Good afternoon, and welcome back.
In last week’s newsletter, I talked about the effects of mental training and how it is possible to use simple cues to improve time to exhaustion. You need to identify cues for the earlier reps and practice them. Cycle out the ones that don’t work, and then use different cues for the ends of reps or more challenging spots during the workout and do the same thing. If you haven’t seen it already, go check out that newsletter in last week’s email.
This week, I’m going to talk about the benefits of hill sprints. I’m going to discuss a few particular studies that cover not only the benefits of hill sprints, but exactly how much of a benefit they can provide in trained runners. I’ll also talk about the optimal gradient for hill sprints to maximize your return on investment.
Be sure to check out the Endurance Lab podcast, where this past week I talked with Jeff Garmire, the record holder for the Appalachian Trail. He completed the entire trail in under 45 days, breaking the previous record by about five hours.
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The Physiology of Hill Sprints
Luckily, the physiology of hill sprinting can largely be explained by the physics of overcoming gravity. For example, we know that mechanical energy can be broken into potential and kinetic energy. Potential energy equals mass times gravity times height:
Potential Energy = Mass × Gravity × Height
Kinetic energy equals one-half mass times velocity squared:
Kinetic Energy = ½ × Mass × Velocity²
We know that if you drop a ball from a height of 10 m, it will have exactly as much kinetic energy at the bottom as it had potential energy at the top, assuming that energy is conserved and there is no loss to friction or air resistance.
When you think about hill sprinting, you’re essentially just displacing your mass vertically and horizontally. It’s quite easy to calculate the amount of additional energy required when running uphill because we know your velocity, as well as your vertical and horizontal displacement. We can calculate the work that was done and convert that into potential energy, or we can take your velocity and split it into both horizontal and vertical vectors to do the same thing. Regardless, when you run uphill, you’re doing more work, such that with any given stride, you’re producing higher power outputs.
The Mechanics of Uphill Running
When it comes to the mechanics of uphill running versus flat running, there are some obvious biomechanical differences. For example, during uphill running, you’re typically going to have a higher step frequency. You’ll spend less time in the air and more time on the ground (i.e., longer ground contact times). Some studies also show a quicker swing phase, which is consistent with higher step frequencies, longer ground contact times, and shorter flight times relative to flat running.
Moreover, when running uphill, you’ll see much higher power outputs, even at a similar relative effort. To illustrate this, I did some sprints this past week on the track and on a hill. Both were about 70 seconds in duration. On the hill, my power output reached as high as 750 W, while during the flat running, it was only about 550 to 600 W.
Power output during hill sprints on the left. Power output during 400m sprints at 71s shown on the right.
The other thing to keep in mind is that my heart rates were actually HIGHER for the 400s. Now, clearly, the specificity of uphill running may not generalize perfectly to flat running, which is why it’s important to do flat running in addition to hill sprints. You can’t just do a set of hill sprints and expect to get all the same benefits you would from also running fast on flat ground. You’re potentially going to lack the ability to reposition your limbs as quickly or deal with the shorter ground contact times required during faster flat running.
So, What Do the Studies Actually Say?
So, what do the studies actually say about hill sprinting and what it does? Well, the good news is that the findings are largely beneficial.
Study 1: More Oxygen at the Same Effort
In the first study, 17 well-trained runners performed 4 × 5 minutes of uphill running at an 8% grade and horizontal running at a 1% grade, with 90 seconds of recovery [1]. As expected, uphill running produced higher mean and peak VO₂ values throughout the workout.
More importantly, participants accumulated 9.1 minutes above 90% of VO₂max during the uphill condition compared with 6.4 minutes during flat running. That’s about 42% more time above 90% of VO₂max from the same basic workout structure.
Figure 1. Time90 is the time spend above 90% of VO2max [1]. This study showed that hill running resulted in 2.7 more minutes spent at VO2s >90% of max. That adds up!
What blew my mind, though, was that heart rate, blood lactate and RPE were comparable between conditions. So they consumed more oxygen and spent more time near VO₂max without a meaningful increase in how hard the workout felt. So, how can this be?!
Well, it’s probably because uphill running requires:
Higher power output at any given running velocity because you are overcoming gravity i.e., you are creating potential energy.
Lower velocities and longer ground contact times, even when the effort is maximal. Basically, there’s a tradeoff between force and velocity.
Greater recruitment of large lower-body muscles and contribution from the upper body, all of which consume oxygen and contribute to the higher VO₂.
One thing to consider when doing uphill sprints is that they may not generalize perfectly to the specific demands of fast, flat running, as I just stated. They will, however, elicit a massive metabolic stimulus that, when combined with flat sprints and track work, could yield better results than not incorporating them.
Study 2: Running Economy and 5K Performance
Not only does uphill interval training increase oxygen consumption, but we also know that it can improve running economy and 5K time-trial performance. A study published in 2013 compared several uphill interval programs in well-trained runners [2]. After six weeks, 5K time-trial performance improved by an average of 2.0% across the different hill-training conditions.
There was no single best protocol for the 5K. However, the highest-intensity training was optimal for running economy, improving it by approximately 2.4%, as well as for the neuromuscular measures. Other aerobic outcomes tended to respond best near the middle intensity.
Basically, almost any form of high-intensity uphill interval training appears to help 5K performance, but the best hill and repetition length probably depend on the exact adaptation you want.
But Wait, There’s More!
A recent study looked at not only the benefits of hill training, but also the effects of different hill grades on maximal velocity, anaerobic endurance, and 800-meter time-trial performance [3]. The study compared shallow (2.5%), intermediate (5.1%), and steeper (7.6%) grades over eight weeks.
Unfortunately, this study is challenging to interpret because the paradigm they used was confounded by the fact that participants in the steepest-hill group performed repetitions lasting 30 to 90 seconds, while participants in the shallow 2.5% group performed repetitions lasting two to three minutes.
In a sense, these are different physiological stimuli. In one condition, you have higher power outputs because of the shorter and steeper repetitions, but probably less total aerobic demand per repetition. In the other condition, you have a greater aerobic demand because of the longer repetitions, but relatively lower power outputs compared with the steeper hill.
The authors stated that all groups were held between 85% and 100% of their maximal heart rate. As we know, going from something like 170 to 175 beats per minute can have massive physiological consequences because of the nonlinear relationship between workload and time to exhaustion.
Figure 2. Changes in maximal velocity following eight weeks of training at different uphill gradients [3].
Nonetheless, the steepest 7.6% group produced the greatest improvement in maximal velocity. This didn’t surprise me as you’ll have the highest power output during this condition, and you have the shortest reps, so this is most akin to doing max velo sprinting. This fits the force-velocity relationship: when force requirements are extremely high, velocity is low, and when force requirements are low, velocity can be much higher. Optimal power is generally achieved somewhere in the middle, where relatively high forces can still be produced at relatively high velocities. It’s likely that anything over 10% would be lower velocities because the forces are so high.
The other thing I can’t figure out about this study is that the steepest hill group’s 800-meter time trial appears to go from roughly 2.11 minutes to 1.53 minutes. If those values represent true decimal minutes, 1.53 minutes would equal approximately 1:32, which would be faster than the 800-meter world record. However, they may have intended 1.53 to represent 1:53 rather than a true decimal value. Either the notation is misleading, something is off with the statistics, or I’m not interpreting it properly.
Figure 2. Changes in 800-meter time-trial performance following training at different uphill gradients [3].
Regardless, the overall pattern favored the steeper hill. The 7.6% group also produced the largest improvements in the study’s strength-endurance test, which was measured using burpees.
Figure 3. Changes in strength endurance following training at different uphill gradients [3].
How I Would Use Hill Sprints?
So, what should you actually do with this information? It depends on what you’re trying to improve.
If the goal is neuromuscular power and maximal velocity, use shorter repetitions on a moderately steep hill, roughly 5% to 8%, with enough recovery to maintain high power and good mechanics.
If the goal is VO₂max, longer uphill intervals around an 8% grade can increase the amount of time you spend above 90% of VO₂max without making the workout feel substantially harder.
If the goal is 5K performance, the exact protocol probably matters less. Across six weeks, multiple high-intensity uphill protocols improved 5K time-trial performance.
Keep some flat strides, sprints, or track work in the program because uphill running does not perfectly reproduce the velocities, ground contact times, and repositioning demands of fast, flat running.
Progress the volume carefully. The metabolic and power demands are high, even if the lower velocity makes the workout feel mechanically safer.
Summary
Hill sprints are not magic, but they give you a pretty unique combination of high force, high power, and high oxygen consumption at lower running velocities. They can increase the amount of time you spend near VO₂max, improve running economy, and improve time-trial performance.
The grade should match the goal. Steeper, shorter hills probably make the most sense for power, maximal velocity, and middle-distance performance. Longer repetitions on moderate hills make more sense when the goal is aerobic development. Regardless, keep some flat running in the program so that you retain the actual mechanics and velocity required to race fast.
In other words: run hills, but don’t only run hills.
Cheers,
Dr. Evans
References
1. Held, S., et al., Increased oxygen uptake in well-trained runners during uphill high intensity running intervals: A randomized crossover testing. Front Physiol, 2023. 14: p. 1117314.
2. Barnes, K.R., et al., Effects of different uphill interval-training programs on running economy and performance. Int J Sports Physiol Perform, 2013. 8(6): p. 639-647.
3. Alemu, Y., T. Tadesse, and Z. Birhanu, The effects of uphill training on the maximal velocity and performance of middle-distance runners: a randomized controlled trial. Sci Rep, 2025. 15: p. 22709.