Lactate Threshold, Critical Velocity, And Other Stories


Some time went by, and I never bothered to elaborate on the training approach I've taken over the last four weeks.

I mentioned that I was going to start doing two fast runs per week (Mondays and Wednesdays), plus a plyometrics day on Fridays. I never circled back to the blog to say that I was also going to incorporate P90X's "three weeks on, one week off" monthly training cycle into my regimen, then change again. Tony Horton bills this as "muscle confusion," but that concept doesn't really apply to running. One doesn't really want to confuse one's running muscles. Still, there's a lot of good evidence in support of taking on a lighter load every fourth week to help reduce fatigue, and that means the fifth week is as good as any other to make another adjustment to the training regimen. Then, on for another three weeks, and yet another lighter week at week #8. Lather, rinse, repeat.

Last week was my fourth week, making it a lighter or "transition" week between what I was doing previously, and what I will be doing now. Interestingly, my overall training load increased last week, rather than decreasing:

Notice that my "relative effort" training load (from Strava) indicates a consistent upward trend for the past four weeks, up to and including last week, which was my "light" week. (The data from Garmin tells a much different story, though, and according to that data, my load did indeed decrease last week.)

As part of my one-month cycle, I did a guided lactate threshold test using my Garmin watch and chest strap HR monitor on Saturday. I will do this again next month in an attempt to chart my training progress using some semblance of cardinal measurements and real data.

Garmin's lactate threshold test produces a lactate threshold heart rate value and a lactate threshold running pace value. My numbers on Saturday turned out to be 167 beats per minute and 6:37 per mile. These results surprised me. I frankly expected a higher lactate threshold, meaning a higher heart rate value and a faster pace time.

Skeptical, I decided to read up a bit more carefully on lactate threshold. The USATF's VO2 max pace chart, as quoted here (p. 2), indicates that 10K race pace corresponds to approximately 92% of VO2 max, and from this value we can calculate various other estimated paces using the percentage values in the USATF table.

My most recent 10K time, taken in early October 2019, was 39:40, or about 6:23 per mile. With the help of some algebra, we can see that lactate threshold pace -- 88% of VO2 max -- corresponds to 6:35 per mile. Thus, assuming I have not lost any fitness between October and today, Garmin's estimate was only 2 seconds off. That's far more robust than I expected! I have gained some faith in Garmin's lactate threshold estimation technology.

Lactate Threshold Training

Having now established a 2020 training benchmark for myself, the next logical question to ask is, "How can I improve my lactate threshold?" The internet is replete with articles on improving lactate threshold, but why read all those articles when it can be summarized in a single sentence? 
The most common recommendation for improving lactate threshold is to run 30-minute sessions at lactate threshold pace
For me, this means something like this: 2-mile warm up, 30 minutes at 6:37/mile pace, 2-mile cool down. Pretty basic stuff. I might try it. 

However, while reading up on lactate threshold improvement, I came across an interesting article here. Read the whole thing. It is highly informative and, if you're a training geek like me, absolutely fascinating. In particular, the article contains a discussion about training above lactate threshold pace. Summarizing the approach used in a York University study, the article states:
The idea that intense workouts are best for boosting LT was even more strongly reinforced in research carried out at York University by Stephen Keith and Ira Jacobs (‘Adaptations to Training at the Individual Anaerobic Threshold,’ Medicine and Science in Sports and Exercise, vol. 23(4), Supplement, no. 197, 1991). In the York investigations, one group of athletes trained exactly at LT, a very popular way to attempt to heighten LT, for 30 minutes per workout. A second group divided their 30-minute workouts into four intervals, each of which lasted for seven and a-half minutes. Two of the intervals were completed at an intensity above LT, while the other two were carried out below LT. Each group of athletes worked out four times per week for a total of eight weeks.
What happened? (Emphases mine.)
Which strategy was better for boosting LT – working at LT intensity or putting in the time above it? After eight weeks of workouts, both sets of athletes achieved similar increases in VO2max and LT. The actual gains in LT were absolutely tremendous, averaging 14 per cent in both groups! Advances in muscle-cell enzymes were also rather splendid – and nearly identical in the two groups. In an endurance test in which group members exercised for as long as possible at an intensity which corresponded to their pre-training LT, the above-LT trainees seemed to hold an edge, continuing for a total of 71 minutes, while the at-LT subjects could last for only 64 minutes. However, this difference was not statistically significant. 
At first glance, these results seem to suggest that there’s not much advantage to be gained by sweating through above-LT workouts, but wait! If you’ve been following carefully, you probably noticed that the above-LT athletes really logged only 60 minutes of quality work per week (4 x 15 minutes), while the at-LT subjects put in 120 weekly minutes of quality exertion (4 x 30 minutes). To put it another way, the above-LT athletes achieved the same gains in LT and VO2max as the at-LT folks (and perhaps enjoyed a slight advantage in endurance) – with only HALF the total training time. It’s reasonable to assume that had the above-LT athletes stepped up their volume of above-LT work a little bit, they would have outdistanced the mundane at-LT trainees.
So, training above lactate threshold corresponds to greater increases in lactate threshold than simply training at lactate threshold, because training above LT increases LT more efficiently on a per-minute basis.

This all reminded me of so-called "Critical Velocity" training.

Critical Velocity

The article I mentioned above when citing USATF pace percentage values, by Chris Puppione of UC Davis, includes several amusing discussions about how coaches and trainers are always looking for a new magic training elixir that will enable athletes to suddenly and momentously acquire a tremendous advantage over their peers. Here is one such excerpt:
There are no secrets in distance running—no new revelations and no magic bullets. Somewhere, some other coach has already done it. Somewhere, some exercise physiologist has already written about it. Knowing this, however, has not stopped coaches from exploring better ways to train their athletes year to year. Knowing this does not stop us from picking through our copies of Running with Lydiard, Road to the Top, or Daniels’ Running Formula to find that one piece of information that we may have glanced over without giving it the attention it was due.
Puppione is right, of course. There really is nothing new under the sun. He mentions that "Critical Velocity training," which is gaining lots of new press thanks to the quite admirable success of the Tinman Elite racing team, can trace its roots all the way back to the 1960s! That's more than half a century ago. 

Still, Puppione does incorporate CV training into his coaching of athletes at UC Davis, and reports good results in doing so. He explains that the advantages of CV training over LT training are mainly that the athlete can reap many of the benefits of both LT and VO2 max training, simultaneously, and at substantially reduced overtraining risk compared to VO2 max training.

It makes sense, but keep in mind that the difference between LT and CV training is about 2%, or about 7 seconds per mile. To be sure, seven seconds per mile is a substantial increase in pace over the course of a few miles, but the difference is not enormous. Think of it this way: If my lactate threshold pace were to run a 10K against my critical velocity pace, my CV pace would win by about one minute. My race pace would win by two minutes.

Can seven seconds per mile really result in such great training improvements? It's tempting to buy into the hype, but again Puppione offers a voice of reason. He points out that he uses CV training early in his athletes' season to quickly ramp up their lactate threshold. Then, he focuses on VO2 max training during the middle of the season while reducing weekly mileage, to improve his athletes' speed without overtraining them or over-taxing their muscles. Finally, he incorporates a bit more CV training at the end of the season so that he can reduce the athletes' training load even further as they prepare to taper for the final, major competitions of the season.

In other words, CV training is a good tool to have in the tool kit... but it's not the whole kit.

Back to Me

As for me, what can I learn from all of this? How can I apply my newfound knowledge to my own recreational training regimen?

Looking back across the past month, I realize that I probably was overtraining. By the end of my third week, my muscles felt exhausted, and I couldn't really complete the workouts I had scheduled for myself. Well, I could complete them, but I wasn't getting the most out of them. I was essentially training at VO2 max pace twice a week, and adding a quite difficult plyometrics day to the mix. My weekly mileage decreased a bit, and my body started to feel worn down. 

I can improve my training, at least in the near term, by doing more workouts at or above lactate threshold, although not so fast as VO2 max pace.

I had originally planned on making speed the focus of my next three weeks of training. Speed, of course, involves a lot of training at VO2 max. I am less excited about that approach now, however I did happen to notice an interesting aspect of Puppione's recommended training sessions. He structures his CV training workouts as follows:
  1. 5-10 minutes warm up
  2. CV intervals (say, 4 x 2K at CV pace with 2 minutes recovery in between)
  3. 5-10 minutes recovery run
  4. VO2 max intervals (say, 5 x 200m at VO2 max with 200m recovery in between)
  5. 5-10 minutes cool down
You'll notice he adds some VO2 max intervals at the end of the workout to condition athletes to "run faster in a fatigued state." I believe that adding some VO2 max intervals to the end of my threshold runs and/or CV runs will enable me to improve the quality of my training runs.

So, friends, that's what I'll be doing for the next three weeks. Two weekly hard workouts at-or-slightly-above lactate threshold pace, with recovery runs and a weekly long run.

Let's see how it goes!

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