Does six weeks pre-season training influence the physiological fitness of amateur soccer players?

Typically in team sports, such as amateur soccer, the pre-season period is a short amount of time (~ 6-7 weeks) that is used to facilitate gains in fitness and match readiness for the competitive season (1). During this time the players strive to reach their previous fitness levels as well as develop skills to become match ready (2). It has been reported that during the off-season, soccer players undergo periods of inactivity and a significant de-training effect has been shown to occur after only 8 weeks (1). Therefore pre-season training must prepare players so that they can sufficiently maintain high intensity actions throughout a game as the average work intensity during a soccer match has been estimated to approximate ~70-80% of maximum aerobic power (3, 4).