Ultrasound Biomicroscopy and Magnetic Resonance Images in the Characterization of Rat Muscle Submitted to Stretching Training – a Preliminary Study

This pilot study aimed to test the potential use of imaging techniques, ultrasound biomicroscopy (UBM) and magnetic resonance (MRI), to quantify muscle architecture parameters and evaluate, in vivo, structural adaptations of rat lateral gastrocnemius (LG) submitted to chronic stretching protocol with characteristics similar to those used in humans. After 20 daily static stretching sessions, both UBM and MRI images were acquired. Muscle architecture parameters such as muscle thickness (MT), pennation angle (PA), anatomical and physiological cross-sectional area (ACSA and PCSA) were measured in images of the elongated right hindlimb and compared with the contralateral member, used as control. The results show reductions of approximately 15% in MT, 17% in PA, 11% in CSA and 10% in PCSA of the GL muscle of the treated leg. These values indicate that the intensity of the applied protocol was sufficient to cause structural changes in this muscle. This preliminary study indicates the potential of MRI and UBM images in the, in vivo, quantification and tracking in vivo parameters of muscle architecture of rats submitted to chronic stretching training.