Evaluation of individual skeletal muscle activity by glucose uptake during pedaling exercise at different workloads using positron emission tomography

Abstract

Skeletal muscle glucose uptake closely reflects muscle activity at exercise intensity levels <55% of maximal oxygen consumption (VO2max). Our purpose was to evaluate individual skeletal muscle activity from glucose uptake in humans during pedaling exercise at different workloads by using [18F]fluorodeoxyglucose (FDG) and positron emission tomography (PET). Twenty healthy male subjects were divided into two groups (7 exercise subjects and 13 control subjects). Exercise subjects were studied during 35 min of pedaling exercise at 40 and 55% VO2max exercise intensities. FDG was injected 10 min after the start of exercise or after 20 min of rest. PET scanning of the whole body was conducted after completion of the exercise or rest period. In exercise subjects, mean FDG uptake [standardized uptake ratio (SUR)] of the iliacus muscle and muscles of the anterior part of the thigh was significantly greater than uptake in muscles of control subjects. At 55% VO2max exercise, SURs of the iliacus muscle and thigh muscles, except for the rectus femoris, increased significantly compared with SURs at 40% VO2max exercise. Our results are the first to clarify that the iliacus muscle, as well as the muscles of the anterior thigh, is the prime muscle used during pedaling exercise. In addition, the iliacus muscle and all muscles in the thigh, except for the rectus femoris, contribute when the workload of the pedaling exercise increases from 40 to 55% VO2max.

Cyclists’ Improvement of Pedaling Efficacy and Performance After Heavy Strength Training

“…Other researchers have reported that the iliopsoas muscle is an important contributor during pedaling. 12 The rectus femoris muscle, which crosses the hip joint like the iliopsoas muscle, but in addition crosses the knee joint, is considered a top transition-extensor muscle, where "top" refers to the top dead center of the crank revolution. 13 Increased rate of force development in the hip-flexor muscles would reduce the time from muscle activation to production of a force of sufficient magnitude to flex the hip, lift the leg mass against gravity, and eventually relieve the pedal from the mass of the leg.…”

Treadmill Exercise Inducing Mild to Moderate Ischemia Has No Significant Effect on Skeletal Muscle or Cardiac 18F-FDG Uptake and Image Quality on Subsequent Whole-Body PET Scan

“…First, the duration of exercise stress testing in our patients was relatively short and the intensity relatively low. By comparison, studies in healthy volunteers involved much more demanding regimens (6,9,15,16). Although our patients achieved a reasonable work load, the exercise capacity in a predominantly elderly group of oncology patients is probably lower than that of healthy (and mostly younger) volunteers in applied physiology protocols.…”

“…Exercise-induced 18 F-FDG uptake in skeletal muscles has been studied (9,10,15). With treadmill exercise, 18 F-FDG uptake increases in the soleus, gastrocnemius, gluteal, and quadriceps muscles, followed by adductors and hamstring muscles.…”

“…Increased mitochondrial biogenesis and increases of GLUT4 and hexokinase are detectable within hours to days of initiating an exercise program (8). The resulting increased glucose uptake in muscles can be visualized with 18 F-FDG (9,10). Guidelines recommend that patients refrain from physical exercise for at least several hours before 18 F-FDG PET (11,12) to improve tumor versus muscle 18 F-FDG uptake and overall PET image quality.…”

Glucose Uptake Is Decreased in Affected Lower Leg Muscles of Hemiparetic Persons during Level Walking

“…Various reports have quantified muscle activity using 18 F-FDG PET (Fujimoto et al 1996Tashiro et al 1999;Gondoh et al 2009;Shimada et al 2011). Fujimoto et al (1996) were the first to use this method and reported muscle activity during running.…”