Whoever sits behind the pilot is responsible through stillness. What the posture means, what studies say on head loads and why you learn it with a coach.
When the bob is on its way through the ice channel, the push is over and your task as push athlete or brakeman changes: you sit, you make yourself small and stay still. The honest answer to "Do I still have to do anything?": yes, you must move almost nothing, and that is the art. The pilot steers, you do not disturb.
Clinical literature describes the posture of the push athletes thus: they adopt a seated position with head tucked and trunk maximally flexed [2]. The pilot sits in front and steers, behind him the push athletes sit in this crouched posture [2].
Why the posture matters: head and neck are loaded in the ice channel. A study of 12 bobsleigh athletes wearing a mouthguard with an accelerometer recorded 1900 head acceleration events over 48 training and 53 competition days. The peaks averaged about 12 g (men 12.4 g, women 11.9 g) [3]. 12 g means: your head briefly experiences twelve times its weight force. That is no small thing.
Whoever sits still protects himself and the crew.
Entry criteria (practice standard):
After loading the push athletes sit with the head tucked and the trunk maximally flexed [2]. Your coach shows you the posture on the ground in the sled or in a dry model. It is preparation, not training for home. What matters is that you can hold the posture without pain even after several minutes. Mention complaints in the neck, lower back or hips at once instead of sitting them out.
Milestone: You explain the posture and why it is chosen, without looking.
Because the pilot steers, you want no uncontrolled movements. The bob is a system of pilot, crew and sled, and every shift changes the behaviour. How much movement is wanted when, the pilot or coach tells you. That is practice, not documented.
Milestone: In an exercise on the ground you sit still for 60 seconds without changing position.
Under the IBSF rules hand holds are mandatory so that athletes can hold on in a crash [1]. You hold on, but without cramping. Cramped muscles tire and raise the injury risk. (practice)
Milestone: You find the hand holds in the sled blind.
Sports physiotherapy suggests training neck strength and stability because of the required head position, to reduce head accelerations and concussion risk [2]. In the mouthguard study men had greater neck strength than women, but the head loads did not differ [3]. That means: neck strength matters but is not a free pass.
Milestone: You have planned neck training with your coach.
Concussions are common in sledding sports: according to a systematic review 13 to 18 percent of sledding athletes are affected [4]. Athletes coined the term "sled head" for the complaints [4]. Report every headache, every dizziness, every light-headedness after the run immediately. Whoever has a "fog in the head" after a run does not continue until a doctor has seen them. That is a practical rule and applies regardless of how strong you feel.
Milestone: You know the symptoms and report them immediately.
Sliding is risky, even for pros. In an analysis of injuries at the Whistler Sliding Centre over four years and more than 43,200 runs, the overall injury rate was 0.5 percent of runs, severe injuries under 0.1 percent. More athlete experience reduced injury frequency [5]. A fatal accident resulted from being thrown out of the track [5].
Before the first run do a "mind run": close your eyes and imagine the run, with your posture and your seat. Sliding athletes use such mental runs as a fixed part of training [2]. The effect is not documented in figures in studies, but it prepares you calmly.
Push athletes sit with the head tucked and the trunk maximally flexed [2]. A coach shows you the exact execution in the sled.
Under IBSF rules a full-face helmet to ECE, OKM or DOT standard that is commercially available [1].
In a study of 12 athletes, 1900 head acceleration events were recorded over a season, with peaks averaging about 12 g [3].
A systematic review names 13 to 18 percent of sledding athletes [4]. Report at once if you suspect it.
No. You learn the posture in the sled and dealing with the track only with a coach.
Pushing at the Side Handle in the Four-Man Bob: Getting Force Into the Sled