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About a decade ago, I was coaching a new runner who was formerly a sedentary, pack-a-day smoker. Nonetheless, she was talented. Her first few races indicated a lot of talent, and I was excited about helping her achieve her potential.
But as we continued working together, I realized that her heart rate was abnormally high during easy runs. In fact, it was hovering near a lactate threshold or tempo effort for almost all of her running—even during her easiest recovery runs.
Needless to say, I was concerned. When heart rates are persistently high over long periods of time, the risk of over-training syndrome or suffering a running injury increases. Plus, having a heart rate approaching an anaerobic zone most of the time is just not effective for long-term improvement. It could also be the sign of bigger health concerns.
This was a new problem for me to solve as a coach, and I realized I had to learn more about the physiology of beginner runners who previously lived sedentary lives. My background as a collegiate track and cross-country runner did not help me understand this unique issue and how to train through it.
As I educated myself on heart rate, I discovered that my athlete was most likely suffering from something called Aerobic Deficiency Syndrome. It can be common in some new runners. And thankfully, it’s something that runners can work through and grow from.
What Is Aerobic Deficiency Syndrome?
Aerobic Deficiency Syndrome can be simplified as a lack of aerobic fitness. For sedentary folks or even athletes in power-based sports (say, softball or wrestling), their aerobic metabolism is under-developed and struggles to provide oxygen to hard-working muscles for lengthy periods of time. The result is a skyrocketing heart rate, even for low intensities.
Athletes in sports that require anaerobic fitness, power, and strength—but very little aerobic development—often have anaerobic systems that are highly developed. These folks (like some CrossFitters or HIIT enthusiasts) are doing very little easy, aerobic exercise but a high amount of anaerobic exercise like VO2 max efforts, sprints, or very heavy weightlifting.
If our hypothetical new runner is either previously sedentary or a power athlete, their aerobic metabolism will not be efficient. It will struggle to deliver oxygen during easy exercise that would be a simple Zone 2 effort for most experienced runners. The aerobic system just isn’t up to the task because it’s rarely been asked to perform this task before.
Thankfully, this is not a career-ending problem for aspiring runners. Even if you’ve spent all of your training time in Zone 3 or above, we can reverse this trend and make you into an aerobic powerhouse.
What To Do If You Have Aerobic Deficiencies
Once we understand that persistently high heart rates are usually caused by Aerobic Deficiency Syndrome, we have the solution to this problem: a massive amount of easy, low-intensity, aerobic exercise.
Because the aerobic system is under-trained in athletes with Aerobic Deficiency Syndrome, we must train it by doing all the things that boost aerobic fitness:
- Easy and recovery runs
- Cross-training that mimics the demands of running (like cycling or pool running)
- Long runs
The key to these training sessions being productive is the intensity. It must be kept to a Zone 1 or Zone 2 effort to build the aerobic base without overly stressing the anaerobic system. The more of this easy, low-intensity work that you can do, the better.
You may also learn that you need to incorporate walking breaks into your running to maintain a lower heart rate. That’s OK! Our focus is on heart rate so that’s a viable strategy to continue building aerobic metabolism.
Aerobic Deficiency Syndrome Q&A
You might be asking yourself how long this process will last. Truthfully, there are no shortcuts, and it may take several months for you to build an endurance foundation sufficient to support higher intensity training. Just be patient and trust the process.
Earmark a two- to three-month period that focuses on base training. The goal is volume and a focus on easy running with little to no workouts. If you do decide to run faster workouts, keep them to a weekly basis and make them shorter than what you’d normally run. You can still maintain foot speed and coordination by regularly running strides.
If you have some running experience and don’t want to give up on the race that you might be training for, you can still continue training for the race (and even keep doing some higher intensity workouts).
In this situation, try to…
- Add more Z1 and Z2 running or cross-training to your program to continue developing the aerobic system
- Reduce the pace of easy runs so that they are truly easy (Zone 2 FTW!). Don’t be afraid to walk if that’s what it takes
- Reduce the intensity of most workouts so they’re easier: lactate threshold efforts can be run at half marathon pace, half marathon efforts can be done at marathon pace, etc.
- Consider eliminating very hard workouts with long reps at VO2 Max intensities (like 5×1,000m at 5K Pace)
Even with a reduction in workout intensity, you may achieve a faster race finish time with this approach because of the additional development of your aerobic metabolism.
For most runners, this is far more advantageous than more anaerobic training (even if you don’t have ADS), since middle-distance and long-distance events are mostly powered by the aerobic metabolism anyway.
Aerobic Deficiency Syndrome can be common in new runners depending on their athletic background. If you find yourself struggling to run at an easy effort and your heart rate is consistently higher than what it “should be,” then consider a season dedicated to base training. You’ll not only reduce your heart rate, but you’ll also build an aerobic engine that will carry you through your next running season.