Running Economy for Ultrarunners: Why Two Runners at the Same Pace Can Spend Very Different Energy

This article is about running economy, the energy cost of running at a given pace, and why it matters to ultrarunners trying to move faster with less strain.

Running economy helps explain something every experienced runner has seen. Two athletes can run side by side at the same pace, with similar race results on paper, yet one looks smooth and controlled while the other is working much harder. The difference is not always motivation, toughness, or even aerobic fitness in the usual sense. Sometimes the simpler explanation is that one runner is spending less energy to produce the same speed.

In exercise physiology, running economy usually refers to the oxygen cost of running at a steady, submaximal pace. Submaximal means below all-out intensity, a pace you can sustain for more than a few minutes. If two runners are both moving at 8:00 per mile and one needs less oxygen to do it, that runner is more economical. Oxygen use is the classic laboratory measure, but the broader idea is energy cost. How expensive is this pace for your body?

That matters a great deal in ultrarunning because ultras are long enough that small differences in cost accumulate. A pace that is only slightly more expensive per minute becomes a large penalty after four, eight, or twelve hours. A runner with better economy is not just saving energy in the abstract. They may be preserving glycogen, accumulating less muscular strain, producing less heat for a given speed, and arriving later in the race with more usable capacity left.

Running economy sits beside two other familiar performance concepts, maximal aerobic capacity and lactate threshold. Maximal aerobic capacity, often written as VO2 max, is the highest rate at which you can use oxygen during intense exercise. Lactate threshold refers to the exercise intensity where lactate production and clearance begin to shift in a way that makes the effort less sustainable. If VO2 max describes your aerobic ceiling, and threshold describes how much of that ceiling you can use for a long time, running economy describes how much oxygen or energy you must spend to produce a certain pace. All three matter. A runner can have a large engine, a strong threshold, and still waste energy.

That is one reason performance prediction is messy. The fastest ultrarunner is not always the person with the highest VO2 max. They may be the one whose aerobic system, neuromuscular system, and mechanics all work together with less waste. If you have read our piece on critical speed for trail and ultra runners, this is part of what critical speed does not fully capture. Critical speed is useful, but it does not tell the whole story about how costly movement becomes over long durations and varied terrain.

To understand running economy, it helps to start with where the energy goes. When you run, your body must repeatedly support body weight, absorb impact, stabilize joints, store and release elastic energy through tendons, and propel you forward. Your muscles create force, but they do not do so with perfect efficiency. Some energy becomes forward motion, some becomes heat, and some is lost through braking forces, unnecessary vertical oscillation, poorly timed muscle activity, and extra movement that does not help you travel.

A useful way to think about economy is that it reflects the total cost of all those tiny actions added together. Good economy does not mean looking pretty. It means solving the movement problem with less energy. Sometimes that looks fluid and compact. Sometimes it looks idiosyncratic. Elite runners often have individual styles, but they also tend to be very good at reducing waste within their own structure.

Several factors influence running economy.

One is tendon and muscle behavior. The lower leg, especially the Achilles tendon and calf complex, acts a bit like a spring. With each step, elastic tissues store energy as they lengthen and then return part of that energy as they recoil. If that spring system works well, you get some propulsion at a lower metabolic cost than if muscle fibers had to do all the work actively. This is one reason stiffness can be helpful in the right amount. Not general whole-body stiffness, but functional leg stiffness, the ability to resist collapse and return force efficiently.

Another factor is neuromuscular coordination, the timing and pattern of muscle activation. A coordinated runner activates what is needed, when it is needed, and not much more. An uncoordinated or fatigued runner may co-contract, meaning opposing muscles fire together more than necessary. That can make movement safer in the short term, but it also costs energy. Late in an ultra, economy often worsens partly because coordination degrades.

Body size and limb properties matter too. Longer legs, lighter distal mass, and favorable tendon structure can influence economy, although these are not traits you can radically change. This is why economy is partly trainable and partly individual. Two athletes can train equally hard and still not arrive at identical efficiency.

Biomechanics also matter, but this is where many runners get misled. There is no single ideal stride that everyone should copy. Research reviews have found associations between economy and factors like vertical oscillation, contact time, stride frequency, and ground reaction forces, but the relationships are not simple enough to justify universal technique rules. A stride that improves one runner may make another less efficient. Forced changes often backfire because they interfere with patterns your body has already optimized around your anatomy and training history.

Footstrike is a good example. It is tempting to search for one best answer, rearfoot, midfoot, or forefoot, but the evidence does not support a universal winner. What matters more is whether your overall pattern produces force effectively with manageable cost and tissue stress. Chasing a fashionable form cue can raise injury risk without improving economy.

Terrain complicates the picture further for ultrarunners. Most running economy studies are done on treadmills or flat surfaces because they are easier to standardize. Trail running adds climbing, descending, uneven footing, and constant pace changes. On steep climbs, economy is affected by hiking skill, posture, and local muscular endurance. On descents, the issue is not only oxygen cost but eccentric damage, the muscle damage produced while muscles lengthen under load to brake your body. On technical terrain, foot placement and balance become part of the cost. A runner can be economical on flat ground and relatively uneconomical on rocky singletrack.

That is why ultrarunners should think in the plural. You do not have one single economy that applies everywhere. You have context-specific economy. How costly is smooth dirt at moderate grade? How costly is steep hiking with poles? How costly is downhill running after four hours? The principle is the same, but the expression changes with terrain and fatigue.

Fatigue is central here. Running economy is not fixed from the first minute of a run to the fifth hour. As fatigue builds, form shifts, muscle recruitment changes, elastic return may become less effective, and protective patterns appear. The result is often a higher oxygen cost at the same pace. This overlaps with fatigue resistance, the ability to maintain output and movement quality as the session gets long. If you want the deeper version of that idea, see our article on fatigue resistance in ultrarunning. A runner with strong fatigue resistance is often protecting economy deep into the event.

Heat raises the cost too. When body temperature climbs, your heart rate tends to rise and more blood is directed toward the skin for cooling. Perceived effort increases, and sustaining pace becomes more expensive. Some of that is captured by cardiac drift, where heart rate climbs over time even if pace stays steady. Some is thermal strain itself. Either way, if conditions are hot, your practical economy on race day is worse than it would be in cool weather. That is one reason environmental context matters when you compare workouts.

How do you improve running economy?

The first answer is simple and unglamorous. Run consistently. Repetition matters. Years of aerobic training refine the movement pattern, improve stiffness and coordination in task-specific ways, and build tissues that tolerate the repeated demands of running. Economy is one reason experienced runners often improve without dramatic changes in VO2 max. They become cheaper movers.

The second answer is to run at more than one pace. Easy volume builds the aerobic base and repetition that support economical movement at sustainable intensities. Faster running, used carefully, exposes the neuromuscular system to higher force production, shorter ground contact times, and more demanding coordination. Strides, hill sprints, and controlled faster intervals can all contribute. They are not magic, but they give your body practice producing force quickly and cleanly.

Strength training can help as well, especially when it improves force production and the ability to apply force without excessive collapse. Systematic reviews in distance runners have found that heavy resistance training and plyometric training can improve running economy even without changes in VO2 max. Plyometrics are explosive jumping or bounding exercises that train rapid force production and elastic return. The likely mechanisms include improved musculotendinous stiffness, better motor unit recruitment, and better use of stored elastic energy.

That does not mean every ultrarunner needs an elaborate power program. It means that stronger tissues and better force transmission can reduce the energy cost of each step. In practice, many runners do well with a small menu of repeatable work: heavy calf raises, split squats, deadlift variations, step-ups, and low-volume jumps or hops if they tolerate them well. The best strength plan is the one that supports running instead of compromising it.

Small doses of fast running belong in the plan too, and they may be the most efficient economy tool you have. Studies find that four to six weeks of two to three short sessions a week with 30-second fast intervals improve running economy by about 3 to 5 percent, more than most other training changes. Speed is a skill that fades without practice, so keep a little of it in most weeks, even in ultra training: short hill or flat strides at least twice a week, and perhaps one light workout with five to ten minutes of total fast running.

Hill running also deserves mention. Uphill work increases force demands, especially at slower cadences, and can improve specific strength for trail running. Short hill sprints sharpen recruitment and stiffness. Longer uphill intervals build aerobic power with less impact than flat speed. For mountain athletes, uphill economy may matter as much as flat running economy, and hiking economy can be a major separator in steep races.

Technique changes should be approached carefully. If you are injured, extremely overstriding, or obviously limited by a clear mechanical issue, coaching cues may help. But most runners should be cautious about trying to engineer a perfect-looking form. Small, indirect changes are usually safer than dramatic overhauls. Improving ankle strength, hip control, cadence awareness, and exposure to varied paces often changes mechanics in useful ways without forcing them.

Footwear affects economy too. Shoe mass has a measurable effect, and lighter shoes usually reduce energy cost compared with heavier shoes, all else equal. Midsole properties matter as well. Modern racing shoes with compliant and resilient foams can improve economy for many runners, though not equally for everyone and not in every terrain context. Trail shoes complicate the story because grip, stability, and foot protection may outweigh small laboratory savings if the terrain is technical. The most economical shoe for a road half marathon is not automatically the most economical shoe for a rocky 100K.

So how can a non-lab runner tell whether economy is improving?

You usually cannot measure true running economy directly without laboratory equipment, but you can infer changes. If you can run a familiar steady pace at a lower heart rate, lower breathing strain, and lower perceived effort in similar conditions, that suggests lower cost. If you finish long steady runs with less mechanical breakdown, that matters too. If moderate paces feel smoother and more repeatable, that is often what improvement looks like in real training. A coach who reviews your workouts over time can help spot those trends. Train Ultra gives you an evaluation of every workout, which is useful when you are trying to tell the difference between true improvement and noise from terrain, heat, or accumulated fatigue.

Be careful, though. Heart rate is influenced by heat, hydration, sleep, fatigue, and terrain. A better reading is a pattern across time, not one workout. This is also where understanding cardiac drift in running helps. If drift decreases during similar steady runs, it may reflect better aerobic conditioning, better fueling, better heat management, or improved durability. Economy can be part of that picture, but it is rarely the only cause. When you want to ask how your own training is trending, you can ask the coach about your own training and get help interpreting what changed and what probably did not.

For ultrarunners, the practical question is less "What is my laboratory economy number?" and more "Where is my movement becoming expensive?" Maybe your flat running is solid, but your downhill form deteriorates after three hours. Maybe your hiking posture on steep grades drives heart rate too high. Maybe technical terrain forces so much braking and hesitation that you burn energy faster than expected. Those are economy problems in the field, even if they do not show up in a treadmill test.

That leads to a useful training approach. Match your training not only to race distance, but to the type of economy your event demands. A flatter, faster 50K asks for economical steady running at moderate intensity. A mountainous 100 miler asks for running economy, hiking economy, downhill resilience, and the ability to preserve all of them under fatigue. If you train only the aerobic engine and ignore the movement demands, your physiology may be ready while your cost of motion is still too high.

One final point is worth keeping in mind. Better economy is valuable, but cheaper is not always better if the strategy raises injury risk or limits performance elsewhere. A stride that saves a little oxygen but overloads your calves may not be a good trade. A shoe that tests well in a lab but makes you tentative on loose rock may not be the right choice for your race. The goal is event-specific efficiency, not abstract perfection.

For an ultrarunner, running economy is best understood as the price you pay for every mile. Training can raise your ceiling, push your threshold, and improve your fuel use, but if each step costs more than it should, you carry that bill all day. The athletes who move well late are often not just fitter in the broad sense. They have built a body and movement pattern that spend less to keep going.

Written by Wade Wegner. Train Ultra is a private AI coach that reads every workout from Garmin, COROS, Apple Health, or Health Connect. Try it free.