Part 2: Developing Aerobic Speed
—The maximum aerobic function test
Dr. Phil Maffetone
For a 1:59 marathon time, a runner will have to develop his aerobic system to great heights. This will be reflected in training by the ability to run faster paces with the same effort as measured by heart rate. I refer to this improvement as “aerobic speed,” which is accompanied by improving the body’s ability to convert fat to energy. (Of course, sugar, in the form of glucose and its stored form glycogen, is also an important fuel.)
The aerobic system includes a number of important components, certainly more than are listed here. The “slow-twitch” muscle fibers will be important to power a runner’s training at submaximal paces, and on race day. The miles of blood vessels contained within these muscles will deliver oxygen and other nutrients, and require an efficient heart to help the body’s muscles pump blood throughout. And, an efficient breathing mechanism that obviously includes the lungs and diaphragm muscle will help pull oxygen-rich air and, just as important, eliminate carbon dioxide. Developing the aerobic system to its highest level is what I call maximum aerobic function.
A vital component of the aerobic system is the ability to provide the muscles with endurance fuel, which requires a high level of fat burning. The use of sugar for energy is important too, and the optimal mix of fuels—a key feature of maximum aerobic training—will be important to complete a marathon in 1:59. If too little fat is available for energy, more sugar will be burned with the risk of reducing glycogen levels too much, slowing the race pace.
With the right equipment, assessing the mix of fat and sugar burning can be accurately measured on a treadmill by testing the oxygen uptake and carbon dioxide output—it’s called the respiratory quotient or RQ. Correlating high fat burning with certain heart rates can provide a valuable assessment too. But fat burning need not be quantified in a laboratory. As aerobic training progresses, fat burning increases at the same heart rate, and so does pace. This phenomenon can be easily measured on the road or track, and in fact during each run on a familiar course by comparing pace and heart rate. This simple evaluation, which, on a track, includes five one-mile splits at a specific heart rate, I call the maximum aerobic function (MAF) test. But to use it effectively, the runner’s optimal training heart rate must first be found.
Training Heart Rate
Since the mid-1970s, assessing, treating and coaching athletes meant using a wide variety of assessment procedures to help find a particular level of training intensity that would produce optimal gains in the aerobic system while minimizing stress. When this is accomplished it’s evidenced by significant improvements in aerobic speed, reductions in RQ indicating increased fat burning, balanced hormone levels, optimization of gait, improvement in race performance and other factors. This level of training is referred to as the maximum aerobic heart rate.
Determining the maximum aerobic heart rate is highly individualized, and began with an extensive assessment process. It includes a detailed history of fitness (training and racing patterns), health (including how much illness each year), any and all stress factors, and a complete inventory of signs and symptoms—a process that required the athlete to complete many pages of forms followed by a consultation that typically took two hours.
This was followed by a physical evaluation, which provided more information about muscle balance, bone health, foot function, and other aspects of the mechanical body. Evaluation of posture and gait were included, and entailed watching an athlete run on a treadmill and track at various heart rates. Blood and urine tests were commonly employed, as was an extensive dietary analysis.
From these and other assessments, I would derive the maximum aerobic heart rate for use during all aerobic training. Confirming whether this heart rate was effective became an additional assessment process that often continued for several weeks. For example, running for an extended period—60 to 90 minutes depending on the athlete’s level of fitness—or following a higher volume week of training at the maximum aerobic heart rate was not associated with gait disturbances, did not cause muscle imbalance, there was no significant water weight gain or loss, and recovery, as measured by other assessments such as heart rate variability, hormone levels, morning heart rate, and aerobic speed, were not adversely affected.
(From this information, I separately developed the “180 formula” for use by athletes who could not obtain such an evaluation. By considering a variety of factors, from age to injuries, an athlete could determine his or her own individual maximum aerobic heart rate that would be very close to what I would find through extensive evaluations. I never employed the 180 formula with athletes but instead maintained my individualized assessment process.)
The MAF Test
Once a runner had a maximum aerobic heart rate for training, it was also used to perform the MAF test on a track. This begins with the athlete slowly warming up with much lower intensities, followed by running five miles while maintaining the maximum aerobic heart rate, with each mile split recorded. As the weeks pass, increases in pace are expected, and differences between the first and fifth mile should be less. Below are the results of a 30-year old male runner’s first MAF Test 1, and another recorded four months later (Test 2), all while maintaining a heart rate of 148.
MAF Test 1
Mile 1 6:07
Mile 2 6:11
Mile 3 6:18
Mile 4 6:26
Mile 5 6:37
MAF Test 2
Mile 1 5:34
Mile 2 5:34
Mile 3 5:37
Mile 4 5:39
Mile 5 5:41
While a monthly assessment such as this one is important, one need not necessarily run on a track to evaluate improvement. During any given workout on a familiar training course, the same type of general assessment can be made. One-mile splits are not necessarily required. A one-hour loop, for example, will take less time to complete with each passing week. So almost every day, the runner will have a good sense of whether the body is training at least as well or better than yesterday or last week—or not as effective, indicating a potential problem if that trend were to continue. However, I still prefer seeing an MAF Test on the track every month, which provides a consistent, more controlled assessment on the same flat accurate course.
During the period of training where development of the aerobic system is the focus, called an aerobic base, all runs should be at the maximum aerobic heart rate. Anything that interferes with the ongoing increases in aerobic speed should be avoided. One factor that can interfere is stress, and the most common stress for an athlete is training above the maximum aerobic heart rate while base building. The reason for this is unclear, but most likely it’s due to the production of stress hormones as discussed below.
Initially, most runners feel this maximum aerobic pace is slow. But as the aerobic system develops, speed increases and the pace feels more difficult, despite being at the same heart rate. This level of progress, which should being early in the program, may take several months or more depending on the athlete. If the MAF tests show increases in aerobic speed each month, I prefer continuing with only aerobic training, and not exceeding the maximum aerobic heart rate during any workouts.
At some point in the training process, daily runs at a 5:30 pace, for example, become physically demanding, and running at this pace for a period of time during each workout is difficult. This is the time for alternating hard-easy days or fartlek workouts—but at or below the maximum aerobic heart rate. Another option is what I refer to as aerobic intervals, where one runs a slower pace for a few minutes, then runs at the maximum aerobic heart rate for a few minutes, then recovers again with a slower pace.
For many athletes, continuing to gain speed while training at the maximum aerobic heart rate may be all that is required to run a 1:59 marathon. The rationale for this is simple: about 99 percent of the energy required to run a marathon comes from the aerobic system with only one percent coming from the body’s anaerobic mechanism.
For other athletes, anaerobic work can become part of the schedule. However, the addition of harder training, whether faster running, weight lifting or regular racing too soon during the building of the aerobic system can potentially cause a plateau or regression of aerobic speed. This problem is usually obvious from daily runs and quite clear from the MAF test.
The reason for this probably has to do with the stress response by the body following anaerobic efforts. The frequent increased production of cortisol, a stress hormone produced by the adrenal glands, and orchestrated by the brain and pituitary gland within, can impair fat burning and aerobic function. (The measurement of salivary cortisol is another effective way to assess overall stress.)
If stress begins to affect the aerobic system, the athlete may initially feel fine. But if allowed to continue, poor performance, injury, ill health, or some combination of factors demonstrate the athlete may be in the earliest stage of overtraining. Proper assessment prevents these pitfalls.
Let’s use an example of a 31-year old marathoner whose maximum aerobic heart rate is determined to be 150, which allows him to run under a 6-minute per mile pace. Progressing to 5:30 pace is not difficult with proper training, but with every few seconds of improvement past this level, it gets more difficult to increase aerobic speed. Even minor imbalances or other stresses can impair the process. Optimal function of all the body’s parts are required, especially the aerobic system. If something interferes, the cause or causes must be found and fixed as quickly as possible, otherwise progression can cease, and the risk of regression rises. But by maintaining optimal aerobic function, with the help of regular assessments, continued progress ensues—from 5:30 pace to 5:15, then 5:00, to 4:50—all at the same heart rate.
I used an example of a 31-year old runner because the ideal age for a 1:59 marathoner may be between 30 and 35. This is when the body’s endurance capabilities have matured, aerobic pace is faster, fat burning is better, and optimal gait evolves. Over the past two decades, the average age of the top international marathoner is about 29 years for men and 30 for women. The best marathoners may be slightly older. Haile Gebrselassie was 35 when he set the current world record in 2008. But after the race, he told the press that he was too old to run a 1:59 marathon.
How Much Aerobic Speed?
A runner’s increasing aerobic speed will also be reflected in faster race paces. This can occur even before implementation of anaerobic training. Of the many hundreds of runner’s I’ve coached, over 75 percent ran personal bests for a 5K or 10K on official courses (these were the distances for which I had accumulated the most data) following a period of aerobic base that lasted between three and six months. This phenomenon also occurs for other endurance distances, including the marathon.
How fast will a runner’s aerobic pace have to be to run a 1:59 marathon? While this can only be precisely answered after the race, there are relationships between ones aerobic speed and race pace. For example, for a runner to break 14 minutes in the 5K, ones aerobic pace would have to be around 5:30, which would equate to a 4:30 race pace. Likewise, for a sub-30 minute 10K, an aerobic pace of around 5:15 might be necessary.
The relationships are different for the marathon. It appears that the aerobic pace is about 15 to 20 seconds per mile slower than ones marathon race pace. In the early 1980s when I put a heart monitor on Grete Waitz, she ran a 6:05 aerobic pace, which corresponded to a 2:32 marathon, averaging 5:48 pace. Likewise, Priscilla Welsh ran a 2:30 marathon, a 5:44 pace, and had a 6:00 aerobic pace.
Running better than 4:35 miles more than 26 times is what’s required for a 1:59 marathon. To accomplish this, an athlete would have to run about 4:50 to 4:55 minutes per mile at his or her maximum aerobic heart rate.
These relationships between aerobic pace and race pace are those that exist in healthy athletes. An odd outcome is sometimes seen in an athlete who is significantly out of balance—unhealthy—but has a great race. This phenomenon occurs in the early stages of overtraining as noted above, where personal records are sometimes set; unfortunately, this is often where the downward spiral begins, with poor performance, exhaustion, physical injury or combinations of such as part of the “overtraining syndrome.”
The relative balance between an athlete’s maximum aerobic pace and race pace can be an important assessment in itself. If, for example, the training pace is significantly slower than a runner’s race pace, it typically indicates some type of physical or biochemical problem, often associated with injuries. One elite runner, who visited my clinic many years ago with a variety of physical impairments, had such a distortion of paces. While correcting his leg pain was relatively easy (with the use of biofeedback to correct muscle imbalance), there was more to this case. Running at his maximum aerobic was very slow—8:45 minutes per mile. Yet his 10K times were well under 30 minutes. Against my advice, he ran the upcoming Boston marathon. He astonished everyone by finishing second overall with a time of 2:14. But he had further sacrificed his health for this fitness feat. His injuries recurred, and others quickly followed. He chose to not make the necessary training and lifestyle changes that would balance his body. Despite being in his mid-twenties, this athlete never recovered nor did he ever compete again at an elite level.
Being healthy and fit is a requirement to achieve an aerobic pace of 4:50. But this is unknown territory—a healthy runner may never have achieved this level of aerobic function that we know of.
I have experience with two athletes who had exceptionally fast aerobic paces. Triathlete Mark Allen progressed to a 5:19 pace (heart rate 152), probably more than required for his six Hawaii Ironman World Championships (not to mention years of success in other triathlon distances). Although he broke the 30-minute 10K barrier in a road race, Mark didn’t usually perform in these shorter events—but this huge aerobic base was one reason he excelled in triathlons (his 2:40 marathon in the 1996 Hawaii Ironman Triathlon still stands today).
Olympian Matt Centrowitz had a 5:00 mile aerobic training pace (heart rate 153). This was accompanied by a 13:12 for 5K, an American record.
The 1:59 marathon could happen soon. Ethiopia’s Kenenisa Bekele is 29 years old, the current 10K world record holder (and 5K too), and, if he’s ready to move up to the marathon, a prime candidate for 1:59. And, if genetics plays a role in endurance sports, Kenenisa’s brother Tariku is five years younger, and his specialty is the 5K, with a PR of 12:52. These and other great runners also have an incentive—they can make more money from one marathon than they have in all their previous years, as middle distance events don’t pay big dividends like many marathons. This becomes another key feature in the quest for 1:59.
There are many others who may be able to run 1:59 with the right training on the best race day. Twenty-six year old Ethiopian Gebregziabher Gebremariam ran 2:04:53 in Boston, good for third place, and the fastest American time ever run was Ryan Hall, age 27—if his fourth place 2:04:58 in Boston this year was not a fluke, he may be dark horse as his body matures.
In the next column, I’ll discuss two key topics that may be important for a 1:59 marathon—training schedules and gait.
The Big Book of Endurance Training and Racing
The 180 Formula