The Burn Is Real
We’ve all been told the same thing by nearly every coach, physical trainer and fellow athlete in existence, namely that lactic acid is the enemy, a nasty gunk that makes your legs burn, seize up and eventually slow down against your will. While there are some elements of truth to this misconception, modern research has dramatically changed the story we’ve all been told. I’m going to risk spoiling the ending for those who aren’t necessarily here to dive into the science behind what is happening when we run hard. Simply put, during anaerobic efforts, lactic acid isn’t what’s causing your legs to feel heavy and unresponsive, it’s a different byproduct altogether. While this doesn’t mean that we need to throw all of our lactate threshold workouts (AKA tempo runs) out the window, we can better tailor them to cope with what’s actually happening. In fact, by teaching our bodies to deal with the true culprit of “the burn” we can prepare our anaerobic system for more realistic race specific scenarios and even take advantage of a range of stimuli in order to cause a more robust and extensive adaptation. Interested in the science of it? Read on! Here for the training impact? Skip ahead!
It All Starts With Energy Demand
All endurance coaches and athletes have their own differing definitions for the exertion level where our bodies begin processing glucose anaerobically (without oxygen). For our purposes however it’s important to nail down some common language. At the risk of oversimplifying it, lactate threshold (LT) is the point on the spectrum at which an endurance athlete can train hard but still keep it aerobic, clearing lactate as quickly as it accumulates in the muscles and in the blood.
To understand lactate and why it gets such a bad rap, it helps to understand how we generate energy while we run. During fully aerobic exercise the body uses glucose (fuel) to create ATP (energy) through several complex reactions and processes. Even in an aerobic state, byproducts such as lactate are still created but they are able to be utilized or diffused back into our bodies. In an anaerobic state however, the demand for oxygen is too high for the amount of oxygen we are taking in and/or processing. While we can still utilize glucose anaerobically in order to create ATP, it’s up to 18 times less efficient than aerobic glycolysis and this results in the “boogeyman” of anaerobic activity, lactate, more commonly known as lactic acid. However, the lactic acid that supposedly gums up our muscles is a fallacy. Rather, almost as soon as lactic acid is created it immediately dissociates (separates) into lactate and Hydrogen ions. The excess Hydrogen causes an acidification of our muscle fibers and blood and affects muscle contraction speed and muscle contraction power resulting in our legs feeling like they’re unresponsive and moving through molasses. While this acidification does correlate with an increase in lactate, it isn’t caused by it. However, the fact remains that our legs still feel heavy and inefficient as we exert ourselves farther and farther past our lactate threshold for longer periods of time.
Variety Is The Spice of Life
If lactate doesn’t cause our legs to seize up and feel unresponsive, then why should we bother training our body to deal with lactate at all? As it happens, lactate can actually be processed as a fuel in the liver, heart and brain and can even be used to create additional glycogen to be used as fuel. This “recycling” can relieve small amounts of the energy demands we are experiencing, and help us to clear out some of the byproducts that are building up. We just need to consistently train this adaptation in order to take advantage of it. For example, the traditional lactate threshold workout is roughly 20’-30’ at a pace sustainable for approximately an hour (this is also the pace most often spit out by online running calculators, anywhere from 10k to half marathon race pace depending on the runner). In this sort of workout, the idea is to steadily adapt to running at a faster pace while still processing all the lactate that you are creating. While such workouts certainly work to a point, they’re one dimensional and don’t teach our bodies to also take advantage of our ability to use lactate as a fuel. Additionally, as studied by Dr. Jan Olbrecht, ten to twenty days after traditional workouts such as these, physiological changes begin to manifest. Unfortunately however, these same adaptations begin to level off after a relatively short period of time, resulting in a plateau as the runner will need increasingly larger stimuli in order to continue adapting. Essentially, the runner will have become efficient enough at 20’ LT runs that their body no longer needs to adapt significantly in order to “survive”.
This is where varying LT comes in. Rather than just targeting 20 minutes at a steady pace, alternating paces both faster and slower than your target LT pace will work the LT system, but from a different direction. Rather than riding the line steadily, as traditional tempo workouts would have, attempt to push it down by throwing in quicker segments that will dump some lactate into your system, while also mixing in slower ones to force your body to deal with it by processing and utilizing that lactate. At the same time, by throwing faster paces into the mix, LT workouts are immediately more specific to racing any distance. After all, since when are all races the same pace and effort throughout? There is no exact recipe to this style of LT workout, faster paces can mean anything from 800m pace – 10k pace, and there is an endless assortment to the work/rest ratio that could do the trick.
As a second option, try flipping the traditional “finish with the fast stuff” thinking on its head by adding small doses of LT work to the end of more anaerobic workouts such as hill sprints or intervals. Doing so will force you to again practice clearing and utilizing the lactate that has built up throughout a workout. Training for a marathon? Try adding variable paces to the end of your long run. Accelerating through marathon pace, half marathon pace and 10k pace (or faster) has the same “over/under” LT effect while simultaneously being very specific to marathon racing due to the large aerobic component.
Caveats and Tips
First off, there’s nothing inherently wrong with traditional steady LT runs. They’ve stood the test of time for a reason, they work. At some point though, every runner will need to change their stimulus in order to advance, it’s the nature of the sport. Second, as modern research proves what many renowned coaches such as Bill Bowerman, Arthur Lydiard and Renato Canova (among many, many others) have known for decades, it doesn’t prove other coaches necessarily wrong, just that there was more to the story than previously thought. Below I have included a few potential workout suggestions for various target races. Have some questions? Not sure where to start? Want some suggestions for your own workouts? Shoot me an email, there’s nothing I love more than talking running or diving into training! – (See bio and contact info at bottom of this article.)
P.S. – This fact is so wild I can’t not include it. Some of our earliest misunderstandings of lactate came from…FROG LEGS. Seriously!
Now Let’s Have Some Fun!
Workout #1 – 20’ alternating between 3min at LT effort and 30s at 5k effort.
A Good Fit For – A beginner, intermediate or advanced runner trying LT variations for the first time, can fit anywhere in a training cycle.
Description – For 20’ of continuous running, alternate between 3min at a LT effort and 30s at 5k effort. Oftentimes the hardest part isn’t the faster segments, it’s settling into the LT pace without slowing down as we are accustomed to doing after a faster rep.
Workout #2 – 3-5×5:00@LT with the middle (3rd) minute at 5k effort
A Good Fit For – A beginner or intermediate 5k-half marathon runner who is beginning to add LT variations into their runs, or who has plateaued after several weeks of traditional LT work.
Description – Run 3-5 LT intervals on 60s-90s rest, press the middle minute at an effort around 5k. This gear change is great practice for racing shorter distances and adds in small doses LT variation.
Workout #3 – 5-7x(800-400) of continuous running, alternating between 800@10k pace and 400@marathon pace
A Good Fit For – An intermediate or advanced runner in the late stages of training for a track 10k or even a marathoner in their last 4-6 weeks of training.
Description – Continuously alternate between 800@10k effort and 400@MP. Again, the challenge is often in the rest! We are trained to “let up” after harder intervals and easing up on the gas without stopping is challenging at first.
Workout #4 – 2000 – 1600 – 1200 – 800 Advancing through 10k, 5k, 3k, mile pace respectively with the last 400m of each dialed back to LT effort.
A Good Fit For – An advanced runner training for anything from the 3k up to the half marathon
Description – In the same vein as the Michigan workout, complete a 2k@10 effort, a 1600@5k effort, a 1200@3k effort and an 800@ mile effort with the final 400 of each rep cut back to LT effort. For rest, take anywhere from 90s-3:00. The target here is to get some specific and high-end anaerobic running in while again adding a dose of LT clearance and utilization.
Workout #5 – 3x(3×300) cut downs + 2mi@LT pace, 90s between reps and 3:00 between sets
A Good Fit For – An advanced runner in the late stages of training for a 1600-10k
Description – Run three sets of 3×300 starting around 3k effort for the first set and advancing to a little faster than mile effort for the second set and closer to 800 effort for the third. It’s never too late to maintain your efficiency at faster paces. By taking a few minutes and tacking on a 2mi@LT, we again work to clear and utilize the lactate we build up in these types of faster, very anaerobic workouts.
Andrew Dionne is a coach with Team RunRun. To learn more about him or to work with him, check out his coach profile.