To utilise your muscle power as much as possible and prevent exhaustion too quickly while mountain biking, it is important that you find a comfortable way to sit on your bike while riding.
There are some basic tips and techniques that I use myself with good results.
In order not to overload your knees and to get the best power transfer to the pedals, it is a good idea that you ride with your knees close to the bike frame.
Bend/Angle on Elbows.
It is important that you ride with bent elbows to absorb impact forces. Otherwise your wrists, arms, elbows, shoulders and upper body will be overloaded, hurt and get sore when riding the single track and obstacles.
With bent elbows, it will also be much easier to manage your mountain bike handlebar and turn sharp corners because your upper body and centre of gravity are lower.
You have to use your abdominal and back muscles in collaboration with your leg muscles to keep you on the mountain bike. Arms, wrists and hands are to steer with and operate brakes and gears, not to lean all your body weight on.
When mountainbiking and overtaking another rider, or being overtaken make yourself wide by rotating/sticking your elbows/arms to take up more space/buffer. This can prevent you from being pushed around by accident (going nose down in the dirt) by other riders.
Select the right gears in time and not on the hill. Get a good grip on the handlebars, rotate your arms and elbows inward and let your elbows point downwards. The steeper the hill is, the more your forearms should rotate into a horizontal level. Your butt must also be moved backwards in the saddle.
All this should be done to prevent the front wheel from losing contact with the ground, thus keep traction on the rear wheel.
The saddle height is determined by the angle of your knee when the pedal/shoe is in the lower position. Your knees must not be fully extended, there should be a certain angle so it feels comfortable while riding. The heel of your shoes should not be below the horizontal level while you measure.
If your hips rock up and down while riding, then your saddle height is too high.
Try to imitate the angle from my knee which you can see on the picture to the left. You must probably hit the single track/road before you finally find the right saddle height that suits you. For me personally, it normally takes 2-3 mountainbiking trips before I find the correct saddle height.
Your transfer of power to the pedals should be carried out in a horizontal motion whenever possible. This is to economise your energy and muscles, and it is also more comfortable to ride in this way.
Therefore when your shoe/pedal is in the lower area, move it in the direction of the rear wheel, just as if you wipe something off your shoe.
And when your shoe/pedal is in the upper area move it in the direction of the front wheel, just like your are trying to throw your knee over the handlebars.
Rules of thumb for using the three chain rings in front and gear shifting tips.
1. Use the large chain ring on wide plane singletracks, dirt roads and asphalt roads.
2. Use the medium chain ring on narrow and rough singletracks.
3. Use the small chain ring when you ride total 'offroad' off singletracks and very steep climbs.