Lewis Hamilton says he is in peak condition for his hunt for a seventh F1 title this season - and believes Red Bull and Ferrari will have gained on Mercedes to create an epic and "rewarding" championship battle.
F1 2020 will be Hamilton's 14th season in the sport and it could also potentially be a historic one, with the Englishman closing in on Michael Schumacher's title and win records.
At winter testing in Barcelona, Hamilton and Mercedes have hit the ground running - setting the fastest times and completing the most laps so far.
"I really do feel the best I've ever felt," said Hamilton after his 106 laps in a busy morning session on Day Two.
"I've never done the race run and got out and asked if we could keep going. We just ran out of tyres. That's the first time in 13 years that I've asked to continue testing - because I don't like testing! It was quite good today."
Hamilton, who strictly follows a plant-based diet, added that he had upped his training sessions and was now "leaner".
"I'm at my optimum weight in terms of performance," he insisted.
Hamilton on hope for 'rewarding' title battle
After two long months without F1, anticipation for the new season is ramping up in Barcelona as the drivers test their 2020 cars for the first time. Much of the intrigue surrounding the campaign is around Red Bull and Ferrari - and whether they can finally stop Mercedes' unprecedented run of success.
The Silver Arrows have won both the drivers' and constructors' championships in six consecutive seasons, with Hamilton on top in five of those years.
The last three seasons have seen Hamilton and Mercedes challenged more than they were at the start of the hybrid era, and the six-time champion claims he wants even more battles in 2020, the last year before F1's major rules revamp.
"I race because I love racing other cars," Hamilton told Sky F1's Ted Kravitz. "I don't like driving around on my own on the track, that's for sure.
"I'm hopeful that in this last year of this era of car, the gap has closed. You saw it at the end of last year, the gap was closing between Ferrari and Red Bull and I anticipate that will be the same this year, we're going to have a closer battle and I'm down for that.
"That's what I think everyone wants to see, and from my point of view, it makes it more rewarding when it goes the way that I want it to go."
Mercedes turned heads with their debut of a new 'DAS' (Dual Axis Steering) system in Barcelona on Thursday - but Hamilton insisted that the team are already at their "peak amount of development" and won't find "huge gains".
"Those that are not at that peak have bigger [jumps] to make," he added.