Mechanomyogram amplitude correlates with human gastrocnemius medialis muscle and tendon stiffness both before and after acute passive stretching

Stefano Longo, Emiliano Cè, Susanna Rampichini, Michela Devoto, Eloisa Limonta, Fabio Esposito

Research output: Contribution to journalArticlepeer-review

Abstract

The study aimed to assess the level of correlation between muscle-tendon unit (MTU) stiffness andmechanomyogram (MMG) signal amplitude of the human gastrocnemius medialismuscle, both before and after acute passive stretching. The passive torque (Tpass), electrically evoked peak torque (pT) and myotendinous junction displacement were determined at different angles of dorsiflexion (0, 10 and 20 deg), while maximum voluntary isometric torque (Tmax) was assessed only at 0 deg. Measurements were repeated after a bout of passive stretching. From the MMG signal, the root mean square (RMS) and peak to peak (p-p) were calculated. The MTU, muscle and tendon stiffness were determined by ultrasound and Tpass measurements. Before stretching, correlations between MMG RMS and MTU, muscle and tendon stiffness were found (R2 = 0.22-0.46). After stretching, Tpass, Tmax, pT and MTU, muscle and tendon stiffness decreased by 25 ± 7, 16 ± 2, 9 ± 2, 22 ± 7, 23 ± 8 and 28 ± 5%, respectively (P <0.05). During voluntary and electrically evoked contractions, MMG p-p decreased by 9 ± 2 and 5 ± 1%, while MMG RMS increased by 48 ± 7 and 50 ± 8%, respectively (P <0.05). Correlations between MMG RMS and MTU, muscle and tendon stiffness were still present after stretching (R2 = 0.44-0.60). In conclusion, correlations between MMG RMS and stiffness exist both before and after stretching, suggesting that a slacker MTU leads to larger muscle fibre oscillations. However, care must be taken in using MMG amplitude as an indirect index to estimate stiffness owing to the relatively small R2 values of the investigated correlations.

Original languageEnglish
Pages (from-to)1359-1369
Number of pages11
JournalExperimental Physiology
Volume99
Issue number10
DOIs
Publication statusPublished - 2014

ASJC Scopus subject areas

  • Physiology
  • Medicine(all)

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