[Effects of the COVID-19 lockdown on physical performance parameters in professional football].

Background: Governmental measures in 2020 to contain the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) brought training and competition in professional soccer to a temporary halt in many countries. As a result of the lockdown, training possibilities were mostly limited to nonspecific home-based training methods. It is unclear whether the lack of sport-specific stimuli led to a reduction in the physical performance of soccer players. Methods: For the narrative review, the PubMed, Google Scholar and BISp-Surf databases were selectively searched for studies examining the effects of the lockdown on physical performance parameters in adult professional soccer players. Results: In this review six prospective longitudinal studies were included. In all studies home-based training was performed during quarantine. Of the studies four compared the performance of the soccer players with data from previous seasons and two studies assessed the performance of players immediately before and after the lockdown period. Discussion: While general strength and endurance performances can be maintained through home-based substitute training programs, the studies indicated that the lack of football-specific stimuli could have an impact on the rapid power and speed performances of soccer players. Progressive loading control especially for speed training should be considered when returning to regular training in order to reduce the risk of injuries.