I am a hard core gymer. I work out 2hrs a day at a single stretch. However I am unable to keep the intensity of the workouts halfway. I mean not being able to maintain the vigour and stamina with which I began. Currently I am working out for weight gain and lifting heavyweights so I warmup for 8 -10 minutes. Its cold winters here in haryana, india. Can you suggest ways in improving my stamina? Is there some thing I should do to improve stamina or take certain supplements before working out? Will taking lot of carbs before working out really help??
Train smarter not harder™.
On a serious note, most workouts plans can be finished within an hour. Even bodybuilding workouts generally don't take that long. Mostly because if you have enough energy to go two hours, then you probably aren't challenging yourself enough in the first hour. Also there is a period of diminishing returns in which more work doesn't necessarily mean more gains.
Having said all that, the question is about energy. Some workouts you just feel sluggish and need a boost. Energy can be best derived from fat and carbs. Carbs will give you a quicker, faster boost. Simple carbs (sugar) will give you a much quicker boost of energy that goes away quicker. Complex carbs (vegetables, potatoes, grains, oats, beans, etc.) will give you a longer, more sustained energy. While fat can give you even more prolonged, sustained energy.
So, before a workout, it would be beneficial to have a bit of both complex carbs and/or fat. I'm not sure what is easily available in India or what kind of dietary restrictions you have. I personally like eggs and oats. Eggs are a very good source of healthy fats and proteins. Oats are a very fibrous, complex carbohydrates which is great for a sustained energy. During more intense workouts, I will eat jellybeans which are basically pure sugar which is a simple carb for a much faster energy boost. About 30 grams spread throughout the workout is enough.
You can substitute for whatever food you like/have access to which follow similar macro-nutrients. Also use this advice as a guideline rather than a strict rule to follow. Not everyone responds the same so you should experiment with different variations to know what works best for you. (Some people workout better on a completely empty stomach for example.)
If you are able to maintain the intensity till half-time of your workout, you, then you are almost done with what you are doing. Pushing a little further till failure would help, but pushing yourself more is only going to have negative effect on strength and mass. Have a look at the graph of strength/mass vs workout duration.
This is the site http://scoobysworkshop.com/. Credits for the image goes to Scooby and the site above and not me. The person is a qualified engineer and always uses science in all his workouts.
Now as you see in the image, after a period of time( which is usually between 30 minutes to an hour for strength training depending on the person), anything done in excess only fetches you negative returns. Your muscles crave for energy and they break beyond repair.So, stick to a time that suits you. There's no reason to push yourself for 2 hours and look for stamina, if your goal is purely strength and mass.