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Shouldn't I be wearing a chest harness?

Discussion in 'Tech Tips and Gear' started by ratagonia, Aug 18, 2014.

  1. ratagonia

    ratagonia

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    There is an oft-repeated claim, though it is perhaps now lost in antiquity, that climbers would be safer if they wore chest harnesses or full-body harnesses, rather than just a sit harness. I was asked today if we at Black Diamond (when I worked there) had any research on this issue. BD used to sell a chest harness, but of course, only a very tiny minority of climbers EVER used a chest harness.

    My response:

    There is no formal writeup on it, but we did do some research into the oft-repeated claim that climbers should wear a sit-harness. We found:

    A. the claim comes from the UIAA, from an old report (1960?) analyzed deaths in the Alps, and found that climbers hanging in free space who were unconscious or close to it died from asphyxiation. In how much time was not stated. These deaths from asphyxiation would have been prevented if the climbers had been wearing a chest harness; in which case the climbers would have died from exposure.

    B. I found no other sources of any kind of data to support this claim - just repetition of that the UIAA recommends this. This is the fallacy known as "Argument from Authority".

    C. A sit harness attaches to about the only part of the human body that can sustain substantial loads with out substantial damage. A sit harness encloses the center of gravity, and transfers the falling load to some of the largest muscles in the body, and is in the are of the three largest and strongest bones in the body (2 femurs, one pelvis).

    D. A chest harness attaches to a part of the body with flimsy bones around some of the most important organs in the body.

    E. If a fall is taken and load applied via a chest harness, the center of gravity is not within the grasp of the harness, and the body is likely to experience large and unpleasant torques. (An industrial full-body harness avoids this problem because all industrial harness users always fall upright in full control).

    F. The way climber's chest harnesses are used, with a sliding attachment to the rope, they are thankfully rather ineffective, there only result being that they pitch the torso forward until the sliding attachment hits the knot, and then essentially the fall is taken via the sit harness.

    G. Climbers do not use chest harnesses, take lots of falls, and rarely have an event where a chest harness would have improved the outcome.

    H. We did some testing with a very small (teen) climber and children's harnesses. We found that even on a small body, a full body harness essentially acted like a sit harness. The load was transferred into the sit harness portion of the harness and body, no matter what position the body was in then it hit the end of the rope. The high tie in point was responsible for some dangerous torques applied to the body when the faller irresponsibly did not fall perfectly vertically.

    I. While children do not immediately appear to have the well-defined waist one would want for a harness in a fall, on further inspection, the soft material from which most children are made falls out of the equation, and the harness grips them around the waist and thighs, as designed.

    J. If there is a problem with a waist-harness only, it is with poorly-fitted ones (not uncommon); with caving harnesses designed for climbing a rope with a chest harness/croll in place (which emphasize a low-as-possible tie in point at the waist, often lower than the center of gravity); and with certain men who carry a lot of mass in their upper body and/or have enough squishy stuff around the waist (aka "table-muscles") to disrupt a good harness-to-waist grip. A chest harness may be a good choice for some of these people, although the exact geometry of that is difficult to discern as different activities (climbing a rope, rappelling a slab, rappelling vertical or overhanging rock) have different parameters for effective use.

    No.

    Tom
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