the ball. In 2007, the AFL began introducing rules aimed at attracting more juniors by reducing the forceful contact and aggression in the game. Significant controversy was caused by the introduction of the "hands in the back" rule. Zero tolerance was given for players putting hands on the back of a player in a marking contest. The AFL rules committee argued that this was simply a stricter interpretation of a rule which had been relaxed over the decades. The league also attempted to reduce head injuries by introducing new rules on bumping, including severe penalties for forcible bumping of players from front-on when their head is over the ball. In 2008, reacting to an incident involving the Sydney Swans playing 19 men on the field, new interchange rules were introduced to supersede the head count. Also, through the AFL Tribunal, it began to outlaw tackles which pinned the arms of a player and drove their head into the ground. Towards the end of the season, the league also increased the number of boundary umpires from 2 to 4. Adoption of the laws by Australia and regional leagues Players, ground and equipment The number of players on the field in the year years of game could consist of 20 or more players in 1899 WAFL was the first competition to introduce the rule that a maximum of 18 players were allowed to be on the field. Since that change it has been universally adopted across all leagues that 18 players are permitted to be on the field per team at any one time, with an additional four players on an interchange bench (although this number often varies in exhibition and practice matches). The equipment needed to play the game is minimal. As in other kinds of football, players wear boots with stops (known as "cleats" or "studs" in some regions) in the soles, shorts, and a thick, strong shirt or jumper known as a guernsey, normally sleeveless, although long sleeve jumpers are sometimes worn in very cold weather by some players. Protective gear is minimal. Most players wear a mouthguard but only a very few wear a helmet, normally a bicycle style helmet with a soft outer covering, and only after medical advice, such as if they have been concussed numerous times. Some players, predominantly ruckmen, wear shin guards. All protective equipment must be approved by the umpires to ensure that