Age-related structural and functional changes of low back muscles.
During aging declining maximum force capacity with more or less unchanged fatigability is observed with the underlying mechanisms still not fully understood. Therefore, we compared morphology and function of skeletal muscles between different age groups. Changes in high-energy phosphate turnover (PCr, Pi and pH) and muscle functional MRI (mfMRI) parameters, including proton transverse relaxation time (T2), diffusion (D) and vascular volume fraction (f), were investigated in moderately exercised low back muscles of young and late-middle-aged healthy subjects with (31)P-MR spectroscopy, T2- and diffusion-weighted MRI at 3T. In addition, T1-weighted MRI data were acquired to determine muscle cross-sectional areas (CSA) and to assess fat infiltration into muscle tissue. Except for pH, both age groups showed similar load-induced MR changes and rates of perceived exertion (RPE), which indicates comparable behavior of muscle activation at moderate loads. Changes of mfMRI parameters were significantly associated with RPE in both cohorts. Age-related differences were observed, with lower pH and higher Pi/ATP ratios as well as lower D and f values in the late-middle-aged subjects. These findings are ascribed to age-related changes of fiber type composition, fiber size and vascularity. Interestingly, post exercise f was negatively associated with fat infiltration with the latter being significantly higher in late-middle-aged subjects. CSA of low back muscles remained unchanged, while CSA of inner back muscle as well as mean T2 at rest were associated with maximum force capacity. Overall, applying the proposed MR approach provides evidence of age-related changes in several muscle tissue characteristics and gives new insights into the physiological processes that take place during aging.
Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany. Electronic address: patrick.hiepe@med.uni-jena.de.
Patrick
P
Hiepe
Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Alexander
A
Gussew
Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Reinhard
R
Rzanny
Department for Trauma-, Hand- and Reconstructive Surgery, Division of Motor Research, Pathophysiology and Biomechanics, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Eduard
E
Kurz
Department for Trauma-, Hand- and Reconstructive Surgery, Division of Motor Research, Pathophysiology and Biomechanics, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Christoph
C
Anders
Institute of Medical Statistics, Computer Sciences and Documentation (IMSID), Jena University Hospital - Friedrich Schiller University Jena, Germany.
Mario
M
Walther
Department for Trauma-, Hand- and Reconstructive Surgery, Division of Motor Research, Pathophysiology and Biomechanics, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Hans-Christoph
HC
Scholle
Medical Physics Group, Institute of Diagnostic and Interventional Radiology, Jena University Hospital - Friedrich Schiller University Jena, Germany.
Jürgen R
JR
Reichenbach
D000367:Age Factors; D000375:Aging / Q000502:physiology*; D064131:Back Muscles / Q000098:blood supply / Q000473:pathology / Q000503:physiopathology; D050218:Body Fat Distribution / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000473:pathology / Q000502:physiology; D015203:Reproducibility of Results; D055815:Young Adult
Aging; Diffusion weighted imaging; Low back muscles; Magnetic resonance imaging; Phosphorus magnetic resonance spectroscopy