Physiological Durability and the Demands of Uphill Running

In long distance endurance sport, physiological durability is gradually becoming recognised as the fourth determinant of performance alongside VO2max, the lactate threshold and running economy. Durability (also named physiological resilience or fatigue resistance) refers to the extent in which an athlete’s physiology changes under fatigue compared to their fresh state physiology. The research in this area is still growing, but the running specific research so far has primarily focused on the road marathon, and the first trail running durability study released last week is limited in terms of novel findings that road-based studies haven’t already found.

This article aims to piece together historical studies around uphill running which should help in finding clues to either improve an athlete’s uphill running durability or to improve general long-distance off-road running durability, where uphill segments can be a substantial contributor to fatigue. 

Remi Bonnet at the Pikes Peak ascent, a 13 mile long uphill race. Image by Brian Metzler.

How Uphill Running Changes Muscle Demands

It’s important to begin by discussing the potential differences in physiology between flat and uphill running. A study by Sloniger et al. (1997) compared the muscular work required for flat treadmill running and running at a 10% gradient. Firstly, they found that uphill running demanded an overall greater muscle activation than flat running which may explain the findings of Paavolainen, Nummela and Rusko (2000) who discovered that oxygen uptake contributes more to uphill running compared to flat running, likely due to the increased muscle activation required to propel the body uphill. A larger general greater muscle activation may explain why road runners, despite possessing world-class physiological markers, struggle to adapt to races with steep gradients (tendon dynamics could also play a role, which I will discuss in a future article).

Alongside a general greater activation, Sloniger’s study compared the most active muscles contributing to both flat and uphill running. They found that uphill running required larger activation from the calves and glutes while flatter running relied relatively more on the hamstrings and adductors (full image based on the study data is below). This may be valuable information but it’s worth noting the flaws of this study, too. The participant group included twelve women with a VO2Peak of 48.6 ± 5.2, meaning this study was not conducted on a group of elite athletes, who may possess different biomechanical patterns to reduce the cost of movement. Additionally, the uphill segment of this study was conducted at a 10% gradient on the treadmill, which may not be steep enough to make accurate conclusions regarding muscle activation in shorter races with steeper gradients. It would be a real stretch to take these findings at face value but they may provide clues as to the types of muscular activation changes that occur between flat and uphill running. For now, a safe conclusion might be that as the gradient increases, the mechanical work from the muscles that cross the hip also increases, which is supported by Yokozawa, Fujii and Ae (2007). 

Major differences in muscle activation between flat and uphill treadmill running. Data from Sloniger et al. (1997).

Training Strategies to Enhance Uphill Durability

There’s limited but strong research supporting at least one influencing factor of uphill durability: maximal mechanical power, which is the highest rate in which the muscles can generate work. Simply, how powerful the athlete is. A study by Giovanelli et al. (2016) found maximal mechanical power to be associated with smaller changes in uphill running mechanics during the Mount Etna uphill only marathon (42 kilometres and over 3,000 metres of elevation gain). In a similar study design at the same race, Lazzer et al. (2015) found athletes with better maximal mechanical power showed smaller increases in oxygen cost of running throughout the event. To be clear, a smaller oxygen cost of running is associated with better performance through more efficient movement. The underlying message of both studies is that maximal power of the lower limbs correlates strongly with a runner’s ability to maintain their form (and as a result, continue to be oxygen efficient) during prolonged uphill running of multiple hours. 

There are a selection of training methods available when looking to improve maximal power. Although not specific to the movements of running, developing power in the gym is likely the most effective method of training. There’s a rather large selection of power based exercises available, but those most specific to uphill running (based on the results of the Sloniger study) include jump squats with a barbell to target the vastus group, kettlebell swings to target the glutes and hamstrings as well as variations of plyometric exercises to target the calf region. Plyometrics will also enhance elastic energy storage and release from the achilles tendon but whether this is something that might benefit steep uphill performance is inconclusive due to the varying tendon dynamics between steep and flat gradients. 

Structuring these exercises over the long term is another important consideration. My current view on gym-based training is that the athlete should develop a strong base of strength before transitioning to power exercises. General strength training recruits fast twitch muscle fibres, but power training will help those muscle fibres contract quickly enough to propel the athlete forward or upwards at a faster rate (Blagrove, 2015). A large portion of the athletes I’m currently working with will undergo general strength training (alongside smaller volumes of plyometric work), before a transition towards some more power-based exercises with an increase in plyometric volume closer to goal races. Periodising the gym-based work in this way should allow the athlete to recruit as many faster-twitch muscle fibres as possible before maximising that recruitment by ensuring they’re able to contract fast enough to contribute to the next stride.

In summary, the primary muscles in locomotion seems to shift closer to those that cross the hip as the gradient steepens and there’s a strong correlation between maximal mechanical output and a maintenance of running biomechanics (and thus running economy) during prolonged uphill efforts of multiple hours. The key message of this article is to not neglect power-based gym exercises (through powerlifting and plyometric work) in the build up to a long race with significant elevation gain, whether it be a double vertical kilometre race or a long race with large portions of steep climbing, like Sierre-Zinal.

References

Blagrove, R. (2015) Strength and Conditioning for Endurance Running. Crowood.

Giovanelli, N., Taboga, P., Rejc, E., Simunic, B., Antonutto, G., & Lazzer, S. (2016). Effects of an Uphill Marathon on Running Mechanics and Lower-Limb Muscle Fatigue. International journal of sports physiology and performance, 11(4), 522–529. https://doi.org/10.1123/ijspp.2014-0602

Lazzer, S., Salvadego, D., Taboga, P., Rejc, E., Giovanelli, N., & di Prampero, P. E. (2015). Effects of the Etna uphill ultramarathon on energy cost and mechanics of running. International journal of sports physiology and performance, 10(2), 238–247. https://doi.org/10.1123/ijspp.2014-0057

Paavolainen, L., Nummela, A., & Rusko, H. (2000). Muscle power factors and VO2max as determinants of horizontal and uphill running performance. Scandinavian journal of medicine & science in sports, 10(5), 286–291. https://doi.org/10.1034/j.1600-0838.2000.010005286.x

Sloniger, M. A., Cureton, K. J., Prior, B. M., & Evans, E. M. (1997). Lower extremity muscle activation during horizontal and uphill running. Journal of applied physiology (Bethesda, Md. : 1985), 83(6), 2073–2079. https://doi.org/10.1152/jappl.1997.83.6.2073

Yokozawa, T., Fujii, N., & Ae, M. (2007). Muscle activities of the lower limb during level and uphill running. Journal of biomechanics, 40(15), 3467–3475. https://doi.org/10.1016/j.jbiomech.2007.05.028