Figure 1.

The solid black line shows the actual trunk extension velocity (ω_T) of one older adult from slip onset to the instant of recovery (negative values indicate trunk extension). The dotted gray line shows the model-derived trunk extension velocity using the actual shoulder flexion velocities at each time point. The difference between the model-derived and the experimentally-derived data at the instant of recovery yields the variable Δω_T(recovery). The dashed gray line shows the model-derived trunk extension velocity calculated by using the maximum shoulder flexion velocity at each time point. Δω_Tmax is the maximum possible amount that the upper extremities could reduce trunk extension and is calculated at the instant of peak trunk extension, which in this case is the final data point.