One of the biggest mistakes made when swimming is not using the hip to provide thrust. Most novice swimmers will kick from the knee, which is a shorter lever than the entire leg and gets significantly less thrust. Instead, think about the entire hip moving up and down. This will produce more downward force, which moves you forward more with each kick.
How to Correct
First, make sure your hip flexors and hip joint have good mobility. If not, it will put more stress on your lower back. Having good hip mobility is key to gaining the strength necessary to endure a good swim session. Second, you must have sufficient rotary core strength—without it, you lose energy transfer, and you move less with each kick. Exercises that help with this are bird dogs and supine trunk rotations.
Pool Drill: 500m Kick Focused Repeats
Once warmed up, do 200m of freestyle, followed by 200m of backstroke. Both of these require a good kick to generate forward momentum. Then do 100m with the kickboard, making sure not to make any big splashes—think about kicking from the hip rather than the knee (your feet should stay just under the surface of the water). Allow your arms to reach out as far in front as possible while resting on the kickboard. You should notice slight trunk rotations with each reciprocal kick. Start with big, powerful kicks for 50m and progress to quick, shallow kicks that generate forward momentum for the last 50m. Repeat this cycle three to five times for a 1,500-2,500m session.
Dr. Chris Ingstad is a physical therapist, educator, author, and co-founder of Level4 Physio-Wellness-Performance in Encinitas, California. He is also an avid cyclist and triathlete.