Grenades are crazy powerful and this is just an incident that regularly happens everywhere (in every military) -- however! Looks like it happens more in China. They dug specific Grenade trenches for it and they both get up and carry on like it's "no biggie".
The smoke stream coming from the grenade is the fuse cooking off (4 seconds). It's worth noting that the Chinese don't require the use of body armor, or helmets during this training while the U.S. Does.
