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I’ve read and heard all about the benefits of training at lactate threshold intensity. But what’s the best way to figure out my lactate threshold heart rate?
There’s actually nothing particularly special about training at lactate threshold intensity. Yes, it is a powerful fitness booster, but so is training above and below lactate threshold intensity. The apparent specialness of lactate threshold intensity has been artificially inflated by the choice of scientists to single it out for individual attention.
Basically, it works like this: If scientists choose to study the effects of lactate threshold intensity on performance, they will have one group of runners train strictly at moderate intensity and another group add one or two lactate threshold-intensity workouts to their training. Both groups will be subjected to performance tests before and after the training intervention. The group that does lactate threshold training improves more, so lactate threshold intensity is confirmed as this magical intensity “sweet spot” with unparalleled fitness-boosting powers compared to other training intensities.
But wait a minute: Wouldn’t any addition of higher-intensity training, whether slightly below or slightly above lactate threshold, improve running performance more than training only at moderate intensity? To really determine whether lactate threshold training has special powers, its effects should be compared to training at slightly lower and slightly higher intensities.
This experiment has been done. British researchers recruited 14 moderately trained runners and divided them into two groups that followed slightly different training schedules for four weeks. Members of one group incorporated two conventional threshold workouts—consisting of continuous running at lactate threshold intensity—into their weekly regimen. (Actually, they ran at maximal lactate steady state speed, which is considered synonymous with lactate threshold speed by some scientists and slightly below lactate threshold speed by others, including these researchers.) The second group of runners did a matching amount of variable-intensity workouts in which they alternated between running 0.5 km/hr faster than lactate threshold speed and 0.5 km/hr slower than lactate threshold speed.
Before and after the four-week training period, all of the runners were tested for their maximum lactate steady state speed and their lactate threshold speed. Those who did traditional threshold runs saw a bigger improvement in their velocity at maximal lactate steady state speed than those who did the variable-intensity workouts, who in turn saw a bigger improvement in their lactate threshold speed, which was fairly close to the speed at which they performed the faster segments of their workouts. What do we learn from these results? Runners seem to improve more at the speed they focus on in workouts, whether that speed is at, above or below the lactate threshold.
The upshot is that it’s not important to identify one’s precise lactate threshold and run at the pace or heart rate that exactly corresponds with that intensity to get a boost in fitness. In fact, it may be best to hit a variety of intensities in a range surrounding the “true” lactate threshold. In practical terms, this means you can simply not bother identifying your lactate threshold and incorporate regular efforts at “moderately high” intensities—defined by feel—into your training. For moderately fit runners these would be efforts falling in the range of the maximum speed sustainable for 30 to 60 minutes. For highly fit runners, moderately high intensities fall in the range of the maximum speed sustainable for one hour to marathon race pace.
One taxing “threshold” effort per week plus perhaps one shorter threshold effort per week are plenty. For example, on Tuesday you might run a 20-minute threshold effort between a warm-up and a cool-down and on Sunday run the last 10 minutes of a 90-minute long run at threshold effort. You’re better off including an even higher-intensity speed workout in your training than doing any more threshold work than that.