The 100m world record holder clearly struggled with the different requirements needed for football and was struggling for breath after a gentle four lap warm-up jog around Central Coast Stadium this morning.

During the lengthy 90 minute training session in front of celebrities including NRL legend Brad Fittler and Australian sprint ace Matt Shirvington, Bolt often looked to be suffering, frequently walking with his hands on his hips or sitting or lying on the turf as he caught his breath.

"I'm doing the programs with the guys now," he said after training. "It shows I'm getting better and I have to keep pushing myself.

"The more I play, the more comfortable I get. It's all about fitness and getting touches of the ball. I'll be fine. I think they're pretty happy with the effort I've been putting in.

"I've going through the paces, doing what they say and trying to get up to speed.

As a sprinter he is used to sudden quick bursts of energy, focused on one direction with plenty of time for recovery... which is very different to the way football is played and its sustained energy requirements and frequent change of direction.

He admitted the most challenging aspect of the transition from sprint star to budding footballer was the stop and go drills.

"I'm not used to the back and forth," he said. "It's all about practising, going through the rounds and pushing myself to get used to the system.

"I have time so I'm just going to take my time."

Mariners new coach Mike Mulvey admitted Bolt's skills were "rudimentary" after seeing him in action today. 

"He's going through these motions," said the former Brisbane Roar coach. "He's had a few individual sessions.

"I think the thing that he's struggling more than anything else right now with getting used to the football fitness

"When you do track and field it's virtually a straight line and a track coach will never ask you to decelerate or accelerate the way that we do.

"It's multi-directional movement in football so we have to get used to that so we're quite pleased with the way he's progressing.

"He'll be sore every night because the sessions are quite gruelling but he's determined."

Bolt played a far greater role in today's training session compared with the similar session last week which he largely sat out after the warm up.

Today he got involved in ball drills and attacker-defender action, although he tended to steer clear of tackles and struggled to control longer balls sent cross field towards him.

He showed basic skills on the ball, capable of making and receiving short passes but often without too much urgency, and towards the end of the session became largely anonymous on the wing.

Mulvey admitted: "He's doing okay. The thing that we're asking him to do is something that he's not done for quite a number of years.

"He plays football as a as an athlete in between athletic meets and things like that. So he's got rudimentary skills, no problem about that.

"It's about being able to do at the speed that we do it."

But Bolt enthusiastically embraced a shooting drill as the session drew to an end and fired three shots at goal, two on target but easily saved and one more powerful shot which went over the bar.

Bolt will be the star of a trial match at Central Coast Stadium on Friday night when the Mariners take on a local select side, with the sprint star expected to come on for the last 15 minutes or so.

"There will be nerves," Bolt admitted today. "It's not like it's a charity game any more. This is a career I am pursuing.

"I expect to make mistakes but I also expect to push myself and make myself proud. It's just on elf those things...I know I'm not going to have a perfect game!"

Mulvey added: "I don't see him as this or that I see him as you know he could play in the number of positions so we'll see what best suits the team on Friday."

The coach paid tribute to the impact Bolt has had on the squad since his arrival last week.

"When Usain Bolt walks through the door you don't lower your standards so I've seen an uplift in the quality

"It's a really good team spirit you can see there's a lot laughing and joking but also, once we cross the line, it is very, very serious."