A systematic approach to training involves targeted training, or training directed toward particular training effects. The key to achieving a desired training effect is using the appropriate training intensity associated with it.
There are many different training zone systems available for athletes. But in one way or another, the different systems are based on one or more of three key physiological metrics. To understand different training intensity zones, let’s first discuss these three key physiological metrics:
- Aerobic Threshold (AeT)
- Lactate Threshold (LT)
- Aerobic Capacity (VO2max)
Aerobic Threshold (AeT)
Endurance training and aerobic training are often synonymous. When we train for endurance events, we spend lots of time developing our aerobic systems. Endurance athletes often talk about “base training” and runners talk of “long slow distance” during the base training phase.
Your aerobic threshold (AeT) is the intensity level at which base training takes place. Training at or below your aerobic threshold is foundational to building your aerobic endurance, allowing you to better metabolize fat and spare glycogen (stored carbohydrate) as a long duration energy source.
Your aerobic threshold (AeT) corresponds to a “conversational” nose-breathing effort. You should be able to breathe through your nose and hold a back-and-forth conversation with someone running next to you. Breathing is moderate and not labored.
The aerobic threshold (AeT) should not be confused with the lactate threshold (LT), which we’ll discuss next.
Lactate Threshold (LT)
As you increase the intensity level of exercise, you will reach a point known as the lactate threshold (LT), or what some call the anaerobic threshold because it effectively marks a point where the body starts to rely more on anaerobic energy pathways than aerobic energy pathways. Experienced endurance athletes can maintain an intensity at or just below their lactate threshold (LT) for an hour or even 90 minutes or more; those new to endurance training may only be able to maintain an intensity at or just below their lactate threshold (LT) for only 5 minutes. Holding your pace at lactate threshold takes some getting used to. But learning how to push the aerobic envelope is key to successful race performance.
Training done around your lactate threshold (LT) helps raise that threshold by improving lactate tolerance and decreasing lactate accumulation, allowing you to stay aerobic at faster speeds. Let’s say before training you can run a mile in 10 minutes while at your lactate threshold (LT). After training, a 10-minute mile would represent an intensity below your lactate threshold (LT).
In physiological terms, lactate is a by-product of anaerobic energy production and the lactate threshold (LT) is the point at which blood lactate begins to accumulate in the bloodstream. This occurs when the rate of lactate production increases faster than the rate of removal. In other words, when you reach your lactate threshold, your bloodstream begins to accumulate more lactate than it can clear.
In the lab, you can draw blood to find this point, but such an invasive technique isn’t required for training purposes. We can do a field test to approximate the lactate threshold (LT); and that threshold is an important point around which our training zones can be set.
Intensity at your lactate threshold (LT) is a “comfortably hard” effort. Below your lactate threshold (LT), you should still be able to breathe through your nose, but your ability to talk will be limited to 2-3 sentences at a time. Breathing is deep and labored. As you approach and cross over your lactate threshold (LT), your nose-breathing gives way to mouth-breathing. You may be able to say 5-7 words at a time, but will need to breathe through your mouth.
Aerobic Capacity (VO2max)
Aerobic capacity is a term used synonymously with VO2max (volume of maximal oxygen consumption). Technically, there should be a dot above the V to indicate that one is talking about a rate. The concept refers to the highest rate of oxygen transport and use by the body during maximal physical exertion. VO2max can be expressed in absolute terms as liters per minute (L/min), but is typically expressed relative to body weight so that comparisons among individuals can be made. Relative VO2max is therefore expressed as milliliters per kilogram per minute (mL/kg/min). One way to improve your VO2max is to simply become leaner.
The higher your VO2max, or aerobic capacity, the faster you’re able to move over long distances. This is because a higher VO2max means a higher stroke volume — that is, for each heartbeat your heart will pump a greater amount of oxygenated blood to your muscles.
Some of the top male endurance athletes in the world have recorded VO2max scores over 80 or even 90. For example, Greg LeMond’s VO2max was 92.5. Steve Prefontaine’s was 84.4. Mountain runners Matt Carpenter and Kilian Jornet have measured 92.0 and 89.5, respectively, and track runners Jim Ryun and Steve Scott measured 81.0 and 80.1, respectively.
Some top female endurance athletes have recorded scores over 70. For example, 1984 Olympic marathon champion Joan Benoit Samuelson had a VO2max of 78.6; marathoner Rosa Mota had one of 67.2.
By comparison, anything above 55 for 20-29 year old men, above 52 for 30-39 year old men, above 50 for 40-49 year old men, above 49 for 50-59 year old men, or above 44 for men over 60 represent scores in the top 10 percentile of the male population, according to the norms provided by the American College of Sports Medicine.
Likewise, anything above 49 for 20-29 year old women, above 45 for 30-39 year old women, above 42 for 40-49 year old women, above 37 for 50-59 year old women, or above 34 for women over 60 represent scores in the top 10 percentile of the female population.
Although an individual’s aerobic capacity is based to an extent on genetics, it is also highly malleable. Endurance training can substantially raise your VO2max — and, per the reversibility principle, a lack of endurance training can lower your VO2max. As you can see from the norms mentioned above, it also decreases with age.
Being born with a high VO2max does not necessarily make a champion endurance athlete. If that were the case, we might as well just all go to the lab to get our VO2max tested and turn in the lab results to race organizers. Obviously, there are many factors involved in being successful at endurance events, including mental skills, nutrition, and race tactics, just to name a few.
Even when it comes to VO2max, two athletes that vary in their aerobic capacities may still possess equivalent effective aerobic capacities when taking into account economy of motion. In other words, Athlete A may achieve a 5K run time of 17 minutes with a VO2max of 62 and fair running economy while Athlete B may achieve that same 5K time with a VO2max of 58 and excellent running economy. The bottom line is that laboratory numbers are only a starting point.
Intensity at your VO2max is an “uncomfortably hard” mouth-breathing effort. You may be able to say a single, short word, but only if you have to. Breathing rate is rapid with short, forceful breaths. Training at this intensity level is used to increase the maximal rate of oxygen transport, build lactate tolerance, and increase anaerobic endurance.
