Have you heard of the term “burning matches?” We usually associate that phrase with hard efforts (surges) that occur when riding or racing. A well-paced time trial will have few if any, surges while a criterium or road race may have several short, powerful surges. Depending on our fitness and training, we all have a limited amount of these matches to burn. When they are all used up, guess what? You’re toast!
We can generally get an idea of how frequent and intense these surges are by what we call a Variability Index (VI) which is calculated by dividing Normalized Power by Average Power. A low variability can be 1.0 and a high variability can be 1.3 or higher. Variability and burning matches are not necessarily a bad thing in road races and criteriums, and in fact, being able to respond to those can sometimes mean the difference between success and failure.
Triathlons, however, are usually best done with low variable or little to no hard surges in power while maintaining a smooth steady endurance effort, especially full-distance Ironman events. Burn a lot of matches in a 112-mile bike split and you may find that it negatively impacts you on the run.
There are a number of moments throughout a triathlon where these surges can occur. ? Surges can happen on a hill, when you speed up to re-pass a competitor who has just passed you, and it can simply happen when we feel really good and decide to ride at a higher power than planned for short periods. Not only will these moments cause matches to be burnt, but that higher variability comes at a higher metabolic cost as opposed to a steady smoothly paced ride.
In a full IM, it’s doubtful you will see matches being burnt to the intensity of a road race or criterium, both of which are raced with efforts that can regularly reach into Zone 6 or Zone 7. Instead, surges that repeatedly occur above Zone 4 (Threshold) during an Ironman could potentially be a match being burnt. In this case, we need to reframe our thinking when it comes to how we measure the “matches” in these low variability events to better understand the physical cost.
Consider the chart below from an athlete who raced the 2018 IM race at Lake Placid. The race goal for the bike split was to stay at the high end of Zone 2 (Endurance Power) and each of those red and green lines (spikes) represents a time when the power went above Zone 4 (Green) and Zone 5 (Red). They look short enough but add them up and we learn this athlete spent 36 minutes in Zone 4 and above. This is not where we want to be if we are riding for 6+ hours and plan to run a marathon afterward. This ride also equated to a VI (Variability index) of 1.15, which again is on the high side of what should have been a steady effort.
So how do you fix this? The answer is simple: practice pacing in your training. This needs to be done in the months leading up to race day so you know how to properly control and apply your power. Focus on keeping your power smooth and stay disciplined throughout your long endurance rides. Even on climbs, there is no reason to surge. With enough practice, you’ll start to get the feel of this on the bike and will be able to notice before even looking at ride data whether your effort was high versus low variability.
P.S. – Don’t forget to tune in my webinar, IMLP by the Numbers, on 4/21 where I will discuss how we use power to plan, race, and analyze bike and run splits.