The post exercise meal is of crucial importance. The reason being, that it helps your body to recovery and improves your ability to train consistently. The three main aims of post exercise nutrition are (A) return the body to pre exercise levels of hydration, (B) restore glycogen levels (source of energy most used for exercise) and (C) aid muscle repair and growth.
(A) Hydration - The first priority after exercise is to replace any fluid and electrolytes lost during exercise which help the body to function properly. The best way to determine how much to drink is to weigh yourself before and after exercise and replace the fluid lost. A handy rule of thumb for this is to drink 1 litre of water for every 1 kg lost.
(B) Glycogen Replenishment - After exercise muscle glycogen stores are depleted. The first 30 minutes is the most crucial time to restore these glycogen stores. If you don't replenish glycogen rapidly, your performance will suffer the next time you train and you may even lose some muscle along the way due to muscle protein breakdown.
(C) Muscle Repair and Growth - After exercise, protein breakdown goes way up, thus creating a negative protein balance. If sufficient fuel is not replaced the muscles will break down and begin utilising proteins to fuel the body. Which essentially means you eat yourself from the inside. Protein replenishment is important as it provides the amino acids necessary to rebuild the muscle tissue that is damaged during intense exercise. It can also increase the absorption of water from the intestines and improve muscle hydration.
Research shows that combining protein with carbohydrate within thirty minutes of exercise nearly doubles the insulin response which results in more stored glycogen. Basically if you are looking for the best way to refuel your body after exercise, a 4:1 combo (4 grams of carbohydrate for every one gram of protein) would be the best choice. While solid foods work as well as a sports drink, a drink maybe easier to digest. The bottom line is after a hard training session make sure you consume a meal high in carbohydrates and protein and drink lots of fluid.