Crystal Palace goalkeeper Wayne Hennessey has revealed the secret behind their form improvement.

To try and improve general fitness levels among the squad, Palace have introduced Altitude Resistance Masks, which simulate altitude training to allow players to push and increase their heart rates without having to exert as much physical pressure on their bodies.

Hennessey insists that the masks, made by Dubai-based company Altitude Mask, have been a real benefit to the players.

"The masks have really been a massive help and are giving us additional benefits as we prepare for the challenges that come with playing in the Premier League," he told the club website.

"All the lads have really taken to them and are seeing the benefits to their overall fitness levels and those who are coming back from injury and doing rehab with the coaches are also using them and seeing the advantages of the masks."