Reliability of tensiomyography and myotonometry in detecting mechanical and contractile characteristics of the lumbar erector spinae in healthy volunteers.

PURPOSE: Tensiomyography™ (TMG) and MyotonPRO® (MMT) are two non-invasive devices for monitoring muscle contractile and mechanical characteristics. This study aimed to evaluate the test-retest reliability of TMG and MMT parameters for measuring (TMG:) muscle displacement (Dm), contraction time (Tc), and velocity (Vc) and (MMT:) frequency (F), stiffness (S), and decrement (D) of the erector spinae muscles (ES) in healthy adults. A particular focus was set on the establishment of reliability measures for the previously barely evaluated secondary TMG parameter Vc. METHODS: Twenty-four subjects (13 female and 11 male, mean ± SD, 38.0 ± 12.0 years) were measured using TMG and MMT over 2 consecutive days. Absolute and relative reliability was calculated by standard error of measurement (SEM, SEM%), Minimum detectable change (MDC, MDC%), coefficient of variation (CV%) and intraclass correlation coefficient (ICC, 3.1) with a 95% confidence interval (CI). RESULTS: The ICCs for all variables and test-retest intervals ranged from 0.75 to 0.99 indicating a good to excellent relative reliability for both TMG and MMT, demonstrating the lowest values for TMG Tc and between-day MMT D (ICC < 0.90). Absolute reliability was suitable for all parameters (CV 2-8%) except for Dm (10-12%). Vc demonstrated to be the most reliable and repeatable TMG parameter (ICC > 0.95, CV < 8%). CONCLUSION: The reliability for TMG Vc could be established successfully. Its further applicability needs to be confirmed in future studies. MMT was found to be more reliable on repeated testing than the two other TMG parameters Dm and Tc.

Determination of the Maximal Lactate Steady State by HRV in Overweight and Obese Subjects.

The study assessed if the maximal lactate steady state (MLSS) may be determined by HRV in overweight and obese individuals. Fourteen obese (OB) and 14 overweight (OW) participants performed an incremental exercise test and several constant-load tests on a bicycle ergometer to determine the MLSS. HRV was analysed by using time domain and non-linear parameters of the Poincaré plot. Various HRV thresholds (HRVt) were detected and compared with the MLSS. Overall, Bland-Altman plots demonstrated moderate to strong agreements between the power at the MLSS and the power at HRVt, with all HRVt overestimating the MLSS (range: - 14.6 to-19.8 W). All HRVt were detected at higher intensities (69.2-78.8%P max ) compared to the MLSS (62.6-66.8%P max ). The primarily vagally modulated parameter HRVt SD1 revealed higher correlations (r=0.66-0.76) and lower differences (16.8-19.9%) compared to the parameter HRVt SD2 (r=0.56-r=0.66; 22.4-22.9%). The data suggest a delayed vagal withdrawal during incremental exercise in obese and overweight individuals. For this population, the use of HRV to determine the MLSS seems questionable.