I recently posted to Facebook a statement about the benefits of aerobic activity at existing at less than 30 minutes per session. The discussion in the comments highlighted the common misconception aerobic training can be replaced by HITT, sprints or CrossFit style metcons. Conceptually this idea was popularized in and by CF and HITT. It is true, many of the adaptations elicited by high intensity work are in many cases better, or at least more sought after, than those brought about by purely aerobic training. But this is only the case if those adaptations are the goal of the athlete. Either way, I thought it might be beneficial for some to do a quick write on aerobic work to explain specifically what it is and why considering it the same as endurance or stamina training might leave your training lacking the benefits of it.
Aerobic work should be intentionally low intensity and at a steady, or near steady, exertion rate. It should not be confused with lactate, speed, speed strength, anaerobic/strength endurance or endurance training. In other words, the best training for aerobic specific benefit remains aerobic specific work. Aerobic work is typically associated with 55-70% of a person’s so called max heart rate. There are a few ways to figure max heart rate. The most common, and least painful, method* is to subtract your age from 220. So for me that is 220-41. My max heart rate by this calculation method is 179. 55% and 70% is 98 and 125 respectively. So my aerobic training is a sustained effort with my heart rate between 98 and 125 beats per minute. It is actually pretty difficult for me to keep the intensity this low. Running at a pace that raises my heart rate to only 125 bpm can seem painfully slow, but if aerobic is the goal of the training session, adhering to the parameters is imperative.
*The 220 minus age equation is not accurate in that it does not factor fitness levels. An example is a trained sprinter, or other high intensity athlete, who is accustomed to and trained at higher heart rates, will have a higher max heart rate than this equation tallies. Other tests require a heart rate monitor and the will to push your heart rate up via high intensity efforts. A running example would be to complete a thorough warm up and then complete an 800m sprint at 80-85% exertion, rest long enough for the heart rate to lower by 30-40 bpms and then repeat 800m at 90%. Repeat the rest and allow your heart rate to reduce by 30-40 bpm again. Then hit the 800m sprint again, but this time reaching and holding max effort for at least the last 45 seconds of the effort. You repeat this last effort until the measured heart rate is less than the previous effort. The effort with the highest heart rate indicates your max. This method is not perfect either as people with less tolerance to the stressors involved will not produce as high a heart as they are actually capable of. In my experience, the 220 minus age equation gets most people within the same range as the exertion test most of the time. I suggest doing both so you can compare and assess for yourself.
Aerobic training, aka cardio… or cardio-respiratory training, targets and improves the body’s use of oxygen. While it requires movement and movement requires muscles, it is not the target of aerobic work to improve the muscles performance per se. Muscle performance comes from training lactate, speed, speed strength, anaerobic/strength endurance or endurance training. One way to look at it is aerobic training elicits systemic benefits and endurance training elicits benefits more specific to a groups of muscles or to a movements. This is very simplified explanation, but understanding this, and how the two are separate physiological adaptations with separate physiological benefits is important to properly programming aerobic work for athletes.
One of the most important things to point out is that even in what is considered by many to be our most “anerobic” of activities, our bodies are still very aerobic. Paul Gastin’s works cover this well. In his study Energy System Contribution During 200m to 1500m running in Highly Trained Athletes he shows us…
200m run: 29% aerobic; 71% anaerobic
400m run: 43% aerobic; 57% anaerobic
800m run: 66% aerobic: 34% anaerobic
1500m run: 84% aerobic; 16% anaerobic
The 400m sprint is by and large considered an anaerobic activity, yet over 43% aerobic… in HIGHLY trained athletes who are conditioned to and capable of pushing their systems to much further extremes than the avid running. When most people think 400m sprint they tend to think a respectable time being anywhere from 65 to even 80 seconds. It is worth noting over 2,100 runners have completed the 400m event in less than 45 seconds. The fastest at 43.03 putting 2100 or so folks within 1.7 seconds of each other’s time. I digress.
Take a quick look at the 800m and the mile… the average avid will be much more aerobic than those numbers.
The benefits of aerobic work are specific to it and come from the associated LACK OF intensity and LACK OF stress it places on the body. I.e., a speed run at 90% effort for 40 minutes does not equate to the same aerobic benefits as an easy paced 60 minute aerobic run at 70% effort. The first is pushing into lactate, the latter is purposely avoiding it. The first is for improving running in and around the 40 minutes time period, the later is for improving cardio-respiratory conditioning using running as the means.
Is there transfer? Absolutely. Doing metcons or HITT will provide some aerobic benefits. Aerobic training using running as the means will give aid to running endurance. And so on. However, specifically training each “system” will elicit the best response in said system.
A pure strength athlete, powerlifters and weight lifters, can use aerobic training to improve their health without interfering with their strength gains. Three 20-30 minutes aerobic sessions a week won’t exhaust them and detract from their training. Adding HITT or metcons certainly will. I have my strength athletes use a cycle, swim or other low impact machine for aerobic work as opposed to running to further reduce the stress and not negate the benefits.
For the CF or HITT athlete, aerobic training can be used to improve resting recovery without adding load to an already overly taxed or even chronically fatigued body. The typical high intensity athlete benefits greatly from just two aerobic sessions each week.
Endurance athletes blur the line between their primary training goal and aerobic work the most. The longer an athlete goes the more their training begins to look like aerobic work. Obviously due to the intensity / volume curve. They too can benefit from purposely pulling back on the intensity on a long slow training session from 85% effort to 70% effort. The lessened intensity not only specifically targets their cardio, but if programmed at the correct time, can be used to still get the athlete’s miles in, but with less impact and trauma.
During deload/reload weeks, the steady state work I give my athletes is all aerobic. I give athletes two high intensity training weeks and 1 deload/reload week for a 2:1 training to reload schedule. So at a minimum, my athletes get 5 purely aerobic sessions every 3 weeks. That is at least one during training weeks and 3 during deload/reload weeks. The number during training weeks vary per the type of athlete, their goals, and where they are in their training cycle in relation to their goals.
The bottom line here is aerobic conditioning its own physiological adaptation. For some just trying to not be sick, it may be the primary and only fitness goal. For athletes, it is tool in the physio toolbox. When used a tool is used properly, it will make the job easier and produce a higher quality finished product.