Characteristics, changes and influence of body composition during a 4486 km transcontinental ultramarathon: Results from the Transeurope Footrace mobile whole body MRI-project.

Background: Almost nothing is known about the medical aspects of runners doing a transcontinental ultramarathon over several weeks. The results of differentiated measurements of changes in body composition during the Transeurope Footrace 2009 using a mobile whole body magnetic resonance (MR) imager are presented and the proposed influence of visceral and somatic adipose and lean tissue distribution on performance tested. Methods: 22 participants were randomly selected for the repeated MR measurements (intervals: 800 km) with a 1.5 Tesla MR scanner mounted on a mobile unit during the 64-stage 4,486 km ultramarathon. A standardized and validated MRI protocol was used: T1 weighted turbo spin echo sequence, echo time 12 ms, repetition time 490 ms, slice thickness 10 mm, slice distance 10mm (breath holding examinations). For topographic tissue segmentation and mapping a modified fuzzy c-means algorithm was used. A semi-automatic post-processing of whole body MRI data sets allows reliable analysis of the following body tissue compartments: Total body volume (TV), total somatic (TSV) and total visceral volume (TVV), total adipose (TAT) and total lean tissue (TLT), somatic (SLT) and visceral lean tissue (VLT), somatic (SAT) and visceral adipose tissue (VAT) and somatic adipose soft tissue (SAST). Specific volume changes were tested on significance. Tests on difference and relationship regarding prerace and race performance and non-finishing were done using statistical software SPSS. Results: Total, somatic and visceral volumes showed a significant decrease throughout the race. Adipose tissue showed a significant decrease compared to the start at all measurement times for TAT, SAST and VAT. Lean adipose tissues decreased until the end of the race, but not significantly. The mean relative volume changes of the different tissue compartments at the last measurement compared to the start were: TV -9.5% (SE 1.5%), TSV -9.4% (SE 1.5%), TVV -10.0% (SE 1.4%), TAT -41.3% (SE 2.3%), SAST -48.7% (SE 2.8%), VAT -64.5% (SE 4.6%), intraabdominal adipose tissue (IAAT) -67.3% (SE 4.3%), mediastinal adopose tissue (MAT) -41.5% (SE 7.1%), TLT -1.2% (SE 1.0%), SLT -1.4% (SE 1.1%). Before the start and during the early phase of the Transeurope Footrace 2009, the non-finisher group had a significantly higher percentage volume of TVV, TAT, SAST and VAT compared to the finisher group. VAT correlates significantly with prerace training volume and intensity one year before the race and with 50 km-and 24 hour-race records. Neither prerace body composition nor specific tissue compartment volume changes showed a significant relationship to performance in the last two thirds of the Transeurope Footrace 2009. Conclusions: With this mobile MRI field study the complex changes in body composition during a multistage ultramarathon could be demonstrated in detail in a new and differentiated way. Participants lost more than half of their adipose tissue. Even lean tissue volume (mainly skeletal muscle tissue) decreased due to the unpreventable chronic negative energy balance during the race. VAT has the fastest and highest decrease compared to SAST and lean tissue compartments during the race. It seems to be the most sensitive morphometric parameter regarding the risk of non-finishing a transcontinental footrace and shows a direct relationship to prerace-performance. However, body volume or body mass and, therefore, fat volume has no correlation with total race performances of ultra-athletes finishing a 4,500 km multistage race

Relaxometry of tendons, ligaments and menisci in the knee joint at 3 T

Within the last years a variety of pulse sequences have been published which visualize musculoskeletal tissues such as menisci, tendons, or ligaments with positive contrast despite their relatively short T2-values. For optimization of sequence parameters by numerical simulations based on Bloch’s equations, knowledge of tissue relaxation times is essential. So far there has been no comprehensive MRI study regarding the systematic measurement of their inherent relaxation properties. Therefore, the purpose of this study was to exemplarily quantify the T1lower case Greek rho, T1, T2, and T2* relaxation times of rapidly relaxing tissues in the human knee joint at 3T in an acceptable examination time

Distribution patterns of intramyocellular and extramyocellular fat by magnetic resonance imaging in subjects with diabetes, prediabetes and normoglycaemic controls

AIMS: Intramuscular fat contributes to peripheral insulin resistance and type 2 diabetes mellitus (T2DM). Intra- and extramyocellular lipids (IMCLs&EMCLs) may be quantified by magnetic resonance imaging (MRI) and serve as imaging biomarkers in impaired glucose metabolism. MATERIALS & METHODS: Subjects from a population-based cohort were classified with T2DM, prediabetes or normoglycemic controls. Total myosteatosis, IMCLs and EMCLs were quantified by Multi-echo Dixon MRI as proton-density fat-fraction (PDFF in %) in abdominal skeletal muscle. RESULTS: Among 337 included subjects (median age 56.0years (IQR:49.0-64.0years), 56.4% males, median BMI:27.2kg/m2 ) 129(38.3%) were classified with an impaired glucose metabolism (T2DM: 49(14.5%); prediabetes: 80(23.7%)). IMCLs were significantly higher than EMCLs in subjects without obesity (5.7%(IQR: 4.8-7.0%) vs. 4.1%(IQR: 2.7-5.8%), p<0.001), whereas the amount of IMCLs and EMCLs was shown to be equal and significantly higher in subjects with obesity (both 6.7%, p<0.001). Subjects with prediabetes and T2DM had significantly higher amounts of IMCLs and EMCLs as compared to normoglycemic controls (p<0.001). In univariable analysis, prediabetes and T2DM were significantly associated with both, IMCLs (prediabetes: β:0.76, 95%-CI:0.28-1.24, p=0.002; T2DM: β:1.56, 95%-CI:0.66-2.47, p<0.001) and EMCLs (prediabetes: β:1.54, 95%-CI:0.56-2.51, p=0.002; T2DM: β:2.15, 95%-CI:1.33-2.96, p<0.001). After adjustment for age and gender, the association of IMCLs with prediabetes attenuated (p=0.06), whereas for T2DM, both IMCLs and EMCLs remained significantly and positively associated (p<0.02). CONCLUSION: There are significant differences in the amount and distribution ratio of IMCLs and EMCLs between subjects with T2DM, prediabetes and normoglycemic controls. These patterns of intramuscular fat distribution by MRI might therefore serve as imaging biomarkers in both normal and impaired glucose metabolism