The goal for all of the main set swims is to maintain :05/hundred better than your regular hundred interval. In my case, that would be 1:25/hundred. Although you don’t have to do this if you don’t want, my goal was to descend within each round. So, the first 300 was 4:13, the 2nd 4:15, but the last was 4:11. I didn’t quite get that first round of 300s, but the rest I did. It’s a challenge to pace, especially as the distances increase, but it is good practice. The 100 easy is just recovery so that yo can turn around and push the next round.
If you have more time and want to swim more yards, a possible set would be:
Original main set, then drop the slowest interval of each distance (e.g., Set 2: 2 x 300 on 4:30/4:25, 2 x 200 on 3:00/2:55, etc., Set 3: 300 on 4:25, etc.) Keep the 100 easy in between. There will be attrition. It will get harder. That would give you a 4500 main set.
Be sure to adjust the intervals, rounds, and distances to fit your fitness and speed. Honestly, it’s not about doing my workout, but doing what is good for you.
55-minute swim workout, mid distance Wednesday
500 warmup (~7:19 min)
Warmup set (600 yds, 9:20 min)
3 x 150 on 2:20
Main set (2100 yds, 34 min)
3 x 300 on 4:35/4:30/4:25
100 easy on 2:00
3 x 200 on 3:05/3:00/2:55
100 easy on 2:00
3 x 100 on 1:35/1:30/1:25
100 easy on 2:00
Bonus set (100 yds, 2 min)
4 x 25 sprint on :30
100 warm down
Total yards: 3400