After stroke technique, the next most important thing to improving your triathlon swim speed is understanding swim threshold pace (STP). You can swim hundreds of thousands of yards each month and if you don’t understand swim threshold pace, those training yards may not have been as effective as they could have been – and they may have been wasted time altogether. On race day, without an understanding of swim threshold pace, you will likely be swimming to fast – leading to lactic acidosis with the obvious negative effect; or swimming too slow – with the equally obvious negative effect.
So what is swim threshold pace?
While this is not an article about human energy pathways or metabolism, we do need to look at some basic theories in order to understand swim threshold pace.
Most athletes are familiar with the idea of a physiological point above which exercise performance becomes limited. Several terms have been used to describe this point:
- Lactate threshold
- Anaerobic threshold
- Aerobic threshold
- Onset of blood lactate accumulation (OBLA)
- Maximal lactate steady state
Although these terms are used interchangeably, they do not describe the same thing. Of interest to distance swimmers, including triathletes racing any length triathlon, is the concept of Maximal Lactate Steady State (MLSS).
Maximal Lactate Steady State – The exercise intensity at which maximal lactate clearance is equal to maximal lactate production.
Above MLSS, lactate begins to accumulate at the cellular level. Below MLSS, the body is able to clear lactate.
A common misconception is that blood lactate or lactic acid, has an adverse effect on muscle performance. Research has shown however that any negative effect on performance associated with blood lactate accumulation is due to an increase in hydrogen ions. When lactic acid dissociates it forms lactate and hydrogen ions – which leads to an increase in acidity. The increase in hydrogen ions and subsequent acidity of the internal environment is called acidosis. This unfavorable acidosis is the result of an increased concentration or accumulation of hydrogen ions.
Swim threshold pace is the pace you swim while at your maximal lactate steady state.
If you swim above this pace (faster) you will quickly go into lactate acidosis and you either need to slow down or your body will force you to slow down.
If you swim below this pace (slower) you are not swimming to your full potential.
When you’re swimming at your swim threshold pace you are theoretically swimming at the maximum pace that you can sustain indefinitely.
Swim threshold pace becomes a very effective guide to setting race pace. For example:
Beyond setting race pace however, STP has a very important role in training. If you can increase your swim threshold pace, or the pace you swim while at your maximal lactate steady state, your race speed will improve.
Remember what you are training for. Your ability to sprint or work anaerobically above MLSS is irrelevant in distance swimming and triathlon. Yet many triathletes continue to train with swim teams or masters swim teams above MLSS – they get in the water and crush set after anaerobic swim set. In the process, they do absolutely nothing towards raising their swim threshold pace.
The secret to raising your STP is to train at or just slightly below your current STP.
For most swimmers, changing to STP sets will probably mean more total distance, shorter repetitions, and less recovery time. You will likely find STP sets to be relatively easy at first. Stick with it and you will be feeling the training effect of training at threshold pace by the end of the set. The desire will be there to go faster than your swim threshold pace. Don’t bow to the temptation! By controlling your pace you develop the ability to accurately swim at a specific pace.
If you are unable to maintain your swim threshold pace it is preferable to slow down slightly rather than take a longer rest interval. You should feel like you are working very hard in the later part of the set.
How to determine swim threshold pace
We recommend you reset your swim threshold pace every 6-8 weeks during active training.
