Training Fins Create Increased Resistance In The Water. Strengthen Leg Muscles - Added Resistance Increases The Workload On Your Leg Muscles Which Improves Strength And Endurance. Increase Workout Speed - Training Fins Add Extra Propulsion To The Stroke, Which Increases Speed With Minimum Effort Leaving You Free To Ingrain Correct Technique. Develop Ankle Mobility - The Increased Surface Created By The Training Fins Forces Ankle Extension During Kicking, Which Makes The Kick More Propulsive And Efficient.