The purpose of a protein shake is to rapidly deliver amino acids to an athlete's muscle cells. Delivery of these amino acids kickstart a process called muscle protein synthesis (MPS), or the rebuilding of damaged muscle proteins. Each time your body rebuilds these damaged proteins, they become bigger and stronger to better handle stress in the future. This adaptation is essential for your progress as an athlete, and you can see that protein plays a vital role.
To maximize muscle growth and recovery, MPS needs to be constantly elevated. The best way to achieve this is to keep a steady flow of nutrients, especially protein, in your bloodstream. This can be achieved by eating a good source of protein at every meal and snack. A majority of your protein should come from whole food sources, but there are definitely scenarios where drinking a protein shake could be the better option.
So the question is, when should you drink a protein shake? Studies have shown that protein supplementation pre- and post-exercise greatly improves muscle growth as opposed to drinking a shake at any other point in the day. After reading about MPS, your first instinct might tell you that a protein shake is most beneficial post-workout, but that's not always the case. Every athlete has different needs based on his or her type of training, competition and timing of last meal.
When to Drink a Protein Shake Before Your Workout
If you haven't had anything to eat in the last 1-2 hours . . .
Your body needs fuel during exercise and competition, and if you haven't put gas in your tank, your body will do whatever is necessary to fuel itself. This includes breaking down precious muscle tissue to convert into glucose, or fuel. A pre-workout protein shake ensures that your body has adequate amino acids in the bloodstream to prevent muscle protein breakdown.
If you're an endurance athlete or train for over an hour (including practice) . . .
Even if your last meal was close to your workout, it doesn't take long for your body to use up the nutrients during exercise. If you know you will be training or competing for well over an hour, drink your protein shake right before or even during exercise if possible.
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If you will be eating a meal shortly after training . . .
If you have a routine of going home to a meal right after practice or training, there's no need drink a shake since you'll be replacing the nutrients with food. In this scenario I recommend having the protein shake pre-workout to ensure a steady flow of amino acids surrounding the session.
When to Drink a Protein Shake After Your Workout
If you consumed a mixed meal close to your workout . . .
A mixed meal consists all three macronutrients—protein, carbs, and fat. When they consumed together, digestion is slower than normal. So it's likely your body will continue to absorb your meal's nutrients throughout and even following a workout. Digestion of a mixed meal can last upwards of 8 hours depending on size!
If your post workout meal will be more than 2 hours after training . . .
Even with adequate fuel before a workout, it's important to keep the flow of amino acids going to support MPS. Another requirement, one we haven't talked about, is hydration. Without proper hydration, your muscle cells can't start the recovery process. So if you have a habit of consuming nothing at all post-workout, drink your protein shake afterwards.
If you have a short training session . . .
On days when you have a training session under an hour or a lower intensity competition, it's unlikely you will be at risk for muscle breakdown. Just remember that as workout intensity and duration increase, your need for protein increases too.
If you don't have an appetite after training . . .
Although exercise increases most people's appetite, intense exercise can have the opposite effect. If you find yourself unable to eat anything after a long workout, a shake is your best bet to replace nutrients and hydrate without forcing down a meal.
If drinking a shake prior to training doesn't agree with your stomach . . .
I don't advise chugging down a full shake immediately before training. The last thing you want during a workout is to have water sloshing around in your stomach. Allow yourself time to consume a shake at a moderate pace pre-workout, and if it still doesn't agree with your stomach, drink it afterwards.