Background/objective: To determine the effects of spasticity on anthropometrics, body composition (fat mass [FM] and fat-free mass [FFM]), and metabolic profile (energy expenditure, plasma glucose, insulin concentration, and lipid panel) in individuals with motor complete spinal cord injury (SCI).
Methods: Ten individuals with chronic motor complete SCI (age, 33 +/- 7 years; BMI, 24 +/- 4 kg/m2; level of injury, C6-T11; American Spinal Injury Association A and B) underwent waist and abdominal circumferences to measure trunk adiposity. After the first visit, the participants were admitted to the general clinical research center for body composition (FFM and FM) assessment using dual energy x-ray absorptiometry. After overnight fasting, resting metabolic rate (RMR) and metabolic profile (plasma glucose, insulin, and lipid profile) were measured. Spasticity of the hip, knee, and ankle flexors and extensors was measured at 6 time points over 24 hours using the Modified Ashworth Scale.
Results: Knee extensor spasticity was negatively correlated to abdominal circumferences (r = -0.66, P = 0.038). After accounting for leg or total FFM, spasticity was negatively related to abdominal circumference (r = -0.67, P = 0.03). Knee extensor spasticity was associated with greater total %FFM (r = 0.64; P = 0.048), lower % FM (r = -0.66; P = 0.03), and lower FM to FFM ratio. Increased FFM (kg) was associated with higher RMR (r = 0.89; P = 0.0001). Finally, spasticity may indirectly influence glucose homeostasis and lipid profile by maintaining FFM (r = -0.5 to -0.8, P < 0.001).
Conclusion: Significant relationships were noted between spasticity and variables of body composition and metabolic profile in persons with chronic motor complete SCI, suggesting that spasticity may play a role in the defense against deterioration in these variables years after injury. The exact mechanism is yet to be determined.