It's widely accepted in the professional game that interval training improves football fitness - but is there any research to support this theory?
For years the answer was no, but recent research from Norway has proven that interval training dramatically improves football fitness.
Researchers from the Norwegian University of Science and Technology in Trondheim assigned players to either a training group or a control group - the difference between the two groups was that in addition to their regular training and play (four 90-minute practices and one game per week), members of the training group performed interval training twice a week for eight weeks.
By contrast, the control group received extra technical training - heading drills, free kicks, receiving the ball and changing direction etc.
Not surprisingly, after eight weeks of twice-weekly interval training, the players in the training group had improved their VO2 max by almost 11%, their lactate-threshold running speed by 21% and their running economy by 6.7% - by contrast, the control group not improved at all.
These are key physiological markers indicating improved fitness, but how did they affect performance where it really counts - on the field?
When the players' performance in games was analysed, the interval-trained athletes were found to have increased the total distance covered during games by 20%, doubled the number of times they sprinted during games, and most important of all, had increased their number of involvements with the ball per game from 47 to 59, an increase of 24%.
These 'involvements' were defined as situations where the player was either in possession of the ball, or directly pressing an opponent who was in possession of the ball, and are thus a key indicator of a player's involvement in the game.
So while there is no substitute for skill, adding increased fitness via interval training will improve the involvement of any player in the game, and thus, ultimately, their contribution.