METHODS
Participants
Eighteen male soccer players recruited from the Junior Soccer Team ‘Cagliari
Calcio S.P.A.’ (age: 16 ± 0 years; body mass: 65 ± 10 kg; height: 1.74 ± 0.10 m;
BMI: 21.3 ± 1.5 kg m–2) volunteered to participate in this study. The inclusion
criteria were: elite national-level soccer practice, >5 years training (9.3 ± 0.8
years) and >8 hours of training per week in addition to the weekly official
game. The participants were familiar with shuttle running training and had
been participating at the national championships (middle season) at the time
of the investigation. The participants gave their assent, and written consent
was obtained from participants’ parents/guardians after being thoroughly
informed about the purpose, benefits and potential risks of the study, in
conformity with the Ethics Code of the World Medical Association
(Declaration of Helsinki). All experimental procedures were approved by
the institutional human ethics committee, which followed ethical standards
(CONI Italian Olympic Committee, Sardinia).