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Neuromuscular Function and Blood Flow Occlusion with Dynamic Arm Flexor Contractions.

Abstract

INTRODUCTION

Blood flow restricted or occlusion exercise enhances muscle hypertrophy and strength during resistance training. The acute effects on voluntary and electrically evoked muscle contractile characteristics with impaired blood flow at low and high contraction forces has not been explored.

METHODS

On separate days, nine males completed two different protocols of concentric elbow flexor contractions. A repetitive low-force (~25% of isometric maximum voluntary contraction, MVC) with blood flow occlusion (BFO; 300mmHg) protocol was compared to a high-force (~80% MVC) free blood flow protocol (HF), until range of motion (0-90°) was impaired. Torque, velocity and power were compared to baseline and between protocols. MVC and voluntary activation (VA) were assessed during and following each protocol. Muscle twitch, low (20Hz) and high (50 Hz) tetanus, and compound muscle action potential (Mmax) area were measured at 0, 2, 5, 10, and 20min of recovery.

RESULTS

Repetitions to failure (FP) were lower for HF (~16) versus BFO (~21), and MVC at FP was reduced more during BFO (~77%) compared to HF (~23%), with no difference in VA (~10% loss) between protocols. At FP, velocities for BFO and HF were similarly reduced by ~63% and ~56%, respectively, however peak power decreased more during BFO (~90%) compared with HF (~67%). Total work for BFO was ~40% lower than for HF. Peak power for HF was recovered by 2mins, whereas BFO required 20mins. Low-frequency fatigue (20Hz/50Hz) was greater following BFO (~70% decrease versus ~29% decrease following HF), while Mmax area was unaffected.

CONCLUSION

Concentric elbow flexions at low-force with BFO causes greater impairments in strength and power than HF and therefore may be a replacement for high-force exercise used in chronic training.

Authors+Show Affiliations

Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, Canada.Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, ON, Canada. Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31318712

Citation

Copithorne, David B., and Charles L. Rice. "Neuromuscular Function and Blood Flow Occlusion With Dynamic Arm Flexor Contractions." Medicine and Science in Sports and Exercise, 2019.
Copithorne DB, Rice CL. Neuromuscular Function and Blood Flow Occlusion with Dynamic Arm Flexor Contractions. Med Sci Sports Exerc. 2019.
Copithorne, D. B., & Rice, C. L. (2019). Neuromuscular Function and Blood Flow Occlusion with Dynamic Arm Flexor Contractions. Medicine and Science in Sports and Exercise, doi:10.1249/MSS.0000000000002091.
Copithorne DB, Rice CL. Neuromuscular Function and Blood Flow Occlusion With Dynamic Arm Flexor Contractions. Med Sci Sports Exerc. 2019 Jul 16; PubMed PMID: 31318712.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Neuromuscular Function and Blood Flow Occlusion with Dynamic Arm Flexor Contractions. AU - Copithorne,David B, AU - Rice,Charles L, Y1 - 2019/07/16/ PY - 2019/7/19/entrez PY - 2019/7/19/pubmed PY - 2019/7/19/medline JF - Medicine and science in sports and exercise JO - Med Sci Sports Exerc N2 - INTRODUCTION: Blood flow restricted or occlusion exercise enhances muscle hypertrophy and strength during resistance training. The acute effects on voluntary and electrically evoked muscle contractile characteristics with impaired blood flow at low and high contraction forces has not been explored. METHODS: On separate days, nine males completed two different protocols of concentric elbow flexor contractions. A repetitive low-force (~25% of isometric maximum voluntary contraction, MVC) with blood flow occlusion (BFO; 300mmHg) protocol was compared to a high-force (~80% MVC) free blood flow protocol (HF), until range of motion (0-90°) was impaired. Torque, velocity and power were compared to baseline and between protocols. MVC and voluntary activation (VA) were assessed during and following each protocol. Muscle twitch, low (20Hz) and high (50 Hz) tetanus, and compound muscle action potential (Mmax) area were measured at 0, 2, 5, 10, and 20min of recovery. RESULTS: Repetitions to failure (FP) were lower for HF (~16) versus BFO (~21), and MVC at FP was reduced more during BFO (~77%) compared to HF (~23%), with no difference in VA (~10% loss) between protocols. At FP, velocities for BFO and HF were similarly reduced by ~63% and ~56%, respectively, however peak power decreased more during BFO (~90%) compared with HF (~67%). Total work for BFO was ~40% lower than for HF. Peak power for HF was recovered by 2mins, whereas BFO required 20mins. Low-frequency fatigue (20Hz/50Hz) was greater following BFO (~70% decrease versus ~29% decrease following HF), while Mmax area was unaffected. CONCLUSION: Concentric elbow flexions at low-force with BFO causes greater impairments in strength and power than HF and therefore may be a replacement for high-force exercise used in chronic training. SN - 1530-0315 UR - https://www.unboundmedicine.com/medline/citation/31318712/Neuromuscular_Function_and_Blood_Flow_Occlusion_with_Dynamic_Arm_Flexor_Contractions L2 - http://Insights.ovid.com/pubmed?pmid=31318712 DB - PRIME DP - Unbound Medicine ER -