Honing your swimming skills: constrain to gain!

Andrew Sheaff explains the ‘constraints-led’ approach to improving swimming skill and stroke technique, and how you can use it for faster times in the water

s a swimmer looking to improve, and now as a coach working with national level swimmers, I have always had an obsession with improving swimming skill. Beyond my personal fascination, this search has been utilitarian in nature. To a much greater extent than other endurance sports, the technical aspect of swimming is the ultimate determinant of performance - as I am sure any novice swimmer can attest! Discovering the best ways to enhance skill acquisition therefore give swimmers a big competitive advantage.

As a competitive swimmer, I was always looking for and experimenting with traditional swimming drills to varying degrees of success. While I got better at the drills, it didn’t really result in what mattered most - faster swimming. It was only during my transition from my swimming career to coaching that I discovered a different way of learning and acquiring skills, which is the constraints-led approach^{M1. Dynamics of Skill Acquisition: A Constraints-Led Approach. Davids and Bennett. Routledge, 2007 Motor Learning in Practice: A Constraints-Led Approach. Renshaw, Davids, Savelsbergh. Human Kinetics, 2010}.

The constraints-led approach is founded on the idea that skilled performance emerges from the interaction of different constraints on performance. These constraints take three primary forms: task, individual, and environmental constraints.

To get a sense of what these different constraints look like in swimming, take a look at table 1. Let’s breakdown each section to better understand the difference between task, individual, and environmental constraints, as well as how they influence performance.

TABLE 1 CONSTRAINTS IN SWIMMING

Task	Individual	Environmental
Velocity Stroke length Stroke frequency Repetition distance Stroke discipline Recovery interval Total volume	HeightAge Gender Level of expertise Specialty Sprint swimmer Distance swimmer Triathlete Strength Flexibility Distribution of mass Anthropometry (body size, shape etc)	Physical characteristics of water Competition course Short course Long course Open water Water temperature

When considering the sport of swimming, velocity is a task constraint. In all strokes, swimmers change their coordination pattern to meet the demands of increasing speed^{J Sports Sci. 2007 Jan 15;25(2):131-41 Int J Sports Med. 2007 Feb;28(2):140-7 Hum Mov Sci. 2010 Feb;29(1):103-13 Hum Mov Sci. 2008 Feb;27(1):96-111}. Take freestyle for example, where swimmers move towards a stroke rhythm characterised by continuous propulsion as velocity increases^{J Sports Sci. 2004 Jul;22(7):651-60}. To illustrate, reflect on your own experience. As you start to build your speed, you shift from a long smooth stroke to a stroke where you are trying to create propulsion continuously. The stroke frequency becomes higher, and there is no longer any gliding or wasted motion.

At the individual level, age, strength, limb lengths, expertise, and specialty (sprint, distance, triathlon etc) can all significantly impact skill and performance. For instance, a fully-grown adult is going to use different stroking strategies than a pre-adolescent^{Eur J Appl Physiol. 2004 Oct;93(1-2):65-74}. Likewise, that strapping 1.90m tall 22-year-old is probably going to have different stroke technique than the 1.65m tall 45-year-old.

Fortunately, the environment is relatively stable in pool swimming, but I am sure any triathlete can recall the effects of really cold or really warm water temperature on performance! Similarly, anyone who has made the transition from the pool to open water knows that is a whole different game.

Importantly, these constraints interact at different levels. Fatigue is going to hit the 100kg sprint swimmer a lot harder in an open-water race environment than it will the 60kg distance swimmer. Clearly, constraints act on our technical skill in many ways. The bottom line is there is no universal idealised technical model in swimming. How we swim is the result of who we are (individual), what we’re trying to accomplish (task), and where we’re trying to do it (environment).

Fortunately, these effects tend to be rather intuitive, and we can use our understanding of different constraints to influence performance. As we’ll see below, we can also apply or manipulate constraints to allow for new skilled patterns to emerge.

Applying the framework

Now that we have an understanding of what the constraints-led approach is, and how it affects our expression of skill, let’s look at how to use it to improve performance. When applying this framework to enhance learning, it is important to consider how it differs from traditional motor learning, where the focus is on breaking down skills into requisite parts. The constraints-led approach differs in that it seeks to retain full movement patterns as much as possible, while shifting performance by changing the constraints. As demonstrated above in the freestyle swimming velocity example, a simple shift in task or individual constraints can greatly change the nature of skill performance. With this knowledge in hand, we can then manipulate these constraints to put ourselves in situations where we have to learn new skills. We’ll explore just how to do so in the following section.

Task master

The simplest and most effective way to utilise this approach is by manipulating tasks. Before we do so, let’s take a quick detour to look at what produces fast swimming. Velocity when swimming is determined by the relationship between your stroke length and stroke frequency. See box 1 for a primer on how swimming speed is generated. As you can see, several combinations of varying stroke length and frequency can result in faster swimming. However, it is stroke length, NOT stroke frequency, that has consistently been demonstrated to distinguish the best swimmers^{Can J Sport Sci. 1992 Jun;17(2):104-9 Med Sci Sports. 1979 Fall;11(3):278-83 Med Sci Sports Exerc. 1985 Dec;17(6):625-34}. Studies show that stroke frequency tends to be similar across varying levels of expertise. Further, taking fewer strokes for a given velocity reduces the energy cost of swimming per metre covered^{J Sci Med Sport. 2010 Mar;13(2):262-9}. Those are two huge benefits for swimmers of all types!

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BOX 1: DETERMINANTS OF SWIMMING VELOCITY

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So, for aspiring swimmers, improving stroke length is of critical importance and stroke length is what all technique drills are aiming to improve, albeit indirectly. However, if you can directly improve your stroke length, you can become a more efficient swimmer more rapidly, and over time, a faster one. Here’s where the constraints-led approach comes in.

By applying task constraints to your swimming sets in the form of ‘stroke-count’ goals, we are forced to experiment with different ways to swim, which can lead to faster and more efficient swimming. By limiting your stroke count (number of strokes required to cover a set distance), you are requiring yourself to lengthen your stroke and to find more efficient ways to swim. It is not only important to reduce your stroke count over time, but also to learn how to choose your stroke count ahead of time. That skill ensures you have control over your swimming stroke.

Going long

While it’s almost impossible for the average swimmer to measure their stroke length with any sort of precision or accuracy, they can use a surrogate marker, which is stroke count per lap. This allows any swimmer to start to measure and monitor this critical variable. It is important to keep in mind that a lower stroke count indicates a longer stroke length. So when working on developing stroke length in the pool, your metric will be stroke count. Over time, you want to see your stroke count per lap/ length decrease, indicating an increase in your stroke length. Take a look at box 2 for some sample sets to get you started with manipulating your stroke counts. Feel free to adjust the volumes up or down based upon your current training regimen.

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BOX 2: SAMPLE STROKE-COUNT SETS

4 x 50 metres (m) with 15-30 seconds rest. Reduce the number of strokes you take during each 50m swim.
*Repeat the set 4 times*

10 x 100m with 15-30 seconds rest. During odd laps, take 1 less stroke each 25m. During even repetitions, take 1 more stroke each 25m.

10 x 75m with 30 seconds rest During odd repetitions, use your normal stroke count per 25m. During even repetitions, take 2 less strokes per 25m.

3 x 50m with 15-30 seconds rest; taking as few strokes as possible. 250m with 30-60 seconds rest; maintain the same low stroke count for the entire 250m.
*Repeat the whole set 4 times*

Notes: All sets are designed with the assumption that you are swimming in a short course (25m) pool. A skilled swimmer can not only reduce their stroke count, they can shift their stroke count on demand. These sets work on managing a ‘shift task’ constraint, where you have learn to effectively shift your stroke count. Work to determine the most effective strategies for reducing stroke counts and how it feels.

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Adding speed

As in all endurance sports, knowing your velocity is hugely important for swimmers. But like stroke length, it’s tough to directly measure velocity in the pool. However, as training distances are constant, knowing our lap times provides us with information about our velocity. Once you’ve become comfortable measuring, controlling, and improving your stroke counts, it’s time to take it to the next level by adding a second constraint - time. In competition, speed is what we’re after and learning to find that speed efficiently is the ultimate goal. By constraining both stroke length and velocity, you’ll get immediate feedback as to how well you’re doing. As you can see in box 3, there are multiple ways to manipulate stroke length and velocity to create novel learning experiences.

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BOX 3: SETS COMBINING SPEED AND STROKE COUNT

4 x 75m with 30 seconds rest. Choose one stroke count for the set and learn to decrease the time for each 75m swim without changing the stroke count.
*Repeat the set 4 times*

5 x 200m with 45 seconds rest. Swim the 2nd 100m of each 200m faster than the 1st 100m while keeping the same stroke count throughout.

4 x 50m with 30 seconds rest. 4 x 50m with 30 seconds rest. 4 x 50m with 30 seconds rest. For each group of 4 x 50m swims, choose a goal time. Within each group of 4 x 50m, reduce your stroke count each 50m swim while still achieving your goal time. For each successive grouping, reduce the goal time by 1 second.
*Repeat the whole set 2-3 times*

4 x 25m with 20 seconds rest. 4 x 50m with 30 seconds rest. 4 x 75m with 40 seconds rest. 4 x 100m with 50 seconds rest. For each repetition, add the number of strokes you took and the total time. For example, if you took 30 strokes for 50m and it took 30 seconds, your score is 60. Work to get this number as low as possible.

Notes: These sets are all about trade-offs. You are always striving to keep the times and stroke counts as low as possible.

WARNING! If you’ve been achieving reduced stroke counts with excessive gliding and kicking, placing time constraints is going to force you to find new solutions! You can use these constraints for any swimming set you do, always looking for ways to improve your numbers. These tasks constraints limit your movement opportunities and force your brain and muscles to figure out how to swim more effectively.

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Self improvement

We’ve examined how manipulating task constraints can result in big opportunities to learn new skills. But how can you manipulate yourself? One of the easiest and most effective ways to manipulate individual constraints is by changing the surface area available for propulsion.

We’ve examined how manipulating task constraints can result in big opportunities to learn new skills. But how can you manipulate yourself? One of the easiest and most effective ways to manipulate individual constraints is by changing the surface area available for propulsion. Research has demonstrated that the use of hand paddles improves stroke length and swimming economy, and bigger paddles have a more dramatic effect on the propulsive contribution of the hand^{J Hum Kinet. 2012 Oct;34:112-8 J Sports Sci. 2013;31(9):1015-23 J Sports Med Phys Fitness. 2006 Jun;46(2):232-7}. However, research has also demonstrated that the forearm is a critical contributor to propulsive efforts^{J Biomech. 2006;39(7):1239-48. J Biomech. 2005 Oct;38(10):1984-90 J Appl Biomech. 2011 Feb;27(1):74-80}. In spite of this finding, many swimmers fail to adequately use the forearm effectively, and this can result in the use of a technique known as pulling with a dropped elbow.

With this in mind, we want to take the opposite approach and actually reduce our hand size to force the forearm to contribute to propulsion. This can be accomplished by swimming with a tennis ball or other similar objects in hand, as well as by swimming while using the hand postures depicted in figures 1-3. By more effectively using your forearms to create propulsion, you’ll be increasing your propulsive efficiency, which another important stroking parameter that directly improves performance^{J Sci Med Sport. 2010 Mar;13(2):262-9}. As an added benefit, your will hands feel like the size of dinner plates when you open them back up!

Manipulating your hand size can be done during any set, and it works really well to combine this individual constraint with the task constraints described above. Without the use of your hands, you have to be ruthlessly efficient with each stroke to accomplish the task goals. The sets described in boxes 2 and 3 are perfect for this purpose. You can either perform the entire set with the hand posture of your choice, or alternate repetitions or rounds with different hand postures.

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FIGURES 1-3: CONSTRAINING HAND POSTURES TO IMPROVE FOREARM PROPULSION

Drills can be useful for providing awareness of how to improve your stroke length or speed, but they don’t accomplish this task by themselves

FIGURE 4: TENNIS BALL GASP AS A HAND CONSTRAINT

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To drill or not to drill?

Traditional swimming drills can still play a part in the skill acquisition process, as they can help you to get a feel for certain aspects of your stroke. However, you need to get back to full swimming as soon as possible to make sure you are working on integrating your skills into the whole stroke, paying attention to speed and stroke count. Improvements in drilling skill don’t matter if you can’t transfer it to fast and efficient swimming performance.

Drills can be useful for providing awareness of how to improve your stroke length or speed, but they don’t accomplish this task by themselves. By applying constraints to your swimming, you not only create relevant technical challenges, you also have the ability evaluate your progress. You can use the sensations and kinesthetic information from the drills and then apply them to stroke-length sets to aid in skill transfer. Some ideas about how to combine traditional drills with the use of constraints are included in box 4.

If you do choose to include drills, use drills that retain as much of the full stroke as possible. As an example, take a swimmer choosing to do one-arm freestyle to improve their pulling pattern, one arm at a time. While this may allow for more focus for the targeted arm, many of the important rhythm and timing skills of freestyle are not included. Using the constraint-led approach to address the same problem, you can swim full stroke with a tennis ball in one hand. This puts a huge challenge on the constrained arm to create the same amount of propulsion as the unconstrained arm, while still retaining all of the important characteristics of freestyle swimming. So, whenever you’re considering a drill, ask yourself how well the drill retains full stroke characteristics, as well as how can you improve it, if necessary.

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BOX 4: INTEGRATING TRADITIONAL DRILLS

Option 1: Integrating drills with constraint sets

4 x 25m choice stroke drill with 15 seconds rest. 4 x 100m with 30 seconds rest. Odd repetitions - as few strokes as possible. Even repetitions- as fast as possible while taking 2 more strokes per 25m than the odd repetitions. *Repeat the set 4 times*

Option 2: Drills during warm up

8 x 50m with 30 seconds rest; choice of stroke drill. 4 x 75m with 30 seconds rest; 3 less strokes per 75m. 2 x 150m with 30 seconds rest; the 2nd 150m repetition is faster at the same stroke count. 3 x 100m with 30 seconds rest; 1 less stroke per 25m. 300m; each 100m is faster at the same stroke count.

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CASE STUDY Constraints-led approach in a breaststroke swimmer

My experience with Chris is a great example of the utility the constraints-led approach. When Chris came to me as a university student, he had had success at the Junior National level in the breaststroke events. However, he was achieving his performances with excellent stroke frequency and less than excellent stroke length. As stroke length is strongly related to performance in breaststroke^{Sports Biomech. 2004 Jan;3(1):15-27}, we knew where we had to place our focus.

Chris’ training diet consisted of heavy doses of breaststroke swimming with reduced stroke counts. Over time, we added velocity constraints to make sure that he was learning to achieve these stroke counts at velocities that were relevant to his racing speeds. With progress, he was able to develop the technical skill and physical conditioning to improve his stroke length while retaining his stroke frequency.

To supplement this focus on stroke length and velocity, we incorporated technical training exercises to address his technical issues. Chris was really high with his breathing action, so he performed a lot of breaststroke where he would restrict his breathing to stay low in the water. This approach allowed for the retention of the full stroke timing and rhythm (instead of breaking his stroke into parts), while helping him learn to feel and maintain a lower breathing position.

Resistance training in the water has also been demonstrated to improve force application^{J Strength Cond Res. 2011 Oct;25(10):2681-90} and we used this approach to enhance both his pulling and kicking actions. Relevant to this article, resistance acts as a constraint to forward motion; swimmers have to be more effective in applying force to overcome this added resistance. To further improve his arm propulsion, he often swam with tennis balls as well.

Whether he was swimming with resistance, reducing his breathing, or using tennis balls, we added stroke length and velocity constraints to further reinforce the need to improve speed at longer stroke lengths. The results? Chris managed to make the United States Olympic trials, and he gained a 1-second PB over 100 yards for two consecutive years. This was accomplished with very little traditional technical work, instead consistently manipulating the key constraints that were affecting his performance.

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Conclusion

Hopefully this article has provided you with some new ways to view the skill acquisition process. By placing constraints on your performance, you must learn to move in new ways to satisfy these constraints, and accomplish the task goals. When you focus on the right tasks, performance improvement is inevitable.

Key points to remember

• *Know your numbers. By consistently being aware of your stroke count and your speed, you’ll find these numbers start to improve. As those parameters are directly linked to performance, good things will happen.
• *Use drills to develop to an awareness of new ways to move, and then quickly move back to full stroke swimming.
• *Drills that retain as many characteristics of the full stroke as possible will more easily transfer to full swimming.
• *Focus on the bottom line. When making any technical change or evaluating training progress, evaluate whether stroke count and speed are improving. If not, the change might not be a positive one. If so, you’re on the right track!