The first team players were older and heavier than the reserves team players, which is of little surprise. Since the initial observations of Reilly (1979), it has been widely documented that successful first teams tend to be comprised of players with a mean age of about 25 years and that reserve team players are younger. Squad sizes are currently reducing in English soccer due to the recent financial situation. This means that reserve team squads tend to be even more developmental in nature. The fact that the older players have greater body mass, is likely to be due to muscular development and the continued growth. The first team players from this Premier League sample are, on average, heavier than previous reviews have suggested for players in other leagues or generations (Reilly, 1994). This is likely to be due to a greater muscular component, rather than greater endomorphy. Vertical jump levels are a similar to those seen in English First Division players (Mercer et al., 1997).