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    Performance
    08.09.15

    Performance: La Vuelta by numbers - part two

    Time-trialists vs. climbers in the battle for GC supremacy. James Hewitt considers the numbers

    Words
    James Hewitt
    Photographs
    BrakeThrough Media

Man, white, twenties, portrait, La Vuelta a Espana 2015, stage 16, Tom Dumoulin

Fränk Schleck’s victory on stage 16 of the Vuelta was his first win since the 2011 Critérium International. His efforts also broke a 45-year drought for Luxembourg riders in the Spanish race; the last Vuelta stage winner was Schleck’s father, Johny, in 1970. On any other day, this romantic narrative would have dominated headlines, but the close battle between the general classification contenders has stolen the hearts of fans and commentators alike.

Stage 16’s seven categorised ascents promised action throughout. Climbing from the gun, severe slopes and a spectacular summit finish at Ermita del Alba were likely to force selections and create time gaps throughout the peloton. In reality, the leaders were relatively conservative until reaching the Alto del Cordal, the third to last climb, when Astana and Tinkoff-Saxo animated the race in support of Aru and Majka.

On the final climb, Joaquim Rodriguez wrestled the red jersey from Aru, but of greater concern to those hoping to mount the top step of the podium in Madrid was Tom Dumoulin. The Giant-Alpecin rider started and finished the stage in fourth place overall after forcing himself to match the pace of the favourites until the final kilometre of the short, but tough Ermita del Alba climb, finishing just 27 seconds behind Rodriguez.

Racing cyclist, black and white jersey, one arm raised pointing to sky, other hand holding necklace, barriers and crowds either side of road, crossing finish line, La Vuelta a Espana 2015, stage 16, Frank Schleck

After 2655km of racing, the peloton enters its second rest day ahead of this edition’s only individual time-trial. 1’51” separates the top four riders on general classification. The figure of eight route around Burgos will likely prove decisive. The course is relatively flat, in contrast to recent years, which featured TTs with more climbing, better suiting the likes of Rodríguez and Valverde. This year’s 38.7km course will is better suited to riders with the capacity to produce high absolute, rather than relative power.

Analysing typical course profiles from the majority of multi-day events reveals that, for the most part, races takes place on flat roads and hills of moderate grade (less than seven per cent). In such contexts, the difference between climbers and rouleurs is reduced. High speeds and group riding mean that drafting provides a significant advantage to all. While larger riders may be able to produce higher absolute power, smaller, lighter riders might benefit more when following in a slipstream.

The true differences are seen in climbs over eight per cent, where aerodynamic advantage is reduced, speeds are slower and power to weight ratio is more significant, and flat time-trials, when absolute sustainable power and drag are the primary factors to determine performance.

Stage 17 is being viewed by many as Dumoulin’s opportunity to seize control of La Vuelta. However, arguably it is easier to win a stage race in the mountains than to secure overall victory in the time-trials. Why? It is significantly more difficult to generate a time difference in a time-trial compared to a climb.

Racing cyclist, green jersey, red shorts, white bike, pained expression, crossing finish line, mouth open, La Vuelta a Espana 2015, stage 16, Joaquim Rodriguez

Aerodynamic drag increases exponentially with speed. Consequently, a rider who is capable of producing five per cent more power than his competitor in a time-trial will only gain 1.7 seconds per kilometre if the time trial specialist’s speed is 51km.hr, versus their climbing rival’s 50km.hr. However, a rider who is able to produce five per cent more power on a climb when the speed is reduced to 20km.hr will gain 9.5 seconds per kilometre relative to a competitor riding at 19km.hr.

velofacts.com, a website specialising in ‘data mining’ cycling news and results, posted a comparison of recent TT performance for this year’s Vuelta contenders. Interestingly, the author of the feature also extrapolated the results to predict the time difference if the courses in question were 38.7km in length.

The closest reference point is Stage nine of this year’s Tour de Suisse, a 38,4km course around Bern won by Dumoulin. Here, the Dutchman gained 1:26 over Rafal Majka. If this performance differential is replicated, it should be more than enough for Dumoulin to overhaul the Tinkoff-Saxo rider and move up on GC. Dumoulin has only raced against Fabio Aru in one time-trial this season, the Paris-Nice prologue. Here, the Dutchman bested Aru by 20 seconds over 6.7km, representing a predicted 1:55 difference over the Vuelta TT.

We may be tempted to think that Dumoulin has the GC sewn up, but we would be mistaken. In this year’s Vuelta Ciclista al Pais Vasco, Dumoulin only beat Rodriguez by four seconds over the 18.3km course. This translates to an eight-second time difference over a 38.7km course, not nearly enough to surpass the Katusha rider on GC. Rodriguez TT performance in this year’s Vuelta Ciclista al Pais Vasco, by contrast, was sufficient to secure him the overall victory. Does Purito have enough power left to defend in the time-trial, consolidate on the remaining climbs and keep his red jersey until Madrid?

James Hewitt is a performance coach at HINTSA Performance, Geneva

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