(57) THE EFFECTS OF STRETCHING ON MUSCLE CROSS SECTIONAL AREA AND ECHOGENICITY

Static stretching is a common practice prior to performance as part of a “warm-up” routine. Traditionally warm-up routines are used to increase core temperature and increase blood flow to working muscles. If in fact stretching increased blood flow it could be seen as part of a warm-up routine, this may offset the possible negative effects that have been reported as a result of stretching. Ultrasound imaging allows for us to measure increase blood flow through increase in CSA and echogenicity.


Purpose: To determine if acute static stretching increases cross sectional area (CSA) and echogenicity of the Vastus Lateralis as a response to increased blood flow.


Methods: Thirty-eight participants (68.2 ± 3.9 cm, 72.3 ± 16.9 kg, Age 23.6 ± 8.8 years) had three panoramic ultrasound images taken of the largest circumference of the vastus lateralis before and after static stretching. The transducer was positioned in the center of the muscle belly just inferior to the largest circumference of the muscle. Static stretching was performed via a standing quad stretch where the participant reached back and grabbed their foot and pulled posteriorly and superiorly until a slight discomfort caused by the stretching muscle was felt. This was repeated for 5 sets of 60 seconds with 30 sec rest in-between for 5 total minutes of stretching. Images were analyzed for cross sectional area and echogenicity. Values were then averaged across all three images (pre and post) and compared using paired t-tests.


Results: There was no significant difference between pre and post CSA (P=0.13) and echogenicity (P=0.18) measurements. Values for CSA (mean± SD) were pre 15.1±3.8 vs post 15.4±4.4 cm². Values for echogenicity (mean± SD) were pre 59.9.7±12.0 vs post 60.81±8.7 au.


Conclusion: There was no significant difference for CSA or echogenicity following stretching. Changes in muscle size and echogenicity following intervention is commonly believed to be because of an increase in blood flow to the muscle. Since there were no changes in CSA or echogenicity then an increase in blood flow to static stretched muscle is unlikely.
PRACTICAL APPLICATIONS: Stretching appears not to have an effect on muscle size and echogenicity. Static stretching should not be considered part of a “warm-up” routine and does not elicit increased blood flow to the muscle; it may serve other purposes, but should not be considered to increase blood flow.

Acknowledgements: None