Running Economy – Running Style

CURRENT RESEARCH SHOWS…THERE ARE TWO WAYS TO IMPROVE RUNNING PERFORMANCE

The first, running efficiency, looks at the structure of the body and things like biomechanical efficiency of running technique, stride length and frequency [SR], and breathing rate, among others.  Running efficiency is about improving running technique to gain higher mechanical force and power output for the same unit of energy.  Running efficiency was covered in part I (December issue, 24-10) of this two part series on running with style.

The second major way to improve running performance is running economy. Running economy is the energy required to run at a given velocity.  It’s measured as the amount of oxygen consumed per unit time or per unit distance.  A well-designed study by Morgan and Craib (1992) found a clear relationship between elite runners and faster times due to superior economy.  Other studies confirmed that oxygen consumption at a given running speed is less for world-class middle distance runners than for less successful middle distance runners (Margaria et al. 1963, Dill 1965, Kollias et al. 1967, Daniels and Oldridge 1971).

A runner with good running economy uses less oxygen to run at the same given pace as a less economical runner, enabling him to run longer and faster.  He can race at a faster pace (i.e. exerting greater force) while processing the same amount of oxygen than a less economical runner, which will ultimately win him the race.  As Dr. Jack Daniels puts it in his book, Daniel’s Running Formula, “Improved economy is a highly desirable result of training because the runner can now race at a faster speed than before without using more energy to do so”. Running economy and efficiency are closely intertwined.  Biomechanical efficiency contributes a major part to running economy because efficient movement consumes less oxygen at a given running speed.

The Contribution of VO2 Max to Running Economy

If we look at the effect of VO2 max on running efficiency and economy and vice versa, we get a better idea of their interrelationship.  A runner with a low VO2 max and good running efficiency will probably perform as well as one with a high VO2 max and poor running efficiency, all other things being equal.  Thus high VO2 max plays a key role in running economy.  For example, Dr. David Costill, in his book Inside Running: Basics of Sports Physiology, describes two runners, with VO2 max values of 60 ml/kg/min (Runner A) and 70 ml/kg/min (Runner B), who are asked to run at a six minute mile pace.  Both runners would consume about 50 mls of oxygen per minute for each kilogram of body weight.  But because of the difference in their aerobic capacities (60 vs. 70 ml/kg/min) the demands placed on their cardiovascular systems would be markedly different.  Runner A would be working at 83% of his VO2 max, whereas runner B would only operate at 71% of his aerobic capacity.  Runner B could sustain that pace for a longer period and feel less distress than runner A.  This fractional use of aerobic capacity is an important indicator of running economy.

Ultimately, high VO2 max levels enable runners to use lower percentages of those levels to meet the aerobic energy demands of distance competition and avoid heavily taxing their oxygen transport systems.  Thus a high VO2 max is of critical importance.  Sadly, VO2 max levels are heavily (80%) genetically determined, so the less-gifted runner in this department has to look elsewhere to improve running performance—running efficiency.

What Does Research tell us about Running Economy?

The question that must be asked here is, how can we improve our running economy? Let’s look at what the scientific literature tells us about this topic.

More Training Miles = Better Running Economy

There is a trend among runners who train and race over longer distances towards a higher level of running economy, according to some research. Various studies (6, 7, 8, 9, 10) of trained middle distance and marathon runners show that marathoners are more efficient than the middle distance runners by 5% to 10% at a given pace, for example.

This has even been found with sub-elite runners (11, 12, 13). In general, runners who’ve been training for long periods of time (such as marathoners) are shown to have higher economy of running. This is due partly to reductions in pulmonary ventilation during sub-maximal exercise.

Muscle Fiber Typing and Running Economy

Muscle structure and composition clearly play a major role in running economy. Specifically, the higher the percentage of slow twitch muscle fibers a runner possesses, the more economical his running (14). Scientists’ eyebrows were raised from this study when marathon training was found to increase absolute power output by 50%, something that is not supposed to happen to slow twitch muscle. Clearly then, training significantly changes the muscle’s ability to contract and produce power.

The idea that endurance athletes who have trained longer become more efficient and more economical over time is illustrated by data (15) on Lance Armstrong, 6 times Tour de France champion. His muscular efficiency (and thus power production) improved 8% between ages 21 and 28. It’s believed his 3-6 hours of intense daily training stimulated changes in his muscle myosin type, perhaps from Type IIb muscle fibers to IIa. However, it should also be noted that Armstrong dropped 15lbs between 1992 and his first Tour de France victory, resulting in decreased resistance while riding and a 10% increase in power output, a result that almost surely catapulted him from an average rider to the best of the best.

Cycling studies (16) also give an interesting insight into how important muscle fiber type is to the economy of endurance athletes. It was discovered that the most economical cyclists have a high percentage of slow twitch (type I) muscle fibers in their vastus lateralis muscle. We would certainly expect this to be the same with runners because of the similarity of motion and endurance nature of both sports.

Respiration Muscles and Running Economy

Training is largely concerned with decreasing the energy and oxygen costs of the breathing muscles; the diaphragm, intercostals and abdominals. These muscles can account for 11% of total oxygen consumed during heavy exercise and up to 15% of cardiac output. Training also increases the glycogen stores in the respiratory muscles, providing energy for longer running efforts.

What other training factors might contribute to improved running economy? Apart from an efficient running technique, improved pulmonary ventilation, an abundance of type I muscle fibers, and running for many years, there appear to be three other promising factors: interval training, strength training and stretching—and their effects are surprising.

Interval Training and Running Economy

The effect of high-intensity interval training on running economy has been examined (17) with promising results. Various studies of interval training at intensities ranging from 93% to 106% of VO2 max are linked to improvement in running economy. Likewise, a French study (18) found that four weeks of interval training at 100% of VO2 max increased running economy 6%.

The Effects of Strength Training on Running Economy

Exercise scientists have long suspected that strength training improves running economy by improving core body stability during the running action. Thus less energy would be required to correct inappropriate movements such as erratic side-to-side trunk sway. Strength training also enables runners to sustain a given pace with lower energy cost.

A study (19) at the University of Illinois took nine men, non-runners, through a 10-week leg-strengthening program of squats, knee flexion, knee extension, leg press, calf raises, and dead lifts. There was no running or cycling in the training program. As one would expect leg strength increased dramatically by 38% to 50% depending on the leg exercise.

The participants’ oxygen consumption changed only slightly (4% for cycling, 0% for running) yet their cycling times to exhaustion increased from 278 seconds to 407 seconds (47% improvement) and running from 291 seconds to 325 (12% improvement).

Since lactate tolerance was not improved in the subjects, the only factor remaining to account for these dramatic improvements was economy. Since the leg muscles were much stronger, fewer leg muscle cells were required to pedal at the submax VO2 intensity, saving energy and enhancing economy.

A follow-up study (20) by Hickson, this time using runners and cyclist, found similar results. Cycling time increased from 71 to 85 minutes (20%) and 10K times improved from 42:27 to 41:43 (2% improvement). Although the running improvement was not statistically significant, the researchers were still able to conclude that strength training can boost performances of runners, notably running economy.

A Finnish study (21) found that a 9-week combined explosive-strength and endurance training resulted in lower 5K times by 3% and improved running economy by a staggering 8.1%. The researchers of this study attributed the improvements to improved neuromuscular benefits.

A nicely designed study (22) on female distance runners had them perform weight training for 10 weeks in addition to their standard running programs.

Their pulse rate dropped from 187 beats/minute to 183 beats/minute while running at 6:30 mile pace. This translates into being able to run at a 6:17 mile pace at the same effort as the previous 6:30 pace. Thus can be extrapolated to an improvement of 80 seconds over a 10K. And in fact, all the weight-training women who raced after this study reported improvements in race times from the 5K to the half marathon.

To help hone in on what type of strength training is most effective to improve running economy, researchers in Brazil (23) had two groups of well-trained runners do heavy weight training or explosive training for 4 weeks. The heavy weight-training group improved running economy but not the explosive training group.

Plyometrics and Running Economy

Even plyometrics have been shown to improve running economy, according to an Australian study (24) by Spurrs et al. A six-week program of explosive drills (with a total of 15 workouts) improved running economy from 4% to 7% and reduced 3K running times by almost 3%.

Hill Training and Running Economy

A Swedish study (25) involved 11 marathon runners who added a different kind of strength training, hill workouts, to their training for 12 weeks. They improved their running economy by 3%, equating to a significant decrease in racing times from the 5K up. The uphill running enabled the leg musculature to contract with greater force, thus improving efficiency and economy.

Tapering and Running Economy

And lest we forget the importance of the tapering period before major races, one study (26) stands as a great reminder.When training was reduced over 7 days, but included a with a high-intensity interval workout of 400meters, 5K times dropped by 3% and running economy by 6% in a group of well-trained endurance runners.

How Does Strength Training Improve Running Economy?

The evidence in favor of strength and explosive training improving running economy is overwhelming. How then, could strength training improve running economy?  Here are four plausible theories.

1. Improved Core Stability

It’s feasible that the strength trained runner’s more stable body causes a decrease in unnecessary motion while running, thus requiring less oxygen.

2. Increased Tensile Strength of Muscle Tissue

The increased tensile strength of muscle tissue in runners’ leg muscles enables fewer muscle fibers to be activated during running, lowering the oxygen demand of the legs.

3. Increased Storage and Release of Elastic Energy

Closely related to (2) is the idea that increased strength of muscle and tendon tissue enables it to store more elastic energy, producing a faster rebound (or energy recoil) off the ground with every foot strike, in turn causing faster running.

4. Improved Neuromuscular Coordination

An equally plausible theory is that strength training improves muscular coordination via the nervous system, allowing more efficient forward movement for each energy unit expended.

The Effects of Flexibility on Running Economy

Several recent studies show that increased flexibility is correlated with decreased running economy. That’s right—the less flexible a runner, the better his running economy! The studies suggest that runners with tight and limited flexibility in the trunk have the best running economy at every test speed.

A study (27) at Nebraska Wesleyan University found exactly this: less flexible runners tend to be more economical, while identical results were found in another study (28) at the University of North Carolina—runners with less flexibility in hips and trunk demonstrated more economy.

Yet another study (29) by Jones at Manchester Metropolitan University, England, found identical results. Likewise another study (30) at the University of Lethbridge, England, found that a group of stretching runners failed to improve their running economy.

Other studies (30) conclude that inflexibility of the Achilles tendon and calf muscle complex results in a greater relative stretch of tight muscles and tendons, storing more elastic energy for the recoil phase. This reduces the work of the muscles. Physiology studies show that the elastic recoil of muscle and tendons contributes 25% to 40% of the energy necessary for movement in maximally stretched muscle, so the “elastic energy recoil” theory would seem to have some merit.

The perturbing results of the anti-stretching papers all fly in the face of what stretching evangelists have been preaching since the beginning of the running boom. Do your stretching, they’ve said, or you’ll get injured and won’t run as fast. But perhaps tight muscles reduce energy expenditure by enhancing the elastic energy storage and return in muscles and tendons. More than a few researchers now believe that tight leg, hips, and trunk musculature may increase the storage and return of muscle energy, providing greater and faster bounce off the running surface while minimizing the need for muscle stabilizing activity of the core.

How Do we Improve Running Economy?

All this information leaves us questioning the necessity of stretching and the opposite with heavy or explosive strength training. The inclusion of stretching and exclusion of resistance training have been sacred beliefs in the temple of running since the beginning of running time. To preach the opposite would still be considered heresy in some circles.

Where do I stand on these issues? Perhaps it’s time we cut back on the stretching and boosted the strength training a bit more. Fortunately, other training icons of the running world such as interval training, tapering and the superior efficiency of marathoners still stand fast against the onslaught of research by the bright young minds in universities around the world.

But don’t be surprised when more of what we hold to be solid and true in running lore is challenged and left in the dust.

Very best regards,

Teressa