Evaluation of Extension of Blood Vessels during Static Stretching Using Ultrasound 2D Speckle Tracking Imaging

BACKGROUND- During static stretching, a muscle extends longitudinally, and blood vessels seem to extend simultaneously. However, it is difficult to visualize, and few findings have seen. The recent progress with ultrasonography enables measurements of movement in vivo using 2D speckle tracking imaging, as well as detailed evaluation of extension in tissues at the same site. The aim of this study is to evaluate longitudinal extension of blood vessels during static stretching using this methodology.METHODS- Participants were 10 healthy female volunteers (age of 39.4±11.6). They extended their right wrist with elbow extended. Then the ulnar artery was measured by using 2D speckle tracking imaging with a general-purpose ultrasound instrument. Tissue extension per unit time at the stretching site was calculated from before stretching to maximum of stretching. Simultaneous changes in the caliber of blood vessels during stretching were measured using ultrasound M-mode.RESULTS- The maximum angle of wrist extension was 0 to 83.6±12.5°. The muscle extended by 3.80±1.65% per unit time during stretching, and blood vessels simultaneously extended by 3.20±1.96%. These changes were significant compared to measurements before stretching (p<0.01) and shows the correlation between muscles and blood vessels (r=0.56, p=0.1). The calibers of blood vessels per unit time before and during stretching were 2.24±0.27 and 1.64±0.53 mm with a significant decrease during stretching (p<0.01).CONCLUSIONS- Imaging of static stretching showed extension of both the muscle/skeletal system and blood vessels longitudinally. The finding suggests that endothelial function might be activated by mechanical stress on vascular endothelial cells.