Quantifying Human Quiet Balance Performance and Control to Inform Therapy

Addressing Balance Impairment and Fall Risk

• ⚠️ Falls are a major public health concern, affecting millions of older adults and stroke patients annually, leading to severe consequences including death and significant economic burden.
• 💡 Current balance assessments are often subjective and clinician-dependent, highlighting a critical need for objective, quantitative, and continuous monitoring methods, especially with an aging global population.
• 🎯 This thesis aimed to develop and validate methods for quantifying quiet balance ability and control in both unimpaired and impaired human participants.

Continuous Balance Performance Monitoring

• 🛠️ A novel algorithm was developed to quantify balance ability using force and motion sensors embedded in an instrumented cane, estimating established measures like sway velocity and Romberg quotient.
• ✅ The instrumented cane is ideal for continuous at-home monitoring as it travels with the user, allowing for tracking changes in balance ability and fall risk over extended periods.
• 🧠 Studies showed that hand motion was closely linked to body motion, providing valuable data for estimating sway velocity in both younger and older adults.
• 🚀 Future work includes expanding the method to diverse postures, integrating activity recognition, improving device robustness for real-world data collection, and extending its application to fall risk prediction.

Modeling Balance Control Strategies

• 🔬 The research investigated motor control mechanisms by developing a simplified double inverted pendulum model stabilized with an optimal controller (LQR) to reproduce human balance data.
• 📊 A novel intersection-point analysis, based on foot-force direction and point of application, was used to identify and quantify specific control strategies.
• 💡 This approach helped clarify the extent to which biomechanics and neural control contribute to balance, demonstrating that neural control plays a significant role in reproducing intersection point patterns.

Insights into Aging and Post-Stroke Balance

• 👴 Older adults were found to rely more on neural feedback compared to younger adults, potentially compensating for age-related effects like muscle weakness (sarcopenia) and increased neural delay.
• 🧠 In post-stroke patients, the non-paretic limb compensates for the paretic limb's abnormal coordination patterns by strongly favoring neural feedback, indicating altered control strategies.
• 🎯 The model revealed that ankle-hip torque coordination shifts significantly with stroke, suggesting compromised coupling mechanisms, joint weakness, and ankle over-stiffening in the paretic leg.

Impact and Future Directions

• 📈 This work enables timely detection of balance impairments and informs targeted therapeutic interventions by quantifying individual control strategies.
• 🏥 The methods offer potential as a diagnostic tool, allowing clinicians to identify specific impairments for personalized treatment in under a minute of testing.
• ✨ The long-term vision is an integrated system where clinic-based force plates quantify control strategies, and calibrated instrumented canes provide continuous at-home performance monitoring, ultimately preventing falls.