[MRI changes of Achilles tendon and hindfoot in experienced runners and beginners during training and after a (half)-marathon competition]

Background: Marathon running is gaining in popularity. Its benefits regarding the cardiovascular system as well as the metabolism are beyond doubt. However, whether or not there are detrimental side effects to the musculoskeletal system such as wear and tear is an unsolved question. We therefore prospectively looked at beginners and experienced runners at a city marathon during training and after the competition for lesions to the Achilles tendon (AT) or hindfoot.

Material and method: 73 healthy subjects were prospectively included in our study. They were recruited from the applicants of the city marathon or half-marathon. They underwent an initial clinical orthopaedic as well as three magnetic resonance (MRI) examinations. The MRI were conducted at the time point of study enrolment, near the end of training and directly (up to 72 hours) after the run. MRI evaluation (fat saturated T (2)-weighted sagittal STIR sequence) was performed by two independent experienced radiologists blinded to the clinical context. The results were compared for subgroups of runners, also a factorial analysis was performed. Statistical results were deemed significant for p ≤ 0.05.

Results: 32 women and 41 men were included. In the end there were 53 finishers and 20 non-finishers; 28 seasoned runners and 25 novices. 57 runners had no foot complaints, while 14 had foot pain during training and 13 during the marathon. Mean body weight was 71.6 kg, height was 173 cm, age was 40.2 years. Mean AT diameter was 7.0 mm and showed no change during training or after the marathon. There was no significant influence of gender on other variables investigated. There was a significant and positive correlation between AT diameter and weight (r = 0.37), also AT and height (r = 0.34), while there was negative correlation between height and signal intensity of calcaneus (r = -0.50). The signal intensity of the AT decreased during training. The signal intensity of the calcaneus decreased from inclusion until after the marathon, while the mean retrocalcanear bursa volume and AT lesion volume increased. Some of the non-finishers stopped the training because of orthopaedic symptoms. These runners generally had an apparent lesion visible in their initial MRI examination. Regarding the factorial analysis of the data, there were no risk factors predicting non-finishing or development of new lesions to be detected. Interrater reliability was moderate for retrocalcanear bursa, while it was good to excellent for AT diameter and calcaneus MR signal intensity.

Conclusion: In our sample of primarily asymptomatic German runners, the AT diameter was higher than in symptomatic American patients. The diameter did not change during training or after the marathon. Non-finishers with orthopaedic reasons generally had a lesion on MRI in the initial examination. Apart from this, no new lesions to the AT or hindfoot are to be expected during normal training. Adaptive processes seem to be the main effect of this training.