Friday, July 3, 2015

Glide Is A Dirty Word

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This week's post is a re-visit of our popular (and detailed) 2012 blog Overgliding, Inefficiency And The Overgliderometer :

Glide Is A Dirty Word

Many well meaning swimmers and coaches talk about the benefit of 'gliding' through the water when swimming but have you ever thought what it actually means to glide?

A strict definition of gliding is to consider the time between one arm finishing a stroke finishing at the rear and the next commencing the catch at the front:

This gap between strokes is the true 'glide time' when there is no propulsion from either arm and you are truly gliding through the water.

Elite Glide Time

The interesting thing is that many elite swimmers look like they're gliding when they swim but what actually is their gap between strokes? The answer may surprise you. If we study footage frame by frame of greats such as Ian Thorpe, Rebecca Adlington, Michael Phelps, Katie Ledecky, Alex Popov and Sun Yang, the gap between their strokes is remarkably similar: between 0.10 and 0.20 seconds (see examples here and here).

1 to 2 tenths of a second is literally less than a blink of an eye and goes to show that although these great swimmers appear to be glide down the pool this is actually an illusion brought about by the smoothness of their strokes.

Your Glide Time

So what does it feel like to swim with a 'glide time' of 0.1 to 0.2 seconds? When you swim with this timing you are hardly aware of any gap between your strokes - it feels like you are stroking smoothly and continuously from one stroke to the next without any perceptible pause at the front.

If you have added a deliberate pause-and-glide into your stroke then it's likely the gap between your strokes is at least 0.4 to 0.5 seconds:

Classic Overglider: Glide time 0.45 sec, swimming speed speed 1:42 /100m
This gap is now long enough for large inefficiencies to be developing as you start to decelerate and sink deeper into the water (creating additional drag) between strokes.

If you've tried to *really* emphasise a glide in your timing then your gap between strokes may be as long as 0.7 to 1.2 seconds (we define anything over 0.7 seconds as extreme Overgliding). Now the stroke is becoming so inefficient it's unlikely you can swim more than a few lengths without feeling exhausted and having to stop for rest:

Extreme Overglider: Glide time 0.84 sec, speed 2:56 /100m
Notice how this swimmer has sunk completely beneath the surface creating huge amounts of drag and making finding the surface to breathe extremely challenging.

Getting Very Geeky

If (like us) you love your numbers and data then you will be interested in the chart we've plotted below. This is the data from 75 swimmers of all ability levels from beginner level to Olympic champions. It includes most of the famous swimming demonstration clips on Youtube.

We plotted each swimmer's speed versus their glide time:

The remarkable thing about this data is the strength of the relationship between glide and speed. The longer the gap between strokes, the slower and less efficient the swimmer is.

Of course the real clincher for our argument against actively gliding is the circled region:

In that area would be swimmers travelling quickly and efficiently but with a significant glide in their strokes. But there aren't any. None. These swimmers simply don't exist.

Glide Is A Dirty Word?

When we wrote the Swim Types website in 2010, we described 'Glide As A Dirty Word'. Perhaps unsurprisingly we copped a bit of flack from old-school swim coaches for making that statement but perceptions in the swimming world have shifted hugely over the last five years and now our argument stands largely unchallenged.

Glide is a term that has been used by well meaning swim coaches since the 1980s to encourage swimmers to lengthen out their strokes. However the reality is that when asked to glide down the pool swimmers overly lengthen their strokes by adding an intentional pause-and-glide at the front.

As we have seen this dead-spot is very inefficient and once ingrained it is very hard to remove from the stroke timing. It also causes other significant flaws in the stroke to develop:

- Putting on the brakes

- The overglider kickstart

Far better that we explain to swimmers that the goal isn't to make the stroke as long as possible (elite swimmers don't). And better to avoid the word 'glide' because it too easily introduces a deliberate pause. Let's talk about 'range' or 'extension' in the stroke but not 'glide' - swimmers will be much much better off for it.

Swim Smooth!

[After the original blog a few fellow swim geeks asked us why we plotted the data against glide time, not percentage of the stroke cycle. Time is a more meaningful analysis because deceleration (and so the impact on speed/efficiency) is dv/dt not dv/d-cycle.]


David Mitchell said...

I was developing a glide in my stroke several years ago - I was trying to "improve my efficiency". Luckily, I stumbled across Swim Smooth on the internet. I have now eliminated the glide. Thanks Swim Smooth! By the way, I am 194 cm tall, 53 years old and swim 1:40 per 100 m over distances of 1.5 to 2 km. My stroke rate is only 36 strokes per minute. Unfortunately, I can't turn my arms over any faster. I just don't seem to be able to push backwards fast enough during the stroke - my arms are too scrawny! In any case, I am swimming to maintain my fitness, not to compete.

Greg Williams said...

Never thought I'd see calculus in a swimsmooth blog post - love it!

Greg (a fellow geek)

Anonymous said...

I would imagine that adding a glide could only be of benefit at the longer distances, but your graph is in terms of 100 meters. Wouldn't the analysis be more convincing if you showed data in terms of time over a longer distance, say 500, 1000, or 1500 meters?

Adam Young said...

Thanks guys!

Hi Anonymous - this is the pace per 100m but does not mean they are only swimming 100m! It includes people swimming at steady pace over longer distances such as 400 and 1500m. In fact most of the datapoints are from longer swims.

It may seem counter-intuitive but it tends to be the 200m guys who have the longest glide times as they have an extremely powerful kick to push them through the gap in arm propulsion. Once you're out to 800m and beyond the glide times tend to reduce down to 0.1 or even zero seconds as they cannot sustain the powerful kick and so need to keep the arm propulsion more continuous.

HTH, Adam

Paul said...

I'm definitely an overglider and trying to reduce this by increasing my stroke rate through the tempo trainer. However, even just raising from my current rate of 47 spm to 50spm is proving very difficult. Any advice on how to gets the arms moving faster?

Adam Young said...

Hi Paul, yes it's all about developing your catch technique. When you 'learn to glide' nearly all overgliders harm their catch technique because a poor catch slows the stroke at the front. Improving catch technique nearly always reduces the time the catch takes and starts to lift the stroke rate.

Well worth checking out:


Paul said...

Thanks Adam...

Anonymous said...

Thank you so much for this fantastic info! There are so many coaches promoting the glide and I was taught that this is a great technique for open water swimming, lol. Thanks to your blog, I've been able to quickly fix one swimmer's very wonky stroke (scissor kick, sagging body etc, etc) by stopping him from over gliding and upping his stroke rate - now he almost looks pro! (Being an "over thinker", he had to see the evidence for himself.)


ridermax said...

Hi, 'ciao' from Italy. Thank you very much for information. I feel to be a little overglider and now I know I have to improve my stroke rate. To improve, not only to turn my arms faster: I'm sure I'll have to modify several things (catching, kicking, breathing...). I'm 184 cm tall, 57 years old and I swim swim about 1:45 per 100 m over distances of 1.5 to 2 km. The last thing: how do you calculate the 'gap' between two strokes? Thanyou to everyone, Max

Adam Young said...

Hi Max,

You need an underwater video of your stroke and then some software to look at it frame by frame and time the gap between one stroke finishing at the rear and the next starting at the front. A bit techy for everyone to easily do it I'm afraid!

Yes improving your catch is very much part of the process to reduce the deadspot and increase your stroke rate. See:


Oliver K said...

Perhaps it's a bit late, but I can't resist to make some comments:

1. I think there is a partial misunderstanding about "overgliders". In the text, the argument that it's *over*-gliding is purely based on speed --- but there are quite a few folks out there for whom this isn't of big importance. I think that for those who practice the long stroke, it provides quite a joyful experience. If you work on your technique, I believe for a pool-speed up to say, 1:30 for 100m average it can work quite well. I know some guys who really *love* swimming that way. And if you avoid the crossing-over, and your stroke is relaxed, then I think there are no general health problems.

2. My own experience with training for a higher stroke rate:
First I should say that my perspective is likely different, since I concentrate on the shorter distances (and thus for my a higher stroke rate really means higher speed). But I guess my basic experiences should be transferable.

My basic advice is: if you want to swim with a higher stroke rate, you must swim with a higher stroke rate!
Now there's deep wisdom hidden here ;-) --- just do it!
For example, every session you spend some time swimming first 7 strokes per minute more, then 14, then 21. Just swimming 25m's or 50m's, with enough rest. Try to get used to it. It seems very important to me to relax with the higher stroke rate.

I think the danger is that's it's too tense, if you go only higher in very small steps, always trying to stay "in control". You must let loose. The whole style of swimming must necessarily change with higher stroke rates, and one should allow that, and observe.

My own experience is, that one must again and again go back again to slower stoke rates, to strengthen the catch, and one must again and again push higher.
And and least for me it is beneficial to go really rather high, up to 120 strokes per minute (after some time). Pushing the limits, so that your ordinary stroke rates feels rather slow (at least for some time).