LONDON // McLaren-Mercedes's Lewis Hamilton reported back to work in peak condition after a winter workout high in the Colorado Rockies.
The 2008 world champion had not driven a Formula One car since last November but he returned to the cockpit at Spain's Valencia circuit with a clear sense of optimism about the campaign ahead.
With a new full-time trainer in Finland's Antti Vierula, who has previous experience coaching Olympic athletes, Hamilton said he had gone higher than ever to make sure he started the season fitter and faster than ever.
"It's perfect being at high altitude, it's a lot more hard work so that when you come back down to sea level you really start seeing the benefit," he said after lapping in last year's car.
"I just enjoy it. Waking up in the morning and going hiking up a mountain with clear blue skies: There's no substitute for that...it's also good for the soul, good for your spirit, to be in nice beautiful places."
Hamilton said he felt fitter than ever after training two or three times a day.
"I think every year I always approach the same but sometimes your training doesn't go as well, or you are more drained by appearances that you do, or certain things that you do," added the 26-year-old.
"This year it has been a lot clearer and the training has been a lot better and more efficient. I'm feeling a lot better about the car and I always want it more."
Hamilton will also have his father and former manager Anthony around the paddock more than last year, when they ended their business relationship, since Hamilton senior is now managing the British rookie Paul di Resta at Force India.
The McLaren driver has yet to appoint a new manager but he said that situation was close to being resolved as well with clear candidates identified.
His team are due to unveil their new car in Berlin on Friday, later than their main rivals who already had theirs on track in Valencia.
Ferrari's Fernando Alonso, his every move followed by eager fans on home soil, was quickest on the second day of the season's first test in the new F150.
Sebastian Vettel, Red Bull's world champion, was second on the timing screens on a frustrating day for Australian teammate Mark Webber who managed only 17 laps late in the afternoon after set-up problems.
Pastor Maldonado, the Venezuelan rookie, had his first taste of the new Williams while Team Lotus gave their T128 its track debut, although their running was cut short with a power-steering problem.
Mexican newcomer Sergio Perez also had his first outing in the new Sauber, completing 42 laps despite long hours in the garage wrestling with various problems.
"It was a difficult day with not much running and we obviously could not complete our programme," he said. "But for me it was still good to get my first laps in the new car, and I am beginning to feel confident with it."