Authors Laura M. Horga, Johann Henckel, Anna Di Laura, Martin A. Belzunce, Harry Hothi, Alister J. Hart, of the Royal National Orthopaedic Hospital, discuss the results of their Exercise for Science multidisciplinary medical research project.
Long distance running (>21 km) including marathons (42 km) and ultramarathons (>42 km), has significantly increased in popularity over the last decade [1-2]. Despite its various cardio-respiratory benefits, long-distance running has been anecdotally associated with a risk of injury, varying widely between 19-80% . However, there is no reliable scientific evidence to support these numbers and clarify whether there is any cause for concern.
Exercise for Science  is a multidisciplinary medical research project aiming to answer the question: Is long-distance running bad for the hip joints?
The project is led by Professor Alister Hart and is based in London. It’s unusual in bringing together specialists from diverse fields to focus on the medical effects of exercise. Key is the collaboration with Consultant Radiologists Dr Anastasia Fotiadou at the Royal National Orthopaedic Hospital and Dr Anna Hirschmann at the University Hospital of Basel, together with engineers and scientists.
The research team has applied high-resolution magnetic resonance imaging (3 Tesla MRI), which enables anatomical visualisation of internal musculoskeletal joint structures including early signs of lesions, to study the hip joints and muscles of first-time marathon runners and high-dose runners.
What have we discovered?
Baseline study 
The research team recruited 52 asymptomatic volunteers who were falling into 3 different categories, based on their activity level: 1) 8 inactive non-runners; 2) 28 moderately active runners (average half a marathon (21 km)/week) and 3) 16 highly active runners (≥ marathon (42 km)/week).
The aim was to compare the hip condition of these 3 groups on 3.0 T MRI scans.
Two musculoskeletal radiologists reported the hip MRI results using validated semi-quantitative scoring systems. The participants completed a Hip disability and Osteoarthritis Outcome Score (HOOS) questionnaires to indicate their perceived hip function.
Results showed that the number of hip abnormalities on 3.0 T MRI was not significantly different among inactive non-runners, moderately active runners and highly active runners in most hip joint structures. This includes the labrum, articular cartilage, ligaments and tendons.
Interestingly, there were no chondral defects or bone marrow oedema in highly active runners.
Only minor non-specific bone marrow abnormalities were more common in runners than in non-runners, which was not deemed to be significant.
No significant changes in hip symptoms or joint functionality were observed.
Take home message: Regular long-distance running does not add damage to your hips!
Pre vs Post-marathon run study 
In this study, the 28 moderately active runners from the baseline study (who previously ran up to half-marathon races, yet never a marathon run) participated in a follow-up MRI scan. The participants were scanned 2 weeks after they completed a 4-month training programme for their first marathon ever plus the marathon race itself, Richmond Marathon 2019.
The aim was to assess and compare the hip condition of this group of novice marathon runners before and after the completion of their first marathon run. Same methodology as in baseline study was used here (MRI scanning, validated hip scoring systems, self-assessment questionnaires).
Before the marathon at baseline, most novice marathoners had pre-existing hip abnormalities before they started training, although they were pain-free.
Marathon running did not damage the hip joints of novice marathon runners. Only very few minor appearances were seen on MRI scans shortly after the marathon, specifically 2 cases of small bone marrow oedema. Both cases were detected in the non-weight-bearing area of the hip which means that they may be attributable to impingement rather than running, and were asymptomatic.
One year later, the few cases of post-marathon bone marrow oedema completely resolved on the MRI scans. There were no changes in symptoms and participants continued their running activity, even training for new marathon races.
Take home message: First-time marathon running does not damage or acutely change your hips!
MRI post-processing [7-8]
We are currently doing research that harnesses the three-dimensional properties of MRI, to find out which MRI measurements will be most useful in predicting muscle health. We’ve completed two studies of gluteal muscles in both healthy subjects and patients with hip pain.
When looking at subjects with different levels of physical activity, we found that those with hip pain, low levels of physical activity, female gender and a higher body mass index also tended to have greater amounts of fat in their gluteus maximus muscles. We have also been able to set a benchmark for measuring infiltration of fat into the gluteal muscles for healthy individuals.
Take home message: Low fat infiltration of gluteus maximus is a sign of good muscle health and indicates healthy hip joints !
Non-runners, half-marathoners and (ultra)marathoners did not have significantly different hip joint health outcomes on baseline high resolution 3.0 Tesla MRI, indicating that regular long-distance running does not add damage to runners’ hips.
Also, marathon running did not show to have adverse effects on the hip joint health of first-time marathoners on 3.0 Tesla MRI. Moreover, participants undertook a 4-month beginner training programme for the marathon, plus the marathon itself, and did not develop symptoms.
We also showed that low fat infiltration of gluteus maximus is a sign of good muscle health and indicates healthy hip joints.
Ongoing studies using NHS apps
A new collaboration has been established with Public Health England for ongoing studies, assessing the impact of NHS-based exercise apps on musculoskeletal and mental health, specifically Couch to 5K (running programme building up to 5k) and Active 10 apps (an incremental brisk walking programme).
The team is set to begin a new round of studies, looking at exercise in its broadest sense.
Further details can be found here: www.exerciseforscience.org
- Cejka N, Rüst CA, Lepers R, et al. Participation and performance trends in 100-km ultra-marathons worldwide. J Sports Sci 2014;32:354–66.
- Vitti A, Nikolaidis PT, Villiger E, et al. The “New York City Marathon”: participation and performance trends of 1.2M runners during half- century. Res Sports Med 2020;28:121–37.
- van Gent RN, Siem D, van Middelkoop M, et al. Incidence and determinants of lower extremity running injuries in long distance runners: a systematic review. Br J Sports Med 2007;41:469–80.Exercise for Science. Accessed online: exerciseforscience.org.
- Horga LM, Henckel J, Fotiadou A, et al. 3.0 T MRI findings of 104 hips of asymptomatic adults: from non-runners to ultra-distance runners. BMJ Open Sport & Exercise Medicine 2021;7:doi: 10.1136/bmjsem-2020-000997.
- Horga LM, Henckel J, Fotiadou A, et al. Magnetic Resonance Imaging of the Hips of Runners Before and After their First Marathon Run: Does it Lead to Acute Changes? Ortho J Sports Med 2021;9(7):1-10. doi:1177/23259671211010405
- Belzunce MA, Henckel J, Fotiadou A, Di Laura A & Hart A. Automated measurement of fat infiltration in the hip abductors from Dixon magnetic resonance imaging. Magnetic Resonance Imaging 2020;72:61-70.org/10.1016/j.mri.2020.06.019
- Belzunce MA, Henckel J, Fotiadou A, Di Laura A & Hart A. Automated multi-atlas segmentation of gluteus maximus from Dixon and T1-weighted magnetic resonance images. Magn Reson Mater Phy2020;33:677–688. org/10.1007/s10334-020-00839-3