Everything starts with stamina, says De Boever, and measuring that load is vital.
There is a famous 1937 photograph of Charlton goalkeeper Sam Bartram standing alone, defending his goal in dense fog, with everything around him obscured except for himself and his goal.
In many ways, this image perfectly encapsulates the traditional perception of the goalkeeper—a solitary figure tasked solely with keeping the ball out of the net and then clearing it as far from danger as possible.
But in the 21st century, the modern goalkeeper has integrated further into the team, effectively functioning as an auxiliary centre-back.
Consequently, the physical demands of the position have changed significantly, with contemporary goalkeepers required to be proficient athletes in addition to being strong shot-stoppers.
AS Monaco Goalkeeper Coach Frederic De Boever, however, believes that it is a more traditional approach to placing physical loads on goalkeepers that is essential in underpinning the physical skills needed to perform as a top-level goalkeeper.
According to De Boever, placing endurance at the heart of his training differentiates him from other coaches. However, he believes modern goalkeepers must be seen as athletes.
He explained: “The foundation, the basis of a goalkeeper is endurance and stamina.” he says definitively.
“You cannot do the short sharp interval exercises when the endurance of your goalkeeper is not 100%.
“And I think that's a big change or a big difference compared to what some other goalkeeper coaches teach. I think the realisation that your goalkeeper is more and more a modern athlete. I think that's the foundation, that's the basis of everything in my opinion.”
Improving a player’s lactic threshold, which is the point at which the rate of production of H+ icons is higher than the body’s ability to break them down, leading to the acidification of muscles, is essential to building endurance.
For De Boever, the only way to do this effectively is to increase the number of repetitions that goalkeepers conduct through a combination of intensity and active recuperation. He continued: “We want to push your lactic threshold higher and higher, and the more repetitions you can do, the better you will feel, the more concentrated you will stay when you're getting tired, and after a while, they see the benefit, they see the advantage, and they start feeling it.”
He went on to outline an example interval training drill that he uses with his goalkeepers. De Boever describes “an interval exercise, for 30 to 45 seconds, where the goalkeeper works at full speed. And that's a repetition of balls. Pre-action, repetition. And then when they are fatigued and they have heavy legs, they have to kick six balls, left foot, right foot, and they have to put it in small five-metre goals.
“That's difficult because their legs are heavy, they feel tired and they have to keep the focus on the quality, they have to keep the focus on the accuracy of their passing and if they don't succeed 4 out of 6, they have to do something else, just to push the limits.
“It’s also about periodisation. All four goalkeepers are working at the same time. So they are kicking, they are throwing, they are diving, they are jumping, they are making distance at the same time in that exercise. No one is standing still.
“If you do this with a goalkeeper who is not used to fast recuperation, it's finished. The six balls will go everywhere except where they want to be or where they have to be. That’s what we are aiming to change.”
Data is at the heart of De Boever’s work and is essential to understanding the physical level of his goalkeeping group. Whilst match data can provide some useful information, De Boever believes the data gathered at training gives the most accurate picture.
He continued: “The most important thing is the internal data that we have. The data from training is much more important. You have your mechanical data - that's your dives, your jumps, all the things that you can actually measure and that you can see.
“That's one part of the story, but for me, the most important part of the story is the cardio data. And that's a hidden parameter for goalkeepers, which allows you to see how fit he is, how his condition is. And that's always an interesting part to see after a training session.
“The lactic threshold is something that you have to push in the daily work with your goalkeeper. In the past, a lot of goalkeeper coaches were thinking if I go full on for one minute and I just kick ten balls at them, I work physically with them.
“That's pure interval style training. You can kill your goalkeeper physically by doing that kind of stuff, but it will not help him to grow physically as a goalkeeper in the longer term. The condition will stay exactly the same.
“That's the reason that I work a lot of time with my goalkeepers, I work on their aerobic base. I want to build that lactic threshold; I want to build it as big as possible. Because that automatically means that his recuperation will be much better further down the line when he is adjusted to this kind of work.”
According to De Boever, collaboration is also at the heart of his philosophy and has been ingrained in his work since his early days collaborating with Guy Martens. As a result, he tries to be as open as possible with his methods to help others improve.
De Boever said: “I worked really close together with Guy Martens of Genk. They have a big tradition in training goalkeepers and it's on a really high standard over there. And he's still my best friend in the world of football.
“We have regular contact, and the philosophy started with him. We talked to each other, we helped each other, we gave exercises to each other and shared thoughts, sharing opinions that made this philosophy grow more and more.
“I can say that he was a really important part of this philosophy also. I know that he is working on exactly the same that we are doing. So it's interesting to know that you have a certain confirmation and then you bring your own input, style, and philosophy.”
In a similar way, De Boever’s philosophy is aligned throughout the club to ensure that young goalkeepers coming into the first team can cope with the sessions.
“Our second team goalkeeper coach, and of the under 19s, they all work in a similar philosophy. They know they need to do cardio work with goalkeepers. We have to work aerobically with them also. When a young goalkeeper joins our group, he knows more or less already what kind of exercises he can expect because he was exposed to it.
“Most importantly, he knows the reason behind those kinds of exercises. So that's the first step. Of course the speed of execution and the tempo and quality of the exercise increases, but away from that, he knows everything already.”
The importance of explaining the purpose of the philosophy to new signings that join the group is also paramount to ensure they can get the most out of the exercises.
“I talk about new goalkeepers who arrive here for the first time because if you explain why you're doing it, and mentally, they are open-minded and they understand why you are doing it, their development is fast.
“They will have questions for sure and in the beginning they will look and they will say ‘f****** hell this is hard!’ Or, ‘why do I have to make that distance?’ or ‘why do I have to make that run’ but at a certain point after three or four weeks they start feeling more and more comfortable and they feel lighter in the training session.
“When we ask them to rate the difficulty of the training session, you see in the beginning that it's it's it's six or seven out of ten, and you see after three, four weeks that they are used of doing this and it goes to five, it goes to four and now we are on a certain level with the goalkeepers that I give exercises where I still know from this is hard to to do, but they don’t find it as hard.”
De Boever has an irrepressible passion for goalkeeping, and helping to improve goalkeepers, which shone brightly throughout our conversation. He admits his approach to goalkeeper fitness is somewhat atypical and not often seen in the mainstream, but for the Belgian, it underpins the success he has had with elite goalkeepers. A different perspective is always food for thought.
