After commitment to funding by the German Research Society (DFG) the 67 TEFR09 participants were asked to join the TEFR project, which was approved by the local ethics committee of the University Hospital of Ulm (UHU, No.: 270/08-UBB/se), Germany (in accordance with the Declaration of Helsinki) regarding the study design, risk management plan and individual protocols. Verbal and written informed consent was obtained from all concurring subjects.
The most important research tool was a 1.5 Tesla whole-body MR imager (Magnetom Avanto™ mobile MRI 02.05, software version: Syngo™ MR B15, Siemens Ltd., Erlangen, Germany) mounted on a mobile unit (MRI-Trailer Model Mob.MRI 02.05, SMIT Mobile Equipment B.V., Division AK Specialty Vehicles, Farnham, UK) pulled by a specially hired truck tractor. The semi-trailer had an internal diesel generator to power the helium cooling circuit for the MRI over the ten-week period. However, it did not generate enough electricity for continuous MRI measurements and was therefore supplemented by a more powerful custom made external diesel generator (150 KVA, Strom Rent™ e.k., Dortmund, Germany) which was pulled by an additional material van. The mobile hardware had a total weight of more than 45 tonnes and was nearly 30 meters long. All of the equipment was installed daily at each stopover and required daily checks and support of all technical systems (Figure ).
Truck trailer with mobile MRI and external generator in working position.
Forty-four (67%) of the race participants (mean age 49.7 years, range 26 to 68 years, male 40 (90.9%), f 4) were recruited for the TEFR project. The inclusion criterion obviously was an official acceptance as a participant at the TEFR09 by the organizers and the race director. The conditions of participation were: minimum age 18 years, the presence of a medical certificate not older than 30 days which indicated physical health and clear proof of appropriate running performance in the field of UM. The specific running history and performance of the individual subjects can be described by different traits, which were requested before the start of the TEFR09: years of regular endurance running training, finished (ultra-) marathons, personal best times in different defined ultra races and extent of training (volume, duration, intensity) before TEFR09.
The investigators additionally performed a resting cardiovascular check using a 12-channel PC-ECG system (Custo cardio 100™, Custo Med Ltd., Ottobrunn, Germany) and blood pressure (RR) measurement using a manual sphygmomanometer (BOSO Clinicus, JungingenGermany: to the nearest 3 mmHg). Cardiovascular exclusion criteria were resting blood pressure > 200 mmHg systolic and/or > 110 mmHg diastolic, acute systemic infection, acute chest pain and new arrhythmias or ECG changes. An orthopedic physical examination was done focusing on contraindications for endurance running such as relevant malalignment and painful joint diseases of the lower extremities. Additional specific exclusion criteria were contraindications against MRI scanning (for example, metallic foreign bodies in dangerous locations, specific cochlear or ocular implants, ferromagnetic vascular clips and relevant claustrophobia). None of the volunteers had to be excluded from study participation due to these criteria.
Four members of the TEFR project comprised the investigator core team that accompanied the TEFR09 for direct data acquisition before and during the race: two physicians, one medical student and one radiological assistant. The latter (HW) was responsible for subject positioning in the scanner and performance of the MR examinations. One of the investigators, the initiator and main organizer of the TEFR project (US), drove the MR-trailer truck, adapted the daily research program to the actual circumstances, controlled and checked the quality of the MR examinations and was responsible for the technical readiness of the whole mobile MRI and its functional circuits and equipment with external and internal diesel generator. Being specialized in radiology and orthopedic surgery, he also did the initial and follow-up physical musculoskeletal examinations of the subjects. The second investigator (CB) was responsible for acquisition of daily anthropometric, laboratory and ECG data. The medical student (ME) made the daily anthropological measurements.
The two physicians were solely responsible for the study and gave neither training advice nor provided medical help.
The study design of the TEFR project is shown in Figure .
Baseline studies were performed within the last four days before the start of the TEFR09 in Bari on every subject. They included group specific MRI examinations and anthropometric and cardiovascular physical measurements with urine and venous blood samples.
Additionally, body height measuring using a wall-mounted stadiometer (to the nearest 5 mm, standing barefoot) and active range of motion measurement (AROM) of hip and knee joints using a manual double-armed universal goniometer (to the nearest 5°) were done before the start. One experienced orthopedic surgeon, trained in a standardized procedure for positioning both the subject and the goniometer, collected these data.
Adapted from the methods of Paley et al
] and Weidelich et al
], analysis of lower limb alignment was done on coronal lower body scout views of pre-race MRI with subjects in the supine position and with extended legs. Measured parameters were: leg length (LL), as the straight line from the middle of the femoral head to the midpoint of the upper talus rim; femorotibial angle (FTA), as the angle between anatomical femoral and tibial axis; the mechanical axis deviation (MAD) as the distance from the point of intersection between the perpendicular and mechanical axis of the limb (straight line from the middle of the femoral head to the midpoint of the upper talus rim) to the midpoint of the knee (medial tibial eminence) and the femoral to tibial length ratio (F/T) [116
A 240-item, 31-dimensional personality temperament and character inventory (TCI) [123
] in addition to a 10-item, 4-scaled questionnaire on self expectancy (General Self-Efficacy Scale, GSE) [125
] were also integrated into the project before its start.
Additionally, 15 of the 44 subjects had an initial separate pre-race test on pain perception (ice-water test) combined with functional cerebral MRI two weeks before the start of the TEFR09 at UHU on 1 to 3 April 2009, because these examinations could not be implemented on the mobile MRI due to technical limitations. Due to the exorbitant physical and mental burden placed on the subjects, there was no opportunity for field experiments, invasive tests or application of psychometric instruments during the transcontinental foot-race.
The observant field studies during the TEFR09 were completed between 15 April and 21 June 2009. Every morning from 3:45 to 4:30 a.m. urine samples and anthropometric measurements were taken. The core team broke down their examination units and drove to the next stage destination. Before stage length dependent arrival of the first runner they had set their systems ready and had refuelled the generators and vehicles. MRI examination time was between 2:30 p.m. +/- 90 minutes and 9:00 p.m.). At the same time anthropometric and cardiovascular physical measurements, blood and urine samples were collected and ECG was done. The daily data acquisition also included measurement and documentation of daily weather conditions (temperature outside and inside, humidity outside) using a calibrated electronic thermometer, the stage length and the individual stage performances of the runners (stage running time).
For MR measurements two groups (22 subjects each) were cluster randomized according to the different research modules. The MR protocols were created in an interdisciplinary content ensuring multifold specific and diverse but precise analyses and measurements for detailed testing of the mentioned hypotheses concerning long distance running (Table ).
MRI protocols of the TEFR project
MRI of feet
For high resolution investigation of the whole foot a special table fixed boot-like designed 8-channel foot-ankle coil was chosen and a sagittal orientated water sensitive T2w MR sequence (TIRM) configured a wide field of view. If on this sequence any pathology was detected, a transversal oriented focused water sensitive sequence with a more structured T2 sequence (fat saturated proton density weighted (PDw)) was added. For investigation of the joint cartilage a specific T2* mapping MR sequence (syngo™ MapIt FLASH T2*w GRE) in sagittal orientation was used [127
], allowing quantitative measurement of hydrophilic changes in the cartilage layers of tibiotalar, talocalcaneal, calcaneocuboid, and calcaneonavicular joints. The specification of these MR sequences (Table ) was done for detection of typical running associated overuse injuries of the feet [52
]: subcutaneous edema, Achilles tendonitis [49
], extensor digitorum tendonitis [48
]), plantar fasciitis [50
], calcaneal apophysitis, arthritis/arthrosis, stress fractures, bone edema, metatarsalgia, Morton's neuroma, and ankle inversion injuries (Figure ).
Figure 4 Mobile MRI of the feet. A: male, 39-years-old, stage 53, 3,669 km (fused colored T2* GRE map sagittal: syngo™ MapIt fusion technique, Siemens Medical solutions, Erlangen, Germany): Colored visualization of focal water concentration in cartilage (more ...)
MRI of knees
With a table-fixed 8-channel knee coil all subjects of group 1 had both knees examined with a sagittal TIRM sequence for water detection in knee-related tissues and evaluation of femorotibial joint. A transversal fat saturated PDw sequence was used to assess the femoropatellar joint. As for the hindfoot joints, specific T2* mapping MR sequences in sagittal and transversal orientations were done for quantification of cartilage layers of the femoropatellar and femorotibial joints regarding intrachondral water proportioning [127
]. The specification of these MR sequences (Table ) was done to evaluate running-associated overuse injuries in the knees [52
]: patella tendonitis ('runner's knee'), arthritis/arthrosis [130
], stress fracture, bone edema [64
], retropatellar pain syndrome [48
], chondromalacia patellae, meniscal lesions [50
] and patellar tendinitis [50
] (Figure ).
Figure 5 Mobile MRI of the knees. Femoral condyle (1), tibial head (2), patella (3), retropetallar cartilage layer (4), ventral femoral cartilage layer (5), dorsal femoral cartilage layer (6), tibial cartilage layer (7), medial meniscus (8), lateral meniscus (9), (more ...)
MRI of hips/pelvis
One flexible 6-channel body matrix coil was used to obtain an MR overview of the pelvis with one coronal water sensitive sequence (TIRM: Table ) to detect injuries in this part of the body: hip arthritis/arthrosis [131
], sacroiliac injuries [52
], stress fractures of the pelvic ring [132
], muscle overuse injuries and so on. Additional case specific sequences were added as necessary (Figure ).
Figure 6 Mobile MRI of pelvis region and hip joints. A: male, 45-years-old, stage 8, 511 km (PDw TSE fs coronal): Massive edema and (peri-)myositis of right proximal quadriceps muscle (1). B: female, 46-years-old, stage 48, 3,290 km (PDw TSE fs, B1: coronal, B2,3: (more ...)
MRI of upper/lower legs
With three to four flexible 6-channel body matrix coils total MR examination of upper and lower legs was possible. To get detailed information about soft tissue edema, muscle perfusion and injuries of the legs different sequences were adapted in transversal orientation (T1w for adipose tissue separation and acute bleeding detection, TIRM for high sensitivity in water detection, fat saturated PDw for structural detailed water sensitive imaging, DWI for perfusion analysis of muscles and separation between intra- and extra-cellular water in the muscles: Table ). With these sequences all of the typical running-associated syndromes could be detected and differential diagnosis done [49
]: anterior compartment pain/syndrome [48
], (medial) tibial stress syndrome [50
], gastrocnemius injuries, peroneal tendonitis, tibialis posterior injury, calcaneal apophysitis, iliotibial band friction syndrome [50
], greater trochanteric bursitis, gluteus medius - hamstring - adductor - abductor - quadriceps injuries, such as tendonitis, strains or tears. Muscle volumetry of different compartments of the upper and lower leg muscles is possible for evaluation of changes in muscle volume: Figure .
Figure 7 Mobile MRI of upper and lower legs. A: male, 49-years-old (coronal slices): A1: stage 12, 789 km, upper legs (PDw TSE fs): Subfascial intermuscular fluid, superficial (1), deep peri-neural (2). Partial quadriceps tear (M. vastus intermedius: 3). A2: stage (more ...)
Cerebral MRI, functional MRI
As for the muscles in the legs, a MRI guided volumetric analysis of the brain was one focus of the cerebral MRI measurements. Therefore, a T1 weighted high resolution (1 mm) turbo FLASH three-dimensional-sequence was used, making an isovoxel based volumetry (VBM) possible (Figure ). For detection of brain lesions and global edema a typical T2-sensitive sequence (FLAIR) in coronal orientation was chosen (Figure ). With diffusion weighted imaging (DWI), ischemia detection was possible. For all these MR sequences (Table ) a table integrated 12-channel head matrix coil with a head restraint system was used. The same coil was used on the stationary scanner for functional MRI (fMRI) using echoplanar imaging (epi) with blood oxygenation level dependent (BOLD) contrast to analyze pain perception in 12 participants of the TEFR09 compared to age-related normal volunteers (Figure ).
Figure 8 MRI of the brain. Male, 52-years-old. A1: stage 57, 3,971 km (T1w turbo FLASH 3D sagittal): High resolution isometric three-dimensional sequence (1 mm) allows isovoxel based volumetry (VBM) of the whole brain. A2: Three-dimensional view shows dominant (more ...)
Cardiac cine MRI
For mobile cardiac cine MRI, a flexible six-channel body matrix coil was used. Cine SSFP gradient echo sequences with retrospective cardiac triggering were generated to obtain plane short axis four-, three- and two-chamber (Figure ) views of the heart. The mitral and aortic flow (Figure ) was measured using phase contrast sequences with 150 cm/second velocity encoded gradient echo imaging (venc). This protocol ensured measurement or secondary evaluation of parameters, such as ejection fraction (%), end diastolic and systolic volume and, therefore, stroke volume (ml), cardiac output (L/minute), myocardial mass (g) (Figure ), muscle volume of ventricles (ml) (Figure ), and so on. MR tagging using a Cine SSFP gradient echo sequence with retrospective cardiac triggering in plane short axis four- and two-chamber view (Table ) made quantification of the myocardial motion with its spatial orientation (Figure ) possible.
Figure 9 Mobile cardiac cine-MRI. A: male, 52-years-old, stage 23, 1,569 km (cine SSFP GRE, 2-chamber view): Focus is the left ventricle (1), myocardium (2). papillary muscles (3), right ventricle (4), lung (5), liver (6), left kidney (7), spleen (8), stomach (more ...)
Vascular cine MRI
For analysis of changes in the arterial aortic stiffness, measurement of the central pulse wave velocity using MRI is the gold standard [137
]. With detection and measurement of the proximal and distal aortic flow and diameter using phase contrast acquisition with venc and prospective two-dimensional cardiac triggering on mobile MRI (Figure ), this and the central hemodynamic changes (peak and mean shear rate differences) and their influence on the vascular (aortic) diameter [100
] during the TEFR09 can be calculated. Additionally, T2 weighted cine FLASH gradient echo sequences with prospective two-dimensional cardiac triggering were generated (Table ) to measure compliance changes of the vessel wall of the distal common carotid (Figure ) and proximal superficial femoral artery (Figure ). In total, for vascular MRI three flexible six-channel body matrix coils for aortic and femoral artery measurements, one four-channel phased dual mode neck matrix coil and ECG triggering makes positioning and preparation of the subjects very time consuming.
Figure 10 Mobile vascular cine-MRI: male, 52-years-old, stage 27, 1,838 km. A1: MR localizer sagittal, A2,3: FLASH transversal: Automatic functional measurement of common right carotid artery diameter just below carotid bifurcation (1). Left carotid artery (2), (more ...)
Whole body MRI
For total body MRI, change of subject positioning from prone head forward to prone feet forward was necessary during a T1 weighted turbo spin echo sequencing using an adapted protocol developed on adipose and diabetic volunteers [138
] (Table ). With topographic tissue segmentation and mapping of the athlete's body using a fuzzy c-means algorithm according to Würslin et al
] a simple and time-saving strategy for assessment and standardization of the tissue distribution in the entire body was possible. With additional manual adaption due to the non-fasting condition of the subjects changes in different lean and adipose body compartments could be measured during the TEFR09 (Figure ).
Figure 11 Semiautomatic tissue separation with mobile whole body MRI of a 32-year-old male finisher of the TEFR09. A: Right row (before start): green: total lean tissue, red: somatic adipose soft tissue, yellow: visceral adipose tissue, blue: adipose bone marrow. (more ...)
Proton MR-spectroscopy with a flexible six-channel body matrix coil for measurement of the intramyocellular lipid (IMCL) content of the tibialis anterior and soleus muscle required the stimulated-echo acquisition mode (STEAM) technique (Table ) and manual shimming of the magnetic field [140
], which makes generation of valuable results on a mobile MRI difficult and unpredictable (Figure ).
Focused supplementary sequences
In addition to the mentioned study protocol, additional MR examinations were done on subjects and TEFR participants, if acute injuries (for example, stress fractures [52
]) and pain syndromes (for example, low back pain [49
]) occurred and a specific diagnostic finding was necessary to prevent further injuries or complications on the endurance runners (Figure ).
Figure 13 Supplementary mobile MRI examinations during the TEFR09. A: male, 61-years-old, stage 38, 2,601 km (PDw TSE fs, A1: coronal, A2: sagittal): Stress fracture of the proximal tibia (1) with perifocal bone edema (2) and focal subcutaneous edema (3). B: male, (more ...)
Anthropometric and cardiovascular physical measurements
Anthropometric and cardiovascular physical measurements were done on all subjects (Figure ) every fourth day. Therefore, the 44 subjects were randomly assigned to one of four groups. Body mass was measured with BIA using a Tanita BC-545™ BIA scale (Arlington Heights, IL, USA: to the nearest 0.1 kg). This balance gave additional results about percentage of body fat and lean body mass based on MR validated calculation procedures [141
]. The measurements took place in the morning (between 4 a.m. and 5 a.m.) and after the stage (between 3 p.m. and 9 p.m.) together with measurement of blood pressure and body temperature (T) using an infrared ear thermometer (ThermoScan IRT 4020 ™, Braun, Germany: to the nearest 0.2°C. After the stage between 3 p.m. and 9 p.m., the skinfold (SF) thickness of the same subjects was measured using a skinfold caliper (GPM ™, Silber and Hegner, Zurich, Switzerland: to the nearest 2 mm) and their segmental body circumference (CF) was measured using a retractable measuring tape (to the nearest 1 mm). For SF, the mean value was calculated from three consecutive intra-individual measurements at eight regions on the right side of the body according to Ball et al
]: chest, midaxillary (vertical), triceps, subscapular, abdominal (vertical), suprailiac (at anterior axillary), thigh, and calf. For CF, mean value was calculated from three consecutive intra-individual measurements at six regions on the right side of the body according to Lee et al
]: upper arm (largest part of the limb), waist, hip, thigh (10 cm/20 cm above upper patella pole), and calf (largest part of the limb). To avoid inter-observer error all the anthropometric measurements were done by the same, specifically trained investigator. Every 800 km a short term ECG was planned on every subject.
Midstream urine samples were taken from all subjects twice each day. Before breakfast in the morning between 4:00 a.m. and 5:00 a.m. and after each stage in the evening after dinner between 7:00 p.m. and 9:00 p.m. Blood samples were taken every 1,000 km from the cubital vein after stage. The samples were immediately centrifuged and frozen (below -20°C) and put on -80°C after the race.
On the day they dropped out, non-finishers (NF) had a last complete measurement of all specific MRI protocols and physical examinations (BIA, SF, CF) and provided blood- and urine-samples. Nearly eight months after the TEFR09, 15 of the 44 subjects (all of them finishers of the TEFR09) had a follow up examination at UHU on the same topics involved during the field studies: specific MRI examinations, anthropometric measurements, ECG and blood and urine samples.
For statistical analysis the software 'SPSS 12.OG for Windows, Version 12.0.1' was used. Data are presented as mean (SD, range) and median (IQR) as appropriate. The coefficient of variation (CV (%) = 100*SD/mean) was calculated only for measured absolute data on performance. The stage severity index (SSI) is an indirect parameter calculated from the mean stage velocity of all runners without a severe handicap v;¯ STAGE* in relation to the total mean velocity of the whole race v;¯ TEFR*. Therefore, the SSI represents the relative burden of each stage, which is dependent on the mentioned multiple external factors that changed daily. It reflects the sum of daily weather and route conditions:
*: values are only integrated in calculation, if the stage performance of the specific runner is more than 87% of his mean race performance