In preparing for IM, there is one swim set that I just love to use as a benchmark of how my (and other athlete’s) swim speed potential and durability are coming along. Its also a great indicator of what your swim time will be in IM.
On a separate day, do an 800 time trial to determine your base interval for the monster set. Once you have this, you set up the workout as follows:
This example is for someone who swam 10:40 for the 800TT. Based on that pace, the base interval for the monster set will be 800TT pace plus 10 seconds per 100. So, 1:30 per 100.
1000 pull on 15:00 easy
9×100 on 1:30 at sustainable best effort
4×200 with paddles on 3:00 at sustainable best effort
7×100 on 1:30 at sustainable best effort
600 pull on 9:00 easy
5×100 on 1:30 at sustainable best effort
2×200 with paddles on 3:00 at sustainable best effort
All of this should be completed continuously on a 1:30 base (800TT pace + 10 seconds). What you will find is that the average pace you can hold for the 100s and 200s is very close to what your IM swim pace will be with a wetsuit. For example, if you average 1:22 pace for the 100s and 200s, you can expect to swim: 42.5 x 1:22 = 58:05 in IM.
Try it out!