Footballers' ability to recover after high-intensity effort may not depend on their age, but on their division level, a new study has suggested.
A multinational team of scientists led by the Complutense University of Madrid (UCM) carried out maximum-effort tests with Spanish division one and division two soccer players.
They then measured the players' oxygen consumption, heart rate and ventilation during recovery.
Professor Francisco Javier Calderón Montero, from UCM, is the study's lead author. He said: "Regardless of a player's technical ability, the ability to repeat sprints is essential in soccer. Players may need to sprint every 90 seconds during a game, meaning the available recovery time will be short."
"We wanted to discover if the difference in the recovery time before the next sprint were linked to the level at which a soccer player competes."
The researchers' findings, published today in Physiological Measurement, show that compared to first division players, second division players took longer to recover from maximum effort exertion.
Professor Montero explained: "Our results showed second division players had higher oxygen consumption and heart rate than first division players after 90 seconds of recovery time. These differences were still clear after 180 seconds of recovery time."
"The second division players, therefore, took much longer to recover to the point where they were able to repeat the effort. They are therefore unlikely to be able to repeat sprints as often and as intensely as first division players."
A huge sample of one-hundred-and-ninety-four male soccer players, from seven clubs in the Spanish Professional Football League, took part in the study. There were 114 first division and 80 second division players comprising: 12 goalkeepers, 57 defenders, 86 midfield players, and 39 strikers.
All underwent the same maximum effort test. They first warmed up by running on a treadmill for two minutes at 4 km/h, before increasing their speed until they reached a heart rate of 120-130 bpm. They maintained this for three minutes. After this warm-up period, they could rest to stabilize the respiratory quotient (RQ) at <1). Researchers recorded the players' carbon dioxide production and RQ every 10 seconds.
The maximum effort test began at a speed of 6 km/h, and a one per cent slope. The players' running speed increased by 2 km/h every two minutes until they reached maximum effort. The players then underwent a three-minute period of active recovery.
Although the team found a difference in recovery time between players from divisions one and two, the position in which they played had no bearing on the results.
Corresponding author Dr Luca Paolo Ardigò, from the University of Verona, said: "A possible explanation may be that the second division players always played in lesser category clubs with lower training demands. However, the players in our study showed no differences in self-declared duration of training or weekly recovery."
"It is possible that the intensity of training differed, and further study is needed to uncover whether this is a factor."