Vertical caving terminology and methods > Prusiking systems, prusiking methods > Step or rope walking systems, sit on the heels systems
A step system for prusiking, which remains popular in some parts of the USA. The legs perform most of the work, and the arms are each used for moving an ascender upwards. The steps are somewhat smaller than rope walking, and the gain feels a little limited considering the effort. While is not widely used for vertical caving, it still has a significant number of users, typically in regions where indestructible rope technique is used. The three phase system variation is perhaps the most common configuration. The Mitchell system can be used for prusik loops.
This system is more inconvenient than the frog system for passing rebelays and deviations, but better than rope walking. It can be used for passing a knot while abseiling or prusiking, but the position of the lower jammer makes this more awkward while abseiling. Reverse prusiking is relatively easy compared with some other techniques. This system is particularly awkward for bottom weighting, since the feet move separately and cannot trap the rope, and the hands are also occupied and cannot pull the rope through the lower jammer. The only remaining option is to push the cam open of the lower jammer, but this really is very fiddly. Mid-rope changeovers are relatively easy. This system lies half way between rope walking and the frog system, in terms of energy transfer efficiency. It is very awkward for sloping pitches, both because of the angle that it pulls the caver compared with the rope, and because neither hand is free to push away from a wall. Taking a rest requires one leg to be bent, so that the top jammer can be lifted. Can be tiring for the arms on long pitches, but the arms can swap roles occasionally to give muscles a rest. The three phase system variation provides perhaps the most flexibility of any prusiking system, though none of them are really convenient for Alpine rigging. In particular, it is useful for crossing the lip of a pitch when using indestructible rope technique, because the ascenders can be swapped over to get one of them past the lip at a time, while always having two ascenders connected to the rope, though since one of them has no safety cord in that variation, this cannot be done safely.
Uses a chest roller with two pulleys, a top jammer with a footloop and a lower jammer with a footloop. The footloop for the top jammer passes through one of the pulleys of the chest roller, while the main rope passes through the other. Both ascenders have safety cords. For sloping pitches, the chest roller is often disengaged, turning it into the Plummer system or Texas system depending on whether you use the top jammer's footloop or not. The sit harness plays a seondary role for safety only. The chest harness is essential for support while the chest roller is engaged.
The three phase system variation (also known as a Cuddington three phase system or third phase system) is the same basic setup as the Mitchell system, without a safety cord to the top jammer. Instead, it has an additional quick attachment safety that is attached to the sit harness via a safety cord. The quick attachment safety is normally not used, when working in Mitchell system mode (phase 1). However, if the Mitchell system chest roller is going to be disabled, then there are two options. Phase 2 has the quick attachment safety connected to the rope instead of the top jammer and chest roller, so that it becomes a top jammer. This results in the system becoming the Texas system. For phase 3, the quick attachment safety is connected to the footloop of the top jammer. This means that the safety cord, quick attachment safety and top portion of the footloop act like a safety cord to the top jammer. This results in the system becoming a Plummer system, with a crazy safety cord that wastes an expensive ascender, just so it could be used to walk up a slope. It would have been better to simply use a safety cord to the top jammer, which would also work as the Plummer system or Texas system depending on whether you use the top jammer's footloop or not, and would have therefore provided the same flexibility, as well as providing safety in case the lower jammer fails. Or use the chest jammer normally like the frog system and remove the lower jammer or clip it to the opposing footloop so both feet work together. Or just anything more simple than the approach that was actually used!
A benefit that the quick attachment safety is supposed to have, is that when crossing the lip of a pitch which is rigged using indestructible rope technique, the quick attachment safety can be clipped to the main rope. The top jammer can be disconnected then clipped on above the lip, providing a higher footloop to stand in while the quick attachment safety is then disconnected to get past the lip. This would allow there to always be 2 ascenders clipped to the rope. However, this theoretical benefit is counteracted by there being no safety cord to the top jammer, so there is only one ascender connected safely to the rope at one point during the manoeuvre, defeating the main purpose of using the quick attachment safety instead of just using two ascenders. A standard chest jammer could instead be used, connected directly to the sit harness, and then the top jammer could have a proper safety cord. This would give the same advantage at the lip of a pitch, but with far better safety. Or better yet, use Alpine rigging, and avoid the problem altogether!
The stair step prusik is the same basic idea as the Mitchell system, done with prusik loops. A carabiner is used instead of the chest roller, and the foot loops are normally passed through the sit harness (which adds a lot of friction). The lower prusik loop is placed a little higher so that it can be more easily reached and pushed upwards, but this limits the range of motion more.
This system was invented by American caver Richard "Dick" L. Mitchell in the USA for mechanical ascenders in 1967, using a simple carabiner instead of a chest roller, as a progression from the Jumar system, trying to keep the ascenders apart so that both legs could have equal priority while taking bigger steps. Originally it was thought to be fast, but probably too energetic for big pitches - something it is actually very good for. The chest roller was added in 1969 by American Keith Wilson. American caver William Franklin "Vertical Bill" Cuddington developed the three phase system variation some time between 1969 and 1974, starting with the Mitchell system as a base. The Mitchell system was described as the stair step prusik in Mountaineering: The Freedom of the Hills edited by Don Graydon in 1992, but this was literally the original Mitchell system with no further developments, so it is not considered to be a separate variation of the system here.
This history section only covers the Mitchell system. This article also has a detailed history of many of the other devices and techniques that are used for vertical caving.
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