Material and Methods
Subjects
A total of 504 records were made of the heart beat signal throughout
a season (36 measurement sessions over 11 months). These
were from 22 professional soccer players (age 25±3; weight
74.2±7.31kg; height 178.85±7.83cm) belonging to a Spanish
First Division club, and excluded the 2 goalkeepers. This team
finished the season in the 6th position of the National Championship,
and was the champion of the UEFA Europa League.
The Local Ethics Board approved the study, which followed all
the principles expressed in the Declaration of Helsinki. All subjects
signed a written informed consent to participate in this study. The study meets the ethical standards of the International
Journal of Sports Medicine [20].