Table 1.

Original studies reporting on the impact of the pandemic on professional athletes.

	Research design	Participants	Target variables	Main findings
Meyer et al. (14)	2-month prospective longitudinal cohort	1,702 male professional football players from German leagues and the officials working closely with them	(1) Onset of typical COVID-19 symptoms, (2) Positive PCR results, and (3) IgG seroconversion against SARS-CoV-2	Of the 1,702 regularly tested individuals, only eight players and four officials tested positive during one of the first rounds of PCR testing prior to the onset of team training, two players during the third round. No further positive results occurred during the remainder of the season.
Pillay et al. (15)	Cross-sectional survey	692 (67% males) athletes from South Africa	(1) Activity (2) Nutrition (3) Mental state	COVID-19 had physical, nutritional, and psychological consequences
Senişik et al. (16)	Cross-sectional survey	418 athletes of 612 volunteers from Turkey	(1) Mental health: depression and anxiety (DASS-21) and posttraumatic stress levels (IES-R) (2) Physical activity (IPAQ-SF)	Mental health status of athletes was better than the non-athlete controls. Depression levels were similar in team and individual athletes. Team athletes had a lower level of anxiety compared to individual athletes.
Costa et al. (17)	Cross-sectional survey	1,125 (45.8% men) athletes from various sports in Italy	(1) Athletic identity (AIMS scale) (2) Cognitive emotion regulation (CERQ scale)	Athletes with higher athletic identity tend to ruminate and catastrophize more.
Håkansson et al. (18)	Cross-sectional survey	1,145 (82% men) athletes in top leagues of soccer, ice hockey, and handball in Sweden	(1) Depression (2) Anxiety (3) Alcohol drinking (4) Gambling behavior (5) Problem gambling	Distress from pandemic is common in elite athletes and associated with mental health symptoms. Gambling increase during the pandemic was rare, but related to gambling problems.
McGuine et al. (19)	Cross-sectional survey	13,002 (53.1% women) USA adolescent athletes	(1) Physical activity (PFABS) (2) Anxiety (GAD-7) (3) Depression (PHQ-9) (4) Health-related quality of life (PedsQL)	Women reported a higher prevalence of moderate to severe anxiety symptoms. The prevalence of depression symptoms was highest in team sports than individual sports. The total PedsQL score was lowest (worst) for athletes from counties with the highest poverty levels.
Graupensperger et al. (20)	Longitudinal survey, before and after 1 month after university campus closures during COVID-19	234 (63% female) USA student-athletes	(1) Athletic identity change (AIMS) (2) Teammate social support (SSB) (3) Teammate social connectedness (4) Well-being (MHC-SF) (5) Depression (PROMIS) (6) COVID-specific worries	Positive correlations occurred between teammate social experiences and identity maintenance, and consequently, identity maintenance was positively correlated with psychological and social well-being and was negatively associated with depressive symptoms.
Mon-López et al. (21)	Cross-sectional survey, retrospective	187 (64.7% men) handball players from Spain	(1) Demographic variables: gender, age place of residence, number of days confined, sport level, playing position and personal experience with COVID-19 (2) Training variables: training days, training hours, intensity, and recovery. (3) Psychological variables: emotional intelligence (WLEIS-S), mood state (POMS), and resilience (BRS-II)	COVID-19 isolation had significant negative effects on the training and recovery of the athletes, as well as sleep quality, and other psychological variables.
Grazioli et al. (22)	Cross-sectional observational, after 63 days of quarantine and compared with retrospective data obtained after a regular 24-day off-season period	23 male Brazilian professional soccer players who returned to training activities after 63 days of quarantine	(1) Body composition (2) Jump and sprint performance (3) Hamstring eccentric strength (4) Intermittent cardiorespiratory fitness	Quarantine caused a substantial increase in body mass, body fat mass, 10- and 20-m sprint times, and a decrease in counter-movement jump height.