30 April 2015

The importance of downhill training for mountain ultramarathon trail running

Winter has passed since my last post and spring here in Sweden has finally arrived after a long period of “in between” the seasons. The winter was unusually mild, but I anyway managed to get over 30 downhill ski days together with my family, much due to the fact that my 8-year old son is very much into downhill ski racing and we went to training camps both in Sweden and the Alps. Skiing, together with functional strength training as I have switched gym and started taking lessons from a great personal trainer approximately once a week, have made me more fit overall than during several years. It was a humbling and painful journey to start to rebuild some of my core strength after several years neglect, although also very fun and I will write more about this later on here. I have managed to build my core without gaining too much weight and loosing running speed, which is great, and I think the new strength will be important for the more technical skyrunning races I am planning this year. The worrisome thing is that I have not logged nearly enough running miles in my legs due to my new job where I now commute to office by train and not by running any longer, but also travel very frequently. I am just recovering from a late season bout of the flu and running for in a very flat Rotterdam earlier this week was indeed humbling. But, still, it feels reasonably good and I have at least logged a lot of vertical meters up and downhill as one of my most common training runs now consists of nightly laps up and down the castle hill in Uppsala.

Writing this I do not know exactly why I have taken this long break in blogging. Partly I guess it has to do with the fact that I had run out of subjects to write about for a while. Looking at what I want to write about now, however, where a number of subjects are in line to be covered, I realize it cannot be the main reason. I guess sometimes you have to just take a break to become motivated again. Also, switching work has forced me to rethink my priorities and I guess most running parents with demanding jobs can relate to the difficulties in getting the right balance in their lives. I view the lack of blog posts in the past months as a clear sign that I did not get this balance right, not only for my blogging of course, but also for life in general. Anyway, this is the first post again of many. I thought it best to start easy, however, and the first topic is going to be one of my favorite ones, and something I have previously written about in for instance this post – the importance of training downhill running when preparing for mountain ultratrail running.

This winter I read with interest a new article about the subject by Vernillo and colleagues from the universities in Milan, Verona and Bologna in Italy entitled “Energy cost and kinematics of level, uphill and downhill running: fatigue-induced changes after a mountain ultramarathon” published in Journal of Sport Sciences.
In this study, they analyze whether the fatigue induced by the Vigolana Trail mountain ultramarathon (MUM) in Trento in Italy in July 2014 led to changes in energy cost and kinematic during level and graded running in 14 healthy male runners. The Vigolana Trail course is taking place at an altitude of 725 to 2100 meters and is 65 km with a total positive elevation of 4000 meters (D+/km = 61.5). The runners were all experienced with, on average, 11 ± 4 years of training in running and 4 ± 2 years of ultra-endurance experience. Their pre-race training consisted of 3–4 weekly sessions in which they ran for 8.0 ± 5.0 h/week and 58.5 ± 28.0 km/week. The experiment in the study consisted of a pre-and a post-race analysis of the energy cost of running (Cr) of running at a speed of 10 km/h for 5 minutes each at a level, moderately uphill inclined (+5%) or a moderately downhill inclined (-5%) motorized treadmill. Kinematics and spatiotemporal gait parameters were also measured using a photocell system. The runners performed the pre-race experiment the week before the race and the post-race experiment within 5 minutes of finishing the race. 

The time of the winner of the race was 6 h 40 min 07 s and the average time of the study participants was 9 h 45 min 41 s (range, 6 h 58 min 34 s to 14 h 12 min 32 s). Body mass decreased by 3.8% during the race and, as expected, the respiratory exchange ratio (RER), measured using the gross VO2 and VCO2 during steady state in the last minute of 5-minute running condition, decreased significantly. This corroborates previous studies on ultrarunning events where RER decreased by 15.6%, 11% and 7.3% between pre and post 24-h treadmill exercise (Gimenez et al 2013), a simulated 60-km ultramarathon (Schena et al 2014) and a 65-km MUM (2500 m D+) (Millet et al 2000), respectively. It is in contrast to findings in the extreme ultrarunning event Tor des Géants, where the same authors found that RER did not change, likely because of the multistage nature of the competition in which the runners were allowed adequate energy intake throughout the race, thus maintaining the efficiency of so called ATP aerobic resynthesis without having to completely switch substrate utilization from carbohydrates to fat as the glycogen stores never become so depleted (Vernillo et a 2013). However, the main finding in the study was that the energy cost of running (Cr) only increased, by a significant 13.1%, in the downhill condition and not after level or uphill running. Another major finding was that albeit there were no statistical changes in the total group, the individual changes in Cr in uphill and level running seemed to correlate well with running performance time with the slower runners having the largest changes. Altogether the authors interpret these results as supporting evidence for a role of Cr as a determinant for ultra-longdistance running performance.

Not surprisingly, the runners of the Vigolana Trail MUM had biomechanical changes in their running gait immediately after the race. Duty factor and stride frequency increased, whereas swing time, cycle time and stride length were significantly decreased in all conditions. Contact time was increased and the rate of force generation was decreased only in the uphill and downhill conditions. Interestingly, the stride frequency was increased only in the downhill running, probably indicating the highest muscle fatigue and thus at least partly explaining the highest increase in the energy cost of running (Cr) in this condition.

There are of course limitations of the study and the authors discuss them also in the paper. Firstly, running on a motorized treadmill is never going to measure the same gait as overground running in particular over more technical terrain outside. Secondly, the low gradient of the uphill and downhill running clearly does not reflect conditions when crossing most slopes during trail MUMs and the authors explain this as a compromise to be able to achieve metabolic steady state in a fatigued state after the race and to not force the participants to switch locomotion from running to walking. Lastly, as all studies of this nature the number of participants were rather small and perhaps not representative of other groups of MUM runners. Nevertheless, I clearly think the study enough generalizable to support the authors final conclusion that their data “show the importance of incorporating downhill locomotion in the training programmes of ultratrail runners to improve the various physiological and biomechanical parameters relevant to ultraendurance performance”.   

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