I know just how it feels when your body wants off the bike around the 2 hour period. You are out there trying to keep your pace consistent and you start thinking and feeling that you are really uncomfortable. The reason why you are feeling uncomfortable is because you are starting to 'hit the wall'. The discomfort you can feel does vary from person to person, but it can be just little things like sore feet and hands which are tell tale signs to look for.
Hitting the wall or bonking occurs when your body runs out of glycogen stores. When cycling the body relies on getting energy from two major sources - glycogen and fat. Glycogen stores are predominantly used during the first 30 minutes of exercise, and then after this point glycogen is used to mobilize fat for fuel. If you work at an intensity beyond the rate in which your glycogen mobilizes your fat stores your glycogen does run out and you hit the wall (this usually occurs between 1hr 45min and 2 hrs in moderately trained endurance athletes).
If it is not too late you can prevent yourself from hitting the wall by reducing your speed and/or intaking more glycogen. Glycogen can be obtained quickly from ingesting drink/food with high carbohydrate levels. So make sure you drink sports drinks and if you plan to be on the bike longer than 2 hours take something to eat as well.
You can train your body to utilise glycogen better by doing long slow rides training.
Hitting the wall or bonking occurs when your body runs out of glycogen stores. When cycling the body relies on getting energy from two major sources - glycogen and fat. Glycogen stores are predominantly used during the first 30 minutes of exercise, and then after this point glycogen is used to mobilize fat for fuel. If you work at an intensity beyond the rate in which your glycogen mobilizes your fat stores your glycogen does run out and you hit the wall (this usually occurs between 1hr 45min and 2 hrs in moderately trained endurance athletes).
If it is not too late you can prevent yourself from hitting the wall by reducing your speed and/or intaking more glycogen. Glycogen can be obtained quickly from ingesting drink/food with high carbohydrate levels. So make sure you drink sports drinks and if you plan to be on the bike longer than 2 hours take something to eat as well.
You can train your body to utilise glycogen better by doing long slow rides training.