The PFA welcomes the Premier League's announcement today, which formally agrees to introduce the International Football Association Board's (IFAB) additional permanent concussion substitutions trial.
Under the trial, each team can have up to two permanent concussion substitutes per match with the opposing team also allowed to make a change at the same time.
PFA Chief Executive, Gordon Taylor said: "We are pleased that English football is taking the lead on this vital issue.
"Player safety and welfare is paramount; we hope that the trials will be successful and leads to permanent adoption within football globally."
In 2019, findings from the PFA Charity funded FIELD Study provided the first major insights into lifelong health outcomes in former professional footballers. The results showed that former players were 3.5 times more likely to die from neurological conditions than the wider population.
Following the research, the PFA lobbied to introduce concussion substitutions in the Premier League, English Football League (EFL) and Women's Super League (WSL).
In December, IFAB, which governs the laws of the game, announced a trial to introduce permanent concussion substitutes and invited competitions to apply to be part of the process.
The Premier League, The FA and WSL have all committed to participate in IFAB's trial. The PFA will now speak to the EFL about working together to include their 72 clubs in this initial pilot.
The PFA believe the inclusion of EFL clubs will provide more data back to IFAB, but also help raise awareness and underline the importance of this issue to players and staff.
PFA Chairman, Ben Purkiss said: "The PFA welcomes the trial of permanent concussion substitutes. However, we would like to see this protocol implemented across all competitions, including the EFL.
"In addition, we will continue to engage in discussions regarding temporary substitutions. Temporary replacements have been used successfully in other sports. It provides medical teams additional assessment time and reduces pressure on injured players to return to the field of play."
The trials of permanent substitutes will help determine whether the rule should be extended throughout football, and feedback will be given to the IFAB's annual general meeting in early March.
As part of plans around improved protection for current players, the players' union also wants to see interventions introduced in other areas of the game.
The PFA has called for a reduction of heading in training and will be working with the clubs, leagues and The FA to create a coordinated strategy to measure, monitor and adapt training, identifying protections that can make a difference to the long-term health of players.