| 摘要 |
A beam having a triangular cross-section, with concave inward side walls forming substantially an equilateral triangle in cross-section, with a convex curved apex at the intersection of each of the three walls, the convex curved apex being formed of a rubber-like material and each having a different radius of curvature to thereby provide a rounded walking surface, each walking surface providing a different degree of difficulty and resulting in a different applied pressure to the foot of the user upon walking along the length of the beam.
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