How are stretch reflexes modulated during voluntary movement?

How did the bodies of animals, including ours, become such fine-tuned movement machines? This paper cuts directly into critical debates about how the ancient spinal cord and the relatively new human brain interact to produce smooth movements and how some neurological conditions disrupt this fine balance and produce slow, inaccurate, jerky, etc. movements in neurological conditions. It adds to the thought leadership about the processing of sensory information and control of reflexes during voluntary movements -- with implications as to how its disruption could give rise to motor disorders in neurological conditions like stroke, cerebral palsy, and Parkinson's disease.