When I served in a Line of Foot infantry Regiment in 1950 part of the yearly fitness test was the mile run in battle order with the SMLE No. 4 rifle followed by a 9 mile run and march alternating every 100 yards. Unfortunately I have now forgotten what times they had to be completed in. Route marches was still part of training in those days which were very tiring in hot weather as the respirator had to be worn for sometimes an hour or more. But still happy days!
PTI or ACI, runs back and forth during the 9 miler giving encouragement to all taking part; probably covers 12 mile or more during the nine mile march so needs to be lightly dressed and vest shows his specialism as PTI (Physical Training Instructor)
After serving 5 years in a Canadian airborne unit, I came to realize the stupidity of it all...like carrying an unloaded ten pound rifle everywhere you went It does help new recruits feel that perhaps they might be called soldiers ( wow, I'm carrying a rifle). I would make more sense if the rifle was carried like Australian troops, in a slung position.. but an empty rifle for ten miles at the shoulder or slope ? No , I am not suggesting that 17 year olds be given ammunition....and it is strength training, but, think about it. Ten pounds for hours a day, week after week, year after year. Perhaps the RAF should carry propellers...