of motion to failure and then doing lengthened partials to failure, led to slightly better gains.

After eight weeks doing nothing but lengthened partials led to 10% growth versus 7% growth for the full ROM + partials group. There was a 96% Bayesian probability that this was a superior outcome. However, the Bayes factor was only 1.2, indicating that in terms of scientific quality of evidence this was very, very weak evidence. Nevertheless, based on the evidence that we have, if you do lengthened partials, you’re probably better off doing it for a whole set as opposed to doing full range of motion and then finishing the set with lengthened partials. The difference is small though, so if you strongly prefer one over the other, just go with that one.

Last but not least, I’d like to share with you a cool new finding on muscle memory. “Use it or lose it” is not completely true. After you stop training your muscle retains some memory of its former size and it’s easier to rebuild the lost muscle mass than it was to build it in the first place. This phenomenon is called muscle memory. Muscle memory is explained by some of the adaptations during training persisting even after you stop training. One of those adaptations is that there is an increase in myonuclei. Muscle cells are relatively unique in that they have multiple cell cores – myonuclei. You can build more of those and they make it easier to make the muscle bigger. They function kind of like command centers that govern a certain region of muscle mass and they can aid muscle protein synthesis and satellite cell activity. These myonuclei stick around for a very long time, possibly permanently. Some neural changes also persist quite well. When we start training and we learn an exercise, our bodies learn to coordinate our movements better and reach higher levels of muscle activity during that movement, which should allow for higher mechanical tension on the muscle, and therefore more muscle growth. Even after you’ve stopped training for a while that increased muscle activity is still there.

The newly established mechanism of muscle memory is proteomic. Certain proteins that were built after just ten weeks of strength training stuck around for at least 2.5 months afterwards. Some of these proteins were related to established epigenetic changes. Our genes are fixed, but gene expression is not. Epigenetics refers to how our DNA is read. Certain genes can become more or less active which can increase the production of proteins that help us build muscle. So while we all have a certain genetic blueprint that remains the same, that’s our genes, that’s hardcoded, how this is expressed, basically how the blueprint is read and interpreted, that can change over time. That’s epigenetics. What’s really cool about this new line of research on epigenetics is that some of these epigenetic changes can actually be passed on to offspring. We see this, for example, in mothers that experience very high stress during pregnancy. So if we take a little bit of a leap, maybe building a lot of muscle mass makes it easier not just to regain that muscle mass if you ever lose it, for the rest of your life, or at least a very long period, it might even be the case that your children will also have a little bit of an easier time building muscle.

All right. That’s all I have for you today. If you want to stay up to date on the latest research on how to master your physique, I’d be honored if you like and subscribe. And if you want to deep dive into everything there is to know about optimizing your physique, health, and becoming a good coach check out my PT courses. Link is in the description.