Limb accelerations during sleep are related to measures of strength, sensation, and spasticity among individuals with spinal cord injury

Wearable accelerometers are commonly used in clinical research as an inexpensive and unobtrusive means of measuring an individual’s movements, mobility, and physical activity, both within and outside of clinical settings. Limb accelerations (LA) as features calculated from an individual’s limb movements while asleep at night, which may capture accelerations from periodic limb movements (PLM), spasms, positional shifts, rolling, and turning. While asleep, an individual likely moves mostly subconsciously for comfort, pressure relief, temperature, or in response to other sensations.

• 1
  LA features were related to measures of impairment with models explaining 69% and 73% of the variance (R²) in strength and sensation, respectively, and correctly classifying 81.6% (F1-score = 0.814) of the participants into spasticity categories.
• 2
  The most commonly selected LA features included measures of power and frequency (frequency domain), movement direction (correlation between axes), consistency between movements (relation to recent movements), and wavelet energy (signal characteristics).
• 3
  Rolling speed (change in angle of inclination) and movement smoothness (median crossings) were uniquely associated with strength.