Swim Tech Video: the catch phase

Swim for Tri logo

Swim for Tri (www.swimfortri.co.uk) head coach, Dan Bullock, brings us his latest technique advice for swimming. Here, Dan highlights the importance of the catch phase in the front crawl stroke as a key to developing an efficient style.


The Catch

One of the key reasons that a good swimmer has such a low stroke count per length is that there are fewer technical inefficiencies chipping away at their ability to pull themselves through water effectively. The negatives that affect swimmers of lesser ability might include some or all of the following:

  • Poor leg kick mechanics
  • Lack of balanced rotation
  • Poor timing
  • Low body position
  • Short arm pull, early exit and early re-entry of the hand back into the water.

Perhaps the biggest barrier to fast swimming though would be the lack of catch as you will only be able to apply limited propulsion through the stroke. Watching a lot of underwater footage it is easy to see where as much as 40% of the stroke cycle is wasted. That waste still costs you energy and oxygen as you are simply pushing water in a direction that is not propulsive. When some of the other barriers are eliminated and an effective catch is learned, the stroke takes on a languid flowing style. The body starts to make the water work for it rather than being in a continuous fight with it.

A 60% efficient stroke needs to work towards the magic goal of 100% efficiency where the body travels forwards over a locked-in hand and the hand exits in almost the same spot that it entered. This figure is very hard to attain even for the elite swimmers since water is not solid and it will move around the hand as you apply pressure – but it is something to work towards.

Remember to work on your sculling to promote a better feel for the water and stop the hand slipping. The closer you get to this figure you can see how your stroke count will come down as each stroke moves you closer to something in the realm of 1.5 metres or more, rather then 1m or less. Dropping from a modest 26 to 18 strokes per length in a 25m pool i.e. making for a stroke count of 8 less strokes per 25m will result in a saving of nearly:

  • 500 strokes less per 1500m (Standard distance)
  • 1200 strokes less per 3800m (Ironman distance)

As mentioned the lack of catch will not allow you to paddle water backwards so that you move forwards. This is a highly simplistic view of how the stroke works. A little more theory might help illustrate how important good overall stroke mechanics are in order to swim well. The catch is key to set things up and ensure what needs to be done to make the stroke work more effectively but it needs help from the rest of the body!

Many things contribute to a smooth passage of the torso over the hand while swimming:

  • Legs should not be generating any drag, but effectively assisting rotation
  • A lack of lateral sway through the body encouraged by effective hand pathways (under the water or during recovery).
  • An effective hand shape/position
  • Still head position unless turning to breathe

Something that will worry a lot of triathletes is some research done by Jan Prins (1) who suggests that good rotation and a solid leg kick will provide the stable base from which to make better use of your arm pull. You may have read or been lectured on the importance of ‘driving from the hip’ while swimming FC, and how this generates more power through the stroke. Jan is skeptical of this interpretation and after swimming recently, with this in mind I found it a useful insight. Without my leg kick, i.e. when using a pull buoy, I could feel how this weakened my pull and made it harder to set up my catch. When your coach gives you kick sets it is not just that vindictive streak coming through! It will actually help your pull! In several sessions I oversee I noticed a correlation that the stronger kickers were also the faster swimmers. Not conclusive by any means but something to think about!

(1) This was discussed in part by Jan Prins at the Aquatic Research Lab at the UNI of Hawaii. The paper was entitled ‘Swimming Stroke Mechanics: A Biomechanical Viewpoint on the role of the Hips and Trunk in Swimming.’

We have had a lot of success when trying to explain the mechanics of the catch by getting away from the idea of paddling water under the body. Rather we encourage swimmers to try to lock the hand into position and then think about how the body moves over it. With a strong catch, the hand and forearm create a position that enables the body to be launched over it.

The pressure applied through the pull phase is generally increasing so think of the hand movement being from slow to fast. There are additional bursts of acceleration and deceleration of the hand within the overall movement but again lots of sculling practice will help you master those. Don’t apply too much strength at the start of the movement. Water is not solid and if you ‘muscle the movement’ you will have the hand slip under the body with minimal movement of the body over the hand.