17 May 2015

Strength training for mountain ultramarathon runners and foot strike patterns

This spring I have spent considerable more time in the gym compared to past seasons. This is of course time I rather should have spent out on the trail running – I am sure that there are no shortcuts and to be good at running you need to run. Hence, I am rather skeptical to the more or less bold statements about the importance of strength training for runners and how you by attending some training classes with exercises to improve core strength and strength and flexibility of the muscles involved in shaping the running stride. So, when I started to add indoor strength and agility exercises in January it was more for laziness and time constraints – it was so much easier to go to the warm gym during lunch than to go out in the rainy and cold winter for a run. However, I quickly realized that the strength training at least did something as the muscle soreness I had in particular in the gluteal and adductor muscles after each training session was tremendous. Gradually, however, my strength has improved and I have now less and less soreness after each time at the gym. Importantly, I have not built muscle mass and gained weight, but the question is whether I have gained speed and endurance when running. One good thing I think is that I have varied the training and also complemented the running specific training with more general strength training, including training also for the upper body, with a personal trainer. In this experiment to include more strength training I think this is going to benefit running speed on more technical trails with some more challenging scrambling.

As I wrote in a blog post almost two years ago there are no good scientific studies of the efficacy of strength training programs for mountain ultramarathon running so my belief in variety in strength training is highly personal. My belief is also in opposition to most “running specific” strength programs, such as the “Runner’s Strength” program by Urban Tribes at SATS that I have attended, and the POSE method and Chi methods, both of which have become very popular in Sweden recently. These programs are all strong proponents of pure forefoot running and makes very bold claims of effectiveness not only in improving running ability over just a couple of months, but also in reducing injuries. Again, the scientific evidence behind the methods is in my opinion almost non-existent and a very good overview of the science behind the methodswas written four years ago by Dr Henderson at the Irunfar website. I do not know the current situation in the US and if these training methods are more or less popular today, but I am not surprised that something which at least was popular a couple of years ago in the US now has become increasingly popular in Sweden as there usually is a lag-time in when things spread here.  Since Henderson’s overview in 2011 no significant studies has been published about Pose running and only one study of Chi running by Goss and Gross showing what was already know that forefoot running may reduce vertical loading rates and knee extensor work, but instead may increase work of the ankle plantar flexors (Goss & Gross. A comparison of negative joint work and vertical ground reaction force loading rates in Chi runners and rearfoot-striking runners. J Orthop Sports Phys Ther. 2013; 43: 685-692). The balance between knee and ankle stress is something I personally have experienced over the past years as my long-standing knee pain abated when switching to shoes with a lower drop and more of a forefoot running technique, only to be replaced by Achilles tendon and lower calf pain. Not surprisingly, this spring I have experienced more pain from in particular my right Achilles tendon, most likely as a result of the running specific strength training as mentioned above mostly focusing on forefoot running.

But, has the strength training done something good? Obviously I think so as I have continued. Using the new gadget Garmin Fenix 3 in doing an analysis of my cadence, vertical oscillation and ground contact time my running stride has improved. Also, my muscle soreness after longer training runs is much less pronounced, rather surprisingly as there has been considerably less such runs this spring, and I therefore contribute it to the strength training. I still think I have much to improve, however, and it was quite humbling to run a very technical trail path, named a “wilderness path” with my 8-year old son Carl last weekend. Despite my attempts to convince him of the joy of running he is much more into downhill skiing during winter and soccer during summer and this was one of the first times we were running together. Obviously, it was entirely a fun run, but when racing downhill on stony and technical terrain Carl was much faster than me - he just flew down naturally without thinking about either having the ride stride, cadence or being afraid of falling. I am sure he had no thought whatsoever whether he was using a forefoot or rearfoot running stride.
 

Uphill slope section of one of my favorite trails. What foot strike pattern would you use? At least when it has rained at least I need to use both my hands here in scrambling up.

Part of the "Wilderness trail" I ran with my son. What foot strike pattern is best to use here? And in what frequency? This is clearly a section of the trail which looks quite strange afterwards when analyzing the run. The ground contact times are indeed quite long when hauling the raft over the water.
There have been several studies published in the last few years of the stride type and gait parameters of mountain ultramarathon runners and the theory that a natural stride is beneficial seem to at least have some support. A video-analysis of gait parameters at level ground was done by Kasmer, Wren and Hoffman of Western States 100 mile (161 km) mountain ultramarathon runners and found no correlation between a particular foot strike pattern and performance (Kasmer ME et al. Foot strike pattern and gait changes during a 161-km ultramarathon. J Strength Cond Res 2014; 28: 1343-50). Rear-foot strike (RFS) was most common used by 79.9, 89.0, and 83.9% of the runners tested at 16.5, 90.3, and 161.1 km, respectively. There was a significant decrease observed for stride rate and length over distance for the whole population, but not among the top 20 finishers who were able to maintain a stable stride rate and length. The top 20 finishers had also a greater use of a non-RFS pattern at 161.1 km than the remaining finishers. There was a trend toward greater post-race blood creatinine-kinase CK (a blood marker for muscle damage) values among non-RFS runners compared with RFS runners, reaching significance at the 90.3 km site (p < 0.05).

Western states is a comparable fast and flat ultramarathon with the biggest challenge compared to other mountain ultramarathons not the altitude difference and technicality of the terrain as I have discussed in a previousblog post. It is perhaps therefore not surprising that a similar analysis of stride and gait parameters of the 100 mile Ultra-Trail du Mont Blanc (UTMB) with more altitude difference yielded different results (Morin JB et al. Changes in running mechanics and spring-mass behavior induced by a mountain ultra-marathon race. J Biomech 2011; 44: 1104-7). In this study, running mechanics was analyzed in 18 male UTMB runners with a finishing time of 37.9 ± 6.2 h (range23.5-46 h) by running at 12 km/h over a 7 meter long electronic pressure walkway pre- and 3h postrace.  In this study, the stride rate was significantly increased post-race (5.9±5.5%), associated with a reduced aerial time and no change in ground contact time. Overall, the results show that 3h post-UTMB, subjects ran with a reduced vertical oscillation associated with an overall lower impact during the braking phase of each step, perhaps as this smoother running pattern might be caused by the need to attenuate painful eccentric (braking) at each step. An analysis of gait parameters following the 65 km long Vigolana Mountain ultramarathon in Italy with a high altitude difference also showed a significant increase in the stride rate post-race, as I noted in my last blog post (Vernillo G et al Energy cost and kinematics of level, uphill and downhill running: fatigue-induced changes after a mountain ultramarathon. J Sports Sci 2015; 9: 1-8 Epub ahead of print). Also a shorter 5-hour hilly running bout induced an increase in stride rate and similar other gait changes, but in a lower amplitude, as in the studies by Morin and Vernillo and colleagues (Degache F et al. Changes in running mechanics and spring-mass behavior induced by a 5-hour hilly running bout. J Sports Sci. 2013; 31: 299-304).

A very recently published, but already very much quoted, study of foot strike pattern analyzed Kilian Jornet’s technique during the 2013 Kilian’s Classik 45-km mountain ultramarathon with 1627 meters D+ (Giandolini M et al. Foot strike pattern and impact continuous measurements during a trail running race: proof of concept in a world-class athlete. Footwear Sci 2015; E-pub ahead of print). One good summary of the article was written by Alex Hutchinson in Runner’s World and we are both fascinated by the possibilities of the new technique using wireless accelerometers to measure the foot strike pattern in real time and to link the findings to synchronized measurements of the environment by a GPS. Unfortunately, in the experiment on Kilian the battery to the GPS died mid-race so only data from the first 20 km, which were predominantly uphill resulting in an average speed of 10.9 km/h by Kilian, could be used. A total of 5530 steps were analyzed  with ~18% of the steps rear-foot strike (RFS), ~33%  mid-foot strike (MFS) and ~49% fore-foot strike (FFS) (see figure below).
 

From Giandolini et al 2015. Foot strike pattern of Kilian Jornet at the first 20 km of Kilian's Classic 2013. Altitude (black line) and speed (grey line). Bar charts represent the repartition of foot strikes (RFS, MFS and FFS) within eleven analysed sections

 
The stride frequency was correlated to slope and speed. The RFS pattern increased towards the end of the first 20 km, perhaps due to increased strain of the calf muscles in running uphill with a FFS. Still, the frequency of RFS was low compared to the studies referenced above. Another interesting finding was that the anterior-posterior and resultant components of tibial acceleration appeared important for impact magnitude and stress, much in line with the changes in postural control in the anterior-posterior plane following the longer ultramarathon Tor des Geants (TDG) as I have written about before in another blog post (Degache F et al. Alterations in postural control during the world's most challenging mountain ultra-marathon. PLoS One 2014; 9: e84554. doi: 10.1371). In summary, Kilian appears to be able to adapt his running stride to both extrinsic (e.g. slope, surface) and intrinsic (e.g. fatigue, pain) factors and that it might be this adaptability which partly creates his advantage. This is far from the strict adherence to a certain stride pattern and encourages me to continue to make sure I have variety in both my strength and running training.

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