Assessment of muscle architecture of the biceps femoris and vastus lateralis by ultrasound after a chronic stretching program.

OBJECTIVE: To evaluate the chronic effects of a static stretching program on the muscle architecture of biceps femoris (BF) and vastus lateralis (VL) muscles in ultrasound (US) images. DESIGN: Randomized controlled longitudinal trial. SETTING: Biomechanics Laboratory of Physical Education School of the Army, Rio de Janeiro, Brazil. PARTICIPANTS: The study included 24 healthy and physically active male volunteers (19.05 ± 1.40 years, 1.73 ± 0.07 m, and 73.15 ± 8.33 kg), randomly allocated to 1 of 2 groups: stretching group (SG, n = 12) and control group (n = 12). INTERVENTIONS: The SG was submitted to 3 sets of 30 seconds of static stretching 3 times a week during 8 weeks. MAIN OUTCOME MEASURES: Ultrasound equipment (7.5 MHz) was used for the evaluation of BF and VL muscle architecture variables (pennation angle, fiber length, muscle thickness, and fascicle displacement) before and after training. Knee range of motion (ROM) and isometric flexion and extension torque (TQ) were also measured. RESULTS: There were no significant changes in muscle architecture, TQ, and maximum knee flexion angle (P > 0.05). However, maximum knee extension angle (MEA) increased significantly in the SG (pretraining: 159.37 ± 7.27 degrees and posttraining: 168.9 ± 3.7 degrees; P < 0.05). CONCLUSIONS: Volume or intensity (or both) of the stretching protocol was insufficient to cause structural changes in the VL and BF muscles. The increase in MEA could not be explained by muscle architecture changes. CLINICAL RELEVANCE: To describe changes in the VL and BF muscle tendon unit using US after a long-term stretching program to identify which structures are responsible for ROM increase.

Reliability of the rectus femoris muscle cross-sectional area measurements by ultrasonography.

The skeletal muscle system can adapt to an external stimulus from either physiological or pathological conditions. This plasticity is measured by imaging techniques such as magnetic resonance imaging or ultrasound. The anatomical cross-sectional area of a muscle is one of the muscle architecture parameters that relates to the maximum muscle strength. The aim of this study was to determine the reliability of anatomical cross-sectional area rectus femoris measurements, obtained by ultrasound, with two different protocols. Acquisition of four anatomical cross-sectional area images of the right rectus femoris in two distinct regions (15 cm above the patella and 50% of the thigh length) was performed in 2 days, from a group of 15 young healthy subjects. The cross-sectional area of each image was measured five times. The reliability of the anatomical cross-sectional area measures was determined by the coefficient of variation (CV), intraclass correlation coefficient (ICC) and typical error of measurement (TEM). In each protocol, there were no significant differences between the means of anatomical cross-sectional area in measurements, images and days (P>0·05). The CVs were 8·53% and 8·9%, the ICCs 0·88 and 0·87 and the TEMs 65·59 and 94·25 between the 2 days in the regions of 15 cm and 50% of the thigh length, respectively. The average values of the cross-sectional area at 50% of the thigh length were significantly higher than those for at 15 cm above the patella (P<0·001). The measurement of rectus femoris anatomical cross-sectional area by ultrasound proved reliable.