Calories, a.k.a. energy, can be a lot like money during a race. You better not spend it too quickly or you'll find yourself with an empty account. As a continuation of the previous post (yes, it's been a few weeks, give a brother a break:) which discussed how changing your speed in different disciplines will influence your race time, this post will analyze how much energy goes into changing those speeds. By a simple analysis, you should be able to estimate the energy cost of going faster and understand how to apply that to race day so you don't empty your account before the finish line.
First, it's important to understand that calculating energy costs isn't an exact science. There are many factors that can influence how many calories you'll burn for a given discipline. Environmental conditions such as wind, heat, cold, downstream, upstream, etc. Technical abilities such as gross efficiency, economy, stride rate, etc. Terrain such as flats, hills, sand, water, etc. For any given race course you would have to combine them into interacting pieces making it nearly impossible to precisely measure energy costs. So, the below estimates are intended to represent ideal conditions such as flat terrain, no wind, ideal temperature, constant speed, and a constant level of efficiency.
Riding a bike one mph faster in an olympic distance race (26 miles) would save you 4 minutes of time assuming an increase from 19 to 20 mph. The energy cost would be approximately 70 calories for that increase. That's not much and could be well worth a little extra effort.
However, there would be no increase in energy cost for running or swimming at a faster rate. Why? Think of it this way: if you were to lift 3 boxes, one at a time from the floor to place them on a 5 foot table, the amount of work that would be done is exactly the same whether you took 2 minutes to do it or 60 seconds (Work=Force x distance). You still have to lift the boxes a total of 15 feet (5 feet x 3 boxes) and the force requirements are exactly the same. In the run, you're traveling the appointed distance, in this case 6.2 miles. If you go faster, you spend less time doing it but you still travelled the same distance.
Now, this isn't entirely accurate as previously pointed out. For one thing, efficiency will decrease as speed increases (in most cases) in running. However, the principle remains and the additional energy cost differences are generally insignificant. In cycling, however, you have to deal with the increased artificial wind created by moving through the air which increases as you go faster. Because of that, more energy would be needed to go faster.
So, What does that mean for race day? Going faster on the bike will empty your energy account more so then the run or swim but it's still not a substantial amount for a shorter race. The longer the race, the more substantial it becomes.
Here's a chart of the numbers.
Scott Flynn, owner, coach and triathlete of 10+ years with Threshold Multisport Coaching, holds a MS in Exercise Science and multiple nationally recognized fitness certifications (CES, CSCS). For more about Threshold coaching packages click here.