Foot locking is probably the most energy sapping event in the tree climbing comps. Over the 15 meter climb you have gravity really working against you. The higher up you go, the more energy expended and the heavier the rope becomes to lift with your feet. For example the weight in Velocity at the top of your footlock is 2.49kg - Globe 5000 10mm would weigh in at only 1.74kg - that's 750g lighter! If you are using a semi-static ( EN1891A PPE rated) footlocking line, like Tachyon you will also have potentially, up to 5% extension in the rope (depending on rope choice) which equals even more energy lost.
Foot locking champs have recognized the above problems. To counter the effects of weight and rope extension top climbers have moved to lighter, thinner diameter static ropes. The two most popular static foot locking lines are Teufelberger Globe 5000 and Liros Racer 10mm. These are completely static, lightweight lines, not designed for treeclimbing, and have virtually no sheath slippage or rope extension. Both ropes sport a 32-plait polyester sheath over a high-strength dyneema core. They are NOT rated for PPE and should NEVER be used as a climbing line.
Using one of these ropes, a fall using a static foot locking strop (eg one made from Armor-Prus), when it is at its loosest point (eg following rope-over-foot crouch) will put severe stress on your body. Since the rope and strop are completely static you need to build some form of energy dissipation into the system in the event of a fall. Using a 8mm 'dynamic' footlocking strop instead of, say Armor-Prus, is the cheapest solution but there are also specialist energy dissipation devices available which allow the rope to 'give' when impact loaded (as in the event of a fall).
Treetools will stock limited amounts of Globe 5000 and Liros Racer for competition climbers only. It will be listed on the website about mid-February but will only be sold POA (Price On Application).
Below: Bernd Strasser preparing to foot lock on 10mm Globe 5000