In:
NMR in Biomedicine, Wiley, Vol. 27, No. 8 ( 2014-08), p. 958-970
Abstract:
Exercise‐induced changes of transverse proton relaxation time ( T 2 ), tissue perfusion and metabolic turnover were investigated in the lower back muscles of volunteers by applying muscle functional MRI (mfMRI) and diffusion‐weighted imaging (DWI) before and after as well as dynamic 31 P‐MRS during the exercise. Inner ( M. multifidus , MF) and outer lower back muscles ( M. erector spinae , ES) were examined in 14 healthy young men performing a sustained isometric trunk‐extension. Significant phosphocreatine (PCr) depletions ranging from 30% (ES) to 34% (MF) and Pi accumulations between 95% (left ES) and 120%–140% (MF muscles and right ES) were observed during the exercise, which were accompanied by significantly decreased pH values in all muscles (∆pH ≈ –0.05). Baseline T 2 values were similar across all investigated muscles ( approximately 27 ms at 3 T), but revealed right–left asymmetric increases ( T 2 , inc ) after the exercise (right ES/MF: T 2 , inc = 11.8/9.7%; left ES/MF: T 2 , inc = 4.6/8.9%). Analyzed muscles also showed load‐induced increases in molecular diffusion D ( p = .007) and perfusion fraction f ( p = .002). The latter parameter was significantly higher in the MF than in the ES muscles both at rest and post exercise. Changes in PCr ( p = .03), diffusion ( p 〈 .01) and perfusion ( p = .03) were strongly associated with T 2,inc , and linear mixed model analysis revealed that changes in PCr and perfusion both affect T 2,inc ( p 〈 .001). These findings support previous assumptions that T 2 changes are not only an intra‐cellular phenomenon resulting from metabolic stress but are also affected by increased perfusion in loaded muscles. Copyright © 2014 John Wiley & Sons, Ltd.
Type of Medium:
Online Resource
ISSN:
0952-3480
,
1099-1492
Language:
English
Publisher:
Wiley
Publication Date:
2014
detail.hit.zdb_id:
2002003-X
detail.hit.zdb_id:
1000976-0
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