Running with STRYD power at Ironman South Africa

It is very common to see Iron man age group athletes start off the run at a pace which gradually deteriorates as the run progresses until a sombre procession occurs prior to the now compulsory pick up on the red carpet to go with the” you are an Iron man Mantra”.

As a coach it is so frustrating to watch an athlete throw away a potentially solid run on a first few km of delusional heroism. And this is where STRYD running Power meter is a game changer.

At Dinamic we were fortunate to have athletes racing Iron man South Africa with STRYD running Power meters.  These athletes had been training using these very clever tools and prior to the race we had identified power levels which we felt, based on testing that each athlete could hold for the run component of the race.

Unfortunately some technology issues ( non stryd related)  meant that for two athletes we were unable to access power and we are also waiting for info from a couple more, but based on four athletes I decided to look at what the data showed.

Ok so what do all these numbers mean?  

  • CP is critical power ( for those of you familiar with bike power it is similar to FTP. Cadence should be self explanitory. Pace m/s is the speed the athlete was running in meters second,
  • Pwr is the power they were producing,
  • PWr/kg is power by body weight,
  • Form power is a measurement of how much power was not contributing to horizontal movement
  • FPR % is the ration compared to total power
  • LSS is a measurement of how well the athletes leg is dealing with the impact of landing each step
  • LSS ratio is that measurement in newtons  divided by their weight to give a meaningful measure
  • RE reflects on how efficient the athlete is in terms of the m/s divided by pwr/kg
  • Changes in FPR LSS and RE in a race  ( normally negative ) are a very good indicator of fatigue.

I split the run into half and wanted to revue what changes we saw in speed, power and RE and if giving target zones to run at would help minimize the aforementioned tendency to go out too fast and blow in the later stages.

As we can see the first three athletes  T G and B were remarkably consistent.

Athlete T managed to produce 2 watts more in the 2nd half of the run.  This along with a stable form power and LSS meant that they were able to improve their pace by almost 2 sec/km. 

Athlete G actually went out slightly harder than was planned and this did reflect in the 2nd half, but the average for the race was consistent with what we had been hoping for so no major damage done.  He did lose around 7 sec a km and this was also due to a decrease in efficiency with form power increasing against the lower total power. 

Athlete B produced 2.8% less power in the second half but by decreasing form power loss and keeping LSS the same her RE actually increased. This athlete actually recorded a huge marathon PB agaist a stand alone marathon. She was also very smart and used bigger athletes ahead of her to draft into the wind on parts of the course.)

For these athletes the ave change in pace was 4 sec/km or 1:24:00 extra for the 2nd half,  this compares very positively with the same calculation of similar athletes around them where across a sample of 6 athletes the times difference was 26sec/km slower. ( best was 10 sec slower worst was 43).

Confidence is a major factor in performance. Training with and running with power gives the athlete confidence.  Long runs in training had been done at a pace slightly slower than we were planning for the race, but there were substantial harder than IM Race pace efforts included into the 2nd half of the long runs.  This meant that the athlete had worked on their fatigue resistance and was used to picking up pace rather than dropping pace in the later stages of a run.  Also being able to refer to a fixed variable in terms of power, which was not impacted by variables like gradient gave them the reassurance that they were sticking to plan. 

I often say that the race in an Ironman starts around 30km into the run.  Prior to that it is a case of resource management. In all three cases the athletes were able to increase their perceived effort in the last 10 kms to overhaul competitors because they were referring to a simple single metric which they believed in and trusted, because they had done so in training using the same numbers and because by sticking to the numbers in the first half of the race they were able to do so.

In the interest of clarity I should point out that Athlete E came into the race under prepared as a consequence of work and family pressures and as such some of their numbers are different from the other three as there was a lot of walking involved in the 2nd half and measurement of power when walking is not optimum.

For any questions about running with Power or queries feel free to get in touch.