Triathlon-specific bikes: how much better in reality than road bikes?

Do triathlon-specific bikes really confer a performance advantage over road bikes of equivalent quality and weight? Andrew Hamilton looks at some science

In the northern hemisphere, we're approaching the winter equinox. That means long nights, short days and the prospect of much colder weather to come. Oh yes, it also means that there are just a few days until 25th December - yes folks, Christmas is 100ming! Now for many people, the whole Christmas thing may be a bit over the top and commercialised, but it does have its upsides. As well as spending some quality time with loved ones and family, it’s a great excuse to think about some new toys – for yourself that is (not the kids). And if you’re a triathlete, the biggest toy in your collection is likely to be your bike.

The best bike

Most triathletes are perfectly happy riding on road bikes. But if you’re pushing for a new PB, you may have wondered whether a dedicated triathlon bike could make a real difference. The past 20 odd years has seen an explosion in ‘triathlon’ bikes. But just how much extra will a triathlon-specific bike give you over a really well set up lightweight road bike fitted with clip-on aero bars? While it’s true that triathlon bikes are designed with steeper seat tube angles of around 76-78 degrees to maximise energy transfer and significantly more comfortable aero bars to help cover long distances with less effort, the latest iterations of road bikes are more aerodynamic and stiffer than ever, and often lighter than their triathlon equivalents – a real advantage over hilly courses.

Bike research

To try and provide some scientific answers, US scientists studied the differences in muscle movement and muscle activation patterns between cycling and running⁽¹⁾. In particular, they looked at how varying the bike’s seat tube angle and hand position affected muscle movement and activation patterns to see whether triathlon-specific bike geometries could reduce the biomechanical challenges associated with the bike-run transition and so lead to better running performance.

In the study, whole body motion and lower extremity muscle activities were recorded from fourteen triathletes during a series of cycling and treadmill running trials. A total of nine cycling trials were conducted in three hand positions (aero position, on the drops and on the hoods) and at three seat tube angles (73º, 76º & 79º). The subjects also ran on a treadmill at 80, 90 and 100% of their 10km triathlon race pace to see how the bike set-up affected subsequent running performance. The findings were as follows:

• Compared to cycling, the movements in running involved required a larger range of motion (and therefore longer muscle/tendon lengths) in the hip flexor muscles, quadriceps of frontal thigh, the hamstrings of the rear thigh and the gastrocnemius muscles of the calf;
• During cycling, increasing the seat tube angle alone had no affect on muscle kinematics, but did induce significantly greater rectus femoris (quadriceps muscle of mid-frontal thigh) activity during the upstroke of the crank cycle;
• Increasing hip extension by varying hand position to aero induced an increase in hamstring muscle activity, and moved the operating lengths of the hip flexor and extensor muscles (glutes of buttocks plus hamstrings) slightly closer to those seen during running.

The researchers concluded that the overall effect of riding a bike with triathlon-oriented geometry helped to induce changes in muscle and tendon movement patterns, which could contribute to the improved running performances previously observed immediately after cycling on a triathlon-specific bicycle (you can read more about the science of improving the bike-run transition here). What this boils down to in plain English is that compared to a general road bike, triathletes are likely to find the bike-run transition slightly easier when using a triathlon-specific bike. So if you’ve been looking for an excuse to indulge yourself in a (big) new toy this Christmas, maybe this is the proof you need. Just check with your bank manager first!

Andrew Hamilton BSc Hons MRSC, Sports Performance Bulletin editor

References

1. J Appl Biomech 2011 Nov 29;27(4):297-305