About the Event

The event comprises:

- Swim 750 m (in the cold water of Hartlepool Marina!)

- Cycle ~20 km (from Hartlepool Marina to Seaton Carew 3 times)

- Run 5 km (around the Marina)

I did the swim by myself with Benjamin supervising from the shore.

For the Cycle, we used our special tandem - a Hase Pino. I aspire to Benjamin helping with the pedalling, but he rarely does, unless I am trying to stay still and talk to someone!

For the run we used Benjamin's cross country wheelchair - an Advance Mobility Freedom chair.

Sunday, 15 September 2013

Energy Requirements

Sorry, but the physicist in me wants to do sums.  Here is a quick go at calculating the total energy requirements for the Sprint (half Olympic distance) triathlon.

  • Swim pace is 1000m in 22 min, which is what I have been doing in the pool.
  • Cycle energy requirement is as per my heart rate monitor results (891 kCal, 3.7 MJ)
  • Run pace is about 7 minute miles.  I add the energy for me running to the equivalent for propelling the wheelchair, which I will assume is a bike for now.
1000m in 22 min is 2.7 km/hr, which is about 45 m/min.  The calculator at http://www.brianmac.co.uk/energyexp.htm suggests that this should only use about 140 kCal (0.6 MJ)
I have a bit of trouble believing this - maybe that is true for someone with good swimming technique, but I think I do it very inefficiently.

I did some calculations here: http://team-bee.blogspot.co.uk/2013/09/a-second-final-bike-practice-and.html, and came to the conclusion that the bike energy requirements are about 891 kCal (3.7 MJ)

My hoped for 7 min/mile pace is 13.7 km/hr.  The calculator at  http://www.brianmac.co.uk/energyexp.htm suggests that the run will need about 300 kCal (1.3 MJ).
There is something to add for the wheelchair - using http://www.gribble.org/cycling/power_v_speed.html suggests that about 20 W would be appropriate, which would be about 0.02 MJ.  I think that that calculator calculates work done.  If I am only 20% efficient, this would mean that I would need to consume 0.1 MJ to deliver that work.
This gives a total for the run of 1.4 MJ.


  • Swim - 0.6 MJ
  • Cycle - 3.7 MJ
  • Run - 1.4 MJ
  • Total - 5.7 MJ
I am quite surprised that it appears that the cycle is so energy intensive compared to the swim and the run.  I suppose it will take over twice the time of each of the other activities, which could account for it, but I thought the event may have been designed to balance the disciplines more.   It could be that I have used inconsistent calculation methods - maybe the heart rate method for the cycle is over-estimating compared to the theoretical methods for the cycle and run.   I think I may become a sport performance geek next.....

Using my new proposed SI unit of energy, the Mars Bar, the calculated energy requirement of 5.7 MJ equates to about 5 Mars Bars, which is quite a lot of stodge to eat!