Football after COVID: Shorter Preseason → Higher Injury Risk

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  • Post-COVID return to play will likely include short preparation and highly congested playing schedules.
  • This preparation phase resembles typical preason periods but is expected to be shorter and the playing schedule to follow more challenging.
  • In this analysis, we show that shorter preseason incur higher injury rates in the following months implying that post-COVID RTP scenarios put players under increased injury risk.
  • Teams need to take this into account by personalizing training and playing routines to keep players safe and by proxy achieve better results.

Looking beyond the peak effects of COVID-19, many professional football leagues will resume play in the upcoming weeks. In an attempt to complete the bluntly interrupted seasons, teams are expected to face several challenges such as short preparation phases and an extremely congested playing schedule.

The German Bundesliga, for instance, is the first major football league that resumed official match play — this past weekend. The official announcement on the matter was given on May 7th giving local teams, a mere 9 days to make the transition from individual training to high-intensity group training. Unfortunately, it doesn’t come as a surprise that eight players were injured in six games on Saturday.

At Zone7 we have the opportunity to provide data-driven insights regarding the effect the preparation and playing scenarios forced by the COVID-19 situation have on injury risk. Our deep learning algorithms are validated to detect 70% of injuries up to 7 days before they occur, with industry-leading false-positive rates. We use inputs such as workload data from training and matches, injury history, biomechanical screening, fitness tests, biomarkers, etc. Over the past few years, we’ve analyzed data for over 30 professional football teams from premier leagues across Europe, North America and Asia. This vast dataset enables us to create reliable analytics and insights.

This is our second blog post regarding the effect COVID-19 related return-to-play scenarios are expected to have on injury risk. In the first blog post, we’ve shown that injury risk is a seasonal attribute that is widely affected by match congested periods and variations in a team’s match schedule. Here we chose to focus on how the length of preseason preparation affects injury risk. For this purpose, we’ve analyzed data from the last two seasons and 11 different teams from top-division European football leagues including Spain, England, Italy, etc.

The playing sequence after the forced break will be short, therefore we find it interesting to examine injury rates in the months that follow preseason phases. Additionally, different leagues and teams have different injury tendencies that should be standardized in this analysis. Given these constraints, we modeled the relationship between preseason length and average injury rates in the first half of the season compared to average injury rates during the entire season. Injury rates were defined as the number of injuries per month and were normalized based on the number of matches per month, as most injuries occur in matches.

Interestingly, we found that when the preparation period shortens, relative injury rates during the first half of the season are higher. This trend is statistically significant despite the relatively small sample (p = 0.048, r² = 0.37). The chart below depicts this trend.

Additionally, we see that most teams schedule preseason periods of over 30 days. Ideally, this should be taken into account by football leagues and federations when announcing when play will be resumed. If we take Bundesliga as an example, we see that’s not the case. Shorter preparation periods generally occur in years following big international tournaments or in teams that play early stages of European competition. Even then, they’re usually able to maintain a preseason phase of over 30 days.

X: Preseason duration // Y: injury rates in first half of season

To further accommodate the fact that different teams and leagues train and play under different schedules and routines, we decided to look into the effect changes in the preseason length may have on injury risks within the teams, separately. 75% of teams for which two years of data were available, demonstrated higher injury rates during the first half of the season in which the preparation period was shorter.

These insights reinforce the understanding that the likely implications of COVID-19 on professional football leagues, will make it challenging for clubs to keep players healthy throughout the remainder of the season. To overcome the challenges caused by the short preparation phase before resuming play, teams will have to personalize training and playing routines, using their knowledge of players’ injury tendencies and physical condition coming back from the break to do so. For example, knowing each player’s aerobic capacity can help determine if his preparation phase should focus on improving it or on tactical/technical elements of the game, given the player aerobic capacity is sufficient. Nature and compliance with at-home training routines will be key to this matter as well.

At Zone7, we believe we are able to provide clubs with significant assistance in managing these challenging times. Our vast experience in analyzing data from seasons with short preparation phases that preceded them gives us the unique ability to so. Our data-driven AI platform has the ability to assist in day-to-day decision making by providing reliable injury risk assessments that can support a team in the unique times ahead of us.