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Characteristics of rectus femoris activation and rectus femoris–hamstrings coactivation during force-matching isometric knee extension in subacute stroke

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Abstract

The spectral properties of surface electromyographic (EMG) signal in the rectus femoris (RF) and the coactivation in the medial hamstrings (MH) were investigated in 45 stroke subjects (22 ± 12 days post-onset) and 30 age-matched healthy controls who performed unilateral knee extensions at maximum effort (100% MVC) and during 5-s force-matching tasks (10, 30, 50% MVC). The spectral properties were obtained through a power spectrum analysis based on Fast Fourier Transform. The coactivation was measured as the MH amplitude (%max) and MH/RF amplitude ratio. Force variability was expressed as the coefficient of variation. Both knee extensors and flexors were weaker in the paretic leg than the non-paretic and control legs (p < 0.001). A significantly higher relative power in the 5–13 and 13–30 Hz bands was found in the paretic than the non-paretic leg across all force levels (p ≤ 0.001) without changes in the 30–60 and 60–100 Hz bands or the mean and median frequencies. Regarding the antagonist coactivation, MH amplitude in the paretic leg was higher than in the non-paretic leg (submaximal levels, p < 0.0001) and the control leg (all force levels, p = 0.0005) with no differences between legs in the MH/RF ratio. The steadiness of the knee extension force was not related to the spectral properties of the agonist EMG or antagonistic coactivation. Greater coactivation was associated with weaker paretic knee flexors (p ≤ 0.0002). The overall results suggest variably altered agonist activation and antagonistic coactivation over the range of isometric knee extension contractions in subacute stroke.

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Availability of data and materials

The data used in this study are available from the corresponding author upon reasonable request.

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Custom codes are available from the corresponding author upon reasonable request.

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Acknowledgements

This work was supported in part by the Wilson Research Foundation and H.F. McCarty, Jr. Family Foundation Fund for Stroke Research (Jackson, MS, USA). We are grateful to Jennifer Sivak, L. Anthony Smith, and M. Dawn Norman for their assistance with this study. Dr. Chow is the Gertrude C. Ford Director of Motion Analysis.

Funding

Wilson Research Foundation (Jackson, MS, USA), H.F. McCarty, Jr. Family Foundation Fund for Stroke Research (Jackson, MS, USA), and Gertrude C. Ford Foundation (Ridgeland, MS, USA).

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Both authors contributed to the conception of research, experimental design, data collection and analysis, and preparation of manuscript.

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Correspondence to John W. Chow.

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The authors declare that they have no conflict of interest.

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This study was approved by the Institutional Review Board of Methodist Rehabilitation Center. The procedures used in this study adhere to the tenets of the Declaration of Helsinki.

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Informed consent was obtained from all individual participants included in the study.

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The consent to publish was included in the informed consent signed by all participants.

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Communicated by Francesco Lacquaniti.

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Chow, J.W., Stokic, D.S. Characteristics of rectus femoris activation and rectus femoris–hamstrings coactivation during force-matching isometric knee extension in subacute stroke. Exp Brain Res 239, 2621–2633 (2021). https://doi.org/10.1007/s00221-021-06162-0

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  • DOI: https://doi.org/10.1007/s00221-021-06162-0

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