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Understanding What Your GPS is Telling You in All Four Paddling Seasons

If you’re from the parts of the world that get cold, icy, and snowy in the winter, you’re probably pretty happy at the moment as things are starting to warm up, the days are getting noticeably longer and summer, on the warmer days at least, seems like it is right around the corner.  

If you’ve paddled all winter, you’re finally beginning to have a few days where you can leave all your cold weather paddling gear at home.  It feels so incredibly liberating to paddle in bare feet and board shorts after a winter in booties and a dry suit.  

If you’re just getting back on the water, you’re probably being a little cautious and dressing warm, realizing that the water is still really cold.  You’re likely finding there are days when you’re a little over dressed once you really start to pull hard.  

In either case, it’s worth remembering that although summer is getting closer and there are some nice summery days we can now start to enjoy, the water is still really cold and won’t be warming up to summer temperatures for a while yet.  Depending on where you live, you may have to wait a few more weeks to a few more months before finishing your paddle workout with a nice refreshing swim.  

The purpose of this post isn’t safety related.  We know cold water is dangerous and can kill.  Spring and fall paddling is the most dangerous paddling of the year, as people tend to dress for the air temperature rather than the water temperature.  It’s pretty easy to get into trouble in cold water if you’re underdressed.  Safety requires you to dress to fall in, rather than dress for the air temperature.  If you’re properly geared up, spring and fall paddling is pretty safe.  If you’re not, you’re taking a pretty big risk.  As far as safety goes, for the purposes of this post we can leave it at that.  

Instead, the purpose of this post is to discuss how spring conditions, specifically water and air temperature, can affect performance and the information your GPS provides you while you’re doing your work.  It may feel like summer while you’re doing your workout, but it’s not, and even if you’ve paddled all winter, you’re not going to be going summertime speeds till things warm up.  

A quick review of your high school science

At some point in your academic career, you most certainly learned about temperature and its effect on atoms and molecules in liquids and gases.  In general, as temperatures drop, the molecules in liquids and gases begin to move more slowly and get slightly closer together, occupying a smaller volume which results in an increase in density.  As temperatures rise and molecules move more freely, gases and liquids expand, getting less dense as they do so.  Although water looks the same as we paddle on it whether its temperature is 5C (40F) or 20C (68C), the resulting changes in its density can have a surprising impact on our paddling by providing either more or less resistance to our board’s movement through it.  

Water temperature and its effect on speed

We’re all familiar with water that’s frozen.  When the ice gets thick beyond a thin skim on the surface, it’s time to hang up the paddle for the winter.  But have you ever paddled in water that is just in the process of freezing?

It’s actually pretty cool to see ice forming around you as you paddle and, if there’s not much wind and the water is really still, you can actually hear your board moving through this “in the process of freezing” water.  It sounds almost like you’re paddling through slush.  There’s definitely a little extra resistance to your board moving through the water.  

The reality is, the water doesn’t need to be “in the process of freezing” to create more resistance on your board.  Water that is 2 to 3 degrees C (35 to 37 degrees F) is not “in the process of freezing” but at a molecular level, things have slowed down and gotten closer together so that the water is denser, to the point where it is more difficult for you to push your board through the water than it is when it is even a few degrees warmer.  

As someone who paddles twelve months a year in a northern climate I see this effect first hand by looking at my GPS when I paddle.  It’s much more difficult, for example, to travel at a 5:45/km pace in the winter when the water is near freezing than it is in the summer when the water temperature in Lake Ontario is close to 20C.  

When I was coaching with the Canadian Canoe-Kayak Team, we used to adjust times over the 200m, 500m and 1000m race distances for water temperature when assessing athlete performance.  Somewhere along the way someone created a correction factor for times in various events depending on the water temperature.  I don’t have that data anymore, but I do have this graph of “Time Correction for Water Temperature” that shows how the performance of athletes in various events is affected by the temperature of the water they are racing in.  I can’t claim that the data behind this graph was generated by Canadian sport science.  I strongly suspect that the graph itself was borrowed from the Germans, who have been all over the finest details of sport science in paddling for decades.  The graph can be seen in figure 1.  

Figure 1

In this graph, water with a temperature of 22.5C (72.5F) is used as the temperature for “zero time”, meaning no time correction is needed for performances done in water at that temperature.  The various colored lines

on the graph represent the corrected times at various temperatures for canoes or kayaks capable of doing certain times over certain distances as follows:

  • Blue: 1000m in 4:00 min.  This is a pretty average time for men in C1 1000m. 
  • Red:  1000m in 3:30 min.  This is a pretty average time for men in K1 1000m.  
  • Green:  500m in 1:55 min.  This is a pretty average time for women in K1 500m.
  • Purple:  200m in 0:35 sec.  This is a pretty average time for men in K1 200m.

(insert figure 1)

What should be interesting to SUP paddlers is represented by the blue and red lines.  For starters, you can see how even a couple of degrees Celsius difference in water temperature can slow you down or speed you up by a second/km.  While this may not seem like much, notice that the relationship between temperature and speed is linear.  At 14C, for example, both a K1 and a C1 are traveling more than 3 seconds/km slower than they are at 22.5C.  Imagine how temperatures just above freezing might affect speed.  

Of even more interest is the fact that the time for the slower craft, the canoe (blue line), is more affected due to water temperature changes than that of the faster craft, the kayak (red line).  We should consider that while the average time for a canoe over 1000m is 4:00, an average traveling speed for a pretty elite SUP paddler in a distance race is 6:00/km.  Although we have no data for the effect of water temperature on the speed of a SUP, we can extrapolate based on what we see in the graph.  It is logical to assume that a SUP is considerably more effected by water temperature changes.  

This graph and assumptions made above entirely support what I observe as I paddle in all four Canadian seasons.  I’m always fastest in the summer.  As the water temperature cools, the pace of my “sustained traveling speed” starts to get slower, despite the fact that I am often preparing for some of the most important races of my racing season.  In the winter, the pace I can sustain for prolonged periods is slowest.  This may be partly explained by all the extra gear I’m wearing but, as we have seen, the temperature of the water I am paddling in has a huge effect.  Finally, as water temperatures slowly rise in the spring, my sustained traveling speed gets faster again.  

Air temperature and its effect on speed

Just as temperature and its resultant effect on density makes the water we paddle in either “slower” or “faster”, there is a similar effect on the air.  Air is composed of gases, and just as the molecules in liquids are affected by temperature changes, they respond the same way in gases.  As air temperature decreases, the air becomes denser.  As it increases, it becomes less dense.  

There’s no graph I can show you that provides corrected times for various air temperatures.  Quite frankly, the changes in air density in still air has a negligible effect on paddling speed.  Where air density begins to make a difference is when the wind begins to blow.  

Denser winter air has a greater effect on surface water than warmer, less dense, summer air resulting in a much greater ability to kick up waves.  When we’re paddling on Lake Ontario in the winter we see this almost daily.  Relatively light winds of 15 km/h which only produce tiny ripples on the water in the summer can kick up some sizeable chop in the winter, especially given sufficient fetch.  This can make for some really challenging paddles when the wind starts to get a little stronger.  

While the increased resistance in still air caused by its increased density in low temperatures has a negligible effect on your speed on a SUP, the effect of the wind blowing in your face, at your back, or creating side chop can have a dramatic effect.  

Using your GPS to monitor your speed

If you’ve followed my writing long enough, you’ll know that I am a huge proponent of paddling with your GPS mounted where you can see it.  In fact, whenever I forget mine or the batteries run out on me, my paddling seems considerably less satisfying.  Being able to glance down to check your speed/pace provides you with the most important, in the moment, feedback you can get and allows you to assess how even the subtlest adjustments you make to your technique, connection or paddling rhythm can impact your speed.  It also allows you to better pace your workouts and assess your performance in important marker workouts.  

Using your GPS for technique feedback isn’t affected by either air or water temperature.  In this case, we’re looking at how subtle changes in what we’re doing from one stroke to the next impacts our speed.  That is unaffected by the temperature conditions as we can assume they are constant for our workout.  

On the other hand, using our GPS to assess our performance in marker workouts or pacing workouts can be dramatically affected by temperature.  It is important that we understand the effects of water temperature on our speed, and that we understand that wind of a particular strength is going to have a greater effect the colder it gets.  If you’re used to adjusting your speed based on the wind conditions in the summer, you’ll need to completely reassess the adjustments you make as temperatures drop.  

If you notice that you’re slower in colder water and just can’t find the speed you think you should, consider the impact water temperature has on speed and don’t panic.  You’ll very likely be going exactly the speed you think you should be once the water gets a little warmer.  On the other hand, if it’s spring, the water is still really cold and you’re comfortably paddling at speeds you were last summer, you’re likely looking at a pretty good season ahead.  

Be careful how much you rely on your GPS data

Though using your GPS in “real time” while you’re paddling is extremely useful, don’t overdo it.  It can quickly go from being your most helpful friend while you’re paddling to an unnecessary burden.  I should write more about this in a future post, but for now I’ll briefly touch upon a couple of things to be aware of.

For starters, paddling with your head down, fixated on your GPS, is going to be hugely detrimental to your technique.  Not only does paddling with your head down, staring at the deck of your board, prevent you from properly reading the water conditions in front of you, it also tends to cause you to “get stuck” after you’ve completed the loading phase of your pull and limit your ability to unload properly and at the correct time.  The idea is to just glance at your GPS, get the information you need when you need it, and then continue paddling with your head up, looking at the nose of your board and the water ahead of it.  

An even bigger problem caused by overusing your GPS is becoming obsessed with the information it is providing.  One of the biggest traps a paddler can fall into is constantly trying to live up to personal best level performances.  I’ve seen other athletes fall into this trap in both canoe and in SUP, and I have caught myself about to go down this path a few times over the years.  

We all want to go fast.  And, when we do, it’s both exciting and addicting.  It feels good.  It’s pretty easy to fall into the trap of thinking that, if you can go, say, 6:20/km pace sustainably one day that you should be able to go that pace or faster, sustainably in neutral conditions, every day.  Similarly, if you can do a 5 km time trial in 30 minutes, then it can be easy to start to think that any 5 km time trial you do that is slower is a failure.  Thinking in this fashion should be avoided at all costs.

Personal best level performances do not happen every day.  If they did, improvement would be ridiculously easy and, if you think about it, everyone would be performing at World or Olympic Champion levels.  We do personal bests when all things come together perfectly, the rest of the time we just do the best we can in our workouts and do the work, knowing that if the quality of the work and the technique is high, we’re going to get better, regardless of how fast we actually are in any given workout.  

Constantly trying to live up to personal best performances or those workouts where everything feels “perfect” only sets you up for disappointment.  They create completely unrealistic expectations that are impossible to live up to.  At best they’ll leave you frustrated by your failure to achieve them.  At worst, they’ll lead you to do things like doing workouts above the prescribed intensity level or focus on pulling hard instead of on your technique and connection.  Both usually result in the last thing you want to have happen happening – getting slower over time, either because you’ve overtrained or you’ve damaged your technique. 

After all my years of paddling, the most important bit of wisdom I can provide to a seriously training paddler is to just do the work to the best of your ability every day.  Don’t worry about how fast you’re going.  Instead, concern yourself with the quality of your paddling and your effort.  Stick to the process and believe that if you do, the results will take care of themselves on race day.  Use your GPS for feedback on your technique and be happy if your data in marker workouts indicates you’re “in the ballpark” of your previous performances.  If you’re not setting a personal best, it’s nothing to worry about.  You only need to worry if you end up way off the pace and it suggests there may be a problem with your training program or your response to it.  In this case, you’ll usually get an idea that something is wrong well before your GPS suggests there is simply because of how you feel.  


Enjoy the improving weather and watching how your paces improve as water temperatures rise.  There is a long summer ahead.  Here’s hoping you all get to make the most of it.  

Happy paddling!


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