Well some soldiers in communist Warsaw pact during cold war were running in the masks.But that were gas masks you know.
By the way - some "joke":
The little son asks his daddy, who is a sergeant in the army:
Daddy, make the elephants run.
But son, elephants are very tired.
But I'm asking you, Daddy.
But son, the elephants are barely alive!
But I'm really asking you a lot. One last time. Let the elephants start running again.
Okay, but it's the last time. Soldiers! Attention! Wear the masks! Four extra laps!
The reality is however -that happened in authoritarian countries and military not respecting conscript recruits. Sometimes it was said soldiers puked in those masks,there were even causes of suffocation because of that. But such training is possible in military - even in USA:
https://www.army.mil/article/56338/soldier_breaks_world_record_running_marathon_in_gas_mask
Well some soldiers in communist Warsaw pact during cold war were running in the masks.But that were gas masks you know.
By the way - some "joke":
The reality is however -that happened in authoritarian countries and military not respecting conscript recruits. Sometimes it was said soldiers puked in those masks,there were even causes of suffocation because of that. But such training is possible in military - even in USA: https://www.army.mil/article/56338/soldier_breaks_world_record_running_marathon_in_gas_mask