Written by Dr Mike Israetel & Dr. James Hoffmann
We train so that we can get better. Bigger, faster, stronger, leaner, and maybe even all of those at different times. Training hard makes us better, but it also tires us out and wears us down. We call this wear and tear fatigue, and it’s as much a feature of the training process as the improvements we’re training to try to get. Fatigue is inevitable so long as we train hard, so there’s no point in trying to avoid it completely. But we if accumulate fatigue for too long, we end up performing poorly, adapting poorly to training (not getting as good as we could be), and getting hurt more often. So every now and again, we have to bring our fatigue down by easing up on our training. Once we’ve brought fatigue down, we can resume hard training again and get back to getting better… until the next time we have to bring down our overly high fatigue. For more on fatigue and its causes, please see this article.
So far, so good, but at least one big question pops up: how can we tell how fatigued we are? Bringing fatigue down when it rises too high is all well and good, but how the heck do we know when we’ve got a high level of fatigue? Maybe we’re just being lazy and taking it easy too often? Maybe we’re being stubborn and grinding through training when we’re already beat up?
The good news is that sport scientists have developed reliable ways to detect the presence of high accumulated fatigue. You can use these detection methods with very limited technology or no fancy technology whatsoever, which means that you can use them with your athletes, with your clients, and with yourself. But before we get into a listing and description of all of the most common and effective indicators of fatigue, we’ve gotta make sure we’re separating them out into 3 very important categories. We have to make this split before we begin using them, because which category they are in greatly determines what it is they tell us about our fatigue state. Generally, the 3 different categories of fatigue indicators are leading indicators, concurrent indicators, and lagging indicators.
Leading Indicators are signs that fatigue is not quite so high YET that we need to take steps to lower it, but it’s on its way there, and soon. Detecting the leading indicators of fatigue can allow us to plan ahead and be ready for fatigue when it hits, rather than just reacting in surprise when it’s already very high.
Concurrent Indicators are signs that fatigue is high RIGHT NOW, and that we had better be doing something about it soon, if not ASAP.
Lagging Indicators are evident after fatigue has already been high for a long time. Sometimes, the leading and concurrent indicators can be missed, masked, or misinterpreted, so that we end up carrying unproductive levels of high fatigue that hamper our training and performance. The lagging indicators are very sure signs that we needed to back off and drop fatigue yesterday, and we had better get to it right away if we want the best results and to be safer from potential injuries. With ALL indicators, it’s important to remember that just one indicator is never enough to draw a definite conclusion about the fatigue state. But if several fatigue indicators are all pointing in the same direction, a high fatigue state (or impending one) is likely, and the more of them that point in the fatigue direction, the higher the likelihood is.
In this article, we’re going to explore two important components of detecting fatigue: what signs to look for and how to interpret what they’re saying. What signs let us know high fatigue is an issue, and whether or not they say it’s on its way, here already, or long overdue for a reduction so that we can get back to productive and safe training. And just to reiterate, the goal isn’t to be in a zero-fatigued state all the time… the goal is to train hard and let fatigue rise slowly, and only when it’s very high (especially when most of the concurrent indicators there) do we want to bring it down by doing something about easing up on our training for a short time. This time of easier training can be a day, a week, or even several weeks depending on where in our training program we are.
Leading Indicators
There are 5 general classes of leading indicator that are important enough to merit mention here. Each of them can tell us that fatigue, while possibly not high at the moment, is slated to be going up to “needs to be reduced” levels soon, probably within several days to a week of the appearance of these leading indicators if you keep training hard. If you detect these leading indicators, it’s not time to back off just yet, but you should be expecting to back off soon. For example, if your program calls for deloading to bring down fatigue in the fourth week of training, detecting some of these leading indicators in the end of the third week is just fine and actually a sign that you’re training just hard enough to get great results. On the other hand, if you are detecting these indicators in the middle of the second week, you might have a problem with your program design or your recovery efforts. Just the same, if you never detect leading indicators, even right before you deload… why do you even need to deload? Your program isn’t hard enough to merit the need for fatigue reduction and you need to train harder next month! Without further ado, here are our 4 main leading indicators and what/why they mean for fatigue and training:
- Previous Days’ (one or several) Nutrition
Nutrition is what provides fuel to both power training and recover the body from hard training. Under-eating calories, carbs, and protein (in that order of diminishing importance) can greatly blunt the body’s ability to recover from normal hard training. The longer inadequate nutrition is consumed, the more fatigue that should be recovered is not recovered, and that fatigue begins to add up on itself and eventually climb too high. If you miss a couple of meals one day, you’re probably not destined for anything too crazy in the way of accumulating fatigue, but the longer you go under-eating calories, carbs, or protein to your needs (fats in special cases), the higher your fatigue will rise, and the more likely it is that your fatigue in the next couple of days will get higher than tolerated. This is one of the only indicators of fatigue that is actually a cause of fatigue as well as an indicator, so there’s something you can do about it… like…. eating well so that fatigue doesn’t get higher than planned! But if you missed some meals for some circumstances not totally in your control (travel, family events, etc…) you should PLAN for rising fatigue, and perhaps adjust your coming training accordingly by taking a few light days to get back on track with normal fatigue levels.
- Previous Days’ (one or several) Stress/Recovery Management
Having low levels of outside stressors (traffic, relationships, work life, etc.…) not related to training itself is important to keeping fatigue in check for as long as possible. Relaxation and sleep also play a role. If your training and nutrition is great but you’re getting into fights with your girlfriend or you’re missing out on sleep from staying up too late playing video games, your ability to recover from normal training stressors will be reduced. A couple days of this, and you’ll be much more likely to be in a high fatigued state. Just like with nutrition, sometimes this is out of your hands, so the best you can do is control what you can… and at the very least consider lowering training volume/intensity in the next couple of days to prevent fatigue from rising too much, and then getting back into the normal rhythm afterwards.
- Previous Week’s Training Volume/Intensity
A couple of days of poor nutrition and recovery can really skyrocket fatigue, but so can a period of unusually high training volume or intensity. For example, if your plan was to do your normal workouts for last week, but an old training partner of yours was in town and you decided to just let loose and slam the training, your fatigue several days to a week later will be much higher than normal and likely in need of a reduction. Usually, your hardest training is already programmed to occur right before a deload, which is a great alignment. But when this is not the case, make sure you consider taking some light days to remedy the fatigue before it gets too high. The common mistake here is assuming your body will just deal with the extra stress no problem, and not keep tabs on your fatigue. Before you know it, you’re still a week before your planned deload but you’re crushed… avoiding this by taking some light days after unplanned forays into super hard training can be a life saver.
- Technical Coordination/Learning Proficiency
This applies more to highly technical sports like team sports or combat sports rather than bodybuilding or powerlifting, but it applies to weightlifting to a considerable extent as well. When your fatigue just barely starts to creep up to high levels, and before it affects much of anything, it will reduce your ability to both learn new techniques fluidly or crisply show off the techniques you already know. Bodybuilders will know this as a reduction in the “mind muscle connection.” Powerlifters will know this as the movement “just not feeling right,” commonly experienced in the deadlift (which tends to fatigue quickly). Weightlifters will miss a lift over and over on small errors of body position rather than strength. Grapplers will feel less athletic, and like their body just doesn’t want to go where they want, when they want. In addition, if any of these athletes try to learn new techniques during this time, they will feel sloppy and uncoordinated. The good news is that you can train through a lot of this stuff and still benefit. The bad news is that this degradation in performance (mostly due to fatigue of the nervous system) is a sign that very high general fatigue is coming, and soon… usually within several days or a week.
- Jump Height
The qualities of the nervous system that govern speed and power degrade faster with rising fatigue than do strength qualities. Thus, a measure of power such as jump height can be sensitive to fatigue before it accumulates to levels we want to avoid for long. The first problem with jump height is that it’s not very precise, so it’s difficult to conclude that fatigue is for sure about to be high with just jumping data, and other leading indicators should also be moving up if we’re going to alter the plan based on jump height. The second problem with jump height is that it’s going to require some measurement equipment. This can be cheap, mechanical equipment like the Vertec reach-jumping calculator, or more expensive equipment like the Just Jump switch mat. Most gyms in which people train simply don’t have these instruments lying around. Lastly, jump height is limited by the completeness of data collection. Unless you have at least a week’s worth of average jump height data, it’s not possible to conclude if your jumps are so low as to predict incoming fatigue. While jump height is of very limited use for individual athletes for those reasons, testing entire teams several times a week can be a great way to get a handle on average fatigue levels and reduce or increase volume/intensity when needed, especially when other forms of assessment (long questionnaires about food intake or sleep times) are not worth the investment of time and energy.
Concurrent Indicators
There are 4 general classes of concurrent indicators to fatigue that are important enough to merit mention. Each of them can tell us that fatigue has already risen to high levels, and should be dealt with now or soon, usually within a week or less. For example, if your program calls for deloading to bring down fatigue in the fourth week of training, detecting some of these leading indicators in the beginning of that fourth week is just fine and actually a sign that you’re training just hard enough to get great results. On the other hand, if you are detecting these indicators in the middle of the third week, you might have a problem with your program design or your recovery efforts. If you never run into concurrent indicators in your training, that’s ok, so long as you run into leading ones regularly at the very least so that you know you’re pushing your training hard enough. It’s important to note that the concurrent indicators are arguably the most important ones to keep track of. When they’re around… you almost certainly need to back off and recover, unlike the leading indicators that only predict rather than detect fatigue. Concurrent indicators are also around soon enough to prevent you from wallowing in a high fatigue state for a needlessly long amount of time (unlike the lagging indicators).
- Bar/Movement Velocity
Losses of velocity come even before strength losses, and are one of the first concurrent indicators of fatigue. This can be the velocity of sprinting (as measured directly by laser gun or indirectly by sprint times), punching, kicking, throwing, or bar movements. If you train with a bar velocity detector of some kind, you can use this measurement to a huge advantage. Because it’s such an early indicator of high fatigue, velocity can actually be used very well to control the training process, and several systems for weightlifting and powerlifting already do this with excellent results. When a certain percent of your 1RM (standardized to one percent or even several different attempts of different percentages) begins to move significantly slower than usual, it is very likely that high fatigue has arrived, and you can make the needed adjustments if necessary.
- Bar Weight Feeling/Perception of Effort
Not as formal as bar velocity but still very effective, “bar weight feeling” can be used to detect currently present fatigue. If the usual weights are feeling much heavier than normal, you’re probably pretty beat up and need to consider backing off. Not a few of us have experienced this with deadlifts especially. You’ll warm up for deads and 315 will feel like 405 usually does… generally a sign that it’s time to deload or at least take some light sessions. Perception of effort of course does not have to be limited to barbell sports. Any sport in which you have reliable tests of ability can utilize this concurrent fatigue indicator. For example, if you’re training in grappling and all of your rolls/matches feel like total crap and you feel like you’re giving it your all just to stay afloat… you’re probably very fatigued. We all have bad days, so don’t just jump the gun and deload every time you don’t feel your best. However, several consecutive sessions of hard effort perception should warrant some thought about backing off.
- Reps Per Set vs. Capability/Relative Performance
Not only does the same effort of performance feel harder when you’re carrying a high level of fatigue, performance can also decline noticeably, especially relative to what you can usually do. For example, if last week you squatted 315 for three sets of 8 reps without about 1 rep in the tank on each set and then this week you hit 325… you should expect (just by the rep-percentage formula) to be able to do at least around 7 reps per set or so at that weight… IF you are not very fatigued. But if you hit 325 for 6,4,2 reps, then you’re not performing to your expected relative standard, and you’re likely to be in a state of high fatigue. This indicator is a great real-world training tool because it’s based on exercises and reps you’re already doing in training anyway, and you don’t have to go out of your way to perform some other kinds of tests. In simpler terms… if all is well and week to week you’re performing at your normal standard, you’re good to keep pushing it. But when performance falls off (and with accumulated fatigue it usually falls off BIG), it’s probably time to back off and recover.
- Grip Strength
When fatigue is present at high levels especially for a couple of days, force production abilities will be lowered and strength will temporarily suffer (often recovering and growing to new high levels once fatigue is reduced). So if your strength is down on your lifts, you can begin to suspect that fatigue is elevated. But why are we using grip strength and not any other movement strength to detect fatigue? Because grip strength is easy to measure without itself generating a ton of fatigue, taking a long time to execute, or risking injury. If we used the max deadlift to indicate our level of fatigue, that would be a very sensitive detection system. But how long does it take to max in the deadlift? Maybe 30 minutes of warming up, maybe more? And what’s the risk of injury when you’re deadlifting multiple time a week? Not insignificant! And how much fatigue does that test itself generate? A ton! By attempting to measure fatigue, we end up adding a ton to it, taking up a bunch of time, energy, and recovery we could have saved for regular training, and risking getting hurt. A grip test, however, just requires a hand-grip dynamometer which is cheap and easy to use. It takes about a minute to perform, and generates so little fatigue or injury risk that it can be done daily. However, if grip strength detection suffers from very high ecological validity problems. When you accumulate a lot of fatigue, your central nervous system, peripheral nervous system, hormonal system, and local muscular systems fatigue. By measuring hand grip strength, you get a good feel for central nervous system and hormonal fatigue (because that applies to all parts of the body relatively evenly), but a lot of potential error from peripheral nerves and forearm muscles. For example, a program with tons of squatting can beat you up worse than a program with tons of bent-rows or pullups, but the muscles and nerves of the forearm only fatigue from the pulling training and not the squatting training, potentially under-detecting general fatigue in the squatting program and over-detecting general fatigue in the pulling program.
Lagging Indicators
Lagging indicators become detectable when you’ve already been in a high-fatigue state for some length of time; between days and several weeks. Lagging indicators have two main uses. First of all, they can be used to gage fatigue during functional overreaching. In functional overreaching, we want to keep training hard and hold fatigue high for a week or two before letting it fall, so that under special circumstances we can get a super-compensatory enhancement in performance several days or weeks later. How long you are expressing lagging indicators can be a sure cutoff sign for ending an overreaching phase, with a week usually being the cutoff. That is, if you’re detecting lagging indicators for a week or longer, it’s probably time to drop the hard training and recover without risking the more serious, long term, and unproductive condition of overtraining. Secondly, lagging indicators can serve as near-definite full-stop signs for normal training. That is, if you are presenting with several of these indicators and are not planning on being overreached, you’re almost certainly well into overreaching and almost definitely need to back off. If one of your clients or athletes presents with them, it’s time to ease up on them… it’s not likely a “well, maybe” situation anymore. There are 8 classes of lagging indicators, as follows.
- Heart Rate Variables
There are three kinds of heart rate measurement methods that can indicate an already-high fatigue state:
HRV: Heart Rate Variability is the amount of variation in time between the pulses of each heartbeat. In normal circumstances, there is a quite a bit of variability in times between beats, due to various physiological reasons. As fatigue rises, heart beats actually begin to occur more steadily and with less variation in time between them. When these fluctuations become detectable form a baseline (with current technology), fatigue levels have usually already been quite high for some time.
MRHR: When a person is in a high fatigue state, their heart rate (when measured in the morning, thus “Morning Resting Heart Rate”) will increase. For enough of an increase to occur with normal detection methods, the fatigue already needs to be quite high and for some time.
RHR: Recovery Heart Rate is the heart rate during some standardized point in recovery after exercise. For example, if 30 minutes after your leg workout your heart rate is usually back down to the 60’s, but for the last week it’s been in the high 70’s, you may very well be in a state of chronic high fatigue.
The important points to note about these methods are primarily of their limitations. A baseline sample must be collected during low fatigue states, a lot of noise from emotional changes or just random error can infect the data, and in general this class of measurement is just not all that sensitive to fatigue. A big series of caveats for using heart rate variables are to either only act on at least several days of consistently indicative measurements, only use the variables on a team of athletes to guide team training (and not an individual to guide individual training), or both. But one thing is almost certain… if your well-performed heart rate data is telling you that you’re fatigued… you’re almost definitely fatigued. The problem is the limit in the other direction… you could be very fatigued but heart rate data hasn’t changed much.
- Desire to Train
When they get fatigued and beat up enough, even some of the most motivated athletes will experience a drop in desire to train. As with the other variables, consistent measurement is key. We all have one session a week when we don’t wanna do anything and would rather be on the couch, but when motivated athletes have a string of several sessions where they simply don’t want to be in the gym anymore and have seemingly lost their passion for training, that can mean something. And that something is that fatigue has likely been high for quite a long time. This lack of desire can be a desire to not train at all, but sometimes it reflects itself in a lack of desire to follow the plan and an increased desire to want to “switch things up” and do some very different types of training. If you feel the need to get away from your normal training bad enough, you’re possibly very fatigued, especially if the other indicators agree.
- Mood Disturbances
When carrying high fatigue for long enough (days to weeks), many people will begin to have disturbances in their mood states. This usually presents as increased restlessness, irritability, and lack of desire to do the kinds of activities normally found enjoyable by that individual. Overly emotional or unpredictable responses to situations can also arise. Because so many other factors can influence mood states, this is not a powerful indicator by itself. Even with advanced mood questionnaires, it’s doubtful that strong conclusions about fatigue can be drawn from mood states alone. But, if the other indicators agree, the presence of mood disturbances can solidify the case for high chronic fatigue.
- Appetite Suppression
If fatigue is bad enough for long enough, low appetite can be a result. When experienced personally, this sensation can be a strange lack of interest in eating food, and an inability to eat a lot of food in one sitting due to a low desire for foods, even tasty ones. This is an especially serious sign of uncontrolled fatigue during a hypocaloric weight loss diet. Normally, weight loss diets upregulate hunger so much, loss of appetite seems like the last thing you’d ever experience. But if you drop appetite even though you’re deep into a cut, you might be in serious fatigue trouble, and many of the other indicators will almost always agree.
- Sleep Disturbances
Longer term high fatigue can cause two kinds of sleep problems. Firstly, it can make falling asleep and sleeping in late harder. Individuals with high fatigue often have trouble falling asleep and will often wake up much earlier than they’d like, being too restless to fall back asleep. Secondly, high fatigue can lead to poor quality sleep, even if there is enough of it. Bad dreams and many episodes of waking during the night are not atypical here.
- Illness
A very lagging fatigue indicator is illness, and this one is very straight to the point. If you beat up your body enough without letting it recover, pretty soon your recovery systems (including your immune system) fall so far behind that they are unable to fend off germs, and illness results. Now, illness can occur even when you’re fresh, and it can also be a leading indicator by itself causing fatigue, but if the other lagging indicators align, illness means it’s almost definitely time to back off. Let’s put it this way… if you ignore all other signs of fatigue and keep pushing it, you’re either gonna get sick or hurt.
- Wear and Tear Injuries
Acute, major injuries can happen any time. You can be in the shape of your life and pop a quad or a pec, precisely because that’s when fatigue is low and you’re strong enough to provide the forces to create such a major injury. Also, wear and tear injuries like aching elbows and rusty knees follow many of the best athletes around all the time, so are not just present when fatigue is high. However, with chronic high fatigue, those wear and tear injuries will start to really act up without letting off. Push it too hard for too long, and your bad shoulders can become temporarily useless shoulders. It’s generally a good idea not to wait to reduce fatigue for this long, but if your injuries get really bad and the other indicators are there, it’s time to back off in almost all cases.
- Actual Competition Performance
This is the last indicator you ever want to use. In reality, the most important reason we use all the others is so that we don’t have to use this one… so we don’t have to find out that we were too fatigued when we had a crappy performance at a meet. Bad meet performance can happen for all sorts of reasons, but if other lagging or concurrent indicators are present on meet day, fatigue is almost a sure contributor. As sucky as this situation is, not all is lost. Next meet prep you can do a better job of keeping fatigue in check by learning from these mistakes.
Implications
What can we take away from all this? Well, you can definitely take away the specific fatigue indicators and pay more attention to some of them from now on, thus getting a better handle on what your fatigue levels are at any given time. But almost as important is the knowledge of when to use which indicators. Using the leading ones to plan the next week of training, the concurrent ones to align your deloads, and the lagging ones as functional overreaching measures or as big warning signs for when to definitely back off is a great way to improve your training process and make sure you’re training hard enough to make your best gains, but not too hard so that you can’t sustain it.
