First, Happy Imbolc, the Celtic first day of spring, more commonly known as St. Brigit’s Day and also known as Candlemas.

Pool and marathon swimmers use intervals to train. One of the regular misconceptions we come across is the belief that our training involves lots of slogging up and down the pool whereas we train the same as normal pool swimmers using intervals as the basis for everything.

So, how do you work out your intervals? well, one way is experience, I know the times to within seconds that I want to hit depending on what I want heart rate or perceived effort I want to exert and recall I posted a chart of heart rate last year. But in the absence of that experience, you can use an interval calculation chart.

But first we need to go back a bit. USMS posted a nice fitness pace chart, useful for calculating estimated times from a 100 metre (or yard) time to help establish pace from a known short distance time.

I’ll loosely define Cruise Speed as the speed you can maintain, with a few seconds left over at the end of each repetition.

On the first table, say your 100m Cruise Speed is 1:45. You will have 5 to 15 secs left over. If you have more than 15 secs your cruise speed is probably 1:40 or 1:35. If you have less than 5 secs left over, your cruise speed is 1:50.

Look at the 1:45 row. So for 200 metres, your pace means you should finish within 3:30. For 400m, it 7:00…and so on. A 1:45 swimmer should be able to do 3,425 metres in an hour, cruising.

(This table does not tell you what your time is, you should determine that yourself.)

USMS Fitness Pace Chart

But for actual interval training you need a bit more. A couple of years back I took an older interval chart and put all the times into a spreadsheet to make it more usable, it’s below.

Measure your Personal Best for a distance (e.g. 100m) and let’s say it is 1:45. Look at this figure in the leftmost column. Now look along the row to the right. This means that your 85% (Moderate) repeat is 2:08 to 2:15. which should include a few seconds rest before the next repetition (100m).

Put this together with the heart rate Zone training chart and you have the basis for building swim sets according to requirement, whether speed, endurance or weight reduction.

Edit: I should make clear, this is an introduction to interval. Therw is more the subject than this, particularly session planning.