Incline Treadmill Tests for Uphill Running Gains
By Doug Stewart, Performance Director, & Reviewed by Steven Harris, Performance Physiologist
At the ETT, we are always looking at ways to improve our understanding of the unique demands of trail, mountain and ultra running. Recently we have developed, in collaboration with the Loughborough Sports Services physiology team, an incline treadmill protocol designed to offer insight into athletes’ performance when running on an incline compared to more traditional velocity based profiling.
Kris in the lab during the incline treadmill testing
We have previously shared with you the benefits of lab testing and how we have done this with our athletes. However, whilst these tests offer great insights into running and each athlete’s physiology, they are based on running on the flat (actually, the treadmill is set to 1% incline, since that most accurately reflects the energy required when running on the flat outside (Jones and Doust, 1996)).
However, given the nature of the races the ETT athletes compete in, with significant amount of time spent running uphill, Performance Director and Coach Doug decided to explore an uphill simulated test. We have also seen very proficient road runners not being able to transfer their flat running speed onto steep trails, whilst other runners have discussed how RPE and HR do not match when running on the flat versus the uphill. Moreover, research has shown that, for short trail races, the classic endurance running model is not sufficient for more comprehensively forecasting trail running performance and using gradient specific running economy testing is worthwhile exploring (Ehrström et al., 2018). All these factors led to thevcreation of an uphill treadmill test.
When you search for ‘Incline Treadmill Test’ on Google Scholar, a number of papers appear relating to horses running on treadmills on an incline (!). However, there are also a few papers exploring runners, which served as a basis for the ETT Incline Treadmill Test protocol.
Balducci et al., explored endurance mountain runners and provided a comparison between a level and an incline treadmill test. This involved 3 separate visits in a random order, where the elite level participants performed a VO2 max test at 0%, 12% and 25%. The results showed that VO2 max was not significantly different across all three incline levels. This approach was not deemed the most optimal for the ETT athletes, as we have already tested their VO2 max, and we were more interested in exploring their lactate profile, rather than a VO2 max at different gradients.
A paper by Doucende et al., (2022) then explored running on a 25% slope, with the speed increasing every minute until exhaustion, followed by a second test, still on 25%, at 105% of the maximum speed achieved in the first test. The athletes ran again until exhaustion, with VO2 max and other metrics gathered. This protocol provides a more comprehensive insight into incline running performance with submaximal and maximal metrics identified; however, when designing our protocol, the 25% incline was deemed to be potentially excessive for applied performance with varying gradients. Equally, our previous testing protocol on the flat aligned more closely with a third paper by De Lucas et al., (2022) leading us to follow a closer approach to theirs.
De Lucas et al., (2022) had the athletes complete a sub maximal test on a 1% slope in 3-minute stages, increasing the speed every 3 minutes by 1 kph. This is similar to the test we use with ETT athletes, although we use 6-minute stages to optimise fuel utilisation data collection. Secondly, the athletes then completed an incline treadmill test, selecting a speed that was 50% of the maximum speed achieved in the first test. The participants then started the uphill test on an incline (of either 3% or 5%, depending on their running speed) and then, every three minutes, the incline was increased by 2%. The participants continued until a stage was not completed. This approach saw the runners go through, on average, 8 different incline levels, and allowed for a comparison with the test completed on the flat.
When discussing our testing plans with Loughborough Sport performance physiologist Steven Harris, it was felt this third approach would be best and provide the most comparable data (flat v incline), with actionable insights for training and racing for the ETT athletes. We did adjust the protocol to make it more specific to our athletes, with longer stages, and customising the starting gradients based on their individual ability.
The results proved fascinating, and, whilst we cannot share individual athlete details, we can share some of the insights.
Chelsea working on her uphill form outdoors
Running Economy at Different Inclines
By using a graded pace analysis, we are able to assess the running economy of each athlete at different inclines. This can help identify potential areas of strength and weakness for each athlete, allowing for more tailored training. It also allows for comparison of running economy on the flat versus incline – if significantly different, then we can look at gait and strength work with Dr Chris Bramah to address this. It can influence race tactics – such as on what type of climb to attack, for example, or if weaker at a certain gradient, looking at where one may be vulnerable in a race.
Incline Heart Rate vs. Flat Test
When comparing heart rate on the flat test versus the incline protocol with grade adjusted pace, we were able to see individual variations in HR response, which allow for more tailored training intensity zones for uphill work.
HR and Blood Lactate Incline Test with Grade Adjusted Pace
As expected, the blood lactate and HR profiles presented similarly with exercise intensity being increased via gradient instead of pace. However, the profile becomes particularly interesting when comparing the incline and velocity based lactate profiles using grade adjusted paces.
When comparing profiles, we saw our athletes continually outperforming the grade adjusted pace models when running on an incline. This may reflect their time spent training on hills, which may have led to the intensity of running being reduced due to a greater proficiency in comparison to a standard runner. Comparisons with a well-trained road runner may provide greater insight to whether this rings true. Equally, this could call into question the validity of grade adjusted paces for trail runners.
Fuel Utilisation
Poppy during the incline treadmill test
In addition to heart rate, pace and blood lactate, we also captured fuel utilisation data. This revealed fat and carbohydrate usage at different gradients and also a different composition compared to flat running, which we will look to explore more. These findings could impact on the race nutrition plans of our athletes.
Ultimately, this is a small sample of high performing athletes that we are experimenting with. Like any research, there are limitations, but we are looking to continue to develop and share more insight in our approaches that we hope will prove beneficial to you and your training, too.
Questions we are still looking to answer include:
Does running economy at X% align with incline performance within our cohort? If so, what metrics/qualities positively influence this?
Do more proficient incline runners have a closer relationship between flat v incline adjusted pace profiles? Does a large difference suggest greater potential to improve incline performance?
References:
Balducci, P., Clémençon, M., Morel, B., Quiniou, G., Saboul, D., & Hautier, C. A. (2016). Comparison of level and graded treadmill tests to evaluate endurance mountain runners. Journal of sports science & medicine, 15(2), 239.
De Lucas, R. D., Karam De Mattos, B., Tremel, A. D. C., Pianezzer, L., De Souza, K. M., Guglielmo, L. G. A., & Denadai, B. S. (2022). A novel treadmill protocol for uphill running assessment: the incline incremental running test (IIRT). Research in Sports Medicine, 30(5), 554-565.
Doucende, G., Chamoux, M., Defer, T., Rissetto, C., Mourot, L., & Cassirame, J. (2022). Specific incremental test for aerobic fitness in trail running: IncremenTrail. Sports, 10(11), 174.
Ehrström, S., Tartaruga, M. P., Easthope, C. S., Brisswalter, J., Morin, J. B., & Vercruyssen, F. (2018). Short trail running race: beyond the classic model for endurance running performance. Medicine and science in sports and exercise, 50(3), 580-588.
Jones, A. M., & Doust, J. H. (1996). A 1% treadmill grade most accurately reflects the energetic cost of outdoor running. Journal of sports sciences, 14(4), 321-327.