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Running Research News And Events
August 30, 2009
GET YOUR LACTATE-THRESHOLD SPEED IN 30 MINUTES
Your running speed at lactate threshold, an important predictor of performance, can be determined fairly accurately with a 30-minute test. This speed can then become an important "frontier" in your training, with velocities above the threshold qualifying as high-quality exertions and speeds below the threshold counting as "easy efforts." However, training at your lactate-threshold speed is not the optimal way to upgrade your velocity at threshold.
As my youngest daughter Sabrina might say, there are at least 30 kabillion ways to estimate your lactate threshold. Some of them are even accurate.
Your running speed at lactate threshold is, of course, something to be concerned about. After all, various studies have suggested that lactate-threshold speed is the best predictor of endurance performance (1 & 2). Lactate-threshold velocity is simply the speed above which lactate begins to accumulate rather dramatically in the blood. It works as an endurance event predictor because lactate is a key fuel, much-preferred by the muscles, and pile-ups in the blood indicate that the muscles lack the machinery necessary to process lactate at high rates (a bad thing, since lactate is such an important source of energy).
Because lactate threshold is important and it can be estimated in various ways, many coaches and training books prescribe or recommend workouts which involve running for varying amounts of time at lactate-threshold velocity. This practice harkens back to the research of Swedish physiologist Bertil Sjodin and his colleagues (3), who appeared to find that a weekly 20-minute workout at lactate-threshold speed, when carried out over a 14-week period, improved lactate-threshold velocity significantly. Bertil's bunnies were not compared with runners, who worked at paces faster than their thresholds, and in fact there was not even a control group in Bertil's inquiry, but the practice of running at threshold caught on, and it is still extremely popular today. In-vogue running books and beloved running magazines recommend training at threshold, and exercise scientists in respected laboratories report that they are regularly contacted by runners and triathletes who would like to know the "best" way to estimate lactate threshold; frequently, these athletes have been instructed by their coaches to carry out a significant amount of training at threshold each week.
So, let's say that you'd like to be a conventional sort of runner and carry out some at threshold training, with continuous runs at your threshold pace. What is the best way to estimate your threshold?
You could have your threshold speed measured at an exercise-physiology laboratory, of course. You would end up with an extensive print-out of your blood lactate readings at various running speeds, and you might even enjoy a chat with an exercise physiologist about what the data points really mean. But, the procedure would be expensive and time consuming, and your test would probably be conducted on a treadmill, with no assurance that your lactate profile would be identical to the one obtained while you were running on something like, say, good-old Mother Earth. Also, you would need to perform the test several times over the course of a season, as your fitness changes, and that means having lots of bucks and - hopefully - living not too far from a hospitable exercise physiology laboratory.
Naturally, you could utilize one of the commercially available, portable, lactate analyzers, which are pretty accurate and have come down in price to reasonable levels. However, you must prick your finger or ear repeatedly to carry out the threshold test, and you must be a little savvy with your blood sampling and handling techniques. With all the bloodletting, your mind may not be completely focused on your running (thus giving you a false reading for threshold speed, and you can easily screw up the bloody part of the process. Don't forget, too, that when the bloodbath is over you will still have to "fit the curve" (graph your blood-lactate levels as a function of running speed). Once your graph looks nice, you also must decide in unerring fashion exactly where lactate threshold is to be found on the upward-curving line.
In contrast with these first two possibilities, Jack Daniels' "VDOT method" for determining lactate-threshold velocity is a bit easier on your wallet and pain receptors. Described in his book, Daniels' Running Formula, the VDOT method calls for you to enter your performances at a variety of distances into equations and tables developed by Daniels (4). Your velocity at lactate threshold, along with other important training speeds (including interval pace and marathon tempo, for example), can then be calculated.
A 3200-meter time trial is also considerably more facile to conduct than a full-blown lactate-threshold exam and has been thought by some to provide a reliable estimate of lactate-threshold velocity. For this test, you only need to do one thing: On a day when you are feeling great and gale-force winds are not whipping across the track, you perform a maximal-effort 3200-meter run. You then calculate your lactate-threshold velocity (LTV) with the following equation:
LTV (in meters/minute) = 509.5 -20.82 X [3200-meter time in minutes]
Let's say, for example, that you completed your 3200-meter run in 12:15. Changing 12:15 to 12:25 minutes and plugging it into your equation, we have the following:
LTV = 509.5 - 20.82[12.25]
LTV = 509.2 -255.05
LTV = 254.45 meters per minute (or 1609/254.45 = ~ 6:19 per mile)
Although this technique appears to be slightly suspect (note in this case how close LTV is to the full blast 3200-meter speed), research has found that it predicts the running speed linked with blood-lactate levels of 4.0 mmol'L-1 pretty accurately, and the running speed coinciding with 4.0 mmol'L-1 is often considered to be LTV (5).
If you don't like surging around the track eight times, you can also employ a 30-minute time trial to reckon your lactate-threshold speed. This method, recommended in lay publications marketed to competitive athletes (6 & 7), involves warming up and then gradually accelerating up to a tempo which is deemed to be the best-possible pace which can be sustained for 30 continuous minutes. When this tempo is attained, the 30-minute time period begins; during the 30 minutes, the pace may be varied up or down slightly, as necessary, but the idea is to work at one's best-possible intensity throughout the 30-minute period. The 30-minute exam can be completed on a track, measured course, or treadmill with a 1-percent grade, and LTV is obtained simply by dividing the distance covered during 30 minutes (in meters) by 1800 seconds (30 minutes). For example, a runner covering 8000 meters in 30 minutes would have an estimated LTV of 8000/1800 = 4.5 meters per second, for a tempo of 400/4.5 = ~ 89 seconds per 400 meters. The calculating can also be done in U.-S. units to derive minutes per mile, i.e., 30 minutes divided by 4.97 miles equals 6.04 minutes per mile, or about 6:02 pace.
And yes, there is also the Conconi test - which is more ponderous to conduct but has been examined carefully in a variety of different scientific studies. To carry out the latest and greatest version of Conconi, you'll need to place cones at 100-meter intervals on a 400-meter track (the name of this test did not come from cones, though). You then begin running rather cautiously - but you also increase your running velocity as uniformly as possible every minute by an amount that boosts heart rate by not more than eight beats per minute(!). So, you have to keep careful track of your heart rate, and you also must pay special attention to your friend (a companion is required for this test), who lets you know about the passing of each minute with a whistle blow; your crony also records the running time for each 100-meter segment. These 100-meter times are used to figure an average running velocity for each minute of the test, and the heart rates during the last 10 seconds of each minute of the test are obtained from the memory of your heart-rate monitor and are utilized to figure the average heart rate per minute at the recorded running speed. Speed continues to increase until near-maximum intensity is attained, and then a final phase of acceleration pushes you up to your max velocity. You're not done, yet, though! Lactate-threshold velocity is then calculated by graphing heart rate (on the y axis) with running velocity (x Axis) for each minute of the test. The LTV is supposed to occur at the point at which the linear relationship between heart rate and running speed abruptly ends - in effect where heart rate shoots up disproportionately as running speed increases by the standard amount (please see ref. # 8 for even-more agonizing details of this whole process). Any votes for the 3200-meter test?
To learn more about how to Get Your Lactate-Threshold Speed in 30 Minutes (the full article can be read by purchasing Vol. 21 Issue 8 of Running Research News) and many more running related topics, simply click-on the Back Issues link, and select the volume and issues number, from the drop-down menu. A subscription to Running Research News is another way to receive valuable information about running. BUY NOW.