Jump as a Fatigue Indicator
The monitoring of neuromuscular fatigue in athletes is very relevant when planning training sessions and competitions.
Injuries are a major concern in football. In fact, a study that analysed 24 teams from 9 European countries during 11 years showed that about 7 or 8 injuries occur per one thousand hours of play, with a higher incidence of injuries related to a lower position in the team’s final ranking.1 Among all, muscle injuries are the most frequent ones, more than receiving a blow, fractures and joint injuries.2 Muscle injuries have significant negative consequences for both performance and the economy of the team, as athletes who suffer them have to be on average two weeks away from the team.3 Therefore, developing strategies to prevent muscle injuries is essential.
Football teams employ different exercise programmes to reduce the incidence of muscle injuries, although they sometimes do it without clear evidence about what works. As a recent systematic review4 concluded and summarised in this thought piece (Preventing muscle injuries in elite athletes, which exercises work?), there is not enough evidence to prevent muscle injuries in elite athletes. Therefore, it has been suggested that, in the absence of high-level evidence, consensus among experts may be the best option to guide evidence on the most effective strategies.
In this context, the group Elite Football Performance (EFP), led by prestigious researchers and coaches of elite football teams, such as Arsenal FC, FC Barcelona, Real Madrid CF or AS Roma, have developed a consensus guideline, called the “Delphi survey”, where they describe which exercises would be the most effective ones to prevent muscle injuries, as well as the optimum moment to implement them.5 The survey was sent to 21 coaches from different European leagues with an average experience of 12 years in elite football and academic experience.
In this survey, the professionals answer multiple questions until most of the respondents (>70 %) come to an agreement. Over the first round of questions, the professionals had to assess (on a scale of 4 points, from ineffective to very effective) the effectiveness of 13 different types of common exercises to prevent injuries, including sprint, plyometric, eccentric, balancing, flexibility and core strengthening exercises.
As shown in Table 1, at the end of the four rounds of questions necessary to reach consensus, they concluded that sprints and maximal running were the most effective exercises to prevent injuries (with 3 of 4 points, i.e. very effective), followed by eccentric exercises (2 of 4 points), which were considered effective by all professionals. On the other hand, several types of exercises were considered simply “effective” (1 of 4 points), including concentric and isometric exercises, horizontal and vertical plyometrics, coordination/technique exercises, flexibility and core stability exercises. On the contrary, they did not agree on the effectiveness of multi-joint exercises, such as olympic movements or functional exercises, one-sided exercises performed on instability conditions, agility and driving exercises (e.g. long passes) or resisted sprints.
With regard to the most effective exercises, the professionals decided that the ideal moment to implement sprints or maximal running is three days before the match, when they have more than five days to rest between matches. When they have less than four days to rest, the authors concluded that it is not necessary to implement this kind of exercises. Furthermore, they concluded that the athletes who do not play should implement these exercises one or two days after the match. What is more, they decided that eccentric exercises should ideally be implemented three days before the match, but there was no consensus whether they could be combined with sprints or maximal running. Besides, the professionals concluded that these eccentric exercises, especially if performed with low intensity and volume, can be carried out when there is less than four days between matches, as athletes are usually accustomed to them. Finally, all or at least most of the professionals concluded that, besides choosing exercises correctly, in order to prevent injuries, it is essential to control the weekly workload, consider previous injuries, perform multidisciplinary work and other recovery strategies.
Interestingly, it can be seen how sprints and maximal running, traditionally viewed as an injury mechanism (especially for the hamstrings), are currently considered key exercises to prevent injuries. In this sense, it is important to highlight that the professionals emphasised the need to individualise the speed at which these exercises are performed, and to combine them with football-specific activities, such as decision making and dribbling with the ball. Moreover, they concluded that eccentric exercises can be implemented before and after training sessions, although one must be careful about how the possible muscle pain induced by these exercises affects performance in other sessions or matches.
In brief, in the face of the scarce scientific evidence about which exercises are efficient to prevent muscle injuries in football athletes, the experts give their opinions and conclude that sprints and maximal running, as well as eccentric exercises, are the most effective exercises, provided that they are well planned and take into account individual characteristics and the weekly workload.
Although there are several studies on this topic, many of them have analyzed these demands by looking at just a few variables or using very broad timeframes. A new study completed by physical trainers from F.C. Barcelona has analyzed several of these details more closely.
The understanding of the modifying variables of the game, based on the degrees of freedom.
Training using eccentric exercises is important to prevent possible damage. However, intensive training can also cause muscle damage, so it is critical to be vigilant in order to keep injury risk to an absolute minimum.
The importance of building a game model in football.
Cardiovascular endurance manifests as a moderator of the load result to which the athlete is exposed.