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Differential Motor Unit Changes after Endurance or High-Intensity Interval Training

  • Purpose Using a novel technique of high-density surface EMG decomposition and motor unit (MU) tracking, we compared changes in the properties of vastus medialis and vastus lateralis MU after endurance (END) and high-intensity interval training (HIIT). Methods Sixteen men were assigned to the END or the HIIT group (n = 8 each) and performed six training sessions for 14 d. Each session consisted of 8-12 x 60-s intervals at 100% peak power output separated by 75 s of recovery (HIIT) or 90-120 min continuous cycling at similar to 65% VO2peak (END). Pre- and postintervention, participants performed 1) incremental cycling to determine VO2peak and peak power output and 2) maximal, submaximal (10%, 30%, 50%, and 70% maximum voluntary contraction [MVC]), and sustained (until task failure at 30% MVC) isometric knee extensions while high-density surface EMG signals were recorded from the vastus medialis and vastus lateralis. EMG signals were decomposed (submaximal contractions) into individual MU by convolutive blind source separation. Finally,Purpose Using a novel technique of high-density surface EMG decomposition and motor unit (MU) tracking, we compared changes in the properties of vastus medialis and vastus lateralis MU after endurance (END) and high-intensity interval training (HIIT). Methods Sixteen men were assigned to the END or the HIIT group (n = 8 each) and performed six training sessions for 14 d. Each session consisted of 8-12 x 60-s intervals at 100% peak power output separated by 75 s of recovery (HIIT) or 90-120 min continuous cycling at similar to 65% VO2peak (END). Pre- and postintervention, participants performed 1) incremental cycling to determine VO2peak and peak power output and 2) maximal, submaximal (10%, 30%, 50%, and 70% maximum voluntary contraction [MVC]), and sustained (until task failure at 30% MVC) isometric knee extensions while high-density surface EMG signals were recorded from the vastus medialis and vastus lateralis. EMG signals were decomposed (submaximal contractions) into individual MU by convolutive blind source separation. Finally, MU were tracked across sessions by semiblind source separation. Results After training, END and HIIT improved VO2peak similarly (by 5.0% and 6.7%, respectively). The HIIT group showed enhanced maximal knee extension torque by similar to 7% (P = 0.02) and was accompanied by an increase in discharge rate for high-threshold MU (50% knee extension MVC) (P < 0.05). By contrast, the END group increased their time to task failure by similar to 17% but showed no change in MU discharge rates (P > 0.05). Conclusions HIIT and END induce different adjustments in MU discharge rate despite similar improvements in cardiopulmonary fitness. Moreover, the changes induced by HIIT are specific for high-threshold MU. For the first time, we show that HIIT and END induce specific neuromuscular adaptations, possibly related to differences in exercise load intensity and training volume.show moreshow less

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Metadaten
Author:Eduardo Martinez-Valdes, Deborah Falla, Francesco NegroORCiD, Frank MayerORCiDGND, Dario Farina
DOI:https://doi.org/10.1249/MSS.0000000000001209
ISSN:0195-9131
ISSN:1530-0315
Pubmed Id:http://www.ncbi.nlm.nih.gov/pubmed?term=28121801
Parent Title (English):Medicine and science in sports and exercise : official journal of the American College of Sports Medicine
Publisher:Lippincott Williams & Wilkins
Place of publication:Philadelphia
Document Type:Article
Language:English
Year of first Publication:2017
Year of Completion:2017
Release Date:2020/04/20
Tag:HIGH-DENSITY SURFACE EMG; MOTOR UNIT ADAPTATION; MOTOR UNIT DECOMPOSITION; MOTOR UNIT DISCHARGE RATE; MOTOR UNIT TRACKING; NEUROMUSCULAR ADAPTATION
Volume:49
Pagenumber:11
First Page:1126
Last Page:1136
Funder:University of Potsdam of the federal state of Brandenburg, Germany
Organizational units:Humanwissenschaftliche Fakultät / Institut für Sportwissenschaft
Peer Review:Referiert