Click the PDF icon to download the abstract

Beckner, M.

Canino, M.

Conkright, W.

Connaboy, C.

Dunn-Lewis, C.

Eagle, S.

Ferrarelli, F.

Flanagan, S.

Germain, A.

Nindl, B.

Proessl, F.

Sinnott, A.

Sterczala, A.

English

TopSCHOLAR

   Normalization Removes Differences in Contractile Properties and Corticospinal Excitability Between Single- and Multi-Joint Exercises     Felix Proessl, Maria C. Canino, Adam J. Sterczala, Courtenay Dunn-Lewis, William R. Conkright, Aaron M. Sinnott, Meaghan E. Beckner, Shawn R. Eagle, Fabio Ferrarelli, Anne Germain, Chris Connaboy, Bradley C. Nindl, FACSM, Shawn D. Flanagan. University of Pittsburgh, Pittsburgh, PA   Single- and multi-joint exercises are commonly used resistance modalities to assess contractile function and corticospinal excitability. Initial work suggests neurophysiological function may be task-specific, but results are constrained to smaller corticospinal excitability ranges. PURPOSE: The purpose of this study was to compare neurophysiological function during stimulus-response curves (SRC) between an isometric squat (SQT) and knee extension (KE). METHODS: Twenty-two young adults (2 women, 20 right-footed, age: 25±5yrs, BMI: 25.9±3.1, VO2: 46.2±8.8 ml·kg-1·min-1) performed isometric SQT (n=7) or KE (n=15), with hip-, knee- and ankle-joint angle at 90° as part of a larger study, exposing participants to operational stress during a 5-day long testing series. Maximum strength and muscle activity (RMS) were recorded during maximum voluntary contractions (MVCs) using a linear force transducer and electromyography (EMG) sensors placed over the vastus lateralis, respectively. SRCs were conducted with transcranial magnetic stimulation and a double cone coil from 5-100% of stimulator output over the dominant motor cortex leg hotspot during intermittent isometric contractions at 15% MVC. Corticospinal excitability was assessed by SRCMAX, SRCSLOPE and SRCV50 (midpoint of the rising phase). As responses did not differ across days, outcomes were grand-averaged and independent t-tests or Mann-Whitney U were used for between-group comparisons. RESULTS: Greater maximum force and muscle activity were evident for KE compared to SQT (Force: 1303.9±407.0 vs. 812.8±189.5N, p<0.001; EMGRMS: 0.24±0.1 vs. 0.14±0.1, p=0.02). During sustained isometric contractions, absolute EMGRMS was higher in KE (0.056±0.014 vs. 0.043±0.003, p=0.03), but similar when normalized to EMGMAX (29.8±15.8 vs. 34.0±11.3%, p=0.21). Absolute SRCMAX was almost twice as high in KE compared to SQT (1.4±0.7 vs. 0.7±0.4mV, p=0.02), but similar when normalized to mean EMGRMS during sustained isometric contractions (KE: 25.3±14.0 vs. SQT: 17.4±10.7mV·EMGRMS-1, p=0.21). SRCV50 and SRCSLOPE did not differ (p>0.05). CONCLUSION: Single- and multi-joint exercises present distinct contractile and absolute corticospinal properties, which vanish after normalization, warranting caution when comparing results between studies.      Supported by the Department of Defense W81XWH-16-PHTBIRP-CR3A.  

Normalization Removes Differences in Contractile Properties and Corticospinal Excitability Between Single- and Multi-Joint Exercises

https://digitalcommons.wku.edu/cgi/viewcontent.cgi?article=4554&amp;context=ijesab

Normalization Removes Differences in Contractile Properties and Corticospinal Excitability Between Single- and Multi-Joint Exercises

Abstract

Similar works

Full text

Available Versions

TopSCHOLAR