Variability in Muscle Adaptation to Electrical Stimulation

Abstract

The aims were to investigate the plasticity of the myosin heavy chain (MHC) phenotype following neuromuscular electrical stimulation (NMES) and to assess the correlation between MHC isoform distribution and muscle fibre conduction velocity (MFCV).14 men were subjected to 24 sessions of quadriceps NMES. Needle biopsies were taken from the dominant vastus lateralis and neuromuscular tests were performed on the dominant thigh before and after training. NMES significantly increased the quadriceps maximal force by 14.4±19.7% (P=0.02), vastus lateralis thickness by 10.7±8.6% (P=0.01), vastus lateralis MFCV by 11.1±3.5% (P<0.001), vastus medialis MFCV by 8.4±1.8% (P<0.001). The whole spectrum of possible MHC isoform adaptations to training was observed: fast-to-slow transition (4 subjects), bi-directional transformation from MHC-1 and MHC-2X isoforms toward MHC-2A isoform (7 subjects), shift toward MHC-2X (2 subjects), no MHC distribution change (1 subject). No significant correlation was observed between MHC-2 relative content and vastus lateralis MFCV (pre-training: R2=0.04, P=0.46; post-training: R2=0.02, P=0.67). NMES elicited distinct adaptations in the MHC composition and increased force, muscle thickness, and MFCV. The MHC isoform distribution did not correlate with MFCV, thus implying that the proportion of different fibre types cannot be estimated from this electrophysiological variable.

Needle biopsy‐derived myofascial tissue samples are sufficient for quantification of myofibroblast density

“…The new quantification procedure described here could possibly be combined with the simultaneous examination of other tissue properties. Such additional properties could include muscle fiber type composition, different cytokines, and gene expression (Maffulli et al, 2011;Minetto et al, 2013;Heinemeier et al, 2016).…”

Combined intermittent hypobaric hypoxia and muscle electro-stimulation: a method to increase circulating progenitor cell concentration?

“…It is worth noting, however, that whereas many types of standard physical exercise can be difficult to implement in the context of hypoxic procedures or when osteoarticular conditions are present, ME is easier to apply and has been shown to be efficient in reproducing training effects [27,28]. That said, muscle adaptations to electro-stimulation could be different [40], and although normobaric and hypobaric hypoxia are similar, they can provoke different physiological responses [41,42]. …”

The effects of neuromuscular electrical stimulation training on the electromyographic power spectrum of suprahyoid musculature

“…After finding no correlations between conduction velocity and the relative content of MHC isoforms in the quadriceps muscle, Minetto et al (2013) (Minetto et al, 2013). The study by Minetto and colleagues supports the claims made by Farina (2008); Minetto et al 2013described that proportions of fiber types and training-induced changes could not be estimated from conduction velocity; they did not find differences between conduction velocity estimates obtained at 70% mean voluntary contraction (when primarily type II fibers should be active) and…”

“…Kupa et al (1995) demonstrated that fast-twitch (glycolytic) fibers of muscles in rat specimens had greater initial values of MF and conduction velocity and greater change of these variables over time. However, the study by Minetto et al (2013) suggested that conduction velocity could not estimate different fiber types. Furthermore, the points made by Farina (2008) exemplifies why conduction velocity would not be an adequate variable alone to suggest changes related to muscle fiber types.…”

“…Addressing phenotypic shifts in limb musculature as a result of NMES training has received great attention in the literature. Significant variability in phenotypic shifts between participants as a result of two months of NMES training was found by Minetto et al (2013),…”