The Spanish coach has called on the Belgium international to increase his endurance and has been pleased with the results, though insists he must keep working hard
Lukaku - who joined Everton on a season-long loan deal from Chelsea - has made a bright start to life on Merseyside, scoring five goals in as many Premier League appearances for the club.
|11/2||Romelu Lukaku is 11/2 with Coral to open the scoring against Tottenham|
"I do feel he is getting stronger for longer in games and remember, Rom [Romelu] plays with real power and that's the way he should be playing every time he's on the pitch," Martinez told EvertonTV.
"It was positive for him to finish the whole game against [Aston] Villa. Now he must try to carry on working hard and make sure that his strength and power can be there to help the team for the full duration of the game.
"Rom had a very important role [against Villa] and he took to it with real maturity and great responsibility and was very significant in us keeping a clean sheet in the game."
Lukaku will be hoping to play another 90 minutes when Everton play host to Tottenham on Sunday, which sees the Belgian face former boss Andre Villas-Boas.