Is your running form holding you back or propeling you forward?

As trail runners we are constantly striving to be better, run further, add more elevation gain, and cover more technical terrain. We can see and feel the benefits of our training as we watch our average pace and heart rate decrease, our mileage increase, and continue to improve in races. While some of this occurs as we put more time in on our feet and miles on our legs, it is also important to pay attention to how your body is moving while you run. Any changes that allow you to use less energy while running allow you to improve your pace without increasing the amount of stress placed on your body (8). Less stress, faster pace, better race, right? In this article we are going to dive into the concept of “running economy.” There are many variables that influence running economy so let’s dive into how it’s affected and what we can do to improve it through the way we move and how and where we train.

What is Running Economy?

Running economy (RE) is defined as “the steady-state oxygen uptake required at a given submaximal speed” (5). What this means in practice is that runners with better RE use less oxygen at the same  speed than runners with poorer RE. When looking at the factors that affect RE, researchers found that there is a strong relationship between RE and distance running performance (6). Which makes sense, a more efficient runner should be a faster runner. VO₂, volume of oxygen, is a unit of measurement used to describe how much oxygen you intake during an activity. A lower VO₂ at a given running speed indicates better RE, while a higher VO₂ at the same speed indicates poorer RE. Again this is because a less efficient runner has to work harder, and in this case ‘use more oxygen.’ VO₂ max is defined as your maximal volume of oxygen uptake. Runners with better RE are able to run at a lower percentage of their VO₂ max than runners with poorer RE. This also results in lower blood lactate levels at a given speed (essentially staying more aerobic), ultimately reducing muscle fatigue and prolonging your ability to perform (6).

RE can differ by as much as 30% in runners with similar VO₂ maxes! Because of this, RE is a better predictor of performance than VO₂ max in elite distance runners (3,6). Good RE stems from a variety of factors, including, but not limited to, training, environment, physiology, body type, as well as physiological, neuromuscular, and biomechanical factors (1,3,7,8). Out of all of these variables, biomechanical factors have the most significant influence on energy expenditure and RE (8). This is cool because we can influence biomechanical factors much more directly.

How Your Stride Impacts Running Economy

Stride angle is the biomechanical feature that has the most significant impact on RE. It is composed of the path taken by the foot after leaving the ground and the ground itself. Runners with a greater stride angle, meaning their foot lifted higher off the ground, had lower VO₂ at a given speed. This shows that having a larger stride angle is more efficient and more economical than having a smaller stride angle (5). Additionally, for every degree your stride angle increases you increase your stride length by two percent.

Another important factor is ground contact time. Running is composed of two phases: stance time and swing time. Stance time, also known as ground contact time, has three phases: initial contact, midstance, and propulsion, with propulsion having the strongest direct link to RE (3,5). Santos-Conjero et al.’s research showed that runners with longer ground contact time during the gait cycle had higher VO₂, indicating poorer economy. Activating the lower leg muscles quicker allows you to get your foot off the ground sooner. So the more efficient your muscles are, the more economically you can run. Shortening ground contact time while maintaining running cadence, which most runners have a natural stride frequency within 3% of their optimal rate, can facilitate larger stride angles and longer swing times, decreasing VO₂ and improving RE (3,5).

What is Vertical Oscillation?

When running, all systems are working together to propel you continuously forward as efficiently as possible. Excessive motion in other directions wastes energy that could be dedicated to moving you forward. Vertical oscillation is the amount your body moves up and down while running. In distance running, high amounts of vertical oscillation decrease economy  because you are spending energy in a non-beneficial direction (2,5,7). Lessen your vertical oscillation to propel yourself forward.

Foot Strike and Running Economy

Foot strike pattern and its effect on RE has been heavily researched. There are three types of foot strike: forefoot, midfoot, and rearfoot. Forefoot striking (landing on your toes) requires you to rely more on the surrounding muscles and is more prevalent among elite performers (4,6). Both forefoot and midfoot striking (landing on the middle of your foot) allow better stretching of the arch of the foot than rearfoot striking. Your arch acts as a kind of bow and arrow mechanism; as the arch stretches, tension is created and energy is stored in the arch and surrounding muscles. That energy is then released as the arch returns to its natural length, leading to a stronger propulsion phase (4,6). Forefoot strikers use more musculature to propel them forward, while rearfoot strikers rely more heavily on their skeletal structures to absorb impact (8). While no difference in RE was found between forefoot and rearfoot strikers, rearfoot strikers had better RE compared to midfoot strikers (3,4). It is also possible that forefoot and midfoot strikers have better RE than rearfoot strikers due to decreased ground contact time (3). When considering changing foot strike pattern, it is recommended that habitual rearfoot strikers not try to force a change, as switching from rearfoot to forefoot or midfoot could be detrimental to RE (3).

Upper Body Mechanics

As runners we tend to forget about our upper body, but biomechanics of the upper body do play a small role in determining RE. While no evidence has been found that you can improve your RE by simply changing your upper body mechanics, runners with better RE typically have less arm movement than less economical runners, and eliminating arm movement entirely by clasping the hands behind the back (which we wouldn’t recommend trying) decreases RE (3,6). Therefore, runners are encouraged to maintain their natural arm swing.

How to Improve Running Economy Through Training

Highly trained runners generally already possess well-developed RE, so further improvements are often difficult to obtain (6). However, strength work, altitude and heat training are three ways to improve RE even in the most economical runners. Strength training improves your ability to increase lactate threshold and utilize more elastic energy to produce shorter ground contact times and faster forces. Adding plyometric training into your strength training can increase your ability to utilize more elastic energy even more efficiently. Altitude training exposes you to less oxygen availability, facilitating a more efficient use of oxygen overtime. When running at sea level, the RE of athletes who live at high altitude was found to be significantly greater than athletes living at low altitude. Utilizing a “live high, train low” approach is one of the best ways to accomplish this. Heat training elevates your core temperature, which leads to an increased efficiency of the muscles, and therefore improved RE. It can also increase plasma volume by up to 12%, which ultimately minimizes the amount of work needed by the heart (6). 

TL:DR

Wrapping it all up – here are the biggest things to remember from the research on how to optimize your running economy:

• Increase your stride angle – Lift your foot up higher off the ground, doing so also increases your stride length allowing you to literally cover more ground.
• Decrease your ground contact time – The faster you get your foot off the ground, the less energy you use.
• You gravitate to your most efficient movement naturally – Maintain your natural running cadence, foot strike pattern, and arm movement.
• Mix up your training – Consider adding strength work including plyometrics, as well as  altitude or heat training to sprinkle in some additional gains.
• It’s all about propulsion – Keep moving forward!

References

(1) Barnes, K. R., McGuigan, M. R., & Kilding, A. E. (2014). Lower-Body Determinants of Running Economy in Male and Female Distance Runners. Journal of Strength and Conditioning Research, 28(5), 1289–1297. 

(2) Heise, G. D., & Martin, P. E. (2001). Are variations in running economy in humans associated with ground reaction force characteristics ? European Journal of Applied Physiology, 438– 442. https://doi.org/10.1007/s004210100394 

(3) Moore, I. S. (2016). Is There an Economical Running Technique ? A Review of Modifiable Biomechanical Factors Affecting Running Economy. Sports Medicine, 46(6), 793–807. https://doi.org/10.1007/s40279-016-0474-4 

(4) Ogueta-Alday, A., Rodríguez-Marroyo, J. A., & García-López, J. (2014). Rearfoot Striking Runners Are More Economical Than Midfoot Strikers. American College of Sports Medicine, 580–585. https://doi.org/10.1249/MSS.0000000000000139 

(5) Santos-Concejero, J., Tam, N., Granados, C., Irazusta, J., Bidaurrazaga-Letona, I., Zabala-Lili, J., & Gil, S. M. (2014). Stride Angle as a Novel Indicator of Running Economy in Well- Trained Runners. Journal of Strength and Conditioning Research, 28(7), 1889–1895. 

(6) Saunders, P. U., Pyne, D. B., Telford, R. D., & Hawley, J. A. (2004). Factors Affecting Running Economy in Trained Distance Runners. Sports Medicine, 34(7), 465–485. 

(7) Thompson, M. A. (2017). Physiological and Biomechanical Mechanisms of Distance Specific Human Running Performance. Integrative and Comparative Biology, 57(2), 293–300. https://doi.org/10.1093/icb/icx069 (8) Williams, K. R., & Cavanagh, P. R. (2018). Relationship between distance running mechanics, running economy, and performance. 30.