Neuromuscular characteristics of eccentric, concentric and isometric contractions of the knee extensors

Ruas, Cassio V.; Taylor, Janet L.; Latella, Christopher; Haff, G. Gregory; Nosaka, Kazunori

Abstract

Purpose: We compared voluntary drive and corticospinal responses during eccentric (ECC), isometric (ISOM) and concentric (CON) muscle contractions to shed light on neurophysiological mechanisms underpinning the lower voluntary drive in a greater force production in ECC than other contractions.

Methods: Sixteen participants (20–33 years) performed ISOM and isokinetic (30°/s) CON and ECC knee extensor contractions (110°–40° knee flexion) in which electromyographic activity (EMG) was recorded from vastus lateralis. Voluntary activation (VA) was measured during ISOM, CON and ECC maximal voluntary contractions (MVCs). Transcranial magnetic stimulation elicited motor-evoked potentials (MEPs) and corticospinal silent periods (CSP) during MVCs and submaximal (30%) contractions, and short-interval intracortical inhibition (SICI) in submaximal contractions.

Results: MVC torque was greater (P < 0.01) during ECC (302.6 ± 90.0 Nm) than ISOM (269.8 ± 81.5 Nm) and CON (235.4 ± 78.6 Nm), but VA was lower (P < 0.01) for ECC (68.4 ± 14.9%) than ISOM (78.3 ± 13.1%) and CON (80.7 ± 15.4%). In addition, EMG/torque was lower (P < 0.02) for ECC (1.9 ± 1.1 μV.Nm−1) than ISOM (2.2 ± 1.2 μV.Nm−1) and CON (2.7 ± 1.6 μV.Nm−1), CSP was shorter (p < 0.04) for ECC (0.097 ± 0.03 s) than ISOM (0.109 ± 0.02 s) and CON (0.109 ± 0.03 s), and MEP amplitude was lower (P < 0.01) for ECC (3.46 ± 1.67 mV) than ISOM (4.21 ± 2.33 mV) and CON (4.01 ± 2.06 mV). Similar results were found for EMG/torque and CSP during 30% contractions, but MEP and SICI showed no differences among contractions (p > 0.05).

Conclusions: The lower voluntary drive indicated by reduced VA during ECC may be partly explained by lower corticospinal excitability, while the shorter CSP may reflect extra muscle spindle excitation of the motoneurons from vastus lateralis muscle lengthening.

• Journal Article Type: Article
• Acceptance Date: Sep 25, 2024
• Online Publication Date: Oct 5, 2024
• Publication Date: Mar 1, 2025
• Deposit Date: Mar 20, 2025
• Publicly Available Date: Mar 20, 2025
• Journal: European Journal of Applied Physiology
• Print ISSN: 1439-6319
• Electronic ISSN: 1439-6327
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 125
• Issue: 3
• Pages: 671-686
• DOI: https://doi.org/10.1007/s00421-024-05626-9
• Keywords: Short interval intracortical inhibition, Voluntary activation, Corticospinal excitability, Evoked muscle twitch, Maximal voluntary contraction