Details

Autor(en) / Beteiligte

• Rzanny, Reinhard
• Stutzig, Norman
• Hiepe, Patrick
• Gussew, Alexander
• Thorhauer, Hans-Alexander
• Reichenbach, Jürgen R

Titel

The reproducibility of different metabolic markers for muscle fiber type distributions investigated by functional 31 P-MRS during dynamic exercise

Ist Teil von

• Zeitschrift für medizinische Physik, 2016-12, Vol.26 (4), p.323

Ort / Verlag

Germany

Erscheinungsjahr

2016

Link zum Volltext

Quelle

MEDLINE

Beschreibungen/Notizen

• The objective of the study was to investigate the reproducibility of exercise induced pH-heterogeneity by splitting of the inorganic phosphate (Pi) signal in the corresponding P-MRS spectra and to compare results of this approach with other fiber-type related markers, like phosphocreatine/adenosine triphosphate (PCr/ATP) ratio, and PCr-recovery parameters. Subjects (N=3) with different sportive background were tested in 10 test sessions separated by at least 3 days. A MR-compatible pedal ergometer was used to perform the exercise and to induce a pH-based splitting of the Pi-signal in P-MR spectra of the medial gastrocnemius muscle. The PCr recovery was analyzed using a non-negative least square algorithm (NNLS) and multi-exponential regression analysis to estimate the number of non-exponential components as well as their amplitude and time constant. The reproducibility of the estimated metabolic marker and the resulting fiber-type distributions between the 10 test sessions were compared. The reproducibility (standard deviation between measurements) based on (1) Pi components varied from 2% to 4%, (2) PCr recovery time components varied from 10% to 12% and (3) phosphate concentrations at rest varied from 8% to 11% between test sessions. Due to the sportive activity differences between the 3 subjects were expected in view of fiber type distribution. All estimated markers indicate the highest type I percentage for volunteer 3 medium for volunteer 2 and the lowest for volunteer 1. The relative high reproducibility of pH dependent Pi components during exercise indicates a high potential of this method to estimate muscle fiber-type distributions in vivo. To make this method usable not only to detect differences in muscle fiber distributions but also to determine individual fiber-type volume contents it is therefore recommended to validate this marker by histological methods and to reveal the effects of muscle fiber recruitments and fiber-type specific Pi concentrations on the intensity ratios between the splitted Pi-components.