Publications

• MyotonPRO quantifies the biomechanical properties of thenar muscles reliably.
• Investigating the biomechanical properties of thenar muscles using a simple technology-assisted, accessible method like MyotonPRO has the potential to objectively assess the effectiveness of hand rehabilitation programs and to establish a successful record-keeping method for monitoring the rehabilitation programs of individuals focused on improving their performance.

Background: Quantifying the biomechanical properties of the thenar muscle can provide valuable insight into hand assessment methods.

Purpose: This study aimed to examine the reliability of myotonometer measurements in determining the biomechanical properties (tone, stiffness and elasticity) of thenar muscles in healthy individuals and explore sex-based variations. Additionally, it assessed the relationship between pinch strength and these properties.

Study Design: Cross-sectional reliability study.

Methods: Fifty-five healthy young adult participants were recruited. Biomechanical properties of the abductor pollicis brevis and flexor pollicis brevis muscles — tone (Hz), stiffness (N/m), and elasticity (logarithmic decrement)—were measured using MyotonPRO, while pinch strength was assessed using a Baseline pinch gauge bilaterally. For intrarater reliability, the first rater (R1), conducted two sets of measurements at 30-minute intervals. Inter-rater reliability was evaluated by the second rater (R2) performing a set of measurements between R1’s two sets.

Results: Fifty participants [mean age = 22.84 (1.01) years, mean body mass index = 20.86 (2.82) kg/m²] completed the study. Test-retest reliability for the biomechanical properties of the abductor pollicis brevis and flexor pollicis brevis muscles showed good to excellent consistency (ICCs: 0.78-0.97). Inter-rater reliability demonstrated sufficient consistency across (ICCs: 0.78-0.93). Sex-based differences were observed on the nondominant side, with males exhibiting lower logarithmic decrement scores for both muscles (p < 0.05). Negative correlations were found between pinch strength and abductor pollicis brevis logarithmic decrement scores on both sides (p < 0.05).

Conclusions: The study confirms the reliability of MyotonPRO in evaluating the mechanical properties of the thenar muscle in healthy subjects, with good to excellent consistency. Sex-based differences in elasticity, along with the positive correlation between pinch strength, underscore the importance of sex-specific considerations, suggesting elasticity may be considered a key factor in grip strength improvement.

Trial Registration: ClinicalTrial.gov/NCT06004635

Keywords: rehabilitation, technology, assessment, skeletal muscle, reliability study

In conclusion, the study demonstrates the MyotonPRO device’s reliability in quantifying thenar muscle properties, with both intra and inter-rater reliability showing good to excellent consistency. This study also highlights sex-related differences in thenar muscle biomechanical properties and their association with pinch strength. Specifically, males exhibit superior elasticity in the nondominant APB muscle, correlating with enhanced pinch strength, while no such relationship is observed for muscle stiffness and tone. These findings emphasize the significance of understanding muscle biomechanics, particularly elasticity, for optimizing musculoskeletal function. Overall, these insights shed light on sex-specific variations in muscle mechanics and highlight MyotonPRO’s utility in clinical and research settings for assessing thenar muscle function, offering valuable implications for rehabilitation and preventive strategies in musculoskeletal health.