EXSC 351 Lecture 16 Study Guide – Stability, Postural Control, Reactive & Proactive Responses 2026

This document contains structured lecture notes and key definitions from EXSC 351 Lecture 16 (2026), focusing on stability, postural control, muscle tone, reactive and proactive postural responses, and central nervous system (CNS) mechanisms involved in maintaining balance and joint integrity . The material presents foundational biomechanics and neuromuscular control concepts essential for understanding injury prevention and motor performance. The lecture begins by defining stability as the ability to counteract internal and external forces that disrupt body, limb, and joint integrity, and explains postural control as the regulation of alignment, orientation, and tone. It distinguishes whole-body balance, segmental stability (core stability), and joint stability, including arthrogenic muscle inhibition. Key components such as alignment (body positioning relative to itself), orientation (position relative to the environment), and tone (resistance to movement) are thoroughly described. Muscle tone concepts are analyzed in depth, including passive muscle tone (elastic properties of the muscle-tendon complex), active muscle tone (neural activation), and postural tone (use of tone to maintain integrity and dampen forces). The document clearly differentiates reactive postural responses (after destabilization) and proactive postural responses (before destabilization), including sensory-evoked proactive responses and anticipatory postural adjustments (APAs). The lecture further explains the four mechanisms of postural control: sensory mechanisms (proprioceptive, visual, vestibular), musculomechanical mechanisms (passive structural stability), neuromuscular mechanisms (muscle activation patterns), and CNS mechanisms. It details three CNS levels involved in postural control: reflexive (spinal, hard-wired responses), autonomic (supraspinal, adaptable and experience-modified), and voluntary (conscious, less efficient with limited experience). The final model integrates reactive and proactive responses across these mechanisms and levels to explain how body, limb, and joint stability are maintained during motor tasks. This document is particularly relevant for: Students enrolled in EXSC 351 or Motor Control and Biomechanics courses Exercise Science, Kinesiology, and Athletic Training majors Students preparing for exams on postural control and neuromuscular mechanisms Learners reviewing balance, stability, and CNS-mediated motor regulation concepts Keywords: stability definition internal external forces, postural control alignment orientation tone, whole body balance segmental stability joint stability, arthrogenic muscle inhibition, muscle tone passive active postural tone, reactive postural responses feedback control, proactive postural responses feedforward control, anticipatory postural adjustments APAs, sensory evoked proactive responses vision, proprioceptive visual vestibular feedback, musculomechanical mechanisms passive stabilization, neuromuscular mechanisms muscle activation coordination, CNS mechanisms spinal supraspinal networks, reflexive level spinal cord responses, autonomic level adaptive supraspinal control, voluntary level conscious stabilization, sensorimotor integration postural model