Wellington Half Marathon

Last Sunday I competed in the 2018 Wellington Half Marathon. I completed the race in 1:19:06. Despite being a flat course, howling northerlies made it anything but a fast race! The weather was so foul that one runner thought it was the worst weather he’d encountered in the last 20 years of entering in the Wellington Marathon!

With winds averaging 20 knots (37.0 km/h), it made a flat course slow and difficult. While Wellington is infamous for its terrible weather, this year seemed particularly bad. The average half marathon finishing time since 2010:

Year

Time

2010

1:55:59

2011

1:59:58

2012

1:57:29

2013

1:58:09

2014

1:57:39

2015

2:01:41

2016

2:01:53

2017

2:00:09

2018

2:05:05

While there’s other factors that could explain the slower finishing time, it’s reasonable to suggest that the weather was largely responsible for the 5 minute slower average finishing time.

But does wind affect everyone the same? I found an interesting paper titled The Influence of Wind Resistance in Running…. Since drag force is proportional to the square of velocity, it comes of no surprise that the faster you are trying to run, the greater the impact of wind.

Using the regression equations from the paper and a couple of assumptions (i.e., when the runner was running with no wind on a 0% incline treadmill, this is equivalent to running outside with a tail wind):

Speed (km/h)

Wind speed (km/h)

Oxygen consumption (mL/kg/min)

VO2 relative to zero wind (%)

13.5

-13.5

43.6

-2.0

13.5

0.0

44.5

0.0

13.5

13.5

47.2

6.1

13.5

37.0

55.9

26.0

16.1

-16.1

46.3

-4.7

16.1

0.0

48.6

0.0

16.1

16.1

55.6

14.4

16.1

37.0

71.7

48.0

In other words, if you were running a flat out and back course where you were either running into a headwind or a tailwind, you’d expect to run slower than the same course on a windless day! And the faster you run, the more wind affects you! The same holds true for any out and back course, where the environmental conditions (wind and wind direction) remains constant.

So how does pace themselves during a windy race? By using heart rate! From my last half marathon race, I know I can hold 176 bpm over the race. Since my max heart rate (MHR) is 189 bpm, 176 bpm is 93% MHR. I regulated my speed based on my current heart rate!

How did the race go overall? I suspect I’ve lost a bit of conditioning since trialing a Ketogenic diet for a month. While the wind did not help, I think I should have done a bit better. From my heart rate data, I should have pushed more from 12.5 km, despite predominately being into the wind. I was 76 kg on the day, had either water or electrolytes during the first three aid stations and did not eat anything on the run.

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