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For s11 it very important to monitor the training load of soccer training in order to optimize a periodized plan to prevent over/de training and raise up the players performance.

In modern soccer the improvement or maintenance of the spesific endurance capacity of football players is achieved mainly by small sided games of various correlations, dimensions and constraints.

During games with 7v7, 6v6, 5v5 and 4v4 number correlations, players need to spend enough time to get into the 90-95% of M.H.R zone.

This zone exceeds the intensity of the match and as a result the player cannot withstand a long time in the production of output.

However, in this area and with the correct breaks, even greater endurance adjustments are achieved, with the components of VO2max, anaerobic threshold and running economy significantly improved.


In the following example you can see a football player participating in mid-range correlation small sided games where the yellow band represents the 90-95% of M.H.R and the red line the player's heart rate.

1.Monitoring heart rate

Teams with GPS and Heart Rate Telemetry monitoring systems have the ability to analyze enough data at the end of training. A careful reading can be beneficial in improving the performance of football players or early diagnosis of problems.

It would be wise not to stay only in determining the intensity of the training based on heartbeats or only the running speed. If the same player for example not "caught" the standards that you set for this training unit as for heart rate, analyze and running intensity, as the deceleration-acceleration-change of direction that are performed during the training or the opposite.

A precise approach to training includes internal and external loads making good sports scientists at monitoring and analysis of training loads imperative nowadays ... Many modern top-level coaches follow the advice of sport scientists by giving them solutions and helping them to improve their team ...

2.Internal and External loads

As football progresses, physical abilities, strength and conditioning, are becoming more important than simple skills and talent. Few years before, it was enough to be skillful with the ball and be able to understand tactics in order to stand out at the pitch.

These days, in order to play football at the highest standard of your abilities you need to first an athlete and then a footballer. Football players are running non-stop during the games, expressing their weakness and strength according their position.

These characteristics are what the head physical coach is trying to improve during the pre-season training and in some cases, when the opportunity arises, during the season through the games or through short training sessions.

Traditional physiological tests are now used just to see if the footballers have the minimum standards in order to start the pre-season training and to monitor the rehabilitation of specific injuries. Having said that, it is important to use daily physiological monitoring equipment (e.g. GPS systems and heart rate monitoring) in order to observe the physiological changes of each of the players i.e. every day, every training session and every minute in the game, must be used in order to understand the physiological adaptations of every single player.


Achieving these physiological adaptations while maintaining athletes health, is what a physical coach should be looking for. This combination is what will help the athlete to improve. However in order to improve we need to keep our athletes on their limits of overtraining. If the athlete is not tired enough, research suggest that the adaptations to the new standards are slower. This was explained with the reduced production of free radicals. Having said that, overtraining (or over-reaching), may also slow down the process of adaptations, due to the fact that the body will shut down neuron to muscle pathway in order to activate the mechanism of over-training protection.

Therefore the role of a sport biochemist is to identify these limits and to keep the player within these fine lines, in order to determine these fine lines. Overtraining could be explained in several levels i.e. pathological, psychological, biochemical or hormonal, while hormonal being the most important.

Hormonal balance is the A to Z of kipping the body into anabolism, something very important to every athlete. Furthermore, specific hormones, like cortisol, may interfere with the good health of our intestines, which in term with cause malabsorption of the nutrients that we take through our diet or through supplementation. Cortisol balance is very important since cortisol is an anti-inflammatory, catabolic hormone.

So in order to keep a healthy athlete, we need to keep in balance the following hormones: testosterone : free testosterone : SHBG : albumin : estrogens : cortisol : prolactin.

If we manage to keep these hormones in balance, then our body becomes an anabolic machine, which means faster recovery, faster muscle gains or fat loss and increase in bone density. Having said that, maintain this balance, we reduce the chances of muscle injury dramatically.


In addition to this, when we need to increase performance, it is important, to have raised levels of testosterone, free testosterone, low levels of cortisol and and low inflammation markers (i.e. like IL-6). So the physical coach and the biochemist of the team should work closely in order to achieve the adaptations needed, but maintain the athletes in good shape in terms of hormones and inflammation markers.

3.The role of Sports Biochemistry in Modernized Football

We came to a point that we are very close to reach maximum availability of games per season and this makes the need of personalized scientific support even more important. Periodization is one of the methods that experienced fitness coaches are using in order to keep their teams in relatively good condition throughout the year. In order to keep them in good condition its important to avoid over-training and muscle injuries, something that will help the athlete to increase performance through official games and training


Biochemical periodization is one the modern methods involved in personalized periodized training. It involves the use of every single data that we can attract in order to personalized training, supplementation and nutrition which will help to have a healthy athlete. In order to make a personalized program we need to take into account aspects like: the position of the player, game minutes, predicted minutes of playing, load of training, total distance covered per game, sprints per game, heart rate monitoring, muscle imbalances, acceleration, deceleration, inflammation markers, muscle recovery rate, oxidation markers, and other biochemical markers. Through these we can adjust the individuals training load as well as the supplementation and nutrition in order to achieve better recovery, better glycogen absorption as well as better training adaptations.


We should never forget that physiological markers directly represent biological responses of the body due to external factors. The role of the scientific support team is to identify these markers, elaborate them in terms of health and performance and advice the nutritional coach, fitness coach and anybody other involved in order to personalize their programs with the goal to have the correct hormonal and biochemical profile according the time of the year.

4.Biochemical Periodization and Training Personalization in Football

The importance of performance monitoring, in today’s football, is widely known. According to Black et al (2016), the ability of monitoring training loads … is of the utmost importance for the athlete’s readiness and the prevention of injuries.

There are two main reasons why it is necessary to record performance:

First, to make sure that footballers perform at their highest level, and second, to minimize the negative effects that can be caused by training such as excessive fatigue, overtraining or detraining. In addition, proper use of performance monitoring systems can contribute significantly to injury prevention.

In addition, through long and continuous performance recording, we are able to know the needs of the sport and more specifically the demands of the game of each position. This way we can maximize the performance of our players through personalized training.

But what is the difference between post-workout performance analysis and live monitoring during training?


The ability of modern systems for live monitoring of performance, gives the advantage to trainers - coaches to accurately control training loads.

Many experienced trainers believe that through their years in the sport, they can now calculate the loads the players receive. Human memory is limited, so it is almost impossible to remember all the events that took place during a game, let alone the parameters of performance. The research by Franks and Miller (1986) showed that less than 45% of football coaches who participated were correct in their post-match evaluation of the events that occurred.

Even though some coaches through their experience can actually calculate the external loads in some way, there is no way they can control the internal loads - heart rate (HR). The HR of our players shows their response to external loads and can vary greatly from athlete to athlete. Keeping that in mind, we are able to know when a player needs more, or less intensity in his training than the average of the team.


Two players run from box to box at a speed of 15km / h. Player (A) works at 90% of his maximal heart rate (HR max), while player (B) works at his 80% HR max. This shows us that for the purpose of the exercise, the speed at which player (A) runs is ideal for his improvement, while player (B) needs to run at a faster speed to obtain the adaptations we want him to.


By monitoring the external loads that players receive during training, we can also check when a player underperforms and intervene where needed. In addition, knowing the requirements of the game, for each position we can complete customized training when needed.


We find that during a mid-week training session, in which we aim to charge players with high loads, our wide defenders (as shown in the graphs below) have not been exposed to high intensity runs. Since the needs of the game for this position require high speed runs, we decide that those players will stay after completing the training session for additional, personalized training.

5.The importance of live performance monitoring

Monitoring performance in small sided games (SSG) 4 Vs 4 + 2 goalkeepers

When designing small sided games in football, we should be aware of the requirements and the stimuli that players will receive as they come to fruition. By reducing the spaces, we minimize the chances for our players to cover high speed distances. At the same time, the requirements for the number of accelerations, decelerations and changes of direction are increasing. This is because the players are forced to change their position constantly so that they find themselves in an empty space to receive the ball. Also, ball possession changes are much more often, which forces players to change their speed much faster.

We have collected data from 4 Vs 4 small sided games with two goalkeepers, which took place on a 20m x 40m (800 sqm - 100 sqm per player) pitch, with an intensity between 85-95% HR max. Data were collected using a performance monitoring system from Catapult.

The table below shows the averages of data per minute:


While monitoring training loads, only the most energy costly for the body accelerations, decelerations and changes of direction are taken account, with moderate to high intensity. The reason is that low intensity accelerations and decelerations are not particularly associated with performance indicators and there can be hundreds, even at a low or moderate intensity training session.

If you use 4 Vs 4 with 2 goalkeepers for example 3 minutes per set, then simply multiply the table numbers by the time your game is implemented (x 3) to see the average expected external load for your players.

Based on our analysis, more than 85% of the total distance covered was at low speeds. According to other researchers, when compared with Large Sided Games or match play, Small Sided Games (under certain conditions) do not simulate the high-intensity efforts and repeated sprints that the full game demands (Casamichana, Castellano, & Castagna, 2012).


In conclusion, Small Sided Games produce more technical elements, such as (passes, shoots, tackles, etc.), which benefit football players more often than medium and large pitches. (Hodgson and et al., 2014; Kelly and Drust, 2009). At the same time, the internal load (Heart Rate) simulates or even exceeds the needs of a normal match, while for the external loads we expect values ​​that fluctuate near the table we quote.

6.Monitoring performance in small sided games (SSG) 4 Vs 4 + 2 goalkeepers

There are different opinions about the loads that the players receive during a football tennis or other called football volley game. There are many who consider that performing this type of games is ideal for sessions aimed at discharging players. There is, of course, the opposite view, from those who believe that it may seem 'innocent' because footballers have fun playing it, but the loads they receive may not be so small.

Trying to clarify this issue, we have collected data from a 3 Vs 3 football tennis game that took place on a 10m x 5m pitch (2 squares of 5m x 5m). When analyzing the data, we noticed that the player of each team standing backwards (the one who was mainly taking the first balls), received more loads than the other two. Specifically, it covered an average of 47.5m / min while the players who stood in front of the net covered 29.3m / min. In addition, they had 1.75 direction changes per minute versus 0.9 respectively. Regarding the number of medium and high intensity accelerations, the number was almost zero for the front players while the back made 0.9 per minute.


At the same time, we considered a parameter relatively unknown to most, which can only be recorded with high tech equipment. It is called IMA (Inertial Movement Analysis) and refers to a set of metrics that measures the movements of all three axes, which are performed in less than 0.3 tenths of a second. What we observed with respect to IMA medium and high intensity accelerations and decelerations was that the rear players performed 0.8 and 0.6 per minute respectively, while the front players performed 0.5 and 0.4.

Lastly, we monitored heart rate variability and observed that the players standing in front were constantly working below 75% of the HRmax, while those who chased the first balls regularly raised between 75-85% of the HRmax.


Before planning such games into training units aimed at unloading, we should know that the loads mentioned above will increase if the square meters corresponding to each player are increased. This can happen in two ways. Increasing the size of the pitch or reducing the number of players.

What we recommend is when organizing these games, we need to make sure that we have a balance in terms of the loads that our players receive, and to do that we have to change their positions frequently.

7.Monitoring performance in a 3 Vs 3 football-tennis game

Distributing the total distance covered by football players in speed zones is an indispensable tool for sports scientists and fitness coaches in modern football. It contributes effectively to understanding the requirements of the sport, and more specifically to each position, giving us the benefit of designing workouts that are tailored to the needs of each player. At the same time, it gives us a clear picture of the physical abilities of each player, while long-term recording and comparing the performance of each player in a series of matches can lead us to very useful conclusions.


The speed zones in which the distance covered is distributed on the basis of the literature are:

0-0.6 km/h (Standing)

0.7-7.1 km/h (Walking)

7.2-14.3 km/h (Jogging)

14.4-19.7 km/h (Running)

19.8-25.1 km/h (High-speed Run)

>25.1 km/h (Sprinting)

Based on long-term records of other scientists in football matches, in terms of the physical demands of each position, in the above speed zones, we quote the following interesting values in a table:

* The above values do not include goalkeepers’ measurements.

As you can see in the table above, regardless of playing position, most of the total distance in a football match will be covered by slow running, while a large proportion will be covered by walking. As absurd as it sounds, that's what the numbers say. The reason many will wonder if this is true or not is very simple. Watching a football match, all of us are often focused on the part of the players involved in the phase, or those close to the ball. What we do not realize is that, at the same moment, there are other players on the pitch who are likely to be moving at very slow speeds. Of course, this does not negate the fact that footballers must be very well trained and prepared to perform the most energy costly for the body actions, as they will most often make the difference in a match.

The speed zone 14.4-19.7 km/h (Running) is highly correlated with the player’s displacement on the pitch. Looking at the table, you can see that the wide midfielders have the highest percentage in this zone, followed by the central midfielders. It is these players who will be most likely to work in defense, especially in game changing, as they will have to cover long distances in a short space of time.


Regarding speed zones >19.8 km/h (High-speed Run and Sprinting), as you can see, the wide midfielders have the highest percentage, followed by the attackers. In football terms, this can be justified by frequent transitions, mainly from defense to attack. In cases where the wide defenders are playing in systems with a three at the back and have the entire line in their area of responsibility, then clearly the percentage in these zones is increasing. As for central defenders, their performance in the specific zones depends heavily on the opponents' actions, as they mostly run at high speeds defensively to intercept them.

Reading the above data and before reaching any conclusion, we should keep in mind that depending on the level of the league, the percentages are likely to vary. In addition, the factors that may influence the above percentages are both the formation of the two teams in the field and the specific instructions of each coach.

Finally, the above information can be used as a basic knowledge of understanding the physical demands of each position in a football match. What we suggest, if possible, is that physical demands of the match for each player be recorded and used individually.

8.Percentage distribution of total distance covered in speed zones

The evolution of elite sport exposes players to ever-higher training loads, crowded competition schedules and shorter rest periods. This causes teams to thrive on the latest technological and scientific advances in the field of sports and medicine in their quest to reduce the risk of injury without compromising performance.

Monitoring workload has become a cornerstone on which to plan and periodize workouts, optimize fitness, and avoid the risk of injury. Training Load is usually categorized as external or internal, respectively defined as the conditioned work performed by the athlete (example: total distance, number of accelerations) and the associated physiological response (example: subjective perception of effort, heart rate, lactate concentration).

In this case we refer to the external load, through GPS, through which we can observe the behavior of the different variables that are analyzed to control the Volume and Intensity of the session.


The variables that we take into account are the following: Total Distance (T.D.), H.S.R., Acc-Decc, Nº Sprints, Peak velocity, H.M.L, Total Player Load,...

Once the variables are obtained, we can analyze what % of Volume we have obtained with respect to the MD, what % of Intensity and thus we can observe by graph the trend that the load has had (Volume and Intensity) during the microcycle. In this graph we can see the Variables of Volume, Intensity and Total Player Load and the references as light, medium or intense.


Another important aspect is the individual analysis of the players, what levels they have given during the micro cycle, and all this compared to the footballer's performance profile.

These values serve as a reference to adjust the training loads of the next day or the next micro cycle. In turn, it is important to activate the individual recovery or compensation protocols if any of the players has exceeded the established limits or is far below the stipulated work.


To finish, it is important to know the conditional profile of each task, in which parameters it is located in terms of total distance, accelerations, and decelerations to be able to introduce said task according to the corresponding day of the week based on the structure of the competitive micro cycle.


All these external load data, in addition to the internal load data (RPE, Wellness, ...) are necessary when rescheduling the training based on the level of fatigue of the footballers with the sole objective of reaching the day of competition. The most recovered possible and with an optimal level to be able to compete in the best possibilities.

8.How to control external load (GPS) Microcycle