19th April 2011 Toronto, Canada
WWF CN Tower Climb 2011
This is John Preece guestblogging about the recent CN Tower Climb, where two teams from the British Consulate-General in Toronto (one of which included myself) raced up the 1,776 steps and raised over $6,600 for WWF Canada. “Where’s the science?” I hear you cry – read on!
First of all, a quick statistical analysis of the climb times. There were 1,568 climbers and the ascent times ranged from 10:21 to 1:35:06 (my own time was 16:14, placing me 160th). The data distribution is heavily right-skewed (i.e. there is a long tail of longer times), with a mean of 24:35, median of 22:07 and standard deviation of 09:04.
What may be of more interest is the amount of energy expended going up the steps. In purely physical terms, climbing speed is irrelevant because the total work done against gravity only depends on the starting and finishing heights. The main deck of the tower is 346 m off the ground, and if we assume that the average climber weighs 70 kg then s/he requires 257,356 J to get there. This is equivalent to 56.5 kCal, or one slice of toast (all the climbers combined expended 403,534,208 J, or one-quarter of an average lightning bolt).
Something else to consider is that the human body, stunningly well-evolved as it is, isn’t particularly efficient at converting food energy into mechanical energy. For an activity like stair-climbing where there isn’t much momentum to take advantage of, only about 25 % of energy consumed as food is converted into actual movement. This bumps our climber’s expenditure up to 1,029,424 J (245 kCal, or one regular hamburger) and the combined climbers’ up to an average lightning bolt.
There are numerous other contributing factors, such as a climber’s fitness level and stride (relative to the height of the stair risers), but the speed of ascent is remarkably unimportant. Moving faster requires more energy, but this is counterbalanced by the shorter workout time (note: taking a rest on the landings will actually add to your energy requirements as you’re keeping your body hot for longer).
Take-home message: When you’re approached to do the WWF CN Tower Climb next year, say yes. It’s only a hamburger!