Everton, who are at 11th spot with 21 points, trail sixth-placed West Ham United by two points ahead of Monday night's meeting with Crystal Palace.
"Every foreign player has to adapt to the physicality of the Premier League but, for a striker like Rom, with his frame, I don't think he had the opportunity to play enough 90 minutes when he first arrived," Martinez told the British media.
"He had an incredible scoring ratio at (West Bromwhich Albion) but I think he played only seven full 90 minutes that season.
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"It's a long process to get to the stage where you can play 90 minutes without losing the power and the pace in every action but now it's very rare that you don't see him finish the last 10 minutes with the same power, pace and control.
"On top of that, he can play three games in a week, which is quite remarkable for a player of that size. I would say that's happening now for the first time this year."
Lukaku's presence has given his team mates an opportunity to build partnerships and develop an understanding with each other and the Belgian striker is near peak form after shrugging off the after-effects of last year's World Cup, Martinez said.
"Any player who can stay fit and reliable gives you an incredible base to work on.
"You can develop a good strategy with other players around them, the understanding of those players, the partnerships you develop.
"At the start of last season, he was catching up after the World Cup. From January, he's been the mature Rom who can play 90 minutes, and there's everything that comes with that."
(Reporting by Simon Jennings in Bengaluru; editing by Sudipto Ganguly)
