![]() ![]() Phil Skiba along with his colleagues Weerapong Chidnok, Anni Vanhatalo, and Andrew Jones derived a formula for tracking the levels of W’ remaining during intermittent exercise, called W’bal, that we can plot alongside power. The further below CP we are the faster we will recover, and for the first 30 seconds of recovery we get the most bang for buck as blood-flow into the muscles is still high from the previous bout. When we work below CP the energy stores within the muscles are restocked. But, we also know that it will also be replenished over time too. ![]() If we keep going hard enough for long enough we will blow when it’s all gone. Now, we know from the Critical Power model that when we work above CP we start eating into our limited W’ stores. In fact almost all training and racing away from the turbo tends to be variable because of this. These intermittent bouts might occur when we climb a hill, or sprint out of a corner or bridge a gap. Unless we’re riding the pursuit or a very flat time trial, when we train and race we tend to ride sustained efforts interspersed with recovery. And so, over the last 50 years, variations of these models have been developed to address this, and it continues to be a topic of great scientific interest. This formula is pretty reliable for durations between 2 and 20 minutes or so, but less so over short and longer durations. Monod and Scherrer also provided a mathematical formula to estimate the maximum power you can go for any given duration using W’ and CP as parameters. You know that if you try to go any harder you are gonna blow up pretty quickly. CP, on the other hand, is that intensity (or power output) where you are uncomfortable but stable, akin to your TT pace. In cycling parlance W’ would be referred to as the matchbook– the harder you go the quicker it will be used up, but temper your efforts and you can ‘save a match’ for the last sprint. The harder we go, the quicker it is used up hence the shape of the curve above. It is in the region of 10-40 kJ, mine for example is typically 23 kJ. But at shorter durations we work at power above CP, and to do this we use a finite capacity (sometimes called the Anaerobic Work Capacity, AWC). As time gets longer to the right, the power you can sustain tends towards the asymptote 'CP'. In the chart above the solid red curved line represents the best power you can perform for a given duration a so-called 'power-duration' curve. They also proposed an ‘energy store’ (later to be termed W’, pronounced double-ewe-prime) that represented a finite amount of work that could be done above that Critical Power. In 1965 two scientists Monod and Scherrer presented a ‘Critical Power Model’ where the Critical Power of a muscle is defined as ‘the maximum rate of work that it can keep up for a very long time without fatigue’. But when it comes to reviewing and tracking changes in your performance and planning future workouts you quickly realise how useful it is to have a good understanding of your own limits. And then thinking about how hard you can go for a very long time will be different again. How hard can you go, in watts, for half an hour is going to be very different to how hard you can go for say, 20 seconds. I wanted to explain what we've done and how it works in this blog post, but realised that first I need to explain the science behind W'bal, W' and CP. This has 4 main elements supporting more cloud services, enhanced modelling, user definable charts using R/Python and improving performance and stability.So, the implementation of W'bal in GoldenCheetah has been a bit of a challenge. Over the last 3 years since the release of version 3.4 we have been focusing on adding functionality to enable users to perform more insightful analytics. We are proud to announce the release of version 3.5 of GoldenCheetah. ![]()
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