Atkinson (2003)* identified that hilly and windy courses tend to lead to slower performances in time trials and whilst this may seem obvious, there are some interesting facts to consider. If you are riding a 10 mile course which includes 5 miles straight into the wind, turning round and 5 miles back with a tail wind, you will ride slower than completing a 10 miles course on a ‘windless day’. The time that you lose on the first part of the course into the wind will generally not be made up on the return leg with the wind behind you. If the course involved 5 miles uphill followed by 5 miles downhill there would be a similar effect - you would not make up all of the time on the downhill section that was lost on the uphill section.
Atkinson et al (2003) used a mathematical formula to examine the relationship between power output, wind speed and gradient incline for several hypothetical riders. They created 3 hypothetical courses completed in a variety of conditions:
1. A 10km time trial course ridden as flat or with alternate 1km sections of uphill and downhill (both 5% and 10% inclines and declines).
2. A 40km flat time trial course complete with no wind or with alternate 5km sections of headwind and tailwind (wind strength 2.2, 4.4 and 6.6 m/s compared).
3. A 40km time trial course consisting of 5km uphill headwind, 5km downhill headwind, 5km uphill tailwind and finishing with 10km flat tailwind. The hills were all 1% and the headwinds and tailwinds a constant 2.2 m/s.
The results
In simple terms their results showed that when you are riding on a flat course on a ‘windless’ day, the best strategy is even pacing. If your bike is fitted with a power meter you should aim to keep it constant for the whole ride. If the course is hilly or windy you should ride the head wind or uphill harder, the tailwind or downhill easier and this will lead to faster times.
Into the strongest headwinds (6.6 m/s) and on the hilliest gradient (15%), those riders who varied their power by 15% saw the biggest gain (if the rider averaged 200 watts for the ride and a 15% variation would be 230 watts on the climb and 170 watts on the descent).
Perhaps more importantly, they did calculations for riders of different ability and found those with the lower average power outputs gained the most by varying their power as outlined above, this means that the weakest cyclists have the most to gain by this strategy!
Why is this so?
We mentioned earlier that you never make up time lost on the headwind section or uphill section when you return with the tailwind or downhill, this is because more of your time is spent going into the head wind or up the hill.
Consider the following scenario…
Rider X rides a 10 miles time trial which involves 5 miles into a head wind and 5 miles with a tail wind. He completes the first 5 miles at 20mph and the next 5 miles at 30mph…. therefore he should average 25mph… right?....wrong!
The first 5 miles take 15 minutes (5 miles at 20mph) and the next 5 take 10 minutes (5 miles at 30mph), that’s 25 minutes in total and 24 miles per hour….. trust me, the maths are right!
Despite the fact that the distances are the same (5 miles out and 5 miles back), Rider X spent more time cycling at the slower speed (15 minutes at 20mph and only 10 minutes at 30mph).
In conclusion
The authors suggest that riders may wish to change their intensity to take into account inclines and wind; ie the steeper the uphill and stronger the headwind, the harder you ride and the stronger the tailwind and the steeper the downhill, the more you recover. REMEMBER…this applies to distances up to 40km and not for a 100 mile sportive where the parallel intensity approach could result in a very troubled final 40 miles……