Managing Fatigue through Velocity Loss

With this article I just want to tell you my experience applying the basic principles of Velocity Based Training to monitor Fatigue.
I had great help through this technique as I am training different customers, from general fitness guys to american football athletes and especially with the latest, the demands of every day life and of the football season tended to fatigue the athlete both pre-season and in-to season. It was hard to find a reference to quantify an adequate workload each week, as every week was simply different from the previous one. I was looking for an easy strategy to optimise the workload so my ahtletes could improve over time optimising their biological and physiological rhythm and we could stay away form overtraining and fatigue based injuries that would delay or even prevent them from reaching their goals. At the same time I was looking for some technique that was simple enough to be taught to my athletes so they could also be independent in applying it. 
Latest research has shown how Fatigue can be monitored through Loss of Speed. This is also named  VELOCITY LOSS  (or VL later on).It has been show how VL i directly connected with the production of Ammonia and Lactate. It also has been shown how VL is a direct indicator for neural fatigue. Finally, by controlling VL, we can drive different and optimal gains in performance and in muscular composition. 
If you’re interested in knowing more, this paper is a good starting point : 
Effects of velocity loss during resistance training on athletic performance, strength gains and muscle adaptationsScand J Med Sci Sports. 2016 Mar 31. doi: 10.1111/sms.12678. [Epub ahead of print] Pareja-Blanco F1, Rodríguez-Rosell D1, Sánchez-Medina L2, Sanchis-Moysi J3,4, Dorado C3,4, Mora-Custodio R1, Yáñez-García JM1, Morales-Alamo D3,4, Pérez-Suárez I3,4, Calbet JA3,4, González-Badillo JJ1.



@AleexHernz offered us this great chart resuming the study on Twitter.
The prize is not always correlated to the amount of fatigue you put in your work. Once again, nature is in favour of smart techniques, rather than blind work accumulation. Actually it looks like if you’re an athlete, there is a thin line between doing optimal and just doing too much, and the latter could easily erase all your efforts.  Specific amount of fatigue (VL) leads to optimal physiological and metabolical gains and people looking to build their physique must train very differently: there is an optimal training for athletes looking for explosiveness and power,the same training strategy won’t be optimal if they are bodybuilders just trying to create the better aesthetics and grow huge quads. Training requirements and the optimal state of fatigue will be very different.  
It is great to know that Fatigue can be monitored and quantified though a loss of Speed. This makes it controllable and manageable.
Velocity Loss is calculated as the relative loss of speed between the first and the last rep of a set which are usually the fastest and the slowest.  
VL = (First Rep Speed - Last Rep Speed) / First Rep Speed
Velocity Based Training Devices like Beast Sensor allow to monitor and manage Fatigue through a quick and interesting feature, so you can control your training Volume and Intensity very easily. 
As a starting point, the correct load or training percentage for the exercise is chosen by the speed. For those already advanced into Velocity Based Training, this method does not require to profile the athlete for the exercise or to know the fastest (v0) and the minimum Speed (MVT) of the exercise. As I will show you later, these values are only required for maximum precision in transferring from Training Percentages (%1RM) to Velocity Based Training.
If v0 and MVT have not been measured earlier, the optimal speed for the exercise can be retrieved, or the typical Speed for the desired Strength Range may also be used as a reference, just pick yours. 
Figure 1 - Shots taken from the Beast Application: the Target Speed can be dialled in at anytime during the Exercise. In this case a Maximal Strength work was set following VL10 rule.   
Let’s overview how to use Target Speed to optimize Velocity Loss
In case of Maximal Strength work, it is usually recommended to choose a weight about 90% 1RM. 
There are several ways to convert this percentage into a speed, if you don’t care to understand about how this is done, I suggest you jump straight and check the tables throughout the article. 
Since we don’t have the Load and Velocity profile available, one easy way to estimate a %1RM to speed conversion could be by doing some approximations.  
Let's assume that MVT (Minimum Velocity Threshold) and max speed for this exercise are somewhere around common values for powerlifting exercises. 
For this example let’s use MVT =  0,2 m/s. 
On the other side we can approximate Maximum Speed during warm up checking the fastest rep, usually produced with the barbell. In this case, we are going to use v0 = 1.4 m/s
For this approximation to be correct, we need to be sure that we’re pushing as fast as we can for a couple of reps.
We can then see how 90% 1RM is 90% of the gap from v0 to MVT. 
Speed Gap = v0 - MVT = 1.4 - 0.2 = 1.2 m/s
speed at 90% 1RM = v0 - Speed Gap * 0.9  = 0,32 m/s 
We will call this our Top Speed for the set and this is also the Speed to determine the correct load to be used.  
To apply Velocity Loss we need to calculate specific speed limit values so they can be referenced during the set, just to know when to stop. 
These values can be calculated in advance as a percentage of this starting value : 
VL10 =  Top Speed - 10% =  0.29 m/s
VL20 =  Top Speed - 20% = 0.25 m/s
VL30 =  Top Speed - 30% = 0.22 m/s
Basing on the amount of fatigue and stimulus, the desired target speed can be selected among these. 
We can repeat this method for many different %RM, targeting different Strength traits. Below the results.
Choose the desired target value and insert it into the Set Target value following indications in Figure 1.  Beast App will provide audio and visual feedback so you can stop set once the optimal amount of fatigue has been reached. 
Max Strength 
0,32 m/s
0,29 m/s
0,25 m/s
0,22 m/s
0,8 m/s
0,72 m/s
0,64 m/s
0,56 m/s
0,95 m/s
0,85 m/s
0,76 m/s
0,66 m/s
0,5 m/s
0,45 m/s
0,4 m/s
0,35 m/s
Table - Different Velocity Loss for the main Strength traits.   
Pay attention using high VL percentages, the risk is to slow down too much, ending in a different speed
Figure 2 - Velocity Loss 

When do I stop my set ?

Once the target speed is set it will be easier to determine the end of each set thanks to the audio and visual feedback in the app. 
A faded bar will appear or a low beep will sound if the target speed is not reached. This will help us greatly.  
Yet, we want to able to control Velocity Loss and, at least for the first times,  we may not really know how fatigue will be kicking in, especially working with relatively heavy loads. 
When the exercise execution is perfectly sound, Velocity Loss should be linear rep after rep:  this simply means Velocity gradually decrease with a certain rhythm. It looks like this rhythm is individual and dictated by many factors, the most important being the lactic acid production of the body and the neural fatigue accumulated. Some of us will “die” slow in the set just like others will be more resistant.
The safest strategy after the minimum velocity has been set as the target velocity is to stop the set after the first faded bar or slow result. 
Now, obviously there may be different reason for that first slow rep and for sure our competitive and macho ego will be tempted to resist and do another rep.. it is usually the safest decision to quit the set anyway. Another extra set can be performed at the end, if you’re not happy with the total amount of reps. Especially working for Power the VL is very thin and it is easy to be misguided by the ego, looking for an extra rep that will only end up being even slower than the previous one, accumulating unwanted fatigue. After all, why should we ask for Instant Live Feedback ?
The chart below will sum up the thinking process involved in this decision.

When do i stop the exercise ? Total Work vs Inter Set VL

Two metrics should be controlled to stop the exercise. 
The first key point indicator is based on the amount of work done. Either total reps performed or a Target Volume (or Tonnage) can be used. This will be named Total Work Limit.
From the Prilepin Chart for example, 10 is the optimal number of Repetitions for 90+%1RM. This should be the general rep target when training for Max Strength. 
In case Hypertrophy is the interest,  this number could grow up to 40-50 reps. 
All these reps could be divided in sets of different length.
Figure - Our Performance Based Model is an upgraded Prilepin Chart with Speed Ranges. Check the Optimal Total (Reps) column on the right for the optimal amount of work in an exercise. This value was retrieved by  A.S. Prilepin, a Soviet era sports scientist, by averaging the Optimal Velocity Loss on a wide group of Athletes
The second key point derives from the same auto regulation principles explained for the set and applies them inter set. This will be named Inter Set VL and can be calculated as following
Inter Set VL = (First Set Max Speed - Last Set Max Speed) / First Rep Speed
Inter Set VL = (First Set Average Speed - Last Set Average Speed) / First Set Average Speed 
Also, assessing when to stop the exercise, Rest time is a constraint that can’t be left out of the discussion. 
Let’s begin with the easiest case: complete recovery is required between sets. This happens when neurological adaptations like being able to increase maximal power, maximal strength or maximal speed are the goal of the exercise. In this case only the best performance is accepted for each set. This means that when the next set begins with lower values than the previous one (Intra Set VL > 5%). either rest time was too short or the maximum amount of work for the day has been reached. 
Some experience and serious knowledge of oneself or of the athlete is required to exceed the optimal total number of reps (see table above) and avoid accumulating excessive neural fatigue for the next day. I’m a stubborn man and I could not resist exceeding the total 10 reps suggested for Strength a couple of time, next day I felt like I was slow and dumb for the whole day. You don’t want that! 
As a final strategy in this case I would suggest to look for Inter Set VL only until Total Work Limit is reached.
Another scenario is when some sort of metabolic conditions are required and there is some kind of pace. This could be bodybuilding work, it could be conditioning for sports, it could be Crossfit or more general circuit work for example. In this case a Pre Set Rest Time is the constraint.  
In this last case the most general purpose of the exercise is to accumulate Volume or to perform resistance to speed (or Power) as a skill therefore Total Work Limit can be the main KPI in this point. 
The only exception to this might be an athlete working for some kind of specific hypertrophy. In this case I would suggest still keep an eye on Intra Set VL because it could reach a serious drop in the early phase of training when he/she might not be accustomed to the Volume of training. 

Some Practical Examples

Example 1 - Hypertrophy Work 

Let’s go through the first example. summing up and applying all what has been discussed previously. 
The goal for this exercise is Hypertrophy. 
The load for this exercise will be selected to allow a max speed of about 0,5 m/s (85% 1RM). As our interest is Hypertrophy, we will look for a VL20. Target Speed will therefore  be 0,4 m/s.

Figure 5 - Data Overview for the Exercise: Speed data from the exercise. Target Speed was set to 0.40 m/s with a 14% Inter Set VL. 

As you may see from the charts, balance between accumulating work through sets or reps while still hitting the desired speed range is critical. Thus, I'm following up with some considerations for the exercise .
This load looks pretty intense and hard for hypertrophy. It is some heavy work for hypertrophy! Average Speed is just at the border line between Max Strength.
As the intensity is high, we expect fatigue to kick in pretty quickly so speed will decrease rapidly. We must take this into strong consideration if we’re looking for a specific VL and every further rep might be too much.
These are probably good conditions to develop Max Strenght (Average Speed = 0,4 m/s) and build some muscle (VL=30%) at the same time. This is a good starting point, from here, the athlete can increase the load and adjust the volume if he wants to go for Strength. On the other side he can just increase the Volume and work for more Hypertrophy. 
Pay attention thou, if a "power athlete" rather than a “bodybuilder” or a “strongman" is lifting in this exercise, this kind of work is probably too heavy to optimise the development of Fast Twitch Fibers, taking into consideration the research cited. If my athletes or myself was prescribed this exercise, I would strongly consider doing 5 maximum 6 reps per set instead of 7 and probably adding one more set. So in this case, 4 sets x 5-6 reps are better than 3x6-7. This set up should work in favour of a smaller VL and prevent from having VL30. The athlete will be able to maintain the same Tonnage at the same time.   
For example, in the last set we have VL40 (see Figure), if he stopped at rep #5 VL would be 30%, had he stopped after rep #4, VL was 13%.

Example 2 - Power

Power will be the goal in this case. Following indications regarding Power work, a load allowing a max Speed of 0,80 m/s will be selected. That is about 55% 1RM  : Target will be set to respect a VL10, so 0,72 m/s. 
Figure  - Speed data from the exercise. Target Speed was set to 0.72 m/s
Totally different set up here. Velocity Loss is very small. Best “quality”, as track and field coaches like to name it, is assured. We are just looking for the best conditions for power output and we just want to rep it and rep it and rep it once more. As you can see from Figure - all sets have the same average and the biggest VL is 14% during 2nd set: all reps are closer to the fastest repetition and there is little difference between the fastest and the slowest rep.  
Also Rest between set is complete and this is proved by numbers : Intra Set VL is basically null and the lifter is repeating the same performance every set!
Now, how is this optimal?
Again, if this is a power athlete, this is definitely a good exercise to increase the power output or Strength-Speed abilities. The total amount of work done is good, there are probably one - two more sets left in the tank that can be spent during all-out days. 20 Total Reps are aligned with the Prilepin Chart as well, suggesting 18 to 30 Reps at 55% intensity with an optimal 24 Total Reps.  
For the Power Athlete, this work requires a great effort by the Central Nervous System and at the same time there is a decent amount of specific-hypertrophy stimulus, even thou this could be increased. 
If this workout is performed by a Bodybuilder instead, in my opinion it just does not fit right. This is very taxing on the CNS while having too little stimulus for mass growth. Not that the muscle cells of the bodybuilder works different than those of a Power athlete… bodybuilders just have different priorities. They usually need to pack on kgs of muscles, independently of what kind of fibres they develop: VL could be much greater for him/her to enhance Slow Twitch Fibres Growth as well. 
One final note: working with VL10 and VL20 requires a lot of precision and attention to details. VL20 can quickly explode with just a couple of reps, erasing the advantages. This must be taken into advantage: as a Power Athlete, I usually have myself and my athletes saving a rep rather than exagerat. Less is more they say.. I just like to exchange reps for sets. If I happen to be short on Total Volume after the prescribed sets, I just like to add a new set. This ensures me best quality. I like to do the opposite with bodybuilders, going for that extra rep, trying to force a greater VL and eventually taking away one set when the fatigue kicks in or when too much work has been generated. 

Wrapping Up

Finally a quick reference table from the Beast guys, you can print and hold in front of your Rack/Platform to choose the correct VL for every situation.