Push athletes in the four-man bob push at retractable side bars. What the rules specify, what studies show and why the technique is built only with a coach.
In the four-man bob the two middle push athletes do not push from behind but sideways at retractable push bars. The honest answer to "Isn't that just sprinting?": no. It is sprinting with a load that decides tenths of seconds, on ice, in spikes and with hands on the bar. Together the crew gets a sled of at least 210 kg rolling [1]. The whole combination with crew may weigh up to 630 kg [1].
The IBSF rules fix the geometry: the side push bars must be retractable, and they must be 670 to 870 millimetres above the standing surface of the runner carriers, roughly hip height of an adult. The total width of the side push bars of the second and third person may not exceed 750 mm [1].
The push itself is hip-dominant. A study of 15 elite male athletes recording ground reaction forces and 3D movement found that start acceleration comes mainly from hip extension and that bobsleigh athletes, compared with free sprinting, rely more on hip than on ankle work [3].
The push is not a race track but a team project in 50 metres.
Entry criteria (practice standard):
The push athletes' goal: to accelerate the sled in the start phase as fast as possible so the bob enters the track at high speed. The specialist literature names as the common objective of the start techniques accelerating the sled precisely and quickly to optimise the speed after loading [2].
Milestone: You explain to the coach what a good start should achieve.
Under the IBSF rules the start block may be stepped on during the start procedure, but the rear edge may not be crossed [1]. That is a rule often forgotten in training because nobody stops the time there. Practise it all the same. The whole team must be present after the call to the start, and the timing must be triggered within 60 seconds [1]. Pushing by third parties is forbidden [1].
Milestone: You know the start rules and keep them in training.
In start acceleration hip extension acts dominantly, with increasing speed the ankle's contribution grows and the knee's falls [3]. Your training therefore relies on strong hip extensors, not just running speed. For you that means deadlift and jump variants belong in. That is a conclusion from the study, not a recipe; your coach plans.
Milestone: You have a training plan with hip and trunk strength.
The hands grip the side bar, the body stands in a staggered position behind the bar [2]. How exactly you place hands, feet and steps is technique you learn with a coach at the push track. A study of the two-man bob found that pilots at the side bar push in a half squat with marching steps [4]. That applies to the two-man; the four-man middle has not been studied, and we do not generalise it.
Milestone: At the push track with a coach you push the standard technique and he no longer corrects you.
When speed is high and you work with the trunk extended, the load on the back of the thigh and the posterior chain rises, which favours acute muscle injuries [2]. So: warm up, build up, no maximal sprint cold. Hamstring injuries heal slowly, and in the bob the way back leads through the push track, not the ice track: plan weeks rather than days for the return. (practice)
Milestone: You train 10 weeks in a row without hamstring complaints. (rule of thumb from practice)
Train the hips without running: heavy hip extensions and jumps, fast and controlled, in the weights room with a coach. That builds the drive without overloading the hamstrings in sprints. It is a conclusion from the hip-dominance study [3], not a ready-made training method; your athletic coach plans it.
The sled with runners must weigh at least 210 kg, the bob with crew and equipment at most 630 kg [1].
670 to 870 millimetres above the standing surface of the runner carriers [1].
Mainly from hip extension. Studies of the start show hip dominance [3].
The specialist literature describes a sprint start over about 50 metres before the crew loads [2]. In a two-man bob study the pilot ran 20 to 30 m, the brakeman around 50 m [4]. Push training on a push track prepares it.
No. You learn the bobsleigh push at a push track or on the bobsleigh track under supervision.
Brakeman Push at the Rear: The Longest Distance and the Most Work