Safety report following ISO-20957 guidelines
Wormermeer, 07-10-2024
Vertical pulling tests
At Hartech our Nordbelt was tested multiple times for maximal pulling force until breakage. We measured it took on average 1552 Newton of force untill breakage of the Nordbelt from 1 side. The weakest link was our buckle made out of of zinc alloy.
Forces during NHC
How much force can a person create using the Nordic Hamstring Curl? Eccentric knee-flexor strength, as assessed with the Nordbord, is largely BM-dependent. Buchheit et al. found that strength in soccer players followed this formula: Eccentric strength (N) = 4 × BM (kg) + 26.1.
We measured our own
Basic physics
Nordbelt works as a pulley because of it's multifocal attachment. Resulting that the tension in the Nordbelt is equal to the force generated by the person divided by two. Tension in the rope (N) = 0.5 x Eccentric strength (N).
Tension in the rope at breakage (N) = 2 x BM (kg) + 13.05.
Six times the margin
Because of the ISO-20957 guidelines we need a margin of safety six times the maximal force a person can generate with the Nordic Hamstring Curl. Therefore Tension in the rope at breakage (N) = 6 x (2 x BM + 13.05)
1552 = 12 x BM + 78.3
12 x BM = 1473.7
BM = 122,8kg
That is why our Nordbelt is intended for users up to 122,8kg.