One cannot begin to fully answer the question of whether a protein shake is best before or after a workout, without understanding how long before or after a workout counts as pre and post workout nutrient timing.
The pre-workout nutrition window can be anywhere from 30 minutes before training to three hours before training. Whereas the post-workout recovery window is estimated to be anywhere from 20 minutes to an hour after you leave the gym.
The pre-workout window is used to supply energy or calories that will be used in your training. This is your opportunity to fill up the gas tank and have more energy and increase endurance in the gym.
If you are consuming a full meal within three hours of your workout, your body has time to properly break it down and utilize it for energy. Unless you are in need of higher calories for performance or are worried about losing muscle mass, this meal is likely more than enough to supply your needs.
If you haven’t eaten before training, consuming some fuel within 30 minutes to an hour before you hit the gym can support your needs. Although the type of fuel you choose becomes more important as you get closer to your workout window.
The post-workout nutrition window is used for recovery and refueling. Training causes wear and tear on your muscles and depletes energy stores. Eating after a workout can help replenish lost fuel and provide recovery nutrients to your hungry muscles.
Additionally, there is an increased amount of blood flow to your hungry muscles after a hard workout, priming them for efficient nutrient delivery and absorption. This is commonly referred to as the anabolic window.
For most people, consuming a regular meal within a couple hours of the gym is more than enough to support your recovery needs. This is especially true if calorie control is important to your fitness goals. However, some may find utilizing the anabolic window helps them with better recovery and future performance.