The world of cycling is on the cusp of a new performance metric that could revolutionize how we understand and evaluate athletes' capabilities. The Compound Score, developed by WorldTour sports scientists, is poised to replace the long-standing W/kg (watts per kilogram) metric, offering a more nuanced and comprehensive view of race performance. This shift is not just about numbers; it's about understanding the complex interplay between power, size, and aerodynamics that determines who wins races.
The Limitations of W/kg
W/kg has been the go-to metric for standardized power comparison in cycling. It's elegant and straightforward: simply divide watts by kilograms. This metric evens out differences in rider size and reduces physical ability to a single, clean number. But, as Cor Vos points out, it wasn't just the ease of use that propelled W/kg into every cyclist's vocabulary. It was also its perceived validity in what is often seen as cycling's testing ground โ climbs, where races are often won and lost.
However, research led by Peter Leo, a research fellow in the Department of Sport Science at the University of Innsbruck and coach with Jayco-AlUla, reveals that W/kg doesn't explain who wins races. Leo found that despite very good W/kg numbers, some riders with better power-to-mass ratios were finishing behind others. This mismatch highlighted the limitations of W/kg in predicting race outcomes.
The Compound Score: A More Comprehensive Metric
The Compound Score, developed by Leo and his fellow researchers in 2022 and published in the Journal of Science and Medicine in Sport in 2023, aims to fill this gap. It combines absolute power with relative power, capturing whether athletes have the raw engine to survive in a chassis and make a difference when it counts. This metric takes into account both the absolute power output and the relative power-to-mass ratio, providing a more holistic view of an athlete's performance.
The Compound Score is already making inroads in pro cycling. Leo's research collaborator, John Wakefield, director of coaching, sports science, and technology at Red Bull-Bora-Hansgrohe, uses it as a key part of his talent evaluation process. Wakefield told Escape that the Compound Score is the first metric he looks at when analyzing riders, and it's become a crucial part of their recruiting and scouting protocols.
Why W/kg Struggles
W/kg struggles on flat and rolling terrain because power-to-weight ratio matters far less than absolute power and aerodynamics. A 65 kg rider producing 390 watts achieves 6 W/kg, while an 80 kg rider produces 4.88 W/kg. However, the key forces working against the rider on these terrains are primarily aerodynamic drag, which doesn't scale with rider size the way absolute power output tends to. On the flat, where gravity isn't a limiter, there is a clear advantage to the heavier rider.
There are exceptions to this rule, such as the relatively lightweight rider Remco Evenepoel, who can beat much larger riders like Filippo Ganna, who is 20 kg heavier, even in flat time trials. This highlights the complexity of race dynamics and the limitations of relying solely on W/kg.
The Future of Performance Metrics
The Compound Score offers a more accurate performance prediction than W/kg alone, particularly in predicting likely podium contenders for major one-day races. This metric could help coaches like Leo and Wakefield more effectively identify and develop talents by better understanding the foundations of elite physiology. However, it's not without its limitations, and further research is needed to refine its application and understanding.
In my opinion, the Compound Score represents a significant step forward in our understanding of race performance. It's a fascinating development that could change the way we evaluate athletes and the strategies we use to train and prepare them for competition. As we continue to explore and refine this metric, we may uncover new insights into the complex interplay between power, size, and aerodynamics that determines who wins races.
What makes this particularly fascinating is the potential for the Compound Score to bridge the gap between absolute power and relative power-to-mass ratio, offering a more nuanced and comprehensive view of race performance. From my perspective, this development could lead to a more accurate and effective approach to talent identification and development in pro cycling.
