What are some threshold specific workouts for swimming?

While so much of swim speed is predicated on stroke technique and balance, there are also physiological gains that can be made to increase swim speed. Namely, increasing speed at lactate threshold will enable an athlete to swim for longer periods of time at an increased speed. Threshold work specifically teaches the body to both produce less lactate at increased effort, and help to speed the buffering and elimination of accumulated lactate when efforts exceed endurance pace. It is imperative that athletes perform threshold workouts at threshold in order to elicit the desired training adaption. Below you will find three workouts that target adaptations at threshold specifically. Incorporating these workouts into your swim regime will enable you to increase your sustainable swim speed. Workout 1: 2250: warm up: 300.10x50 meters 1 arm swimming. 7x50 kick swim set. 10x100 on race pace (Lactate Threshold Pace) with 20 sec recovery. Cool down: 100. Workout 2: 1600. Warm-up: 300 choice 6x50 (kick/swim) on 20 sec rest. Main Set: 8x100 on 20 sec rest, each 100 should be faster than threshold pace, maintain a consistent stroke count and a consistent 100 meter split between each effort. Cool down: 100 back stroke/ 100 back kick. Workout 3: 3500. Warm up: 400. Main Set: 10x300 on 30 sec rest. Cool Down 200. Workout 4: 2100: warm up: 400 choice. Main Set: 6x100 (50 kick/50 catch up) on 15 second rest. 3x300 build each 100 faster. 30 sec rest. Cool Down: 200 back kick.