Photo: iStock.com/pat138241

When it comes to cycling uphill, weight becomes a limiting factor. High-performance sports are renowned for taking every gram into account. But to what extent is this necessary? And how much do body weight and bike weight really affect performance?

Weight is an ongoing issue in the world of professional cycling. Particularly at the major tours, we see wafer-thin athletes with minimal body fat who look practically emaciated. “These people shouldn’t even be racing,” says Swiss professional road cyclist Marlen Reusser in an interview with the NZZ, expressing her concerns about the health of certain athletes. Being underweight not only increases the risk of long-term damage such as osteoporosis but the blood loss after a crash could be fatal.
The evolution of Chris Froome demonstrates the importance of weight in elite sport. The four-time Tour de France winner dropped 10 kg in weight between 2007 and 2011 to around 66 kilograms, which corresponds to a BMI of 19.1 for his height of 1.86 m. Froome then went on to become a multiple-time champion, although his absolute performance data didn’t significantly improve according to the records published. After several years and a near-fatal training accident that resulted in severe injuries, the 28-year-old is a shadow of his previous form.

For how long does weight loss improve performance?

Being lighter makes you faster, but what's the limit? “Anyone who wants to lose weight should be sure to focus on reducing fat mass where possible,” says Lucas Schmid, responsible for sports science with Swiss Cycling, adding: “A loss of muscle mass, which is needed to propel the bike forwards, is automatically associated with a reduction in speed.”
This sounds easier said than done. When it comes to elite endurance sport, finding the ideal compromise between the lightest possible weight while achieving optimum performance remains a delicate issue. There is a fine line between improving by being lighter and negatively impacting form due to a lack of nutrition, which has already caused several elite athletes to experience a slump in performance with long-term consequences.

And what about amateur sport?

Weight-tuning also plays an important role in amateur cycling. However, most people tend to optimise weight through their choice of materials. But how crucial is the weight of the bike and cyclist when it comes to performance? Is that ultra-lightweight bike that's been beckoning at you from the shop window for months the solution to a new personal best? Or is it better to lose a few kilos instead?
Swiss Cycling has developed an exciting calculation tool, the Swiss Cycling Calculator, which lets you simulate a wide variety of configurations. In principle, the heavier the athlete, the less that bike weight matters. For example, if a man measuring 185 centimetres tall and weighing 85 kilos with a 10 kg bike gripping the handlebar drops at an output of 250 Watts over a distance of 10 km and 200 m in altitude change, the calculator reckons a time of 1,624 seconds, or a good 27 minutes. A bike weighing two kilos less (which corresponds to a several thousand-Franc increase), our sample man would reach the finish line 13 seconds faster in a time of 1,611 seconds. If, on the other hand, he lost five kilos, he would improve his time by 43 seconds with the same effort.
The lighter the body weight, the greater the impact of the bike weight. A woman measuring 160 cm and weighing 58 kg would take 1,579 seconds to finish a 10 km route with a 10 kg bike and output of 180 Watts. This would be 18 seconds faster with an 8 kg bike. If she weighed three kilos less, the athlete would be an impressive 38 seconds faster.

Number games from Swiss Cycling

Such number games can be played with the calculator. In addition to body weight and bike weight, other factors such as position on the bike (aerodynamics), handlebar angle, clothing weight, wattage and wind can also be simulated.
The general finding: body weight is an important factor in cycling and a particularly delicate issue in competitive sport. In mass sport, however, bike weight is actually less important than many amateur athletes would believe. For most of these athletes, a heavy bike isn't the reason for potential sub-optimum performance but rather simply a lack of fitness and a little too much weight around the hips.