British pair Sonay Kartal and Katie Boulter were knocked out in the US Open first round as conditions heated up in New York.
Kartal, who has been managing a knee niggle in recent months, suffered physically in a 6-3 1-6 6-1 defeat against Brazilian 18th seed Beatriz Haddad Maia.
Boulter, 29, lost 6-4 6-4 to Ukrainian 27th seed Marta Kostyuk as she was unable to turn around her Grand Slam struggles.
A bizarre deciding set saw a limping Kartal trail 3-0 before being handed a lifeline when Haddad Maia's movement also became hampered - seemingly down to cramp.
Points became slow and laboured in testing conditions - but neither player refused to give in.
Haddad Maia lost serve for 3-1 as she could barely walk but recovered sufficiently, helped by the vocal support of a boisterous set of Brazilian fans, to serve out a remarkable victory.
Kartal, who was making her debut in the US Open main draw, also appeared to be struggling with the knee problem which she had strapped during her memorable run to the Wimbledon fourth round in July.
Kartal, who has been managing a knee niggle in recent months, suffered physically in a 6-3 1-6 6-1 defeat against Brazilian 18th seed Beatriz Haddad Maia.
Boulter, 29, lost 6-4 6-4 to Ukrainian 27th seed Marta Kostyuk as she was unable to turn around her Grand Slam struggles.
A bizarre deciding set saw a limping Kartal trail 3-0 before being handed a lifeline when Haddad Maia's movement also became hampered - seemingly down to cramp.
Points became slow and laboured in testing conditions - but neither player refused to give in.
Haddad Maia lost serve for 3-1 as she could barely walk but recovered sufficiently, helped by the vocal support of a boisterous set of Brazilian fans, to serve out a remarkable victory.
Kartal, who was making her debut in the US Open main draw, also appeared to be struggling with the knee problem which she had strapped during her memorable run to the Wimbledon fourth round in July.
