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One of the outstanding athletes of the unforgettable 2020 was undoubtedly the Kenyan Timothy Cheruiyot, who won in the 1,500m of the Diamond League events held in Monaco and Stockholm, running below 3:29. Always when this great athlete runs, I notice the accentuated inclination of his trunk with respect to the vertical axis, which reaches more than 18°. It gives the sensation that he wants to lean forward to improve his aerodynamics, adopting a posture that reminds me of the walk of the great Groucho Marx.
At the other end we find athletes like the 1,500m world record holder, the Ethiopian Genzebe Dibaba, or my beloved and admired Jesus España, who run with an upright trunk; practically the spine describes a right angle to the ground. In the world of athletics this technique is associated with running with elegance and class, but is it the best technique?
There is a very interesting study from 2005, which compares the technique and anthropometry of Japanese and Kenyan top-level athletes (sub-14 minutes in 5,000 m). The results show that there are very few differences between the two groups, although it does highlight that Kenyan athletes run more forward.
Analysing all the above, we see two different trunk positioning strategies in great elite athletes. The debate is on: which of the two techniques is better? Given that the trunk represents more than 40% of body weight, small changes in the position of the trunk influence the biomechanical demands of running and impact on both the sports performance and the possible appearance of various injuries. Therefore, we should pay close attention to this variable.
What is the inclination of the trunk of the great athletes of the moment?
The next question I asked myself was: what is the trunk inclination of top athletes like? To answer this question, I carried out a biomechanical study from various sources: footage I have taken of some competitions, the analysis I have coordinated of the Valencia Trinidad Alfonso EDP 2020 Marathon and some competitions available on the internet. The results obtained are as follows: Kandie, in his half-marathon world record in Valencia, and Kiplimo, running in 57:37 in the same competition, showed similar values of trunk inclination, around 12°- 13°. Jakob Ingebrigtsen, on the other hand, shows a significant inclination, although less than Cheruiyot, reaching 15°. Mo Farah and Carlos Mayo run a little more upright, but without achieving the angle of Jesus España, presenting about 9°-10°. Galen Rupp's technique is similar to Jesús España, showing a slight inclination of 6°. Finally, two great athletes such as Kipchoge and Cheptegei run with a technique characteristic of the African school, this is around 14° of inclination.
What does science say about the trunk inclination?
In order to contribute to this debate, I carried out a literature review in the main scientific databases. A research group led by the authors Teng and Powers has published several papers focused on this topic. Their main conclusion is that a too upright position of the trunk is associated with greater stresses on the knee during running, a higher braking phase and higher vertical impacts. They argue that a slight forward lean is associated with a reduction of the stress suffered by the knee and the energy absorbed by it, as well as a decrease of the stress on the patella without increasing the load on the ankle. According to these authors, the reason why some runners opt for a very upright position may be due to a weakness of the hip extensors, which has a negative effect on the muscles that manage the mobility of the knee. This is why various studies have highlighted the importance of strengthening the hip and core muscles in order to maintain healthier trunk positions in training and competition.
And what happens if we lean too far forward? An article from 2019 highlights that excessive forward leaning (more than 20°) is associated with one of the most common running knee injuries, ileo-tibial band syndrome.
Another study from 2014 found that in recreational runners the inclination of the trunk tends to increase with fatigue. This must be taken into account as it can affect performance as well as cause injury problems. Here we have yet another reason why we should integrate into our training strengthening exercises that reinforce the muscles and allow us to better manage our body position when we are tired.
From these studies we can conclude that the forward leaning of the trunk reduces the energy generated and absorbed by the knee but increases the participation and generation of energy at the hip. Therefore, we should look for an intermediate trunk inclination, neither too vertical (upright position) nor too forward, both for performance improvement and injury prevention. A correct angulation would be between 10° and 15°.
I would say that running like Dibaba or España can be very beautiful and aesthetic, however, according to the data collected in the scientific studies consulted and seeing how the best athletes of the moment run, it does not seem to be the most advantageous trunk position for running.
Given the allusion to Jesús España that I make in this article, I have spoken with him to find out his opinion on the matter. I draw two conclusions from our conversation: firstly, Jesús agrees with my analysis and, secondly, he has explained to me that he runs so upright as a result of a very personal characteristic of his related to the mobility of his ankles, which prevents him from positioning the trunk at the optimum angle. In fact, he told me that he is particularly good at downhill running with a slight slope. This condition helps him, artificially, to find a more suitable inclination of the trunk that allows him to "fly" at a pace close to 2:40 per kilometre, as he did recently in a 5km test setting an unofficial time of 13:30.
What do we learn from this analysis? Tips for coaches and runners
After this analysis we can conclude the following:
- The inclination of the trunk is a very important variable in running biomechanics.
- We must look for an intermediate position, neither too forward leaning nor too upright.
- The optimal forward inclination is between 10° and 15°.
- The positioning of the trunk can be improved by means of a suitable training plan.
- It is a biomechanical error to run too straight. If an athlete runs at an angle of less than 10°, my advice is to develop a technical workout so that the athlete runs a little more leaned forward.
- It is vitally important to do exercises to strengthen the hip extensors (gluteus) and the core (abs and lumbar) in order to achieve good positioning of the trunk and reduce the effect of fatigue.
Acknowledgements
- To the S.D. Correcaminos for their support in the project conducted to analyse the Trinidad Alfonso EDP 2020 Valencia Marathon.
- To Jesús España for sharing his experience and knowledge
Sources of information
Some of the images have been obtained from various YouTube channels:
- INEOS 1:59 Challenge.
- Valencia Ciudad del Running.
- Wanda Diamond League.
- Olympics.