Author(s): ABELN, V., LORKE, N., HONIG, P., LIMBROCK, A., CHAABENE, H., ADULHAFIZ, H., Institution: GERMAN SPORT UNIVERSITY COLOGNE, Country: GERMANY, Abstract-ID: 1088

INTRODUCTION:
The human muscle can produce higher torque during eccentric (ECC), in comparison to concentric (CON) muscle actions. ECC muscle actions involve lower metabolic cost (Peñailillo et al., 2013) and underly different spinal and supraspinal control mechanisms (Duchateau & Baudry 2013). However, neuro-muscular control mechanisms of the two muscle action types remain insufficiently understood. The present study aims to differentiate electro-cortical activation patterns of CON and ECC muscle actions at lower and higher intensities within one sample and standardized protocol.
METHODS:
21 sport students (9 females) performed CON and ECC dynamic isokinetic knee extensions at 30% and 70% of maximal voluntary contraction (MVC). Each condition consisted of five blocks of 10 repetitions, in randomized order. Electroencephalographic recordings were synchronized with the dynamometer. Movement torque (Nm), EEG amplitudes and latencies of movement-related cortical potentials (MRCP; negative potential (NP): motor planning; positive potential (PP): movement monitoring) as well as EEG evoked power spectrum (delta (0.5-4 Hz), theta (4-8 Hz) frequency band) 2500 ms around movement onset were analysed.
RESULTS:
Average torque was higher during ECC than CON MVC, 30%, and 70% MVC (all p < .001, d: .3- .993). No reduction of MVC was observed after completion of all blocks (ECC p= .114, CON p= 1.0). Higher amplitudes (NP: p< .001, 𝜂2p: .52; PP: p= .003, 𝜂2p: .461) and latencies (NP= .001, 𝜂2p: .751; PP: p= .074, 𝜂2p: .198) were found for CON compared to ECC. 70% MVC resulted in higher amplitudes of both potentials than 30% MVC (NP: p= .008, 𝜂2p .381; PP: p= .006, 𝜂2p: .406), while latency was longer only for PP (p< .001, 𝜂2p: .578). Delta power was higher during CON than ECC (p= .005, 𝜂2p: .462) and 70% compared to 30% MVC (p= .004, 𝜂2p: .493). Theta power was not dependent on muscle action intensity, but was higher before movement onset during CON, and higher after movement onset during ECC.
CONCLUSION:
Despite lower produced force output, higher delta power and higher MRCP amplitudes and latencies were observed during CON. This might assume that cortical processing related to movement planning and error correction requires higher cortical effort during CON than ECC in sportive individuals. Higher muscle action intensity was associated with higher cortical processing intensity, whereas latencies behaved differently in regard to muscle action intensity. Delta power might is associated with muscle action intensity, whereas theta power seems to play a role in movement initiation, but not for muscle action intensity.

References: Duchateau, J. & Baudry, S.(2014). Insights into the neural control of eccentric contractions. J. Appl. Physiol. 116, 1418-1425. Peñailillo, L., et al. (2013). Metabolic and Muscle Damage Profiles of Concentric versus Repeated Eccentric Cycling. MSSE, 45(9), 1773–1781.