British number one Emma Raducanu retired from her first-round encounter with American Ann Li at the Wuhan Open.
Raducanu looked devoid of energy and appeared to struggle with the hot and humid conditions as she trailed 6-1 4-1 in China.
The world number 30 called for the trainer after falling a double break down in the second set, and had her blood pressure and temperature taken before retiring.
Earlier this week play was suspended on all outdoor courts in Wuhan as temperatures reached 34C.
Defending champion Jannik Sinner retired with cramp in the third round of the Shanghai Masters this week, while 24-time Grand Slam champion Novak Djokovic vomited during his win over Yannick Hanfmann.