Republic of Ireland manager Carla Ward said she had players "begging to come off" due to the heat in Ohio in their 4-0 friendly defeat against the United States.
Temperatures reached 30C during the game at the TQL Stadium and, despite cooling breaks in each half, the Republic struggled with the heat.
Whilst Emma Hayes named a completely different starting 11 from the first friendly between these two sides four days ago, Ward made just four alterations due to the Republic missing a host of regular starters.
She said she was forced into more changes during the game to protect her players' health.
"On 22 minutes we had players asking to come off, unfortunately, we couldn't make those changes, then at half-time, three enforced changes as players were physically fatigued and some unwell," she told RTE.
"In the second half players were almost begging to come off and we couldn't do anything about it.
"We can't do anything about the heat, but it is dangerously hot out there and with humidity at 94%, I have never felt anything like it."
Given the concerns about the conditions, the heavy nature of both defeats and the depleted squad, Ward was asked whether the decision to play two end of season friendlies in the USA was beneficial to the Republic, who face a Nations League play-off against Belgium in October.
The former Aston Villa boss was adamant that the camp and the two fixtures against the number one-ranked side in the world have provided valuable learnings for her under-strengthened squad.
"We've looked at two different systems and ways of playing, we have added a couple of layers to what we are trying to do, and it has been such a positive camp overall," she added.
"Naturally, these two defeats hurt, but there has to be some reality to this.
"We played the best in the world, in extreme heat, something I struggled in without even moving, they're in season and we're not, there are many factors, but to still compete across two games, they can take a lot of heart."