Listen on Apple Podcasts | Listen on Spotify | Listen on YouTube

I’m discussing the latest scientific studies on the ways mental fatigue impacts athletic performance, whether caffeine suppresses your appetite, if knee sleeves benefit your performance, and how weightlifting affects visceral fat loss. Listen now to dive into the science!

This podcast is another installment in my Research Roundup series of episodes, where I give you concise and practical takeaways from studies that I think are interesting and that can help us gain muscle and strength faster, lose fat faster, perform better athletically, feel better, live longer, or get and stay healthier. 

There is a ton of scientific research that gets published every year, and even if you narrow your focus to fitness research, it would still take several lifetimes to unravel the hairball of studies on nutrition, training, supplementation, and related fields. 

That’s why my team and I put a lot of time into reviewing, dissecting, and describing scientific studies in articles, podcasts, and books. 

Oh and if you like this type of episode, let me know. Send me an email ([email protected]) or direct message me on Instagram (@muscleforlifefitness). And if you don’t like it, let me know that too or how you think it could be better.


0:00 – Save 20% on my Triton fish oil! Go to and use coupon code MUSCLE to save 20% or get double reward points.

3:36 – Does mental fatigue impact athletic performance?

18:35 – What are the effects of knee sleeves?

21:50 – How do you reduce visceral fat?

25:19 – Does caffeine have an impact on appetite?

Mentioned on the show: 

Save 20% on my Triton fish oil! Go to and use coupon code MUSCLE to save 20% or get double reward points.

My favorite weightlifting cues:

What did you think of this episode? Have anything else to share? Let me know in the comments below!


Hello, and welcome to Muscle For Life. I’m Mike Matthews. Thank you for joining me today for another research Roundup episode, where I am going to walk you through a few scientific studies that. Offer practical insights and takeaways that you can use to reach your fitness goals faster. And these episodes will also, hopefully if I’m doing my job well, help you better understand how scientific studies are conducted and what constitutes high quality scientific evidence.

And so in this episode, I am going to be discussing research on mental fatigue and how that can affect our athletic performance knee sleeves. Do they work? Do they not work? Should you use them? Should you not use them visceral fat? How to reduce visceral fat and finally caffeine and appetite is caffeine actually an effective appetite suppressant.

But first research shows that getting enough omega-3 fatty acids in your diet can benefit you in many ways, including reducing the risk of heart disease, increasing muscle growth, increasing cognitive performance, increasing fat loss, decreasing inflammation, improving mood, reducing muscle soreness after exercise and more.

There is a problem though. It’s hard. To get enough of these vital molecules through diet alone. And that’s why fish oil is a popular supplement. It is a safe, easy and healthy alternative to eating a lot of fatty fish, for example. And that’s why I created Triton. It is a high potency molecularly distilled fish oil with 2,400 milligrams.

EPA and DHA per serving. And those are omega-3 fatty acids that have been specifically linked to a lot of the benefits I just mentioned. And Triton also has vitamin E and lemon oil to prevent oxidation ran acidity and. Nasty fish oil burps Triton is also produced from deep water, Peruvian anchovies and sardines caught by fisheries approved by friend of the sea.

And Triton meets the very stringent purity standards of the European Pharmacopia reference standards. The council for responsible nutrition and the global organization for EPA and DHA omega. And all that is why I’ve sold over 100,000 bottles of Triton and why it has over 900, four and five star reviews on Amazon.

And my. If you want to optimize your physical and mental health and performance, and if you want to reduce the risk of disease and dysfunction, you want to try Triton today, go to BI Legion B I, T R I T O N. And use the coupon code muscle at checkout. And you will save 20%. On your first order.

And if it is not your first order, you will get double reward points. So that is 10% cash back. And if you don’t love Triton for any reason, just let us know, and we will give you a full refund on the spot, no form, and no return is even necessary. So you really can’t lose. Go to BI Use the coupon code muscle checkout and save 20% or get 10% cash back and try tri and risk free and see what.

Okay, let’s start with talking about mental fatigue and how that impacts athletic performance. And my source here is a paper called does mental fatigue affect skilled performance in athletes, a systematic review. And this was published on October 14th, 2021 in the journal P O S one. Now most. Research on athletic performance focuses on physiological stuff, glycogen levels, enzyme levels, hormone levels, muscle mass VO, two max and so on.

And while all of those things are important, they are only part of. The recipe, there is a new school of thought and research largely pioneered by Tim nos and Samuel mark. That believes that the brain gets the final say in our athletic performance, either subconsciously or consciously, or maybe a bit of both.

So in other words, although physiology definitely has a role in determining our absolute. Potential at any given moment, our Headspace determines a lot more than we might realize. It seems to determine how far we can push ourselves in particular. And while that is self-evident to some degree, you don’t need to read research to know that feeling frazzled makes for less productive workouts or.

The opposite that an upsurge of enthusiasm makes for better training. We still don’t fully understand the underlying mechanisms behind this effect and what we can do to counter the negative aspects of it. And so to help demystify this murky field of research scientists at the university, PRA Malaysia reviewed 11 studies that had soccer, basketball.

Table tennis players, complete cognitively draining tasks prior to workouts or competitions. And most of the studies found that mentally demanding tasks caused significant cognitive fatigue and that then caused their performance to dip as a result. And that’s not exactly surprising, especially to those of us who do a lot of cognitively demand.

Work, I can speak for myself. A lot of my work requires a lot of thinking and attention and focus, and I’ve noticed that if I do several hours of that and then go and train, of course I can have a good workout. But generally speaking, that training is. Quite the same as training that is done before I do a bunch of cognitively demanding work or training on days where I’m doing little or no cognitively demanding work where either I’m not working much, maybe it’s a weekend, or I just have to do a lot of.

Kind of routine maintenance tasks that don’t require very much brain power, but what is more interesting in this research is how this drop in performance manifested. So the mental fatigue didn’t seem to have much of an impact on physiology. So things like heart rate, aerobic capacity, maximal strength.

These didn’t really change. But what the researchers found is that mental fatigue SAPs our athleticism by disrupting decision making and our perception of effort. So in a sense, good technique. When you are training can be thought of as just a series of nearly instantaneous conscious and subconscious decisions about how to move your body.

And we know from other research that stream of decision making slowly drains our cognitive gas tank, so to speak, just like when you are writing a book, you have to make a lot of decisions of what words to use and how to string them together. And. To say next and so forth. And the same thing goes for when you are figuring out what to do with investment money allocating investments, or if you are designing a building.

So anything that involves a lot of decisions, Drains us cognitively, and this can manifest in many ways. It can scatter our attention. So you’ve probably noticed that as you are feeling more mentally fatigued, you are more easily distracted. You are less goal directed. You have trouble distinguishing between trivial and crucial details in work, or even in your environment.

Mental fatigue can also give us tunnel vision, which might seem to co. The scattering of attention, but research shows that when we are mentally fatigued, we also have a tendency to miss the forest for the trees. We might become fixated on a particular opponent, let’s say, in a game, and then just lose sight of the rest of the field.

Mental fatigue also makes us clumsier. We become less coordinated. We become more likely to make mistakes that we otherwise would not make. If we. More mentally fresh. It slows down our decision making. So in order to avoid making mistakes, we have to move slower, which of course is a liability in any sport because we’re being forced to choose between speed and accuracy.

And that applies to weightlifting as well. Where having to slow down during a rep means that your muscles have to work harder, which means that you get fewer reps, a good. Training tip is to lift exclusively. Always. Don’t try to lift the weights slowly. The first half of an exercise should take about one second.

Then there should be a slight pause. And then the second half of the exercise should also take about one second. And when you are contracting your muscles and sometimes that’s in the first half of an exercise, like with a biceps. And sometimes it’s in the second half of an exercise, like a bench press.

You want to contract your muscles forcefully. That’s what it takes to move that weight that quickly. And lastly, mental fatigue disrupts our ability to plan and prepare, which of course gets in the way of just about all athletic activities, which pivot on our ability to anticipate the movements of other people and objects.

So those are some of the ways. Mental fatigue can hinder our athletic performance. And another one that I mentioned is the perception of effort research shows that mental fatigue tends to spike our rating of perceived exertion RPE. You’ve probably heard that acronym. And what that means is it makes stuff feel harder.

It makes exercise feel harder. It makes performing feel. Harder. And that makes our exercise less productive and enjoyable and it makes our performances worse. And so the key learning here is try to limit mentally and emotionally draining activities. Directly before your workouts and don’t do them during your workouts.

So for example, don’t spend a bunch of time on social media before or during a workout, because that can be emotionally draining and upsetting. Don’t spend a bunch of time answering email before you go and workout because. That is emotionally draining and don’t do it during your workout. Don’t try to think on some very thy decisions that you have to make immediately before a workout or during a workout, if you can help it.

Of course, if you have to do some of that stuff before you go and. Workout. Don’t use that as an excuse to skip the workout, go and do the workout. You will do just fine. But again, you’ll probably do a bit better overall over the long term in your training. If you follow this recommendation. And if you do have to do mentally or emotionally draining stuff, before you go and train, if you can put a little bit of time in between both of those activities, it’s going to help.

So for me, for example, I do most of my creative work, which is my most mentally draining work first thing in the morning because I find that I just do. Best creative work earlier in the day, rather than later in the day. And so I’m doing a couple of hours of that in the morning, and then I give myself about an hour or so to do some much less demanding tasks before I go to the gym, which is usually around one or 2:00 PM.

And then after that I get back to work in the afternoon and that afternoon block is usually reserved for less cognitively demanding work, more routine stuff, answering emails reviewing things that I need to review that don’t require creative thinking. I’m not trying to creatively solve problems, usually in the afternoon or the early evening.

I am doing stuff that is easier on my. Now something else to keep in mind, based on what I just shared with you is to adjust your expectations. If you are going into a workout feeling mentally exhausted view that cognitive fatigue with the same respect. That you would give to physical fatigue and don’t hesitate to adjust your workout accordingly.

Maybe you need to reduce weight on an exercise or two, or maybe you get a repper two less than the last time you did that workout. Maybe you even need to do a shorter workout depending on how you feel. That is perfectly okay. The fatigue that you’re feeling is not all in your head. It is very real. And for my part, what I notice specifically when I am mentally drained is my performance.

Doesn’t take a hit in the gym. I can still do what I need to do, but those workouts feel harder. I feel like I have to exert quite a bit more effort to get that performance than when I am mentally sharp. Finally before I move on, I just want to share a few comments. Caveats, on this research first is most of the studies on this topic have involved arbitrary mental exercises that were designed to make people’s mental gears grind.

And I would not be surprised if we didn’t see nearly as much of a negative. In mentally difficult activities that people find enjoyable. So writing, practicing music, reading, drawing, drafting, a business plan, if it can put you in a state of flow where you lose track of time and you feel fully absorbed in the task and you feel satisfied and fulfilled.

After the task again, I would not be surprised if that did not have nearly as negative an effect on physical performance and our perception of effort and it might even improve it. Another caveat is I would be curious to know if this effect cuts both ways. So do intense workouts or competitions make it more difficult to complete cognitive tasks later in the day.

Should you periodize your training? Big projects at work or important personal decisions that might sound a little bit silly to you, but I can think of plenty of times where I did pretty intense training first thing in the morning, and then felt a little bit more mentally scattered afterward when I was trying to do my more difficult creative work.

And I remember noticing that time was. Productive that it took me more time to come up with ideas that I liked, that I wanted to communicate, that I thought would resonate and to find words that I liked. And anyway, it’s just something to think about in setting up your days. So you are not just managing your time well, but you are managing your energy well and often managing your energy well is more important than manag.

Your time. If you run a business for example, and you have to make a lot of important high stakes decisions every day, which you probably do. If you are running a business, you might not want to do that immediately after an intense training session. For example, you might want to try to do that before you go and train.

Or as I mentioned earlier, train. And then give yourself a couple of hours to recuperate before you dive into that more mentally demanding work. Another question that this research brings to my mind is I wonder if we can train ourselves to better resist the innovating effects of cognitive. Fatigue, for example, some endurance coaches, such as Steve Magnus have experimented with having their athletes solve math problems in the middle of workouts to enhance their mental resilience, maybe working out after doing a certain amount of cognitively demanding work or the other way around, maybe working out and then doing a certain amount of cognitively demanding work can make us mentally.

Tougher, so to speak. Maybe it can make us more anti-fragile and I think that there’s probably something to that. I think that while we probably can’t fully erase the negative crossover effects between mental and physical fatigue, I would be willing to bet a fair amount of money that we can build our capacity to handle.

Both. And so then practically speaking, I think that what we can probably do through training through progressive overload, through proper recovery, and that applies to both the physically and the mentally demanding tasks. What we can probably do is increase the amount of either. Physically or mentally demanding tasks that we can do before we see a major drop off in the other.

So we can probably improve and increase the amount of cognitively demanding work that we can do before it really starts to impair our workouts. For example, and device versa. Okay. So that was a lot on that study and topic, but I hope you found it. Interesting. Let’s talk about knee sleeves now. And my source here is a paper called effect of a neoprene knee sleeve on performance and muscle activity in men and women during high intensity high volume.

Resistance training. And this was published on December 1st, 2021 in the journal of strength and conditioning research. So knee sleeves just to make sure you understand what I’m talking about here. These are the tight fitting cloth. Tubes they’re usually made of neoprene and you wear them over your knees while you lift weights.

They are not the same as knee wraps, which you will see people wrapping around their knees. Very tightly. The sleeves are neoprene. One piece you slip ’em on over your. Pants for example, over your knees and you wear them usually when squatting or deadlifting and these knee sleeves are popular among power lifters and recreational weightlifters.

And people will often say that they feel like these sleeves help them. Lift a little bit extra weight during a squat, during a lunge, during a dead lift. And they often say that they feel like the sleeves just keep their joints stable and they keep their joints warm. And some people even buy knee sleeves that are so tight fitting that they need to recruit a buddy to help put them on.

And they often say that they’re trying to get a little bit extra rebound. In their squat. So what does the research say? Scientists at the university of Rhode Island set about testing knee leaves by having 20 experienced male and female weightlifters do six sets of the leg press to failure with 80% of their one rep max with three minutes of rest in between the sets.

And they did that with, and without knee sleeves and the researchers measured the weightlift. Peak and average power, muscle activation RPE. So rating of perceived exertion, how hard the sets felt. They measured heart rate, blood lactate, and total reps performed each set. And when the researchers looked at the data they found essentially no difference.

With and without sleeves, but this is a good example of why it’s important to look at the overall weight of the evidence on a matter. And not just one study. If I were to leave it at what I just shared with you, you might conclude that knee sleeves are useless, but there are other. Studies that have shown that knee sleeves can improve joint comfort, instability, and that can increase coordination and that can improve your form and performance.

And according to one study, knee sleeves seem to be most helpful when squatting with low reps and I myself have been using knee sleeves in my lower body workouts for years now. And. I notice that my joints do feel more comfortable, especially with heavier weights, they do feel more stable. And the bottom line is I do perform a little bit better with them than without them.

And so now I always use them when I train my lower body. All right. Next up is a study on reducing visceral fat, which is fat that is surrounding your internal organs and is most associated with the risk of all cause mortality or death from all causes. You do not want to have large amounts of visceral fat.

And my source here is a paper called effects of resistance training with and without caloric restriction on visceral fat, a systematic review and meta-analysis, and this was published on May 16th, 2021 in the journal obesity. Reviews now there was a systematic review and meta-analysis the same type of research as I am sharing with you here, which is an in-depth analysis of a bunch of different studies, high quality evidence.

There was a paper. That came out in 2012 and it was conducted by scientists at the university of Sydney. And it concluded that weightlifting is ineffective at reducing visceral fat. And as a result of that research, many health authorities recommended calorie restriction and cardio as the ticket for getting rid of visceral fat and they pigeonhole weight lifting as purely beneficial for building muscle.

A problem with this research though, was with the data related to diet because some of the studies included in the review and analysis had people maintain a calorie deficit and some did not. And that of course muddies the results. So for example, if someone follows an aggressive weight loss diet lifting weights might not offer that much additional benefit in terms of visceral fat loss, but would still obviously be beneficial for improving overall health and body com.

And so I was excited to see this new research review and meta-analysis that was conducted by scientists at the university of Teran. And these researchers, they analyzed 34 studies involving a total of 2,285 participants. And about a third of the studies compared weightlifting plus calorie restriction to just calorie restriction alone and the rest compared.

Weightlifting to not weightlifting. So weightlifters to non weightlifters and to the pleasure of weightlifting maximalist like myself, the results showed that jacking some steel, significantly reduced visceral fat in obese, non obese middle-aged and elderly participants who were not. Restricting their calories.

And in studies where people were restricting their calories lifting weights did not seem to offer much additional benefit, but that might be due to statistical naughtiness complexities rather than an actual limitation of weightlifting. And so then you can chalk up yet. Another reason why everyone should be doing some sort of resistance training.

It doesn’t have to be weightlifting of course, but resistance training, strength, training of some kind training their muscles. And while we just learned that resistance training alone, Can reduce visceral fatness, regardless of what you do with your diet. If you want to maximize visceral fat loss, you want to combine weight lifting, calorie restriction, sufficient protein and cardio.

That is the winning formula. And that of course also is the winning formula for maximum fat loss in general. Okay. Last up in this episode is caffeine and appetite. My source here is a paper titled caffeine transiently affects food intake at breakfast, and this was published on July 19th, 2018 in the journal of the academy of nutrition and dietetics.

So caffeine is hugely popular, of course, and many people take it when they are wanting to lose fat for several reasons. It increases metabolic rate. Although once you become. Desensitized to it this more or less disappears. It also improves our workouts. It improves strength, endurance, and power. And it also of course, boosts energy levels, which are declining as you get deeper into a cut.

Now, what about appetite though? Many people say that caffeine seems to take the edge off of their appetite, but there. Much research on that. And so to take a stab at this researchers at SUNY university had 50 participants aged 18 to 50 years old report to their lab once per week for three weeks and drink a glass of cold juice containing either zero, one or three milligrams of caffeine per kilogram of body weight.

And that’s about the equivalent of one or three strong cups of coffee. Just for the sake of reference. Now, 30 minutes after drinking their jitter juice, the researchers invited the participants to eat as much as they wanted from a breakfast buffet. And then the scientists jotted down. How many calories people.

Eight, the researchers also had the participants rate several dimensions of their appetite. So hunger fullness, thirst, desire to eat before drinking the juice. 30 minutes after drinking the juice. And then immediately before the breakfast and people used. A scale of one to five, one being, not at all and five being extremely then after the breakfast, the participants left the lab and resumed their normal eating habits, but they also wrote down everything they ate for the rest of the day.

And what the results of this experiment showed is that caffeine did not seem to have much of an impact on the participant’s calorie. Intake. They all ate about the same number of total calories, regardless whether they had caffeine before breakfast or not. And they did not report feeling less hungry after consuming the caffeine.

Strangely though, most people did eat a bit less at breakfast after they took the smaller dose of caffeine. So one milligram per kilogram versus three MIGS per kg, but they also ate a little bit more throughout the rest of the day, wiping out that. Benefit now that’s it for that study, but how does that compare to other studies in the topic?

Other studies have shown that caffeine can modestly reduce appetite for a brief period, but often people tend to just eat more after that brief period of less appetite. And so the key of course is controlling. Your calories and that’s true of all fat loss supplements, the handful of fat loss supplements that actually can help you burn more calories or reduce your appetite.

And that’s true of exercise as well. Of course, those things can only help you lose fat if you also control your calories. And so don’t think that you can just knock back a few shots of espresso and shed an extra pound or two per month. In a best case scenario, a little bit of caffeine might help you be a little bit less hungry for a little bit, but that’s about it.

And so it’s on you to use caffeine and use that effect to improve dietary compliance, which ultimately is what drives results. I hope you liked this episode. I hope you found it helpful. And if you did subscribe to the show, because it makes sure that you don’t miss new episodes and it also helps me because it increases the rankings of the show a little bit, which of course then makes it a little bit more easily found by other people who may like it just as much as you.

And if you didn’t like something about this episode or about the show in general, or if you have ideas or suggestions or. Feedback to share. Shoot me an email Mike muscle for muscle F or And let me know what I could do better or just what your thoughts are about maybe what you’d like to see me do in the future.

I read everything myself. I’m always looking for new ideas and constructive feedback. So thanks again for listening to this episode. And I hope to hear from you soon.

View Complete Transcript