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Time-Course of Neuromuscular Changes during and after Maximal Eccentric Contractions.

Doguet V, Jubeau M, Dorel S, Couturier A, Lacourpaille L, Guével A, Guilhem G - Front Physiol (2016)

Bottom Line: Voluntary isometric torque (-48 ± 7%), evoked torque (-41 ± 14%) and voluntary activation (-13 ± 11%) decreased at POST, but only voluntary isometric torque (-19 ± 6%) and evoked torque (-10 ± 18%) remained depressed at 48 h.Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage.Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

View Article: PubMed Central - PubMed

Affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), Faculty of Sport Sciences, University of Nantes Nantes, France.

ABSTRACT
This study tested the relationship between the magnitude of muscle damage and both central and peripheral modulations during and after eccentric contractions of plantar flexors. Eleven participants performed 10 sets of 30 maximal eccentric contractions of the plantar flexors at 45°·s(-1). Maximal voluntary torque, evoked torque (peripheral component) and voluntary activation (central component) were assessed before, during, immediately after (POST) and 48 h after (48 h) the eccentric exercise. Voluntary eccentric torque progressively decreased (up to -36%) concomitantly to a significant alteration of evoked torque (up to -34%) and voluntary activation (up to -13%) during the exercise. Voluntary isometric torque (-48 ± 7%), evoked torque (-41 ± 14%) and voluntary activation (-13 ± 11%) decreased at POST, but only voluntary isometric torque (-19 ± 6%) and evoked torque (-10 ± 18%) remained depressed at 48 h. Neither changes in voluntary activation nor evoked torque during the exercise were related to the magnitude of muscle damage markers, but the evoked torque decrement at 48 h was significantly correlated with the changes in voluntary activation (r = -0.71) and evoked torque (r = 0.77) at POST. Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage. Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

No MeSH data available.


Related in: MedlinePlus

Example of torque traces for maximal voluntary isometric contractions before and immediately after the exercise (A) and for maximal voluntary eccentric contractions during the exercise (B). Double arrows represent paired stimulations superimposed to contractions (superimposed doublet) and evoked on the resting muscle after isometric contractions (potentiated doublet) or during a passive dorsiflexion cycle (lengthening doublet). Superimposed doublets are enlarged in the top right corner of each panel. Two-way arrows correspond to superimposed torques between the evoked torque and voluntary isometric peak torque (A) or extrapolated eccentric torque (B).
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Figure 1: Example of torque traces for maximal voluntary isometric contractions before and immediately after the exercise (A) and for maximal voluntary eccentric contractions during the exercise (B). Double arrows represent paired stimulations superimposed to contractions (superimposed doublet) and evoked on the resting muscle after isometric contractions (potentiated doublet) or during a passive dorsiflexion cycle (lengthening doublet). Superimposed doublets are enlarged in the top right corner of each panel. Two-way arrows correspond to superimposed torques between the evoked torque and voluntary isometric peak torque (A) or extrapolated eccentric torque (B).

Mentions: For each MVC, (i) a supramaximal doublet was superimposed to the contraction (superimposed doublet; Figure 1A), over the isometric plateau and (ii) a supramaximal doublet was applied at rest, 2 s after the contraction (potentiated doublet). Rectangular paired pulses (duration: 1 ms, frequency: 100 Hz) were delivered by a constant-current Digitimer DS7A electrical stimulator (Digitimer Ltd., Hertfordshire, UK). The cathode (diameter = 1 cm; ADInstruments Pty. Ltd.) was positioned over the tibial nerve, in the popliteal fossa, and the anode (8 × 13 cm; Stimex, Rouffach, France) under the patella. A light pressure was applied on the cathode to stimulate closer to the nerve throughout the sessions. At the beginning of all sessions, the first intensity necessary to evoke the maximal amplitude of the twitch torque was determined using a 10-mA increment stimulation ramp. This intensity was increased by 30% for all following measurements.


Time-Course of Neuromuscular Changes during and after Maximal Eccentric Contractions.

Doguet V, Jubeau M, Dorel S, Couturier A, Lacourpaille L, Guével A, Guilhem G - Front Physiol (2016)

Example of torque traces for maximal voluntary isometric contractions before and immediately after the exercise (A) and for maximal voluntary eccentric contractions during the exercise (B). Double arrows represent paired stimulations superimposed to contractions (superimposed doublet) and evoked on the resting muscle after isometric contractions (potentiated doublet) or during a passive dorsiflexion cycle (lengthening doublet). Superimposed doublets are enlarged in the top right corner of each panel. Two-way arrows correspond to superimposed torques between the evoked torque and voluntary isometric peak torque (A) or extrapolated eccentric torque (B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834740&req=5

Figure 1: Example of torque traces for maximal voluntary isometric contractions before and immediately after the exercise (A) and for maximal voluntary eccentric contractions during the exercise (B). Double arrows represent paired stimulations superimposed to contractions (superimposed doublet) and evoked on the resting muscle after isometric contractions (potentiated doublet) or during a passive dorsiflexion cycle (lengthening doublet). Superimposed doublets are enlarged in the top right corner of each panel. Two-way arrows correspond to superimposed torques between the evoked torque and voluntary isometric peak torque (A) or extrapolated eccentric torque (B).
Mentions: For each MVC, (i) a supramaximal doublet was superimposed to the contraction (superimposed doublet; Figure 1A), over the isometric plateau and (ii) a supramaximal doublet was applied at rest, 2 s after the contraction (potentiated doublet). Rectangular paired pulses (duration: 1 ms, frequency: 100 Hz) were delivered by a constant-current Digitimer DS7A electrical stimulator (Digitimer Ltd., Hertfordshire, UK). The cathode (diameter = 1 cm; ADInstruments Pty. Ltd.) was positioned over the tibial nerve, in the popliteal fossa, and the anode (8 × 13 cm; Stimex, Rouffach, France) under the patella. A light pressure was applied on the cathode to stimulate closer to the nerve throughout the sessions. At the beginning of all sessions, the first intensity necessary to evoke the maximal amplitude of the twitch torque was determined using a 10-mA increment stimulation ramp. This intensity was increased by 30% for all following measurements.

Bottom Line: Voluntary isometric torque (-48 ± 7%), evoked torque (-41 ± 14%) and voluntary activation (-13 ± 11%) decreased at POST, but only voluntary isometric torque (-19 ± 6%) and evoked torque (-10 ± 18%) remained depressed at 48 h.Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage.Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

View Article: PubMed Central - PubMed

Affiliation: Laboratory "Movement, Interactions, Performance" (EA 4334), Faculty of Sport Sciences, University of Nantes Nantes, France.

ABSTRACT
This study tested the relationship between the magnitude of muscle damage and both central and peripheral modulations during and after eccentric contractions of plantar flexors. Eleven participants performed 10 sets of 30 maximal eccentric contractions of the plantar flexors at 45°·s(-1). Maximal voluntary torque, evoked torque (peripheral component) and voluntary activation (central component) were assessed before, during, immediately after (POST) and 48 h after (48 h) the eccentric exercise. Voluntary eccentric torque progressively decreased (up to -36%) concomitantly to a significant alteration of evoked torque (up to -34%) and voluntary activation (up to -13%) during the exercise. Voluntary isometric torque (-48 ± 7%), evoked torque (-41 ± 14%) and voluntary activation (-13 ± 11%) decreased at POST, but only voluntary isometric torque (-19 ± 6%) and evoked torque (-10 ± 18%) remained depressed at 48 h. Neither changes in voluntary activation nor evoked torque during the exercise were related to the magnitude of muscle damage markers, but the evoked torque decrement at 48 h was significantly correlated with the changes in voluntary activation (r = -0.71) and evoked torque (r = 0.77) at POST. Our findings show that neuromuscular responses observed during eccentric contractions were not associated with muscle damage. Conversely, central and peripheral impairments observed immediately after the exercise reflect the long-lasting reduction in force-generating capacity.

No MeSH data available.


Related in: MedlinePlus