Publications

Myoton Clarification Note: A Guide to Interpreting the Inverse Relationship Between Logarithmic Decrement and Tissue Elasticity

Background: Resistance training induces fatigue-related responses that may reduce force-generating capacity through metabolic and neuromuscular mechanisms. Muscle mechanical properties, including stiffness, elasticity, and resting tone, assessed via myotonometry, provide information about the passive mechanical state and functional status of skeletal muscle. However, limited evidence exists regarding how these properties change during and immediately following velocity-based resistance training sessions, and whether their temporal behavior corresponds with performance, metabolic, and perceptual responses.

Methods: Twenty resistance-trained men (25.8 ± 4.6 years) completed a repeated-measures experimental protocol consisting of four sets of Smith machine bench press performed at 70% of estimated one-repetition maximum, with 3 min of rest between sets. Sets were terminated upon reaching a 30% loss in mean propulsive velocity (MPV). Muscle mechanical properties and blood lactate concentration were assessed at rest, following each set, and at 5 and 10 min post-session. Performance variables were recorded throughout the protocol.

Results: Stiffness and resting tone remained stable across sets. At 10 min post-session, stiffness was lower than baseline and the post-set values, whereas resting tone was lower than the post-set values but did not differ significantly from baseline. Elasticity showed no significant pairwise differences over time. Blood lactate progressively increased throughout the protocol. Performance declined across sets, evidenced by reductions in the number of repetitions and movement velocity, accompanied by increased perceived exertion.

Conclusions: Velocity-based resistance training induced fatigue-related responses, as reflected by decreased mechanical performance and increased metabolic and perceptual markers. However, muscle mechanical properties assessed via myotonometry were primarily altered during the post-exercise recovery phase. Within the constraints of this single-session and protocol-specific design, myotonometric changes were detected mainly during the early post-exercise recovery period rather than following each set. Myotonometry may therefore provide complementary information on short-term post-exercise muscle responses; however, these findings do not establish its suitability for real-time fatigue monitoring across different exercises, loading schemes, or repeated training sessions.

Keywords: myotonometry, muscle mechanical properties, velocity-based resistance training, post-exercise recovery

A velocity-based resistance training session in which each set was terminated upon reaching a 30% loss in mean propulsive velocity was accompanied by distinct temporal responses in pectoralis major mechanical properties, exercise performance, blood lactate concentration, and perceived exertion. Under the measurement conditions used in the present study, stiffness and resting tone changed mainly during the early post-session recovery period, whereas logarithmic decrement remained relatively stable throughout the protocol. These findings indicate that myotonometry may provide complementary information about short-term post-exercise changes in passive muscle mechanical properties alongside performance, metabolic, and perceptual indicators. However, because measurements were obtained only following each set and at discrete time points during recovery, the present results do not establish the suitability or limitations of myotonometry for real-time inter-set monitoring under alternatiive measurement timings or exercise conditions. Accordingly, the present findings do not allow the identification of an optimal myotonometric monitoring strategy, and further research across different exercise protocols, muscle groups, populations, and measurement time points is required.