(14) THE EFFECTS OF AN ACUTE BOUT OF LEG EXTENSIONS ON ULTRASOUND CHARACTERISTICS OF THE VASTUS LATERALIS

Purpose: Does an acute bout of high-intensity leg extension affect ultrasound characteristics (echo intensity and cross-section area)? Methods: Thirty-two recreationally trained college students (age 19.79± 1.0 years, height 165.4 ± 12.1 cm, weight 69.7± 13.3 kg) volunteered for this study. Participants visited the laboratory over three days. The first day was for familiarization, in which max single leg strength was determined. The location of the vastus lateral was marked for ultrasound scan focus. Participants were required to perform 3 sets of leg extension bouts at 70% maximum length strength until failure for each set. Prior to and following single leg extension, three panoramic images of the vastus lateralis were taken using an ultrasound device. From the images, muscle cross-sectional area (CSA) and echo intensity (EI) were derived. Means of the three images were used, and a paired t-test was used to compare pre- and post-leg extension leg extension values. Results: For CSA, there was a significant (p<0.001) difference between pre (19.1±7.2 cm²) and post (21.4±8.1 cm²) measurements. For EI, there was a significant (p< 0.001) difference between pre (44.1±9.6 au) and post (48.3±9.1 au) measurements. Conclusions: Transient hypertrophy, as measured via ultrasound using CSA and EI, was observed following leg extension to failure. This indicates that performing leg extensions can lead to a temporary increase in muscle size and blood flow. Even though the mechanical and metabolic pathways contributing to transient hypertrophy may differ, the resulting "muscle pump" effect remains consistent. Transient hypertrophy can now be compared using CSA and EI as measurement that can quantify that intermuscular changes are occurring with high volume training. Further research is needed to determine how transient hypertrophy differs between exercises and muscle groups. Practical Applications: Leg extensions performed to failure effectively increase muscle size (CSA) and EI. CSA and EI maybe potential measurements to help quantify muscle swelling and blood flow. Acknowledgements: Funding provided by Furman Research Fellows