Andy Murray said he felt his troublesome hip after the former world number one reached the Battle of the Brits semi-finals.
Murray's comeback gathered pace with a 6-3 7-5 win over countryman James Ward at the six-day charity event on Thursday.
The three-time grand slam champion, who had not played competitively since November due to a bruised pelvis and the coronavirus-enforced break, battled warm conditions to advance in Roehampton.
While physically exhausted, Murray said his movement was not affected against Ward.
"It's been tough, it's been unbelievably hot conditions in here," Murray said afterwards at the National Tennis Centre.
"I know it's not the worst situation to be in but usually if you're playing a match you'll find a cold space to go to and build up to the match and dropping your body temperature.
"But here there's no air conditioning allowed, it's pretty hot everywhere and it's quite draining.
"I've been feeling it a little bit and obviously I've played three matches, the last two were a pretty high level, it's been tough but I did quite well.
"Physically, it was a very tough match. I felt my hip a little bit but it did not affect my movement.
"When I played in November at the Davis Cup it was – my hip was sore and I was struggling to move.
"I felt I moved the best I had done in the three matches so that's a positive. I'm delighted I have a rest day tomorrow as I'm very tired."
