Muscle oxygenation during dynamic plantar flexion exercise: combining BOLD MRI with traditional physiological measurements.

Matthew D Muller,David C Gallagher,Amanda J Ross,Jeffrey Vesek,Michael D Herr,Aimee E Cauffman,J Carter Luck,Jianli Wang,Qing X Yang,Christopher T Sica,Zhaohui Gao,Urs A Leuenberger,Kristen Brandt,Lawrence I Sinoway,Zhijun Li,Prasanna Karunanayaka,Nathan J.R Winkler,Cheryl A Blaha

doi:10.14814/phy2.13004

Matthew D Muller, David C Gallagher + Show 16 more

Open Access

https://doi.org/10.14814/phy2.13004

Copy DOI

Journal: Physiological Reports	Publication Date: Oct 1, 2016
Citations: 17	License type: CC BY 4.0

Affiliation: Pennsylvania State University

Abstract

Blood‐oxygen‐level‐dependent magnetic resonance imaging (BOLD MRI) has the potential to quantify skeletal muscle oxygenation with high temporal and high spatial resolution. The purpose of this study was to characterize skeletal muscle BOLD responses during steady‐state plantar flexion exercise (i.e., during the brief rest periods between muscle contraction). We used three different imaging modalities (ultrasound of the popliteal artery, BOLD MRI, and near‐infrared spectroscopy [NIRS]) and two different exercise intensities (2 and 6 kg). Six healthy men underwent three separate protocols of dynamic plantar flexion exercise on separate days and acute physiological responses were measured. Ultrasound studies showed the percent change in popliteal velocity from baseline to the end of exercise was 151 ± 24% during 2 kg and 589 ± 145% during 6 kg. MRI studies showed an abrupt decrease in BOLD signal intensity at the onset of 2 kg exercise, indicating deoxygenation. The BOLD signal was further reduced during 6 kg exercise (compared to 2 kg) at 1 min (−4.3 ± 0.7 vs. −1.2 ± 0.4%, P < 0.001). Similarly, the change in the NIRS muscle oxygen saturation in the medial gastrocnemius was −11 ± 4% at 2 kg and −38 ± 11% with 6 kg (P = 0.041). In conclusion, we demonstrate that BOLD signal intensity decreases during plantar flexion and this effect is augmented at higher exercise workloads.

Highlights

During exercise, skeletal muscle requires increased oxygen and nutrient delivery to meet the increased metabolism of contraction
Prior human experiments using cycle ergometry (Welch et al 1977; Proctor et al 2003a,b) and knee extension (Richardson et al 1999; Amann et al 2011) have shown that femoral blood flow increases and femoral venous oxygen saturation decreases during exercise, indicating improved oxygen delivery and a larger arterial to venous oxygen difference
We present a novel application of BOLD MRI to quantify muscle deoxygenation during single-leg dynamic plantar flexion exercise

Summary

Introduction

Skeletal muscle requires increased oxygen and nutrient delivery to meet the increased metabolism of contraction. Prior human experiments using cycle ergometry (Welch et al 1977; Proctor et al 2003a,b) and knee extension (Richardson et al 1999; Amann et al 2011) have shown that femoral blood flow increases and femoral venous oxygen saturation decreases during exercise, indicating improved oxygen delivery and a larger arterial to venous oxygen difference At submaximal intensities, both flow and oxygen extraction increase as workload increases (Proctor et al 2003a,b; Damon et al 2007b; Amann et al 2011; Green et al 2011; Richardson et al 2015). We present a novel application of BOLD MRI to quantify muscle deoxygenation during single-leg dynamic plantar flexion exercise (i.e., a long duration laboratory stimulus similar to upright walking that significantly increases leg blood flow)

Objectives

Results

Conclusion