Maladaptation of skeletal muscle may occur in response to chronic training overloading. Reliable quantification of changes in viscoelastic properties of muscle in a sports setting is challenging. The Myoton-Pro offers a portable, handheld method of measuring viscoelastic properties of muscle based on dampened oscillations of muscle tissue. The intra-rater reliability of Myoton-Pro measurements and symmetry of the viscoelastic properties of the biceps brachii (BB) were recorded in a sample of convenience of healthy, young adult males aged ≥18 to ≤35 years (n=21) who are right-hand dominant. The Myoton-Pro was used to measure frequency (Hz), decrement and stiffness (Nm) of dominant and non-dominant BB on two testing sessions, seven days apart, by the same rater. Within-day and between-day reliability was assessed using intraclass correlation coefficients (ICC3,1), the standard error of measurement (SEM), the minimal detectable change (MDC) and Bland-Altman graphs. Paired t-test (α level =0.05) compared symmetry between body sides. Within-day intra-rater reliability was very high (ICC 0.90-0.99) for frequency, decrement and stiffness. Between-day comparisons were moderate-high (ICC= 0.68-0.81) for frequency; low-moderate ICCs (0.39-0.59) for decrement; high-very high (ICCs 0.88-0.94) for stiffness. No significant difference was found between sides. (p=0.80-0.93). SEM =0.1-0.5Hz; 0.04 0.09 decrement, 3.2-8.7Nm. MDC =0.4-1.3Hz, 0.1-0.25decrement, 8.8-24.1Nm. These results conclude that the Myoton-Pro offers an objective, non-invasive and reliable measurement of frequency and stiffness of biceps brachii in young adult males. Measures of decrement failed to meet the commonly accepted threshold of reliability required for valid use of human assessment tools (ICCs 0.7). Coaches could use the Myoton-Pro to identify true change in muscle to detect abnormalities and aid injury prevention.