State-of-the-Art Methods for Skeletal Muscle Glycogen Analysis in Athletes-The Need for Novel Non-Invasive Techniques

Abstract

Muscle glycogen levels have a profound impact on an athlete's sporting performance, thus measurement is vital. Carbohydrate manipulation is a fundamental component in an athlete's lifestyle and is a critical part of elite performance, since it can provide necessary training adaptations. This paper provides a critical review of the current invasive and non-invasive methods for measuring skeletal muscle glycogen levels. These include the gold standard muscle biopsy, histochemical analysis, magnetic resonance spectroscopy, and musculoskeletal high frequency ultrasound, as well as pursuing future application of electromagnetic sensors in the pursuit of portable non-invasive quantification of muscle glycogen. This paper will be of interest to researchers who wish to understand the current and most appropriate techniques in measuring skeletal muscle glycogen. This will have applications both in the lab and in the field by improving the accuracy of research protocols and following the physiological adaptations to exercise.

Keywords: carbohydrates; electromagnetic sensors; magnetic resonance spectroscopy; muscle biopsy; muscle glycogen; musculoskeletal ultrasound.

Figure 1

A section of a glycogen molecule illustrating individual glucosyl units. It shows the two different types of glycosidic bonds used to make up glycogen.

Figure 2

Muscle glycogen use during exercise at different intensities (adapted from Gollnick et al., 1974).

Figure 3

Relationship between muscle glycogen content, exercise capacity, and diet (adapted from Bergstrom et al., 1967).

Figure 4

Illustration of an invasive muscle biopsy being performed on the gastrocnemius muscle.

Figure 5

Illustrates the Monopty 12 G, disposable core biopsy instrument (BARD, Brighton, UK) being used on an athlete’s vastus lateralis.

Figure 6

The presence of glycogen is shown by the loss of staining after enzyme treatment when compared to the untreated segments.

Figure 7

Example of an MRI machine illustrates how the subject is required to be fully stationary during the procedure.

Figure 8

(A) Application of ultrasound and equipment involved; (B) Example of a grey scale image produced by an Ultrasound when placed directly upon skeletal muscle.

Figure 9

(A) Experimental setup, showing participant on ergometer with sensors attached; and appropriate data acquisition hardware: (B) illustrates placement of sensors both arm and leg during a blood lactate exercise protocol.