No matter how hard you workout, you will not see any gains until you give your body proper time to rest and recuperate. Some people leave recovery for after workouts. This is an old approach to bodybuilding. Supplements like BCAAs, beta-alanine, waxy maize starch, citrulline malate, etc. are present on the market that help in recovery during and after your workouts.
One of the most common intra and post workout recovery supplements right now are Branch Chain Amino Acids (BCAA's). The BCAA's consist of: L-Leucine, L-Isoleucine, and L-Valine. This increases the rate of absorption of amino acids, and allows the amino acids to be shuttled into the blood plasma. By taking the BCAA's in particular, muscle catabolism (the breakdown of muscle) can be prevented quickly, especially for usage in high-volume cardio work.
Another of the very new supplements to hit market popularity is actually a carbohydrate typically referred to as Waxy Maize Starch. There are a few unusual properties of WMS, one of which being the absorption of this carbohydrate. While most carbohydrates are passed to the intestinal tract and broken down to simple sugars for absorption, WMS passes directly through the gastric lining, without needing the gastric emptying for uptake. Additionally, WMS avoids the huge rollercoaster of an insulin ride (needed for the processing of carbohydrates) that is commonly associated with maltodextrin.
A supplement that has made a splash in the endurance world is Beta-Alanine. This forms a di-peptide with L-Histidine, forming the compound Carnosine.
Carnosine works by the reduction of H+ (hydrogen ions) forming in the blood plasma, which ordinarily will cause a drop in pH (acidic condition). By reduction, Carnosine will essentially buffer the overall pH of the body, which delays the onset of fatigue and eventually, failure. In recovery, the stabilization of pH means a lower amount of potential damage to tissue and muscle, due to the changing conditions of the body.