Young's moduli of subcutaneous tissues and muscles under different loads at the gluteal region calculated using ultrasonography.

[Purpose] Young's modulus distributions for subcutaneous and muscle tissues in a large sample of healthy individuals, based on ultrasonography and compression testing, remains uninvestigated till date. This study aimed to separately estimate the hardness of subcutaneous tissues and muscles in the human gluteal region under a range of loads in terms of mean Young's moduli and associated distributions. [Participants and Methods] Data of 21 males aged 20-22 years were acquired using synchronous compression testing and ultrasonography. Stress-strain curves comprised the loads applied (stress) were plotted against ultrasonographic changes in subcutaneous/muscle tissue thickness (strain). Young's moduli were calculated as slopes of approximation curves fitted to highly linear regions of the stress-strain curves. [Results] Young's moduli (mean ± standard deviation) for gluteal subcutaneous and muscle tissues were estimated as: 26.1 ± 19.0 kPa, 1-N load; 2,199.1 ± 1,354.8 kPa, 30-N load; and 62.2 ± 10.3 kPa, 5-N load; 440.4 ± 80.0 kPa, 30-N load, respectively. No correlation between any pair of these measures reached statistical significance. [Conclusion] Young's moduli were successfully measured for subcutaneous and muscle tissues in a large participant sample using ultrasonography and compression testing. Our results may serve as reference data when assessing tissue hardness by palpation.