I well remember the start of two-a-days one August...Morning practice, Coach picked two captains, who then picked their team in alternating fashion. Shorts, t-shirts and helmets..
Half of each team was lined up on the back line of the end zone, with the other half 120 yards away on the opposite end line. Relay races, on the whistle. First, sprint. Then, sprint backwards. Bear crawl, Crab crawl and finish up with a regular sprint.
Winner gets to run a half-mile, loser gets to run a mile. Ok guys, take ten, then we're hitting the pool. Same teams. Relay races in the pool. Hit the showers and break off in groups for skull sessions.
Afternoon was much the same, except after out football field races and half-mile or mile runs, we started putting in offense and defense. Second week, we dropped the races and put on the pads for the next two weeks.
Small fact of life...you can run and projectile vomit at the same time.