Lando Norris said his practice time for this weekend's Styrian Grand Prix was limited by back pain, felt most acutely when racing through high-speed corners.
Norris scored his first F1 podium finish at the Austrian Grand Prix last weekend. This weekend's race takes place at the same venue, the Red Bull Ring.
After a Friday practice session which saw him given a three-place grid penalty for overtaking under cautionary yellow flags, Norris revealed he has been suffering with back pain for a while.
"I've been struggling a bit physically with something," Norris said. "I don't know what, which has been pretty painful and we've had to cut down quite a few of the laps that we were planning to do just to make sure I'm in good condition for tomorrow.
"It's not been ideal, especially coming off from last weekend. Not the best of days, to start the weekend, but we have a good plan of how to make it up."
Norris said the layout of the Red Bull Ring has made it especially difficult.
"I feel fine now and walking around but it's something that when I'm driving just causes me a lot of pain, particularly in the high speed corners and when I'm braking.
"So yeah, I've spoke to my specialist and he tried to figure it out but it's not as obvious as just pointing it out and so on. I've been on painkillers and whatever but it's been setting me back a lot today.
"It's been pretty frustrating, I've not felt confident in the car in terms of pushing it and so on, hopefully I can get fixed and be ready for the next one."
Reflecting on his grid penalty, Norris took full responsibility for what happened.
"It's my mistake to be honest. I was on a push lap, both of these guys were on an out-lap or a cool lap.
"I slowed up for the yellow flag, which you're meant to do, but I just continued to roll past the two other guys. It's my mistake. Bit stupid of me."