title: Validation of musculoskeletal ultrasound to assess and quantify muscle glycogen content. A novel approach.
abstract: Glycogen storage is essential for exercise performance. The ability to assess muscle glycogen levels should be an important advantage for performance. However, skeletal muscle glycogen assessment has only been available and validated through muscle biopsy. We have developed a new methodology using high-frequency ultrasound to assess skeletal muscle glycogen content in a rapid, portable, and noninvasive way using MuscleSound (MuscleSound, LCC, Denver, CO) technology.
  
  
  OBJECTIVE
  To validate the utilization of high-frequency musculoskeletal ultrasound for muscle glycogen assessment and correlate it with histochemical glycogen quantification through muscle biopsy.
  
  
  METHODS
  Twenty-two male competitive cyclists (categories: Pro, 1-4; average height, 183.7 ± 4.9 cm; average weight, 76.8 ± 7.8 kg) performed a steady-state test on a cyclergometer for 90 minutes at a moderate to high exercise intensity, eliciting a carbohydrate oxidation of 2-3 g·min⁻¹ and a blood lactate concentration of 2 to 3 mM. Pre- and post-exercise glycogen content from rectus femoris muscle was measured using histochemical analysis through muscle biopsy and through high-frequency ultrasound scans using MuscleSound technology.
  
  
  RESULTS
  Correlations between muscle biopsy glycogen histochemical quantification (mmol·kg⁻¹) and high-frequency ultrasound methodology through MuscleSound technology were r = 0.93 (P < 0.0001) pre-exercise and r = 0.94 (P < 0.0001) post-exercise. The correlation between muscle biopsy glycogen quantification and high-frequency ultrasound methodology for the change in glycogen from pre- and post-exercise was r = 0.81 (P < 0.0001).
  
  
  CONCLUSIONS
  These results demonstrate that skeletal muscle glycogen can be measured quickly and noninvasively through high-frequency ultrasound using MuscleSound technology.
authors.affiliation: University of Colorado School of Medicine, Aurora, CO. john.hill@ucdenver.edu.
authors.forename: John C
authors.initials: JC
authors.lastname: Hill
authors.forename: Iñigo San
authors.initials: IS
authors.lastname: Millán
mesh_terms: D000328:Adult; D001707:Biopsy, Needle; D004040:Dietary Carbohydrates / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006003:Glycogen / Q000032:analysis*; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000473:pathology; D015203:Reproducibility of Results; D014463:Ultrasonography
chemical_list: D004040:Dietary Carbohydrates; D019344:Lactic Acid; D006003:Glycogen