Anthropometric Prediction of Skeletal Muscle Cross-sectional Area in Persons with Spinal Cord Injury

Abstract

Skeletal muscle is a viable metabolic organ representing more than 40% of the whole body mass. Skeletal muscle atrophy following spinal cord injury (SCI) triggers a spectrum of health related metabolic consequences. Magnetic resonance imaging is considered the gold-standard technique in measuring muscle size in response to disuse and training. However, we are lacking a field method to accurately evaluate muscle size after SCI. PURPOSE: To establish and validate a prediction equation using mid-thigh circumference and skinfold measurements to estimate muscle cross-sectional area (CSA) in persons with chronic SCI. METHODS: Fifteen men (35 ± 10 years old; 80 ± 14 kg; 1.79 ± 0.5 m and BMI of 25 ± 4 kg/m2) with motor complete SCI (C5-T11) participated in the current study. Magnetic resonance imaging was captured to measure whole thigh CSA (Whole thigh MRI-CSA), whole skeletal muscle CSA (Muscle MRI-CSA) and subcutaneous adipose tissue thickness (SATT). This was followed by a circumferential measurement of the mid-thigh (Thigh circum. = 2πr) using a standard inflexible measuring tape and a Harpenden skinfold caliper to measure subcutaneous fat thickness (SFT). The thigh circum. and SFT were used to predict the whole thigh MRI-CSA and thigh muscle MRI-CSA that yielded whole thigh predicted-CSA and muscle predicted-CSA using the following mathematical equations [circumference =2π*radius & area =π*(radius)2]. RESULTS: Whole thigh MRI-CSA, Muscle MRI-CSA, Thigh circum. and SFT were 189 ± 48 cm2, 104 ± 27 cm2, 51± 7 cm, 4.15 ± 1.5 cm, respectively. Predicted thigh predicted-CSA and muscle predicted-CSA were 211 ± 58 cm2 and 96 ± 29 cm2, respectively. Predicted thigh predicted-CSA and muscle predicted-CSA explained 88% (r2 =0.88, P<0.0001) and 69% (r2 =0.69, P<0.0001; (n=14)) in thigh MRI-CSA and muscle MRI-CSA, respectively. The following field equation can be used to predict muscle MRI-CSA; muscle predicted-CSA = thigh circumference/2π-([0.27(skin fold thickness)+0.1153]+0.142), where 0.142 cm represents the radius of the mid femur. CONCLUSION: The present study demonstrated that thigh circumference and skinfold thickness can be used to predict whole thigh and skeletal muscle CSA in persons with chronic motor complete SCI.