We think it's wise to approach the prospect of any challenge ride with some good preparation - do this and you'll enjoy your ride.
For the route options of Y Corrach or Y Diafol - getting a few rides under your belt of 20 to 30 miles leading up to the event are sufficient preparation for most. For the longer options (Y Mynach & Y Cawr) you need to have more substantial 'cycling fitness', but you don't have to be an Olympic athlete by any stretch of the imagination.
To be cycling fit you should have some good base mileage in place. For example, if you would not normally call yourself a cyclist and want to ride a sportive, then a good few months foundation of weekly road mileages working up to 100 miles per week over two to three rides would be the minimum for the shorter option rides. If you have a good foundation of fitness in any other sport it is not likely to be of any great direct benefit for cycling - so four nights a week down the gym or playing squash will not help you too directly in your preparation for the 105 mile ride.
If you leave it late to get cycling fit, you could try British Cycling's 7 week panic plan.
There is simply no substitute for miles totalled up out on the bike. Be honest with yourself about the training you’ve done and if you haven’t put in the kilometres, consider postponing your sportive challenge and targeting an event later in the year.
If you know that you have any medical conditions, you should be wise to consult your doctor for health advice before taking part.