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Blood flow restriction in the presence or absence of muscle contractions does not preserve vasculature structure and function following 14–days of limb immobilization

Abstract

Purpose

Limb immobilization causes local vasculature to experience detrimental adaptations. Simple strategies to increase blood flow (heating, fidgeting) successfully prevent acute (≤ 1 day) impairments; however, none have leveraged the hyperemic response over prolonged periods (weeks) mirroring injury rehabilitation. Throughout a 14-day unilateral limb immobilization, we sought to preserve vascular structure and responsiveness by repeatedly activating a reactive hyperemic response via blood flow restriction (BFR) and amplifying this stimulus by combining BFR with electric muscle stimulation (EMS).

Methods

Young healthy adults (M:F = 14:17, age = 22.4 ± 3.7 years) were randomly assigned to control, BFR, or BFR + EMS groups. BFR and BFR + EMS groups were treated for 30 min twice daily (3 × 10 min ischemia–reperfusion cycles; 15% maximal voluntary contraction EMS), 5 days/week (20 total sessions). Before and after immobilization, artery diameter, flow-mediated dilation (FMD) and blood flow measures were collected in the superficial femoral artery (SFA).

Results

Following immobilization, there was less retrograde blood velocity (+ 1.8 ± 3.6 cm s−1, P = 0.01), but not retrograde shear (P = 0.097). All groups displayed reduced baseline and peak SFA diameter following immobilization (− 0.46 ± 0.41 mm and − 0.43 ± 0.39 mm, P < 0.01); however, there were no differences by group or across time for FMD (% diameter change, shear-corrected, or allometrically scaled) nor microvascular function assessed by peak flow capacity.

Conclusion

Following immobilization, our results reveal (1) neither BFR nor BFR + EMS mitigate artery structure impairments, (2) intervention-induced shear stress did not affect vascular function assessed by FMD, and (3) retrograde blood velocity is reduced at rest offering potential insight to mechanisms of flow regulation. In conclusion, BFR appears insufficient as a treatment strategy for preventing macrovascular dysfunction during limb immobilization.

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Data availability

Relevant study data are available from the corresponding author upon reasonable request.

Abbreviations

BFR:

Blood flow restriction

EMS:

Electric muscle stimulation

FMD:

Flow-mediated dilation

MAP:

Mean arterial pressure

MBV:

Mean blood velocity

NO:

Nitric oxide

OSI:

Oscillatory shear index

PWV:

Pulse wave velocity

SFA:

Superficial femoral artery

SR:

Shear rate

SR60AUC :

Shear rate area-under-curve first 60 s

References

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Funding

This work was supported by a Natural Science and Engineering Research Council (NSERC) Discovery grant (JFB).

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Authors and Affiliations

Authors

Contributions

JTS and JFB conceived and designed the study; JTS, TJK, AMC and RTK collected data; JNC analyzed data; JNC, JTS, TJK and JFB interpreted results; JNC drafted the manuscript. All authors read and approved the final version of the manuscript.

Corresponding author

Correspondence to Jamie F. Burr.

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Conflict of interest

The authors have no conflicts of interest to declare that are relevant to the content of this article.

Ethical approval

This study was approved by the institutional ethics review committee (REB# 17–12-006).

Consent to participate

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

Consent for publication

Participants signed informed consent regarding publishing their data.

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Communicated by Ellen Adele Dawson.

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Cohen, J.N., Slysz, J.T., King, T.J. et al. Blood flow restriction in the presence or absence of muscle contractions does not preserve vasculature structure and function following 14–days of limb immobilization. Eur J Appl Physiol 121, 2437–2447 (2021). https://doi.org/10.1007/s00421-021-04715-3

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  • DOI: https://doi.org/10.1007/s00421-021-04715-3

Keywords

  • Electric muscle stimulation
  • Muscle disuse
  • Flow-mediated dilation
  • Arterial stiffness
  • Pulse wave velocity