Morphology of possible regions in elite soccer players.

The popularity of spatio-temporal analyses in soccer is increasing. As many of these analyses depend on the regions a player can occupy in a certain amount of time (the possible regions), the understanding of this concepts is important for analyses to produce usable results. This study investigated how possible regions of soccer morph with varying times and running speeds. Twenty-four players from the Danish Superliga participated, and 13 players were analysed. The possible regions were analysed with times from 0.5 to 4 s (0.5 s increments) and initial velocities from 1 to 7 m/s (1 m/s increments). In this study, we showed that the possible regions can be described by ellipses (eccentricity of 0.5348 ± 0.1912). When comparing the possible region ellipses at every time and velocity pair, 1.95 % of the ellipses were not significantly different from the others. In conclusion, possible regions are unique in shape and size depending on player running speed and time available. However, as only few strikers participated, the results for this group should be interpreted with caution. Coaches can predict possible regions based on these parameters increasing precision of post-game analyses.

Modelling the potential spread of virus during soccer matches.

Objective: In the present study, we model the potential spread of virus during soccer matches. Methods: Tracking data from 14 elite soccer matches was used. One player in each match was designated as a virus carrier (called 'infected player') for the purpose of the study. The exposure score (measured in seconds) was calculated as time spent closer than 1.5 m from the infected player or time spent in an exponentially declining zone, where the infected player was positioned earlier. Results: The results revealed that, on average, each player was exposed for 87.8 s per match. Conclusion: Potential spread of virus during soccer matches was modelled and it revealed that the exposure to a virus during soccer matches is limited.

The Faroe Islands COVID-19 Recreational Football Study: Player-to-Player Distance, Body-to-Body Contact, Body-to-Ball Contact and Exercise Intensity during Various Types of Football Training for Both Genders and Various Age Groups.

We determined player-to-player distance, body-to-ball contact, and exercise intensity during three training modalities in various football populations. 213 participants were recruited, ranging from 9-year-old boys to young men and 11-year-old girls to middle-aged women. All groups were analysed with video-filming and GPS-based Polar Pro monitors during three types of football training for 20 min, i.e., COVID-19-modified training (CMT) with >2-metre player-to-player distance, small-sided games (SSG), and simulated match-play with normal rules (SMP), in randomised order. Time spent in a danger zone (1.5 m) per-percent-infected-player (DZ PPIP) ranged from 0.015 to 0.279% of playing time. DZ PPIP for SSG was higher (P < 0.05) than CMT and SMP. The average number of contacts (within 1.5 m) with a potentially infected player ranged from 12 to 73 contacts/hour. SSG had more (P < 0.05) contacts than CMT and SMP, with SMP having a higher (P < 0.05) number of contacts than CMT. Time/contact ranged from 0.87 to 3.00 seconds for the groups. No player-to-player and body-to-ball touches were registered for CMT. Total player-to-player contacts were 264% higher (P < 0.05) in SSG than SMP, ranging from 80 to 170 and 25 to 56 touches, respectively. In all groups, a greater total distance was covered during SMP compared to CMT (38-114%; P < 0.05). All groups performed more high-intensity running (33-54%; P < 0.05) and had higher heart rates during SMP compared to CMT. Different types of football training all appear to exert a minor COVID-19 infection risk; however, COVID-19-modified training may be safer than small-sided game training, but also match-play. In contrast, exercise intensity is lower during COVID-19-modified training than match-play.

Danger zone assessment in small-sided recreational football: providing data for consideration in relation to COVID-19 transmission.

During the COVID-19 pandemic, physical inactivity has increased, and a wide range of sporting activities locked down, with possible long-term implications for public health. Football is the most popular sport worldwide, and recreational football training leads to broad-spectrum health effects. Football is, however, deemed a contact sport with frequent close contact important to consider during COVID-19 pandemic. OBJECTIVES: This study investigated time spent with close contact (danger zone (DZ) within 1.5 m), number of contacts and time per contact, and compared game formats in recreational small-sided football games for young and adult male football players. METHODS: Movement analyses were performed on 10 Hz Global Positioning System (GPS) data collected during various small-sided football games prior to the COVID-19 outbreak. RESULTS: Time spent in the DZ was 4.3-7.9 s/h per per cent infected players, corresponding to 34.3-114.8 s/h if one player was infected. Number of contacts with one infected player was 23.5-87.7 per hour, with an average contact time of 1.1-1.4 s, and a total number of contacts of 311-691 per hour with all players. 53%-65% of all contacts were shorter than 1 s and 77%-85% shorter than 2 s. Trivial to small effects were found for number of participants and area per player, whereas standard of play and playing with/without boards had no effect. CONCLUSION: This study demonstrated that during small-sided football limited time is spent within DZ and that player contacts are brief. Recreational football may therefore more appropriately be deemed as sporting activity with brief, sporadic contact.

The Effect of First-Step Techniques from the Staggered Stance in American Football.

The purpose of this study was to evaluate 3 different starting techniques from the staggered stance with regards to sprint time, reaction time, linear impulse and power. 11 male amateur American football players volunteered to participate in a testing session consisting of twelve 5 m sprints, 4 in each technique (normal (NORM), backwards false step (BFS) and forwards false step (FFS)) in random order. Sprint starts were performed on force plates to investigate ground reaction forces, reaction time and total sprint time. Analysis showed significant differences in sprint times, with NORM (1.77±0.10 s) being faster than FFS (1.81±0.12 s) and BFS (2.01±0.13 s), and FFS being faster than BFS, although no differences were found in reaction time. In terms of mean force and power, NORM (331.1±39.2N, 542.2±72.3W) and FFS (320.8±43.2N, 550.9±81.4W) were significantly larger than BFS (256.9±36.2N, 443.5±61.1W). This indicates that when starting from a staggered stance, the BFS is inferior to the others and should be avoided. However, since the force profiles of the NORM and the FFS were similar, the differences in sprint time could arise from a technique bias towards the NORM start.