Injury Frequency in Professional Players: An Analysis of its Epidemiology in Football
On average, a professional football team made up of 25 players experiences 50 injuries over a season, so each player can get injured twice a year.
The warm-up plays an important role in exercise by improving the performance and reducing the injury risk.1,2 Its relationship with performance is so important that it has been studied since the 1930s.3 Its main objective is to reduce the stiffness in our muscles and joints, stimulate the peripheral blood flow, increase muscle temperature, and improve movement coordination.4 In cases in which any of these objectives is not achieved, the main goal will not have been fulfilled. A good warm-up can help optimise performance for the match. A systematic review with meta-analysis showed that an improvement in performance after warm-up occurs in 79% of the cases studied, with an increase ranging from less than 1% to almost 20% depending on the study.5 Moreover, in only 3% of the cases, performance decreased after the warm-up, because the warm-up performed was not appropriate for the activity about to be carried out.5
For an optimal warm-up, you must include specific aspects of the tasks which are goin to be carried out. For example, a study tried to analyse the warm-up, consisting of 12 jumping jacks, on speed, strength, and precision.6 The tests carried out were on a bicycle at high speed on, the maximum distance reached by throwing a baseball and the number of free throws made. However, considering the warm-up did not include specific aspects of the tests that were going to take place later, we could not expect performance to improve. And, indeed, there were no differences between carrying out that warm-up and not warming up at all on the performance in the different tests.6
Another aspect related to warm-up that can influence an athlete’s performance is the time between the end of the warm-up itself and the start of the match, which is known as post-warm-up. Depending on the intensity and duration of the warm-up, performance might improve if the duration of the post-warm-up is enough so as to re-establish the reserves of creatine phosphate (~5 minutes). Also, it is important for the body temperature to not decrease, which depending on the intensity and duration of the warm-up and the weather conditions, starts to take place 15-20 minutes after. For this reason, David Bishop established that an interval longer than 5 minutes but shorter than 15-20 minutes is likely to produce the greatest ergogenic effect on performance in the short term.7
Special attention has also been given to breaks between the two halves in team sports. Often, during half-time, athletes just drink water and listen to the coach’s technical instructions resting in a passive way, which decreases muscle activity and body temperature contributing to a reduced performance and an increased injury risk. Given its importance, many researchers have studied how this rest period affects performance at the beginning of the second half of a match and the different strategies, known as re-warm up, to avoid negative changes that occur during the half-time.8-11
Although warm-up is considered essential to achieve optimal performance, there is not enough scientific evidence to support its effectiveness in specific situations. For that, a recent systematic review published in the prestigious magazine Sports Medicine, in which Dr. Mikel Izquierdo has participated, assessing the potential effects of the strategies during warm-up, post-warm-up and re-warm-up on explosive performance actions in team sports.12 This review included 30 studies, 19 of which were about warm-up, 5 about post-warm-up, and 6 about re-warm-up.
The authors observed that a warm-up consisting in 8 series of 60 m long sprints, improved the sprint ability. Also, 7 minutes of dynamic exercises after jogging for 5 minutes, improved sprint, jump and agility performance. The use of games in confined spaces also seems to be a valid strategy, especially for performance in jumping tests. In these cases, warm-up was followed by passive rest (2-10 minutes) before the match started. When they were sitting down during this period, they experienced a decrease between 4% and 6% of their sprint ability, and between 12% and 20% of their jump ability. During this post-warm-up, strategies such as simply standing up or using thermal blankets produced better outcomes on performance than just simply resting. If the interval between the end of the warm-up and the beginning of the match was greater than 15 minutes, performing explosive actions as a way of reactivation was the most effective approach. During half-time, a decrease on performance was observed when the player remained seated. Thermal blankets, as a re-warm-up strategy, produced a better effect on the sprint and jump abilities than resting. Meanwhile, only eccentric exercises were detrimental to performance, showing a worse effect on sprint and jump.
In elite sports, the difference between winning or losing is very small and these marginal improvements in performance can tip the balance in our favour. For this reason, trainers and physiologists spend most part of the season trying to plan strategies that can help improve the outcomes as well as minimise the injury risk. As we have seen, remaining seated or standing up before the match can really make a difference.
Javier S. Morales