The body can absolutely hit a plateau during your training session. You can identify this plateau with feelings of severe weakness, confusion, fatigue and disorientation. In short, it refers to low blood sugar (hypoglycemia), where both your body and brain have simply run out of fuel. During high intensity or serious endurance exercise, it is easy to use up your stored glucose. Since it has an effect on both your brain and body, you won’t just slow down and stop exercising, you might experience cognitive symptoms as well. If you experience a plateau, you need to take in some simple carbohydrates that can be absorbed instantly. Sports drinks and gels are your best bet. In any case though, 2 and a half hour training sessions should not be the norm – especially without the correct nutritional support. Muscle mass begins to break down after 60 minutes of cardio when glucose stores have not been refuelled, and strength training has proven to be counteractive when exceeding an hour.