The brakeman loads last from behind when the speed becomes too high to run along. What study, rules and literature say and why a coach is essential.
The brakeman runs longest and loads last. The honest answer to "When does he jump?": when he can no longer run at the speed. That is how the first study of the two-man bob start describes it: the brakeman runs around 50 metres until the speed is too high, and then jumps into the sled from behind [3]. That is an observation of top teams, not an instruction.
In the four-man bob the same idea applies in a chain: the clinical literature describes that the crew loads beyond the crest from front to back, in a planned sequence that influences speed as little as possible [2]. The brakeman is the last link of this chain. He also bears responsibility for braking the bob after crossing the finish line [2].
The rules provide the frame: the bob must have a working brake, and in the four-man bob the brake handles lie to the left and right of the brakeman [1]. The rulebook also demands that athletes have a hold in a crash, so every bob has enough hand holds [1].
The brakeman comes last, but everything depends on him.
Entry criteria (practice standard):
The pilot loads first, then the push athletes from front to back, the brakeman last [2].
Milestone: You explain the chain and your place by heart.
The brakeman runs until the speed becomes too high for him [3]. This feel comes only through repetition at the push track and on the track under supervision. It helps if after every run you say in one sentence when you had the impression that the speed was "getting away". That turns a gut feeling into a repeatable point that the coach can compare with the video. The sources I read give no figures in km/h for when this happens.
Milestone: In practice runs you recognise the moment at which you can no longer run along.
The brakeman's handles are immovable [1]. Hands and grip must sit securely before you leave the ground. Before every run check that gloves and grip surface are dry and grippy; on ice and in the cold much slips that seems secure in the hall. (practice) Exactly how the transition from running to sitting works is technique you learn with the coach and not from a text.
Milestone: You know the grip and check it with your eyes closed.
After loading you sit with the head tucked and the trunk maximally flexed [2]. Because you sit at the rear, you have the brake handles on your left and right [1]. You stay still until the finish line is crossed.
Milestone: You sit still, with hands on the hold, until the finish.
The brake is your task after the finish line. The literature names the brakeman responsible for braking in the outrun once the finish line is crossed [2]. How you operate the brake is in the guide on braking in the outrun.
Milestone: In training you brake only on the coach's call.
In a bob crash, according to the clinical literature, athletes can be ejected and lose contact with the sled further up the track [2]. That affects the bob in general, not every position equally; the sources I read give no exact figures by position. That is why hand holds are mandatory [1], and why training under supervision is part of it.
Agree a mini-briefing with your pilot before every run: when you load, who calls, what happens in case of a disturbance. The sports physiotherapy commentary stresses an integrated team of support, medicine and training [2]. The concrete agreement is practice, not a study finding. Keep it short: three sentences everyone knows in their sleep beat ten that get lost in the start house. And repeat it before every run, even if you have known each other for years.
When he can no longer run at the speed; in a two-man study after around 50 metres [3].
At the rear; in the four-man bob the brake handles lie to his left and right [1].
After crossing the finish line [2].
Bobsleigh is a risk sport; Olympic data name 14 to 18 percent injuries in bobsleigh [2]. So train with a coach.
Only at a push track or in try-outs with a coach. Not on your own.
The Pilot Loading: First Into the Bob and Steering at Once