I raise the issue of ankle flexibility because it’s important in kicking and I’m weak in this area, but the entire issue of flexibility is one of the major ways in which swimming differs from other sports. For most sports ankle flexibility is an oft-ignored topic because, generally speaking, you don’t want a lot of ankle flexibility. Understandable given an excessive amount of lateral movement will lead to a sprain. But vertical ankle flexibility, the ability to flex the ankle towards the shin (known as dorsiflexion) allows an athlete to push his or her knee farther over the ankle. The resulting lower centre of gravity along with a relatively vertical torso provides a stronger foundation to deliver and receive blows, accelerate and decelerate, and change direction. So that’s very desirable. Anybody familiar with having their ankle taped will recognize the taping is done in such a way so as to stabilize the joint while still permitting the ankle to flex up and down. Consequently the few ankle stretches in use all concentrate on this type of flexibility.
When swimming, however, the opposite flex is desired. For an efficient swimming kick you need to point your toes by flexing ankle away from the shin. I’m guessing this is called ventriflexion, the opposite of dorsiflexion, but apparently the term is so esoteric I can’t find a dictionary which will confirm my hunch. The best comparable example of this type of ankle flexibility is ballet’s pointé. Apparently the highest caliber swimmers can get
their toes almost to the ground when sitting down with their legs outstretched flat, either by natural ability or by training. This ability to point the toes is important because a kick’s mechanics mean the lower leg travels in an arc moving both backwards and downwards. A foot which continues the leg or, even better arcs backwards, will maximize the backwards force of the kick, thus directly contributing to forward propulsion (big feet help too). This is why swimming with fins works so well, because the flexibility and surface area of the fin maximizes rearward thrust. As the foot returns from maximum ventriflexion towards its normal position at a right angle to the leg the possible amount of backwards force which can be generated from the kick rapidly declines until, in certain cases, the foot can actually create a net forward thrust from the lower part of the kick’s arc. This can result in the kicker literally moving backwards, something which is seen from time to time, especially in long time runners or people with very poor ankle flexibility.
What to do to improve your ankle flexibility for swimming? Well, beyond using flippers when kicking there’s not much out there. Coach Brad recommends the “Sitting” stretch where one kneels on the floor with feet behind and then sits down on the heels to compress the ankles. Apparently ‘Doc’ Councilman of Indiana University had his swimmers use a simple device developed for the school’s gymnastic team which is available by mail order for a reasonable cost. Ballet dancers use what is referred to as a ‘Theraband’, a rubberized elastic sock which the foot is placed into and held in position while the foot is pointed against the resistance. I suspect though this device is primarily intended to strengthen the ankle, the bête noir of ballet dancers, rather than increase the ankle’s flexibility. I’m simply pointing my feet for a few seconds every once and awhile as I sit at my desk. I would think pretty well anything will work; the key is to know the ability to flex your foot downwards will make for a greatly improved kick and taking it from there.