What factor primarily determines the capacity to lift a load?

The capacity to lift a load is primarily influenced by the horizontal and vertical position of the load. When considering the mechanics of lifting, it's crucial to note that the position affects the angle of lift and the distribution of weight. If a load is positioned closer to the body, it is easier to lift than if it is extended away from the body; this is due to the leverage and strain on muscles and joints. Similarly, raising a load vertically versus lifting it at an angle can significantly impact how efficiently and safely a load can be moved.

In contrast, while the weight of the load is important, it is not the sole determinant of lifting capacity. The shape of an object could affect grip and stability but does not have the same direct impact on lifting capacity as position does. Age might influence a worker's strength or experience, but it does not inherently change the fundamental principles of how load lifting mechanics work.