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Maximizing Oxygen Uptake
By John Kellogg, aka JK
March 30, 2004

Terminology

In order for you to produce energy aerobically, your working muscles must consume oxygen. Oxygen uptake (also known as VO2, which stands for "ventilation of oxygen") is a measure of how much oxygen your body is consuming at any given time. It is usually expressed in milliliters (or sometimes in liters) of oxygen consumed per minute of exercise. The "V" in VO2 is often written with a dot over it to represent this "minute ventilation." There is an upper limit to how much oxygen your body can consume. Results from research studies involving twins show that maximal oxygen consumption is 40%-50% genetically determined. However, prolonged training elicits improvements in maximal oxygen uptake which can range between 10% and 30%. These gains are directly related to hypertrophy of the left ventricle, increased capillarization, more efficient oxygen extraction from the blood, and a host of other factors.

Maximal oxygen uptake is customarily referred to as VO2max. VO2max can be expressed in either absolute terms (usually milliliters of oxygen consumed per minute) or in relative terms (milliliters of oxygen consumed per minute per kilogram of body mass) to compare values between individuals.

The average adult male has a VO2max which is roughly 20%-25% higher than that of the average adult female. This is primarily because men have a higher hemoglobin concentration and because men have more muscle and less fat (muscle being a more metabolically active tissue).

Average VO2max values (in ml/kg/min) are 32-36 for adult females and 39-44 for adult males, depending on the testing protocol which is being used. Elite endurance athletes may record values of 70-83 (females) and 80-94 (males). A high VO2max is generally an advantage for a distance runner, although it is no guarantee of elite potential. Runners are often significantly outperformed by others with lower VO2max measurements.

Exercise scientists normally take measurements of an individual's VO2max using a maximum effort running test on a treadmill. When following most testing protocols, which begin at slow speeds and have the subject increase the intensity at regular intervals (a format known as a "graded exercise test," or GXT), there is a speed associated with working at VO2max, a speed commonly known as velocity at VO2max (vVO2max), a term coined by Dr. Jack Daniels. Of course, this value varies from runner to runner, but it is normally the pace which a well-trained runner could sustain for roughly eleven minutes in an all-out, evenly-paced effort.

Values for both VO2max and vVO2max are somewhat dependent on the testing protocol used to measure them (this is also true of values for "lactate threshold" and "lactate threshold velocity"). Using a steeper grade on the treadmill platform during a GXT, for example, results in higher VO2max readings due to activation of greater muscle mass and additional torque.

Laboratory findings

Groundbreaking research on the effects of training at VO2max was conducted in 1982 by Gary Dudley, et al. at State University of New York at Syracuse. Dudley induced rats to run once per day, five days per week, at intensities ranging from 40% of VO2max to 100% of VO2max and for various durations (the faster-running rats completed the shortest work bouts) and examined how these durations and intensities affected mitochondrial enzyme activity across the spectrum of muscle fiber types. His findings contrasted somewhat with conclusions from prior work (Holloszy and Booth, 1976) inasmuch as 10-minute bouts at 100% of VO2max were much more influential in mitochondrial production than were longer work bouts (up to 90 minutes) at slower speeds.

Dudley's 1982 research is often cited to bolster the argument that running at VO2max eliminates the need for running longer distances at slower speeds in order to maximize aerobic development. The practical fruits of this myopic and spurious reasoning were harvested in the United States during the latter years of the 1980s and the first half of the 1990s, as high mileage training fell out of favor and hard track work - sans aerobic base - became the norm. During this time, U.S. distance running performances declined significantly. The truth is that both high-volume, low- to moderate-intensity training and skillfully integrated low-volume, high-intensity training are necessary to completely prepare for any event in which oxygen transport and oxygen consumption contribute to energy production.

Dudley, et al. did demonstrate that from a mitochondrial standpoint, higher intensity is generally preferable to duration. However, running performance is ultimately more complex - a gestalt that depends on the interaction of a myriad of factors, a few of which may not yet be identified (or may indeed not be identifiable at all).

Moreover, the use of rats as test subjects presents a number of problems when attempting to draw conclusions for the human athlete. Rats are often used for laboratory experiments due to their low cost, small space requirements, short time span of generations, large litters, and the fact that they are easy to handle - reasons which have nothing to do with any physiological similarity to humans. The training and study of laboratory rats for no more than a few months also depicts a mere snapshot of a complete running career, so any conclusions drawn only serve to shed light on a short-term piece or two of a long-term puzzle.

The metabolism of a rat is much faster than that of a human, as is evidenced by resting and peak heart rates. A trained rat has a resting heart rate of nearly 300 beats per minute and a maximum HR of roughly 600 bpm. Furthermore, the metabolism is often along different routes in the body. Additionally, rats run on four legs and adopt a horizontal body position, factors which reduce orthopedic stress relative to the stress incurred by a human runner. Decreased orthopedic stress results in lower metabolic cost, enabling the rat to recover from an intense effort more quickly. The bottom line is that one day recovery for a rat is in no way comparable to the same recovery time for a human. This raises the question of how often the human runner should work at the intensity required to improve oxygen uptake.

Trial and error indicates that - for mature, experienced athletes - running at or near vVO2max once to twice per week (ideally, from the late preseason until the middle of the competitive season) will provide a firm stimulus for improvement while allowing adequate recovery. Younger runners (below high school age) or beginners should use high intensity training more sparingly. Note that most races (especially high school cross-country races or track events of 3,000m - 5,000m) elicit VO2max (and obviously require a large anaerobic component) and therefore must be counted as oxygen uptake training.

Importance of regular speed maintenance

To develop muscle contractile properties, promote relaxation and develop familiarity with faster speeds, it is important to incorporate some short buildups or strides (usually between 15 and 35 seconds in duration) once or twice per week during the preseason before introducing more challenging VO2max sessions. A total of 10-15 strides (often divided into 2-3 sets of five strides each, with 5-10 minutes of jogging between sets) will adequately serve as speed maintenance. Form drills can be included within such a workout if desired. A few strides can also be performed before and after the occasional "high end" aerobic outing. Run with the wind (if any) and take sufficient recovery so as to remain comfortable and in complete control on these short strides. The variety this provides will break the monotony of your usual slower-paced, higher mileage running in the preseason, and it may also help prevent injury. Once you are comfortable running these short distances at mile race pace or faster, which should in no way be lactate-intensive, you should have no trouble running longer distances at vVO2max (with recovery periods equal to or slightly shorter than the run periods) when the competitive season arrives.

Every 2-3 weeks during the preseason, it is good practice to perform a reduced-intensity "time trial" of 2-7 minutes in duration to achieve near-maximum stroke volume and as a lead-in to traditional sessions later in the season. This yields best results if incorporated following sets of strides, as the strides serve as a thorough warmup. Run at roughly the speed you could currently maintain for twice the distance if running all-out. Running at this speed will elevate the heart rate to roughly 92%-95% of maximum, somewhat above the HR achieved with traditional "tempo" or "threshold" running. Keeping a small, moderate-intensity middle-distance component in your base training allows you to dovetail nicely with the less intense running which comprises most of your base work, as your "high end" aerobic pace may feel more comfortable with the occasional inclusion of the faster efforts.

You can occasionally use moderate- to high-volume sessions with bouts as long as one minute each during the preseason (e.g., 10-20 x 1 minute "on" / 1-2 minutes "off"), but avoid any tying up, struggling or form breakdown. The feeling achieved should mimic that of a comfortable "fartlek" outing or a strong tempo run, not that of an intense mid-season track session.

Orthodox methods of oxygen uptake training

When doing full-fledged in-season work at vVO2max, your aim should be to create a session which can blend in favorably with other sessions and races and which allows you to accumulate enough time to provide a viable stimulus for improvement without overdoing it.

Avoiding overkill basically means minimizing the negative effects of acidosis, so that your movements remain efficient, muscle groups are recruited in harmonious concert, and aerobic energy production dominates your efforts as long as possible. This is best achieved if you orchestrate the rest intervals between bouts so as to allow adequate recovery while also keeping the circulatory system active, thus reducing the possibility of "venous pooling" and allowing for some lactate to be reconverted to other metabolites by the heart and skeletal muscles. It is also desirable to avoid excessive impact or torque stress (these factors can depend on hills or turns of the road or track).

As mentioned, vVO2max is approximately the speed a well-trained runner could maintain for a race which lasted 11 minutes. A couple of formulas used to estimate this pace relative to common race distances are:

  • vVO2max (per 400m (in seconds)) = 0.1171 x (3,200m time (in seconds)) + 5.22
  • vVO2max (per 400m (in seconds)) = 0.07 x (5,000m time (in seconds)) + 7.32

These equations, though not perfect, show that a runner with a recent 3,200 time of 9:13 (553 seconds) has a theoretical vVO2max of 70 seconds per 400. A time of 14:55 for 5,000 (895 seconds) also yields a theoretical vVO2max of 70 seconds per 400.

Trial and error reveals that prudent use of training at this effort intensity involves repeats of two to four minutes each at vVO2max, with rest periods slightly shorter than the run periods, and with about 15-20 minutes total time spent at pace. Some sample sessions which have been commonly used are:

  • 8-10 x 2 minutes "on" (averaging vVO2max) / 1:30-1:45 "off" (active recovery period)
  • 6 x 3 minutes on / 2:00-2:30 off
  • 4-5 x 4 minutes on / 3:00-3:30 off

A runner with a best recent 5,000 performance of 14:55 would have a theoretical vVO2max of 70 seconds per 400 and could use 8-10 x 700 averaging 2:02 or 6 x 1,000 averaging around 2:55 or 4-5 x 1,300 or 1,400 at about 3:48 (1,300) or 4:05 (1,400). The longer work bouts (near 4 minutes) will obviously be the most demanding and should probably be avoided as mid-week training if a very important competition is imminent. Running longer than 4-ish minutes at vVO2max tends to require too great an anaerobic component to be any more useful for aerobic development. Commonly used "mile repeats" should deliberately be run at a slightly slower pace unless the session is being used as some sort of mental-toughness-promoting, "make it or break it" workout in lieu of a race.

Workouts such as these should generally be used during the beginning or middle of a competitive season. The rationale behind this is that they are liable to promote premature peaking if used in the preseason; moreover, such sessions may be somewhat too taxing to afford sufficient recovery prior to championship events in the latter stages of a competitive season.

These workouts will be quite challenging after 15-20 minutes accumulated at the desired pace, but your lactate levels will hopefully stay somewhat under control, so that you will not be at the mercy of tying up and resorting to flailing, struggling movements (or even slowing down while increasing your effort). For maximum effectiveness, you should pace yourself so that you can run the last few reps in a VO2max session slightly faster than you ran the early reps.

Minor shifts in emphasis

Shorter work bouts (e.g., 12-16 x 60-90 seconds) at a slightly faster pace (about 5% faster than vVO2max) also have a marginal influence on oxygen uptake, as long as the recovery periods are short enough to keep the heart rate elevated sufficiently. The speed used for these short reps is approximately that which you could hold for six minutes in an all-out effort. Physiologist Veronique Billat suggests jogging between reps for an equal duration and at exactly half the speed used for the work bouts themselves. For example, our hypothetical 14:55 runner (whose vVO2max is 70 seconds per 400) could run 12-16 x 400 at about 5% faster (66-67) with a 200 jog in 66-67 between 400s.

Longer bouts (e.g., 5 x 5-6 minutes) at a somewhat slower pace (roughly 5% slower than vVO2max) and with relatively shorter rest periods (2-3 minutes) will also train the same systems with a slightly different emphasis. Mile repeats (even if they are run faster than 5:00 each) should usually be executed at this approximate effort level for maximum profitability. You can accumulate nearly 30 minutes at this more sedate pace with relatively low risk of excessive acidosis. The runner whose vVO2max is 70 seconds per 400 might choose to perform 5 x 1,600 at 4:54 each (5% slower than vVO2max) with recovery intervals consisting of 2-3 minutes of light jogging. If this pace provides little challenge, the recovery period could be reduced or the work bouts could be extended to nearly 6:00 in duration.

It is best to vary the distances used from session to session so as to provide variety in muscle fiber recruitment, to reduce boredom and to prevent obsessive comparison of times from previous workouts. Finding an ideal blend of workouts is part of the "art" of training (which should always complement the "science" of training) and may require a few seasons of experimentation to determine what works best for you.

Should the recovery periods during VO2max workouts be spent standing? Walking? Jogging? Some combination of these?

This depends in part on the length of the recovery periods, which depends in turn on the length of the work bouts. Standing rests are almost never productive. Jogging during the rest periods is usually preferable, as this keeps the muscles warm and the circulatory system active (which allows for greater re-uptake of blood lactate), but short reps may be more intense (faster), requiring a more passive recovery (all walking or some walking and some jogging) to keep muscle lactate at manageable levels. This is particularly true the first time a session involving a pace faster than vVO2max is attempted. As lactate metabolism improves during the season, the entire recovery period can be spent jogging (per Veronique Billat's recommendations) even during these faster sessions.

Should the distances or durations of the work bouts vary during a session or should they remain fairly constant?

Although there are some exceptions (see below re: taper workouts and sessions for young runners), it is normally best to keep the run distances (or durations) constant within the workout (i.e., use all 800s or use all 4-minute runs rather than using "ladders" or "step-downs") and use fairly uniform rest periods. This trains you to monitor effort better and to mount rising fatigue with additional effort in a more linear fashion.

The ups and downs of hill work

Hill training is excellent for improving maximal oxygen uptake because both high heart rate and high systolic pressure (the multiplication of these factors, with the result usually divided by 1,000, is known as the "rate-pressure product") are achieved, and these components stimulate left ventricular hypertrophy and vascular development.

Obviously, some introductory hill work (slower speeds or gentler inclines or fewer reps) is desirable as a lead-in to more stressful hill sessions involving longer work bouts or faster speeds. Once you have developed some measure of structural integrity for hill running, sessions such as the following can complement your normal flat track VO2max workouts:

  • Run 2-3 minutes up a 4%-6% grade (use an effort intensity equal to running at vVO2max on a flat surface), jog slowly for one-half to two-thirds of the distance down the hill, run at a strong pace down the remaining portion of the hill (not so fast as to jar yourself, but fast enough to become somewhat uncomfortable), then jog for about 60-90 seconds on a flat section at the bottom of the hill. Repeat for a total of 5-6 uphills (2-3 minutes each) and 5-6 shorter downhills (about 1 minute each).
  • If a faster pace is desired, try to set up a square course which features a hill of 6%-8% grade and just over 300 meters in length and also has another hill of similar length but not as steep (3%-4% grade) about 150-200 meters away. Run up the steeper hill at an effort which simulates 1,500m/mile race pace (of course, the speed will be slower while running uphill), jog at the "top" of the square over to the more gentle hill (about 60-90 seconds) and run down it at about 800m race pace, then jog over to the base of the steeper hill and repeat for a total of 5-6 uphills and 5-6 downhills. The overall intensity of the session should be comparable to a track workout consisting of 10-12 x 300m at slightly slower than 800m race pace.

Running uphill for 2-3 minutes at a time at moderate to high intensity (near VO2max) will likely provide a greater improvement in the ability of your left ventricle to pump blood to your working muscles than will running with the same effort over level ground or downhill, even though you can run much faster with comparable effort on a level surface. When running uphill, muscle contractions are held longer, meaning the intramuscular pressure and vascular resistance are greater. Since it is harder for the heart to pump blood into muscles which are in a contracted state, the systolic pressure will rise well over 200 mmHg (with a rate-pressure product of over 40) during prolonged, high-intensity uphill running. This creates a high myocardial oxygen demand and provides a strong catalyst for ventricular hypertrophy.

On the other hand, you should not exclusively rely on hill work for your oxygen uptake training. The stride rate, toe-off mechanics, fiber recruitment, and the manner in which muscles act in concert are obviously different when running faster over a level surface than when running with the same effort intensity (albeit slower) uphill. Therefore, since most of your races will probably be contested on flat or predominantly flat surfaces, you also need to train to become fast and efficient at level-surface running.

There is, then, a trade-off between the greater muscle mass activation and greater myocardial oxygen uptake (MVO2) while running uphill and the faster absolute speed attained while running on flat surfaces or on downhills. When faster speedwork is needed in training (during the mid-season or late season), hill work should usually be eschewed in favor of track work. This will reduce the likelihood of Achilles tendon trouble which may result from attempting very fast-paced running up hills.

Twists on standard sessions

There are numerous reasons for runners to occasionally choose to attain variable speeds within a session. Some of these objectives include becoming accustomed to a fast start before settling into a racing rhythm, practicing pace pickups (surges) between segments at race pace, working on finishing fast after being fatigued from race-pace bouts, reducing the volume within a workout for the purpose of "tapering," and achieving various ranges of motion so as to feel "snappier" for an upcoming race. If you desire to change speed within a workout, and if working on oxygen uptake is one of the goals, you should aim to spend at least ten minutes near vVO2max (in bouts of 2-4 minutes each) and include several short reps at faster speeds before and after the oxygen uptake work in order for the session to be productive. Examples of variable-speed sessions are:

  • 4 x 30 seconds "cut-downs" (slowest to fastest, beginning at roughly 5,000 race pace and finishing at 1,500/mile race pace) / 1:00-1:30 rest periods (walk/jog), 2 x 2 minutes on (first rep slightly slower than vVO2max, second rep slightly faster than vVO2max) / 1:30 off, 3-4 x 3 minutes on (averaging about vVO2max) / 2:00-2:30 off, 2 x 1 minute on (first rep somewhere between 1,500 race pace and 3,000 race pace, second rep at about 1,500 race pace or slightly faster) / 1:30 off

This is useful as a variable-speed session inasmuch as most of the bouts are short enough (2 minutes or shorter) that you can tinker around with the speeds and determine how you respond to various degrees of pace pickup; i.e., what combination of speed and duration begins to become markedly anaerobic for you. This can give you an idea of how it may feel to launch a sustained drive during a race.

  • 4-6 x (2:00-2:30 at vVO2max / 30-60 seconds rest, 45 seconds at 1,500/mile race pace or faster) / 2:00-2:30 rest periods (walk/jog) between sets

This workout features a substantial anaerobic component with the segments of 45 seconds at faster than mile race pace. It should be reserved for runners who are already extremely fit in all regards, especially if six sets are performed. This is designed to get you accustomed to the feeling of running at a sustained rhythm while in a moderate state of acidosis.

  • 4 x 30 seconds cut-downs / 1:00-1:30 rest periods (walk/jog), 4 x 2:30 on (averaging about vVO2max) / 2:00-2:15 off, 4 x 30 seconds cut-downs (each slightly faster than in the initial set) / 1:00-1:30 rest periods (walk/jog)

This session is useful as a slight "taper" workout for experienced adult runners or as a complete mid-week, in-season workout for high school runners. It only involves about ten minutes of work at vVO2max, fractionally less than the 15-20 minutes suggested for optimal aerobic development. But weekend races (3M/5,000 in cross-country, 3,200 in track) have high school runners operating near vVO2max often enough that care should be taken to avoid overburdening them with additional work at this effort level within the week, thus jeopardizing future development. It is always much safer to underwork high school runners in terms of intensity than it is to expedite their short-term progress with large amounts of anaerobic training and frequent all-out racing.

A multifactorial issue

Because oxygen uptake is influenced by so many factors, you need the full spectrum of training devices in order to maximize it. This means you should never lose sight of the basics. Without the fundamental aspects of overall fitness in place, application of more "scientific" principles and all the attention in the world to detail is only so much B.S. Attaining peak fitness involves getting a high mileage base, with the lion's share of your faster efforts at a maximum steady state of effort - at or near your "lactate threshold." Among other benefits, this will give you the extensive capillary network needed to supply oxygen to your muscles (a physical attribute which is unattainable through high intensity training alone).

You might ask, "Why not simply adopt the old school approach of 'get out there and work your tail off' without paying attention to any particular speed or effort level? Isn't that what the top runners in the 1970s and early 1980s did?" Yes, to some extent the best of that era did train this way - and they saw excellent results - but they were logging more mileage than you are probably running, and this was the principal ingredient in their success. It also turns out that they did operate fairly close to ideal speeds and durations, arriving at these parameters through the ultimate science of trial and error.

Are there other activities which will improve the ability for the muscles to receive and consume oxygen? Sure, but remember that training is largely "sport specific;" that is, you are best served by practicing the activity you expect to perform in competition! Since many commonly contested distances (3,000m - 5,000m) involve speeds within 5% of vVO2max, working at or close to vVO2max affords the added benefit of familiarizing you with your race pace.

John Kellogg is a full-time, professional running coach. It is his passion in life and career of choice. John has logged over 70,000 miles in 28 years of running, with a highest week of 156 miles. He has experimented with as many combinations of training procedures as is possible in the course of a human running career while still devoting enough time to each mixture of techniques to ascertain their effectiveness. While he never reached the elite level himself, he was able to train himself effectively enough to run 14:22 for 5,000 meters while possessing a best time of only 57 seconds for 400 meters. John also has a Cross-Country 10,000 meters best of 30:46, and was nationally-ranked in the marathon as a Junior (under age 20).

He has trained in America and in Europe with runners of all ages, abilities, and nationalities, including world-class athletes, and has coached runners of all ages for 15 years, producing results at the state-class, national-class, and international-class levels.

LetsRun.com co-founder Weldon Johnson trained under Mr. Kellogg's guidance in middle and high school and credits his return to Mr. Kellogg's training with his huge post-collegiate improvements. A 30:13 10,000 meter runner in college, Weldon recently has run 28:06 for 10k, has finished 4th at USA Nationals twice at 10k.

John Kellogg formerly operated www.paragonrunning.com, we hope to have it up again soon. If you'd like to read JK's 4 training principles click here.

To view his previous article on "becoming a guide" click here.


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