Neuromuscular Adaptations to Electrostimulation Resistance Training
A combination of in vivo and in vitro analyses was performed to investigate muscular and neural adaptations of the weaker (nondominant) quadriceps femoris muscle of one healthy individual to short-term electrostimulation resistance training. The increase in maximal voluntary strength (+12%) was accompanied by neural (cross-education effect and increased muscle activation) and muscle adaptations (impairment of whole-muscle contractile properties). Significant changes in myosin heavy chain (MHC) isoforms relative content (+22% for MHC-2A and -28% for MHC-2X), single-fiber cross-sectional area (+27% for type 1 and +6% for type 2A muscle fibers), and specific tension of type 1 (+67%) but not type 2A fibers were also observed after training. Plastic changes in neural control confirm the possible involvement of both spinal and supraspinal structures to electrically evoked contractions. Changes at the single muscle fiber level induced by electrostimulation resistance training were significant and preferentially affected slow, type 1 fibers.
Available from: Flavio Maciel
- "atrophy, improve blood circulation and alleviate the effects of prolonged immobility (Gondin, Guette, Ballay, and Martin, 2006; Jubeau et al, 2006; Maffiuletti et al, 2006; Marqueste, Hug, Decherchi, and Jammes, 2003). Such benefits may persist for up to 4–6 weeks after the end of the EMS treatment. "
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ABSTRACT: Abstract Background: Electrical muscle stimulation (EMS) is applied to critically ill patients in order to improve their muscle strength, thereby preventing hypotrophy and promoting functional recovery. Objective: To assess the effects of early EMS on the range of movement of the ankle joint, and on thigh and leg circumference in critically ill patients. Methods: This is a prospective randomized clinical trial comprising 11 patients undergoing mechanical ventilation. Before and after EMS the thigh and leg circumference in both lower limbs and the goniometry of the tibiotarsal joint were measured. The angle of 90° on the goniometer was taken as the standard neutral position (NP), with the arm fixed on the lateral malleolus of the ankle joint. Other measurements, namely dorsiflexion and plantar flexion, referred to as mobile arm, were taken from the NP. These recordings were obtained following an active contraction of the patients' muscles. Results: Compared with the electrostimulated limb, a difference in dorsiflexion of the control limb was observed (96.2 ± 24.9 versus 119.9 ± 14.1°; p = 0.01). A girth of 10 cm of the leg was found in limb reduction when compared to the electrostimulated one (24.7 ± 3.1 versus 26.4 ± 4.0 cm; p = 0.03). Conclusions: EMS used at low current intensity and for a short duration failed to prevent muscle atrophy in critically ill patients. However, we did find a significant improvement in active dorsiflexion of the ankle joint suggesting that it could help to prevent against stance plantar flexion in these patients.
Available from: Erick F Dousset
- "The anode measuring 50 cm 2 (10 Â 5 cm) was placed along the middorsal line of the leg, over both medial and lateral gastrocnemii. As in several NMES studies (Boerio & Jubeau, 2005; Gondin et al., 2005, 2006; Jubeau et al., 2006; Maffiuletti et al., 2006; Theurel et al., 2007), rectangular-wave pulsed currents (75 Hz) lasting 400 ms were delivered with a rise time of 1.5 s, a steady tetanic stimulation time of 4 s and a fall time of 0.75 s (total duration of the contraction: 6.25 s). Each stimulation was followed by a pause lasting 20 s. "
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ABSTRACT: We aimed at determining the recovery pattern of neural properties of soleus muscle after a single bout of neuromuscular electrical stimulation (NMES) session. Thirteen subjects performed an NMES exercise (75 Hz, 40 contractions, 6.25 s per contraction). Maximal voluntary contraction (MVC), H-reflex at rest and during voluntary contraction fixed at 60% of MVC (respectively, H(max) and H(sup) ) and volitional (V) wave were measured before and during the recovery period following this exercise [i.e., immediately after, 2 h (H2), 2 days (D2) and 7 days (D7)]. MVC exhibited an immediate and a delayed declines at 2 days (respectively, -29.8±4.6%, P<0.001; -13.0±3.4%, P<0.05). Likewise, V/M(sup) was decreased immediately and 2 days after NMES session (respectively, -43.3±11.6%, P<0.05; 35.3±6.6%, P<0.05). The delayed decrements in MVC and V-wave occurred concomitantly with muscle soreness peak (P<0.001). It could be concluded that motor command alterations after an NMES resistance session contributed to the immediate and also to the delayed decreases in MVC without affecting resting and active H-reflex excitability. These results suggested that spinal circuitry function of larger motoneurons was inhibited by NMES (as indicated by the depressed V-wave responses) contrary to the smaller one (indicated by the unchanged H-reflex responses).
Available from: Julien Gondin
- "On that basis, NMES has been widely used as an adjunct to voluntary resistance training in highly-trained subjects (Delitto et al., 1989; Maffiuletti et al., 2002) and in patients in intensive care units (Gerovasili et al., 2009; Gruther et al., 2010) or affected by cardiac (Quittan et al., 2001) and respiratory chronic (Vivodtzev et al., 2006) diseases. However, growing evidence is emerging illustrating the potential damaging effects of electrically-induced isometric contractions in healthy humans, at least for the lower limbs (Aldayel et al., 2010a,b; Mackey et al., 2008; Maffiuletti et al., 2006). Indeed, three studies conducted in quadriceps muscles under isometric conditions (Aldayel et al., 2010a,b; Jubeau et al., 2008) have recently reported a 10–30-fold increase in creatine kinase (CK) activity coupled to significantly increased muscle soreness as a result of NMES. "
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ABSTRACT: While muscle damage resulting from electrically-induced muscle isometric contractions has been reported in humans, animal studies have failed to illustrate similar deleterious effects and it remains to be determined whether these conflicting results are related to differences regarding experimental procedures or to species. We have investigated in vivo, in rat gastrocnemius muscles, using experimental conditions as close as possible to those used in humans (i.e., muscle length, number of contractions, stimulated muscle), the effects of a single bout of neuromuscular electrical stimulation (NMES). Maximal tetanic force was measured before, immediately after and 1h and 1, 2, 3, 7 and 14 days after NMES. Magnetic resonance imaging measurements, including volume of gastrocnemius muscles and proton transverse relaxation time (T(2)) were performed at baseline and 3, 7, and 14 days after the NMES session. Control animals did not perform any exercise and measurements were recorded at the same time points. For both groups, blood creatine kinase (CK) activity was measured within the first 3 days that followed the initial evaluation. Maximal tetanic force decreased immediately after NMES whereas measurements performed 1h and the days afterwards were similar to the baseline values. CK activity, muscle volume and T(2) values were similar throughout the experimental protocol between the two groups. Under carefully controlled experimental conditions, isometric NMES per se did not induce muscle damage in rat gastrocnemius muscles on the contrary to what has been repeatedly reported in humans. Further experiments would then be warranted in order to clearly delineate these differences and to better understand the physiological events associated with muscle damage resulting from NMES-induced isometric contractions.
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