Effect of external compression on femoral retrograde shear and microvascular oxygenation in exercise trained and recreationally active young men

Abstract

Introduction: Retrograde shear causes endothelial damage and is pro-atherogenic. The purpose of our study was to examine the impact of vascular remodeling from habitual exercise training on acute changes in retrograde shear and microvascular oxygenation (SMO₂) induced via 30 min of external compression.

Methods: Participants included 11 exercise trained (ET) men (Division I track athletes; age 20 ± 3 years) and 18 recreationally active (RA) men (age 23 ± 5 years). Near-infrared spectroscopy (NIRS) was used to measure vastus medialis SMO₂. Doppler-ultrasound was used to assess SFA intima-media thickness, diameter and flow velocity to derive retrograde shear. Vascular measures were made at baseline (BASELINE), during a sham condition (calf compression to 5 mmHg, SHAM) and during the experimental condition (calf compression to 60 mmHg, EXP).

Results: Compared to RA, ET had larger SFA diameters (0.66 ± 0.06 vs 0.58 ± 0.06 cm, p < 0.05) and lower SFA IMT (0.33 ± 0.03 vs 0.36 ± 0.07 mm, p < 0.05). Retrograde shear increased similarly in both groups during EXP (p < 0.05) but ET men had lower overall retrograde shear during the conditions (BASELINE 75.8 ± 26.8 vs EXP 88.2 ± 16.9 s^-1) compared to RA men (BASELINE 84.4 ± 23.3 vs EXP 106.4 ± 19.6 s^-1p < 0.05). There was a similar increase in SMO₂ from BASELINE to SHAM (ET + 8.1 ± 4.8 vs RA + 6.4 ± 9.7%) and BASELINE to EXP (ET + 8.7 ± 6.4 vs RA + 7.1 ± 9.0%) in both groups.

Conclusion: Beneficial vascular remodeling in ET men is associated with lower retrograde shear during external compression. Acute increases in retrograde shear with external compression do not detrimentally impact microvascular oxygenation.

Keywords: Arterial stiffness; Exercise training; Retrograde shear; Vascular.