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J Electromyogr Kinesiol. 2017 Apr;33:83-93. doi: 10.1016/j.jelekin.2017.02.001. Epub 2017 Feb 10.

Correlation between stiffness and electromechanical delay components during muscle contraction and relaxation before and after static stretching.

Author information

1
Department of Biomedical Sciences for Health (SCIBIS), University of Milan, Via G. Colombo 71, 20133 Milan, Italy.
2
Department of Biomedical Sciences for Health (SCIBIS), University of Milan, Via G. Colombo 71, 20133 Milan, Italy. Electronic address: fabio.esposito@unimi.it.

Abstract

The study was aimed at assessing possible correlations of the electromechanical delay components during muscle contraction (DelayTOT) and relaxation (R-DelayTOT), with muscle-tendon unit (MTU), muscle, and tendon stiffness before and after static stretching (SS). Plantarflexor muscles' maximum voluntary torque (Tmax) was measured in 18 male participants (age 24±3yrs; body mass 76.4±8.9kg; stature 1.78±0.09m; mean±SD). During Tmax, surface electromyogram (EMG), mechanomyogram, and force signals were detected. DelayTOT and R-DelayTOT with their electrochemical and mechanical components were calculated. Passive torque and myotendinous junction displacement were assessed at 0°, 10° and 20° of dorsiflexion to determine MTU, muscle and tendon stiffness. The same protocol was repeated after SS. DelayTOT, R-DelayTOT and their mainly mechanical components correlated with MTU, muscle and tendon stiffness, both before (R2 from 0.562 to 0.894; p<0.001) and after SS (R2 from 0.726 to 0.955; p<0.001). SS decreased Tmax (-14%; p<0.001) and lengthened almost all the DelayTOT and R-DelayTOT components (from +5.9% to +30.5%; p<0.05). Correlations were found only between stiffness and the mechanical components of DelayTOT and R-DelayTOT. Correlations persisted after SS but delays increased to a higher extent than stiffness, indicating a complexity of the relationship between stiffness and delays that will be discussed in the manuscript.

KEYWORDS:

Electromyogram; Mechanomyogram; Muscle stretch; Muscle-tendon unit; Ultrasound

PMID:
28232285
DOI:
10.1016/j.jelekin.2017.02.001
[Indexed for MEDLINE]

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