The Effect of Hydration Status and Carbohydrate Restriction on Ultrasound-Derived Muscle Imaging Variables

Background: There is a lack of research investigating the effect of hydration status or intermuscular glycogen content on ultrasound-derived muscle quality imaging in younger adults. Purpose: To examine the effects of varied hydration and muscle glycogen status on ultrasound-measured vastus lateralis (VL) cross-sectional area (CSA) and echo intensity (EI). Materials and Methods: Thirteen young adults (Age: 23 ± 4.2 yrs; Height: 168.5 ± 6.8 cm; Weight: 76.2 ± 17.1 kg) participated in five experimental visits: (1) Baseline (regular dietary intake); (2) hypohydrated and normal carbohydrate (CHO) intake (HH-NC); (3) euhydrated and normal CHO intake (EH-NC); (4) hypohydrated and CHO restriction (HH-CR); and (5) euhydrated and CHO restriction (EH-CR) conditions. Ultrasound imaging of the right VL was used to assess CSA and EI at each visit. A two-way repeated measures ANOVA with Holm adjusted post hoc test was performed for statistical analysis. Results: Body mass was affected by both hydration and carbohydrate restriction (both p < 0.001), while Usg was greater during hypohydration (p < 0.001). VLCSA was lower following carbohydrate restriction (p = 0.010), independent of hydration status, whereas VLEI was not significantly affected by hydration, carbohydrate restriction, or their interaction (all p ≥ 0.063). Conclusions: Overall, these findings suggest that an individual’s hydration and CHO intake may influence ultrasound-derived muscle CSA assessments. Future research should continue to explore the sensitivity of EI and CSA to determine the impact of these findings in both clinical and research environments.