Improving Running Economy
[While iRunFar rarely touches on the technical aspects of running fitness, we received an offer we couldn't refuse from our good friend and exercise physiologist Dr. William Henderson of Endurance Science. In the following article he explains various ways that you can improve your running economy.]
In the previous article, I examined some of the science around footstrike patterns with respect to injury, economy and speed. I think that it is fair to say that proponents of mid/forefoot running have “ a whole lotta ‘splaining to do” before objective observers will believe that it is intrinsically better than the more typical foot strike pattern. There are some useful ideas within the Chi/Pose models – ideas like landing under the center of gravity. I don’t want to give people the impression that I’m a technique nihilist and that I don’t think that there is anything that can be done with respect to technique to improve an athlete’s speed and economy.
For example, in this article I’ll look at the evidence for several areas that I think that a runner can improve technique. Namely, we’ll look at the evidence for: i) foot contact time and cadence and ii) plyometric and strength training – ways to improve speed and economy without necessarily increasing fitness (yea, free speed!). High speed running, another method of improving running economy is not covered in this article
As I’ve said before, none of these ideas are secrets, and you don’t need to buy expensive training courses to learn, utilize or benefit from these strategies. As always, these techniques need to be adopted slowly, preferably under the supervision of an experienced and credentialed coach who can evaluate you as an individual.
Improving Running Economy: Cadence and Contact Time
Do you ever watch other people running? It seems like some of them float along, barely touching the ground, while others seem to labor slowly forward, with excessive movement and heavy footfalls. Think a bit about how the graceful ones look – quick, light steps, no overstriding and no scuffing and scraping noises when their shoes contact the ground. They seem more efficient and it shouldn’t be a surprise that they are. An exercise physiologist might call this “economy.”
Some of these attributes can be developed in an athlete by focusing on one thing – running cadence. Cadence is simply the rate at which leg turnover occurs (i.e., how many steps are taken per minute). If your left foot contacts the ground 70 times per minute, your cadence is 70.
Jack Daniels made the observation that the best athletes in any distance over about 2,000m run with a cadence of about 90. No matter the speed, cadence stayed pretty much the same, only stride length varied. Most beginning runners tend to run with cadences of 80/min or less.
Daniels suggests that quick cadence decreased injury by minimizing vertical oscillation (and, therefore, landing forces) and is more economical because it minimizes “ground contact time” – GCT. GCT is the time that a runner’s foot spends on the ground with each step. As an athlete’s speed increases GCT naturally decreases, but this can still vary between runners. A shorter GCT implies that you are spending less time planted on the ground, but also the force generated by each step occurs over a briefer period of time, which minimizes force absorption and dissipation. Daniels felt that we should all aim to run with a cadence of approximately 90/min, as this was optimally efficient.
I recently came across a great post by Roberto Veneziani on his excellent blog, wherein he charted his cadence versus his Polar “Running Index.” The Polar Running Index is a proprietary measure that attempts to give you a global assessment of your running performance during any workout. Although the exact formula is not public knowledge, it isn’t that difficult to figure out. Basically, it calculates what your heart rate is as a percentage of your max HR (used as a surrogate for VO2max) and measures your running speed at that HR. By normalizing your speed to heart rate, it can compare runs at different speeds. Simply put, it can tell you if you are getting fitter/more economical over time, even if you are running at different speed and HRs. It thus gives a global measure of fitness and running economy.
Roberto compared his cadence to his running index over many runs and found that he got the best running index measures as his cadence approached 90. This would seem to support Daniels’ empiric observation that this is the cadence for optimal performance in longer distance events.
Beyond GTC and decreased vertical oscillation, I wonder whether there might be biochemical reasons why optimal running economy might happen around 90 strides/min. In a study performed in the early 1990s, eight cyclists were asked to pedal on two occasions at 85% of their VO2max for 30 min. The first time, they used a bike gear that required a cadence of 50 rpm, and on the second occasion, a gear that required a cadence of 100 rpm.
With the slower cadence (i.e., higher resistance) pedaling Type II muscle fibers (“fast twitch”) used up glycogen 50% faster than during high cadence (lower resistance) pedaling. Type I fibers (“slow twitch”) used fat and glycogen at about the same rate at either cadence.
So why might this affect economy? At slow cadences, as type II fibers run out of glycogen, they are less able to contract, forcing the recruitment of other muscle groups. This leads to: i) deterioration in form and ii) less efficient use of energy and oxygen. Both of these factors can contribute to less effective cycling.
I haven’t seen similar research in runners, but it isn’t difficult to imagine that a similar process might apply. Very slow gaits, with more vertical oscillation, greater ground contact time and so on require more use of type II fibers, and less efficient glycogen/oxygen use with concomitant deterioration of running form. This could lead to poorer economy. Just a theory, but it is biologically plausible. Something I will have to test in the lab someday, I think!
Take home message? Gradually try to increase your cadence to a number close to 90/min. Changes in speed should come more from variations in stride length than changes in cadence.
- J Kang, J Hoffman, M Wendell, H Walker, and M Hebert. Effect of contraction frequency on energy expenditure and substrate utilisation during upper and lower body exercise. Br J Sports Med. 2004 February; 38(1): 31–35.
- The Effect of Pedalling Frequency on Glycogen-Depletion Rates in Type I and Type II Quadriceps Muscles during Submaximal Cycling Exercise, European Journal of Applied Physiology, vol. 65, pp. 360-364, 1992.
Improving Running Economy: Strength Training
Above, I outline some of the possible benefits on running economy of increasing cadence. Increases in cadence may improve economy by shortening stride length enough to prevent overstriding (and thus braking), decrease ground contact time (and thus improve energy return) and may decrease injury by lessening impact forces on landing. I wonder whether a lot of the alleged benefits of fore/midfoot running aren’t simply due to the effect that they have on stride length and cadence, rather than the actual part of the foot that is landed on per se.
In this section, I review some of the evidence for strength training as a way to enhance running performance.
The first thing to be clear about is definitions. By strength training, I mean focused strength exercises primarily for the lower body. The objective isn’t to “get bigger” but to enhance muscle unit strength and, more importantly, neuromuscular coordination and muscle unit recruitment.
There is a lot of evidence that focused strength training can improve running performance in both short and long distance events. For example, a group of Norwegian researchers found that a focused plan of “half squats” with heavy weights improved running economy by 5% and time to exhaustion at maximal aerobic speed (i.e., the pace you would run at when at VO2max) by 21%. This occurred after 8 weeks of 3 sessions a week. The most relevant figure from this paper is shown below.
What is interesting about both of these studies (and shown in many similar studies) is that this improvement in running times occurred without an improvement in aerobic fitness as measured by VO2max. We can therefore conclude that the improvements were due to better efficiency in running (i.e., running economy). This was presumably because weight training improved the effectiveness of recruitment of the involved muscles or allowed the recruitment of stabilizing muscles – thereby improving stride efficiency.
During endurance training some runners find that their stride length shortened as compared to when they are focusing on speed training. A group of Spanish researchers demonstrated that weight training prevented runners from developing a “marathon shuffle.”
The trick for most of us is to actually find the time to add this type of work into our training regimen. I think that there are a few general rules that apply: start with small doses of weight training, begin in the off season, and don’t become a weight lifter rather than a runner.
In the next section, I outline a strengthening program that combines the benefits of strength and plyometric training for endurance runners.
- K Stkren, J Helgerud, E Stka, and J Hoff. Maximal Strength Training Improves Running Economy in Distance Runners. MSSE 2008
- G Millet, B Jaouen, F Borrani, and R Candau. Effects of concurrent endurance and strength training on running economy and VO2 kinetics. MSSE 2002.
- J Esteve-Lanao, M Rhea, S Fleck, and A Lucia. Running Specific Periodized Strength Training Attenuates Loss of Stride Length during intense Endurance Running. JSCR 2008.
Improving Running Economy: Jumps!
In the previous section, I outlined some of the evidence for ancillary strength training for runners. I think that there is clear evidence that lower body strength exercises can improve running economy (and, therefore, performance) in well trained runners. I received two interesting emails related to this subject that I thought I would expand upon.
The first email asked if it was better to add weight training or more running volume to improve performance. This is an excellent question, as it gets to the heart of many “cross-training” myths. Many people feel that they can cross train their way to better running. I think that cross training in other sports is very beneficial, particularly in that it can allow development of stabilizing muscles, avoids developing the not 100% attractive “runner’s physique,” prevents burnout and is, well, …fun! However, there is no doubt that the strongest predictor of distance running improvement is volume of running. So if you can increase your volume further (without injury or burnout), this is probably the way to go. But… if you have hit the point where more volume leads to injury, excessive recovery time, or if performance has plateaued, then adding non-running training seems prudent.
The second question asked about plyometric training. Plyometrics is a system of exercises that uses rapid, explosive movements to improve power. Examples include hopping, bounding, box jumps and so on. The mechanism by which plyometric training increases power is interesting. Rather than increasing muscle strength/mass, plyo exercises improve musculotendinous stiffness – thereby improving the “energy storage” and energy return during resisted movements. For example, plyo box jumps will, over time, improve the efficiency with which the energy stored in the tendon/muscle during landing is released. In a sense, it improves the “spring action” of the muscles and tendons. If you think back to my explanation about ground contact time, you can see that a more powerful push off during running is beneficial. So what’s the evidence?
There are several studies that show a link between plyometric training and improved running performance. The one I like best (because the scientific method was the most rigorous) was published in 2003 in the European Journal of Applied Physiology. In this study the authors found that a 4 month plyometric program improved running economy and 3km race time by 2.7%.
While 2.7% isn’t a trivial improvement, I do have some concerns about most runners adopting plyo training. Essentially, I think that this is a high risk tool. The rate of injuries doing plyo training is relatively high, and I think that the most extreme drills – box jumps, cone jumps, etc, are probably best done only by experienced athletes with coaching supervision. More traditional drills such as on-track hopping and bounding are probably reasonable if done carefully. However, I think that the large majority of the improvements in economy seen with these drills can probably be achieved more safety with strength training…
- RW Spurrs, ML Watsford, AJ Murphy. The effect of plyometric training on distance running performance. Eur J Appl Physiol (2003) 89: 1–7.
Call for Comments
Do you incorporate any activities in your training specifically to enhance your running economy? If so, what?