For athletes to perform at their very best, they need to feel 'fresh'. Meaning, they need to manage their recovery in order to free themselves of any acute or chronic exercise-induced fatigue. This can be a difficult task considering fatigue manifests itself in the body in different ways and can vary from one individual to the next. This week, Cory Kennedy, Athletic Development Specialist at FITS Toronto, will dissect fatigue and provide solutions on how it can be controlled and monitored. Cory works with a number of athletes, ranging from Olympians to aspiring youngsters and knows when it's time to push an athlete, and when it's time to pull back.
Let's let Cory take it from here!
Neuromuscular fatigue refers to an inability to maintain a certain level of force or power output during an activity. There are acute types of fatigue, and chronic versions. Typically, acute fatigue is related to peripheral factors which are located in the muscle, and can include things like buildup of lactate, hydrogen ions, or ammonia. An athlete will normally experience acute fatigue after an intense training session or competition; however, these symptoms can also resolve themselves quickly. Chronic types of fatigue are usually related to the nervous system and often occurs when recovery is inadequate over multiple training sessions or competitions.
This is by no means an exhaustive review on fatigue, as I would rather talk about using velocity metrics for management purposes, rather than the reasons why fatigue occurs or all the ways that it might present itself.
Neuromuscular fatigue can be thought of like dehydration-- you can’t always tell when it creeps up and hinders performance. In extreme cases the effects are obvious, but before that, you need to find different ways to see ‘inside of you’ to understand what's going on.
Halson (2004) (5) created a diagram (Figure 1) to show the gradual increase in fatigue from a single training session, to a training period or block, possibly lasting over time into a state of over training.
Figure 1. The overtraining continuum
This is where the process of monitoring your preparedness comes from. Preparedness allows you to understand where your performance is versus where it should be. Some fatigue is always expected, but long-term fatigue is not.
Below, Chiu (2003) (1) created a diagram (Figure 2) to outline how the combination of fatigue and fitness, the two results of training, impact performance levels.
Figure 2. Fitness-fatigue theory
There are a handful of ways that you can gather information to help you gauge your fatigue levels. Force plates can give you valuable information but are not accessible to the general public. HRV devices can give a general guideline of fatigue, but individual differences will occur, and it takes some time to figure out your individual response to actual performances. Tracking mood states can be reliable, but its effectiveness can be increased by combining it with some sort of quantitative value/metric.
Movement velocity has also been hard to do for the end consumer because current tracking devices are fairly expensive and not accessible to everyone. With the PUSH Band entering the training-sphere, a new option to track velocity now exists! So let’s explore the different ways we can use that data…
Using Velocity Tracking
The first thing you have to come up with in order to track your preparedness is a baseline measure. I really like the way Sanchez-Medina (2011)(6) did it. They chose a submaximal load for a given exercise (for example back squat) that you can lift at just over 1 m/s without much consequence (NOTE: This was mean velocity throughout the rep, peak velocity would be a different number, but same relationship). This way you can retest anytime you want, and while the output might change, it should always be manageable. Some people have used a CMJ for this kind of test, but as Cormack(2) saw in his work, that jump height isn’t affected by fatigue nearly as much as the time it takes to produce force, due to different strategies athletes will use to achieve their height. In the case of a submaximal squat, if your intention is to move the bar as fast as possible, the resultant bar velocity should tell us a lot about your current output.
If you look at the graph below, the red bars show the velocity of the repetitions at our baseline load, while the blue bars refers to each rep in a 3x12 workout at a load that corresponds with your 12RM. The key takeaways here are that a LOT of fatigue sets in during a set of 12...also, doing 3 sets to ‘maximum’ (your estimated max at that repetition range) has a large effect on your ability to lift your baseline load afterwards (2nd set of red bars).
Figure 3. Quantification of % Velocity Losses
Now that we’ve gone over the basics of fatigue, and how you can see it setting in with velocity measurements, let’s discuss how to use this data to get the most out of training.
The table above was taken from the same study we just mentioned and has some more really interesting findings. If we just focus on the 4th column, it shows how much velocity the subjects lost on their baseline test load we mentioned earlier, after they finished the workout from the first column (for back squats). You’ll notice that there are a few cases where fatigue was minimal: first, any set where there was only 4 repetitions completed or less; second, any set where there was around half of the expected repetitions completed (4 in 8RM, 6 in 10RM, and 6 in 12RM).
So let’s put these findings into some practical advice…
First, if you are in a period of training where you need to focus on another quality (like sprinting for a track and field athlete) you don’t want your strength training to fatigue you before your track work but we know it is still important to do. This is a great time to use training in low-rep ranges like 4 or less.
Another method of training at high-intensity but avoiding fatigue is the use of cluster sets, something Dr. Haff has outlined in the past (3). A cluster set involves taking very short breaks in-between repetitions of a set to maintain the output of your exercise at a given intensity. For example, a normal set of 5 would involve doing 5 repetitions in a row, and the 4th and 5th would definitely see drop-offs like we saw above. In cluster training, you may choose to take 15 seconds between repetitions, which serves to keep the output the same for all 5 repetitions. That means over the course of the workout, if you did 4 sets of 5, you have 20 repetitions of the quality you want. In a traditional method, you may have 10 good reps, 5 that are just ok, and 5 that aren’t very good.(4)
Second, if you are starting a workout in the middle of the week, and when performing your baseline test you see that you have some significant fatigue (low rep velocity), then you can’t be afraid to do a few less reps than you expected. For example, if you were going to do 3x10 of your 12RM then do 6-8 reps for the day! When you hear people talk of deloading, this is what it's for. You continue to improve your skill and capacity at a given exercise, but lower the volume in order to get some recovery in. So during a training week, use this velocity metric to decide if you need to deload on a given training day.
Thirdly, you can use your baseline test to determine what a good training split is. If you are training 4x per week, and you notice that after the first workout, you start every other workout with significant fatigue, it might be better for your performance to take an extra day off and go to a 3 day split. Remember that there is no standard training protocol that is best for everybody. So using a monitoring tool, like the PUSH Band and repetition velocity, can give you data that helps plan your individual approach to maximizing performance.
Neuromuscular fatigue is a reality of training that doesn’t need to be avoided, but definitely needs to be managed. Start finding ways to monitor your fatigue and it will help improve your decision-making around training variables.
1. Chiu LZF. The Fitness-Fatigue Model Revisited: Implications for Planning Short- and Long-Term Training Strength & Conditioning Journal 25: 42-51, 2003.
2. Cormack SJ, Newton RU, McGuigan MR, and Cormie P. Neuromuscular and endocrine responses of elite players during an Australian rules football season. Int J Sports Physiol Perform 3: 439-453, 2008.
3. Haff GG, Hobbs RT, Haff EE, Sands WA, Pierce KC, and Stone MH. Cluster Training: A Novel Method for Introducing Training Program Variation. Strength & Conditioning Journal 30: 67-76 10.1519/SSC.1510b1013e31816383e31816381, 2008.
4. Haff GG, Whitley A, McCoy LB, O'Bryant HS, Kilgore JL, Haff EE, Pierce K, and Stone MH. Effects of different set configurations on barbell velocity and displacement during a clean pull. J Strength Cond Res 17: 95-103, 2003.
5. Halson SL and Jeukendrup AE. Does overtraining exist?: An analysis of overreaching and overtraining research. Sports medicine 34: 967-981, 2004.
6. Sanchez-Medina L and Gonzalez-Badillo JJ. Velocity loss as an indicator of neuromuscular fatigue during resistance training. Med Sci Sports Exerc 43: 1725-1734, 2011.