Ankle flexibility gets a lot of attention when it comes to kicking faster.
Whether it is freestyle or dolphin kicking.
The reasoning makes a lot of good reasons:
- More flexible ankles give swimmers the ability to move more water with each kick.
- They reduce dependency on the knee to position the feet (less knee bend)
- And they cut down on drag, because you can displace more water in a tighter window.
But does that mean ballerina-level ankle flexibility is required to kick (and swim) fast?
Does Increasing Ankle Flexibility Boost Dolphin Kick Speed?
A study (Kuhn and Legerlotz, 2022) took a group of swimmers and tested out how range of motion in the ankles impact dolphin kicking speed.
The swimmers kicked:
- With restricted plantar flexion. Tape was wrapped around the foot to keep the toes from pointing, leading to a 7% drop in kick speed. The “water is wet” finding.
- Normally. To set a baseline.
- With increased flexibility. Swimmers did a series of passive and dynamic stretches to open up the ankles’ range of motion right before the kick trial.
That sudden burst of added range of motion didn’t meaningfully increase kick speed.
Huh.
Reducing ankle flexibility made things worse. To be expected. But adding more ankle ROM didn’t lead to more speed.
Which may not make a lot of sense.
Pair Ankle Strength and Ankle Flexibility
Understanding why a burst of new ankle flexibility won’t always lead to more kicking speed starts with understanding what the ankles do in the kick.
The ankles position the feet, and the feet are essentially paddles for your legs. And just like the paddles on your arms that create all of that propulsion in the pull, the feet need to be able to position themselves and push against the water to displace it.
Suddenly adding a bunch more range of motion to your feet isn’t a guarantee of more kicking speed because:
a) Your feet and body aren’t used to the mechanics of this new range of motion
b) Your feet don’t have the strength, control and coordination developed from actually training in that range
In the same way that swimming with wrists and forearms that don’t flex the hand in place means your pull loses power, that new range in the feet lacks the strength and stability to capitalize on its new larger range of movement.
Swimmers should prioritize exercises that also strengthen the ankles and feet, including:
- Jump rope – Jumping rope is pound-for-pound one of the best dryland exercises for swimmers. Strengthens the stabilizers around the foot, improves ankle control, balance, and motor control of the lower limbs (Treroci et al., 2015).
- Calf raises – The calves are what position your feet and give them the “stiffness” to displace more water. Start with two-foot standing calf raises, progress to loaded single-foot raises.
- Toe raises – The tibialis anterior (shin muscle) is busy especially during the dolphin kick. Leaning with your back against the wall, raise the toes while keeping the heel on the ground.
Adding ankle strengthening exercises alongside your ankle stretching gives you usable range that leads to faster kicking (Willems et al., 2014).
Wrapping Things Up
The main takeaway isn’t that more ankle flexibility is necessarily bad. Swimmers with really stiff ankles should definitely work on them just for the drag reduction benefit alone.
So go ahead and do those ankle rockers, calf stretches, ankle circles, and other ankle mobility drills.
Just make sure you are pairing them with strength (calf extensions, toe raises, building the hips, etc.) so you can kick with more control and power in that new range, too.
The goal isn’t building floppy feet.
But feet that can get into position quickly, firmly, and give your personal best times the business.
Happy kicking!
