StaBLE: digital metrics capture balance performance across a wide spectrum of balance tasks and abilities

Balance is fundamental to mobility and independence, yet it remains difficult to measure in a way that is both clinically meaningful and feasible for widespread adoption. There is a need for more quantitative, objective, and accessible balance assessments. To this end, we created the Stanford Balance Level Evaluation (StaBLE), a battery of 18 balance-challenging tasks and accompanying digital performance metrics computed from video that aimed to capture widely ranging balance abilities across 180 participants. We validated the StaBLE score against existing clinical scales and found that it correlated with age (ρ = -0.76, p<0.001), the Activities-Specific Balance Confidence Scale (ρ = 0.60, p<0.001), a Mini-Balance Evaluation Systems Test task (τ=0.55, p<0.001), 4-Stage Balance Test (τ = 0.55, p<0.001), and Short Physical Performance Battery (τ =0.57, p<0.001). StaBLE overcame ceiling effects in these existing scales and had a different underlying distribution for those identified at risk of falling and not (KS: 0.67, p<0.001). To reduce the time it takes to perform the test, we identified subsets of balance tasks that best predicted the StaBLE score across different populations. Together, our dataset, balance assessment protocol, and performance-based score demonstrate the validity of digital measures of balance.