Aerobic Build Weeks

Classic periodization from legendary coach Arthur Lydiard in the 1960s and 1970s up through Renato Canova and countless others today can sometimes feel a bit like a repeating time loop from the movie Groundhog Day (or the amazing new movie Palm Springs on Hulu). You build an aerobic base with mostly easy running. On top of that base, you build efficient speed/output with added intensity. You do a shorter race, build more speed, another somewhat shorter race or three, build more speed, finish with a key race. Then you recover with an off-season or recovery block.

And it starts all over again. The key race resets the clock, and like Bill Murray and Andy Samberg in those movies, you wake up the next morning to repeat the cycle.

Right now, though, while day-to-day life may feel a bit like a repeating loop, covid-19 has knocked training cycles off previous patterns. With fewer races, most athletes are making it up as they go, with no obvious peaking or rest periods. It’s a never-ending build to nowhere. So basically like the eight seasons of Game of Thrones. HBO, sponsor me or Westworld gets it.

In this moment without many races, I think that there are training lessons that can spur long-term breakthroughs even when things are back to normal. This article focuses on the base-building element. All endurance performance is layered on top of the aerobic foundation. After that foundation is built, even during build periods with intensity and racing, athletes can reinforce the foundation with an emphasis on doing mostly easy running (80 to 90 percent is a good guideline). But eventually in most coaching approaches, it’s important to focus primarily on that foundation, due to some physiological processes discussed below that are diminished with very hard efforts. That’s why each Lydiard-style cycle starts anew with an emphasis on an aerobic base.

What if, instead of the dedicated base-building cycles, athletes incorporate those principles periodically through longer training cycles? That is the theory behind aerobic build weeks, a term my wife Megan and I use for athletes we coach for base-style weeks in the middle of traditional training builds.

What if, instead of the dedicated base-building cycles, athletes incorporate those principles periodically through longer training cycles? That is the theory behind aerobic build weeks, a term my wife Megan and I use for athletes we coach for base-style weeks in the middle of traditional training builds. There’s nothing new or fancy about aerobic build weeks or the principles this article talks about—most training approaches use them or similar “reset”/“volume” weeks in some form. I just like making up names for things, which is why I toast my bread in the Taste Build Appliance.

Whatever these weeks are called, they share DNA with “down weeks.” What sets aerobic build weeks (or whatever you choose to call them) apart is that usually they are equal or higher volume than baseline, with a reduction in intensity. Meanwhile, many traditional down weeks can involve a reduction in volume with a maintenance of some intensity, similar to how taper weeks work, though there are lots of variations in specific approaches. There are five primary justifications for periodic aerobic build weeks.

1) High intensity can increase stress, and the body can have difficulty adapting through excess stress.

High-intensity training, particularly training above lactate threshold and VO₂ max, increases stress on almost all physiological systems. That stress is usually a good thing—it’s the whole point of progressive overload training, the fundamental principle underlying block periodization. The problem is that stress only leads to adaptation in moderation. Smart training is about stepping up to the edge of stress limits. However, if an athlete steps even an inch over the edge, it can cause a cascade of negative physiological effects, such as elevated cortisol, reduced production of sex hormones, lower hemoglobin and fatigue from endocrine system changes.

Aerobic build weeks can act as resets, letting an athlete continue to develop while reducing background risk that might not be evident in how they feel in the moment.

Cellular-level fatigue is a ticking time bomb that can be counting down while an athlete is still able to nail workouts. Easy running primarily below aerobic threshold comes with little risk to hormonal balance, particularly when coupled with plenty of fueling and recovery time. Aerobic build weeks can act as resets, letting an athlete continue to develop while reducing background risk that might not be evident in how they feel in the moment.

2) Harder efforts risk causing muscle damage and raising injury risk.

As output increases, strain on the musculoskeletal system increases with it. I think that principle of musculoskeletal overstress can be hard for runners to visualize since we often don’t think of hard running as particularly traumatic, so it may help to think of baseball. A pitcher can do an easy catch at 70 miles per hour all day with little risk. But each throw at 95 miles per hour is a Tommy John surgery waiting to happen. With time, it’s possible to mitigate the risk, but the injury monster will always be there, lurking under the bed, ready to punish us for going too hard or mixing metaphors.

A pitcher can do an easy catch at 70 miles per hour all day with little risk. But each throw at 95 miles per hour is a Tommy John surgery waiting to happen.

When it comes to running, athletes usually don’t get injured from purely easy efforts unless they are doing excessive volume relative to their background or not eating enough/overstressed outside of athletics. One of my favorite studies looked at collegiate runners and found that 43 percent had asymptomatic tibial-stress reactions. It’s likely that most runners are dealing with some potentially brewing musculoskeletal injury at any time without realizing it. Aerobic build weeks may help prevent those possible-injuries from becoming monster attacks.

3) Aerobic adaptations may possibly be slowed by anaerobic stimuli.

There are theories that excessive anaerobic stresses can slow angiogenesis, where capillaries expand around working muscles, and can alter enzymatic processes that contribute to aerobic development. The same goes for reducing the efficiency of lipid metabolism. Plus, that excess cortisol and hormonal stress can chip away at the strongest aerobic foundation.

You can see some of these principles at work in a Crossfit athlete that only does intense training, who might be mightily strong and really fit and perfectly consistent, but their velocity at aerobic threshold will be subpar relative to their velocity at VO₂ max or harder. An offset between vAeT and vVO₂ will usually lead to worse endurance performances over time as the aerobic system erodes away, a house with amazing photos on Zillow but termites in the basement.

4) Alterations in training stress may help spur adaptations.

Adaptation is tricky because it’s nearly impossible to trace an intervention to an outcome. Even all of the studies I cite could probably be explained away by other variables than the ones that are being isolated. We can try to control for all the variables in the world, but often what we are measuring is way more complex than can be summarized neatly.

In the face of physiological uncertainty, it can be helpful to mix up stimuli periodically. One, variation in stress could help spur adaptations that are not covered in normal training. Two, it’s better to be 20-percent undercooked than one-percent overcooked, and aerobic build weeks can help keep athletes in the safe zone.

On the flip side, increasing volume in an aerobic build week could be higher risk for some athletes, so it’s a balancing act that is individual-dependent. Plus, it’s uncertain whether short-term training interventions like aerobic build weeks can cause enough of an adaptation stimulus to meaningfully alter an athlete’s trajectory. It has worked for some of our athletes, but maybe we’re perceiving correlation or causation or Californication (when I get distracted by the Red Hot Chili Peppers and forget my point). In other words, it depends. And “It depends” is the world’s second-least-satisfying answer, right after “we’re not sure why it burns when you pee.”

On the flip side, increasing volume in an aerobic build week could be higher risk for some athletes, so it’s a balancing act that is individual-dependent. Plus, it’s uncertain whether short-term training interventions like aerobic build weeks can cause enough of an adaptation stimulus to meaningfully alter an athlete’s trajectory.

Some coaches think that down weeks may be altogether unnecessary, so this area is not without controversy. My thinking is that even if reductions in volume or intensity are not universally needed, adaptation can be so difficult to trace back to interventions that I always prefer to err on the side of less stress.

Over six weeks, aerobic blocks may be slightly counterproductive, since down time from intensity may be lost training benefit. Over six months, that reduction in intense stress likely starts to even out, and it will probably help fitness since athletes can perform more sustainably as their aerobic system develops. Over six years, I’d bet that controlled stress would almost always equate to better outcomes. The noise of week-to-week and month-to-month performances are smoothed out by the signal of long-term aerobic growth, and long-term aerobic growth relies on avoiding burning out or burning up.

5) Some athletes think of these weeks as running vacation weeks, encouraging a relaxed focus.

The trial of miles can be fun, and an aerobic build week can feel like running training stripped down to it’s essence. If you love running, but also want to purposefully chase your long-term potential, aerobic build weeks can be a good way to balance recovery and passion and intention.

If you love running, but also want to purposefully chase your long-term potential, aerobic build weeks can be a good way to balance recovery and passion and intention.

There’s no magic to programming aerobic build weeks into your training. For our athletes, we use them in long-term training cycles to prolong base aerobic fitness. Sometimes they’ll last a week, sometimes longer or shorter. Time is a flat circle, so whatever.

But if I had to pin it down, here is a summary of how we put them into practice:

Consider aerobic build weeks every 3-6 weeks in longer-term training cycles.

More frequent aerobic build weeks are good for long-term builds with no end in sight. Less frequent works in more traditional training blocks, or for athletes that are not aerobically limited.

Keep volume steady or increase volume.

Start with your peak volume, and if you’re totally healthy, you can even increase from there by up to 10 percent. Doubles are a wonderful option too, along with cross training. But you can play around with it, reducing volume in times of higher stress, or adding more rest days.

Short strides are good, particularly later in the week

Like during a base period, you can add short strides, just make sure they aren’t strained or long enough to slow down the aerobic-development processes (I prefer 30 seconds or less). And if you’re feeling great, you can progress to steady running or even short tempo runs, like in a Lydiard aerobic block.

Put it all together, and an aerobic build week may look like this for an advanced athlete. Note: to make it a pure down week in a period of higher life/training stress, you can use the same principles and reduce total distance by 10 to 40 percent.

David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts a weekly, 30-minute podcast on running (and other things), and they wrote a book called The Happy Runner.