Workout of the Week: Swim Threshold Work

Threshold training isn’t just for cycling. Figure out your swim threshold speed and use it in this workout.

Underwater shot of a woman swimming laps
Photo: Lund

What’s probably the most commonly used term across all endurance sport communities? Threshold. The maximum speed your body can sustain at a particular intensity. Similar to cycling and running, threshold swimming is training at a pace that will improve your lactate threshold speed and therefore increase your speed when swimming longer distances (anything over 400m/yds).  

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For the most effective swim threshold training, it’s important to establish key data points prior to starting. First, determine your Critical Swim Speed (CSS) for 200m/yds AND 400m/yds. You may need to time trial these distances if you don’t have benchmark times for each. If you choose to time trial these distances, make sure to do them within the same session and include a 5- to 10-minute active recovery between each distance.  

Once the times for these distances have been determined, plug them into a CSS calculator to figure out your 100m/yds Critical Swim Speed. This CSS speed will be your threshold pace time for training.  

Finally, when training swim threshold it’s important to familiarize yourself with the on-deck pace clock and track them during breaths as you swim. Most pools have pace clocks, but if not, a water-resistant or waterproof watch will suffice.  

Remember to listen to your body and adjust the intensity and volume based on your fitness level. It’s important to have a good understanding of your personal fitness level when participating in swim threshold workouts. 

Workout of the Week: Swim Threshold Work | 2,500m/yds 


200 swim  
200 kick 
200 pull with a buoy 

4 × 50 kick with board, building every set 
4 × 50 swim as 25 easy/25 fast 

Main set 

4 × 100 @ CSS/threshold  
15-30 sec. rest between each 100 

2 × 200 @ CSS/threshold 
15-30 sec. rest between each 200 

4 × 100 @ CSS/threshold (same pace as first set of 100s) 
15-30 sec. rest between each 100 


100 freestyle easy  
100 backstroke easy 
100 freestyle easy