Abstracts & Literature Review 2

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Exercise and Blood Flow Restriction

Zachary K. Pope, Jeffrey M. Willardson, Brad J. Schoenfeld
Journal of Strength and Conditioning Research
Publish Ahead of Print

JACO Editorial Reviewer Brandon Steele DC

Published:
Journal of the Academy of Chiropractic Orthopedists
September 2015, Volume 12, Issue 3

The original article copyright belongs to the original publisher. This review is available from: http://www.dcorthoacademy.org © 2015 Steele and the Academy of Chiropractic Orthopedists. This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Authors’ Abstract:

Background: Traditional understanding of exercise suggests moving heavy a load with high intensity is the most efficient way to induce muscle hypertrophy. There is a growing amount of evidence to suggest low intensity exercise with a blood flow restriction devices can also increase muscular strength and hypertrophy. Blood flow restriction (BFR) is achieved via the application of external pressure over the proximal portion of the upper or lower extremities. Restriction of the upper or lower limb venous return can affect the neural, endocrine, and metabolic pathways thereby inducing desired muscular responses. A full detail of such responses and exercise suggestions are presented in this article.

Conclusions: Muscular hypertrophy and strength are observed at considerably lower intensities (20% to 50% of 1-RM) than typical resistance training when combined with BFR. Utilization of BFR exercise may be better suited for populations that cannot tolerate high intensity resistance training. Prescriptive exercise variables for clinical populations are not yet definable; but in healthy populations, BFR exercise may provide an alternative means of obtaining a hypertrophic effect in a relatively short time period.

JACO Editorial Summary

  • The authors present the most current literature concerning the acute responses and chronic adaptations associated with BFR exercise.
  • The purpose of the paper was to compare the acute and chronic responses of muscle associated with both BFR and non-BFR exercise.
  • BFR exercise requires pressurized cuffs or elastic bands to compress the proximal portion of the lower extremity (inguinal crease) or upper extremity (distal to the deltoid muscle) during exercise. External pressure must be sufficient to maintain arterial inflow while occluding venous outflow of blood distal to the occlusion site (50-250 mmHg). Exercises are performed at low intensity with short intervals between sets.
  • Strength and hypertrophic adaptations may take place in muscles proximal or distal to the occlusion site. For example: occlusion of the arm distal to the deltoid during bench press exercises may elicit hypertrophy of the triceps brachii (distal to occlusion) and/or pectoralis major (proximal to occlusion).
  • Current research demonstrates increased muscular strength, hypertrophy, improved localized endurance, increase VO2 max, upregulation of angiogenesis, activation of fast twitch muscle fibers, local decrease in intramuscular pH, and release of growth hormone via BFR exercise.
  • Cell swelling from reactive hyperemia may be a common mechanism induced through BFR exercise to stimulate muscular adaptation. Intracellular swelling stimulates protein synthesis and decreases proteolysis thereby promoting an anabolic response.
  • Practitioners should be concerned over the potential risks associated with altered cardiovascular function during BFR exercise. For example: patients with low cardiovascular risk factors may walk with bilateral BFR at the inguinal crease while other patients may perform isolated knee extensions to lower cardiovascular demands during exercise.
  • Potential side effects include, but are not limited to: cerebral anemia, venous thrombus, pulmonary embolism, rhabdomyolysis, deterioration of heart disease, subcutaneous hemorrhage, numbness and cold feeling. The incidence of significant side effects remains small affecting <1% of patients performing BFR exercises.
  • The application of BFR exercise may be best suited for populations that cannot tolerate the large mechanical loads imposed during high intensity resistance training. This type of exercise may provide an alternative means of obtaining a hypertrophic effect on muscles in a relatively short time period.
  • Exercise prescription will vary dependent on patient goals. It may be performed everyday or as few as 2-3 sets per week. Time under occlusion will attenuate metabolite accumulation. Alternating agonist/antagonist movements with continuous BFR may also be utilized.

Summary

The results from this journal highlight the complexity of the rehabilitation options chiropractic physician’s encounter on a daily basis. Blood flow restriction exercise may be another tool in the toolbox for those patients requiring muscle hypertrophy as a part of their treatment. Clinicians should be cognizant of potential side effects mostly affecting the cardiovascular system. This exercise may be a treatment option to achieve optimal clinical results for the right patient. I would like to see more information on specific exercise prescription and protocols as evidenced in the literature; however, research on BFR exercise is limited at this time.