their moment arms are small. As a result, at maximum PM contraction, severe compression forces and large shear forces act on the lumbar motion segments, vertically crumbling the LS in a sigmoid fashion and forcing it into lordosis while severely shearing the L5/S1 segment.The PM, therefore, cannot be intended to act on the
LS, they argue, but only on the femur. Overstressing the PMs in, for instance, ‘sit-up’ exercises, may dangerously overload the LS.
their moment arms are small. As a result, at maximum PM contraction, severe compression forces and large shear forces act on the lumbar motion segments, vertically crumbling the LS in a sigmoid fashion and forcing it into lordosis while severely shearing the L5/S1 segment.The PM, therefore, cannot be intended to act on theLS, they argue, but only on the femur. Overstressing the PMs in, for instance, ‘sit-up’ exercises, may dangerously overload the LS.
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