Knowing the altitudes and terrain of cycling it is not easy to practice to 100% possible extent down South of India. To an extent training is possible. What is to be remembered is that in those altitude the ability to suck in oxygen out of the thin air is important and crucial.
It is desirable to do 100+kms rides on weekends to get body tuned. Varying terrains are possible by riding to Nandi Hills and ride to nearby hills around Bangalore. One or two rides in these terrains does not help in getting the body tuned up. Atleast 3-4months of preparation is required.
Training in gym on the cycle with resistance level at 11 – 12 and maintaining consistent RPM above 50 helps.
Cross training by running helps improve the lungs power. Supplemented with strength training and some skipping exercises.
The training schedules help in improving the muscle power over all and get the body into shape. After all this just keep fingers crossed that there would not be any problems cycling between Manali to Leh.
Without proper training it is not recommended to take up this arduous cycling event.
Diamox tablet is very useful for high altitudes. It may not be required if the body is tuned when one starts cycling from Kashmir/Srinagar to leh and then down to Manali or getting to Leh via Spiti Valley. The one side-effect of taking this tablet is frequent urination.
The other important medicines would be like
Dolo 650 or any prescribed paracetamol tablet
Vikoryl or any other prescribed tablet for cold reliever
Vicks cough drops incase of throat irritation
Any prescribed pain killer tablet (if required)
A doctor check-up before starting the trip is highly recommended too.