This is technically the second part of a two part series, but it’ll stand alone.
A lactate threshold is not your peak intensity. If you imagine lactic acid being produce like water coming out of a faucet, then the lactate threshold is where your biological “drain” can’t keep up with the water coming out of the “faucet”. If you push yourself past that threshold, say towards VO2 max, you produce more lactic acid than your body can break down. Below that rate you still produce lactic acid, but it get’s broken down by your body.
Cyclists and runners use this to gage their work outs and to tailor them to more direct improvement.
Unsurprisingly, swimmers have been giving this a go as well.
Tradition calls this the T30, or a timed 30 minute swim. Several swim coaching guidebooks actually have tables to figure out from a distance the exact pace over 100 yards that corresponds to the lactate threshold. A T60 gives you the same sort of information. Some coaches use set distances (I like this approach) such as a 3000 yard swim and measure time.
Either way the magic number they are looking for is the average time it takes to go 100 yards.
Recently, there has been a move towards using repeated 300s or shorter distances to determine the lactate threshold. The idea runs something like this: over long distances you tend to average a slower pace. Intensity of effort more closely matches the lactate threshold for faster swimmers swimming shorter distances in competition.
USRPT as a method attempts to ignore this whole process and just train at perceived race pace. No, that’s not fair. It is less worried about lactate threshold than others, but it still is very conscious of pace.
So my own theory is this – the lactate threshold is specific to race distance and intensity, but for the most part swimming workouts runs between 45 minutes – 2 hour or just over. That means in terms of work out lactate threshold 30 minutes – 40 minutes measurement period is great. That means you guess close to your pace and shoot for that distance in a given period.
Honestly, how often you test is up to you. If you want to do weekly tests, I recommend rotating through 2 or 3 tests with one test per week. You can see progress every three weeks in a particular test. If you aren’t seeing progress, you can reevaluate your method or your madness.
If you are cruising somewhere near 2 minutes + or – 5 seconds per 100. Test sets should probably be 500 to 1000 yards. Odds are you are only swimming 2-3 times a week and only for 30 minutes to 45. If you want to improve your best bet is to swim more often (4-5 days a week). At this pace and slower, consider increasing your swim volume and more specifically getting coaching.
I could make some arbitrary judgements about age at this point saying that 2 minutes per 100 is perfectly alright if you are older than such and such, but I know several septuagenarians that hold faster and I know plenty of people in their thirties that are slower. No such generalizations work.
Once you get past that 2 minute mark, then you can really use test sets.
I recommend for most people the T30. It’s a classic for a reason. Measure the distance you can swim at a slightly uncomfortable pace for 30 minutes. Take the 30 minutes and convert it to seconds – 1800 sec – divide it by distance and multiply this number by 100. The result? This is your pace (in seconds) per 100 yards.
For example: If you swam 1500 yards in half an hour:
1800 sec/ 1500 yards = 6/5 X 100 = 120 seconds or 2 minutes per 100 yards
For say 3000 yards in half an hour
1800 sec/ 3000 yards = 6/10 X 100 = 60 seconds or 1 minute per 100 yards
There are people who are even faster than that.
Importantly, this is really only useful if you are swimming more than 3 times a week for an hour or more. If you are swimming less, use your good sense. Swim a 1000 yard test set or a 500 yard test set. Or two 500 yard test sets and average your results.
Ok, you have your pace per 100 yards, what do you do with it now?
When you pass this pace – your building up lactic acid. When you go this pace your body is “draining” the lactic acid as it builds up. You can now design your work outs to push part of the time beyond this level or even up to VO2 Max (max intensity), and allows you to know that you have to ease it back off to let your body recover. It also gives you a measuring point to chart improvement.