title: Muscle oxygenation during dynamic plantar flexion exercise: combining BOLD MRI with traditional physiological measurements.
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.
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania mmuller1@hmc.psu.edu.
authors: Matthew D
authors: MD
authors: Muller
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Zhijun
authors: Z
authors: Li
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Christopher T
authors: CT
authors: Sica
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: J Carter
authors: JC
authors: Luck
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Zhaohui
authors: Z
authors: Gao
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Cheryl A
authors: CA
authors: Blaha
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Aimee E
authors: AE
authors: Cauffman
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Amanda J
authors: AJ
authors: Ross
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Nathan J R
authors: NJ
authors: Winkler
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Michael D
authors: MD
authors: Herr
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Kristen
authors: K
authors: Brandt
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Jianli
authors: J
authors: Wang
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: David C
authors: DC
authors: Gallagher
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Prasanna
authors: P
authors: Karunanayaka
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Jeffrey
authors: J
authors: Vesek
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Urs A
authors: UA
authors: Leuenberger
authors: Department of Radiology, Center for NMR Research, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Qing X
authors: QX
authors: Yang
authors: Penn State Hershey Heart and Vascular Institute, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
authors: Lawrence I
authors: LI
authors: Sinoway
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D011150:Popliteal Artery / Q000000981:diagnostic imaging*; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D014463:Ultrasonography / Q000379:methods; D055815:Young Adult
keywords: Blood pressure; heart rate; sympathetic nervous system