Effect of external compression on femoral retrograde shear and microvascular oxygenation in exercise trained and recreationally active young men
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.
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).
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.
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.
KeywordsRetrograde shear Vascular Arterial stiffness Exercise training
Body mass index
Diastolic blood pressure
International Physical Activity Questionnaire
Muscle oxygen saturation
Pulse wave velocity
Superficial femoral artery
Systolic blood pressure
All authors conceptualized the study and assisted with study design. All authors piloted data collection. All authors prepared documents for ethics review (university IRB). PPL and AJP recruited all participants and collected all data. JPD and WKL oversaw all data collection to ensure high-quality data acquisition. PPL and AJP reduced all data and entered data into spreadsheets. JPD, WKL, and KSH conducted statistical analyses and interpreted results. PPL prepared data tables. All authors assisted with the preparation of the final manuscript. JPD and WKL edited all versions for scientific accuracy and overall presentation.
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