BACKGROUND: The development of shear-wave elastography (SWE) creates a way to quantify the stiffness or elasticity of muscle tissue. SWE data relating to a limited number of specific muscle injuries, overuse, or pathologies currently exist in the literature, however, understanding of normal relationships of muscle due to individual physiological characteristics is lacking. Studies investigating changes in SWE related to age, height, weight and CSA in the gastrocnemius are very limited, but necessary to establish an understanding of ""normal state"" for the gastrocnemius muscle.
PURPOSE: This study aimed to determine how cross sectional area (CSA) and SWE correlate with each other, in both the medial and lateral gastrocnemius muscles of active older athletes participating in the Huntsman World Senior Games.
METHODS: Data was collected from 109 volunteers (participants in the Huntsman World Senior Games) in St. George, Utah, 2022. All subjects (62 females: mean age = 64.1 ± 6.5 yrs, Ht = 165.6 ± 7.9 cm, Wt= 67.2±12.8 kg; 47 males: mean age = 68.9 ± 8.5 yrs, Ht = 177.7 ± 8.9 cm, Wt= 79.9±14 kg) signed an approved consent form and then lay prone on a treatment table for ultrasonic measurement of both CSA and SWE of both heads of the gastrocnemius.
ANALYSIS: All data were analyzed using JMP ver16.2 with a Pearson product pairwise correlation and a multiple regression analysis to determine the effect of age, height, wt and CSA on SWE of the LG and MG independently. Data were normally distributed, not requiring transformation.
RESULTS & CONCLUSION: Stiffness as measured by SWE does not significantly correlate with CSA for either the MG (p=0.3954, r=-0.0822) or LG (p=0.2351, r=-0.1147). However, age (p=0.0064), height (p=0.0027) and CSA(p=0.0319) are variables with a significant effect on MG SWE, while only height (p=0.0178) is a significant variable impacting LG SWE. So although CSA and SWE do not directly correlate, CSA, age and height have some significant effect over MG SWE, while height only demonstrated a significant effect on LG SWE. The results of this study are limited to the gastrocnemius and further research should observe if similar results exist in a more sedentary population as well as a younger population to help determine normal expected values for SWE.