How Does Protein Affect Your Workout?

A post-workout smoothie that includes protein can help you repair.
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Fitness magazine ads for powders and gym supplements brandish pictures of lean, toned women who supposedly achieved their rocking physiques by consuming lots of protein. While protein is an essential macronutrient, eat too much of it and at the wrong times, you may regret your choice when you work out. Protein has an affect on exercise, but this nutrient alone will not build you the body of a fitness model.

Protein's Function

Protein is part of all bodily tissues. It makes up 20 percent of all muscle, but is also a component of bones and the connective tissues that support muscle. Adequate protein helps manage your enzyme production and transports nutrients to cells while helping carry waste products away. Protein plays a role in keeping your body hydrated and your immune system healthy. When you don’t have enough carbohydrates and fat, your body can also dip into its protein stores for energy.

Fuel for Workouts

Your body’s primary fuel source for exercise is carbohydrates. Carbohydrates digest quickly and provide immediate energy for your muscles. Protein digests more slowly and your body does not convert it into energy in an efficient manner. A pre-workout snack consisting primarily of protein may leave you sluggish because once you burn through your carbohydrate stores, your body cannot convert the protein quickly enough into energy. If you are weight training and attempting to build loads of muscle, a small amount of protein – 7 to 10 g -- along with carbohydrates prior to your lifting session, can provide you with amino acids to start repairing your muscles during your workout. An example of such a snack is half a smoothie made with frozen fruit, almond milk and a scoop of whey or soy protein powder.


Not getting enough protein on a regular basis can negatively affect workouts by leading to low energy and could cause your body to burn some muscle for fuel. The average person who exercises for 30 to 60 minutes, three to five times per week, doesn’t need more protein than the Recommended Daily Allowance of 0.40 g per pound of body weight per day. The American diet is already protein-heavy and most people get at least this much and most, far more. Athletes who exercise at a high intensity most days of the week – such as high school or college athletes, endurance athletes training for marathons or triathlons or bodybuilders and power athletes – do need more protein daily. The needs for athletes range between 0.6 and 0.75 g of protein per pound of body weight daily.

Endurance Versus Strength and Power Athletes

Endurance athletes fall more toward the low end of the recommended protein range for athletes while power and strength athletes should aim for the higher range. Endurance athletes need more protein because small amounts of their energy during workouts will eventually come from amino acids -- usually when sessions last longer than 90 minutes. Replacing these amino acids with protein post workout discourages muscle loss and hastens recovery and repair after a long workout. Power and strength athletes need more protein because the nutrient supports muscle growth and strength enhancement. Protein doesn’t make muscles grow, but it provides the building blocks for growth.


Eating more protein than your body needs is not necessary and will not help your workouts or muscle growth. If the extra protein means you are eating more calories than you burn daily, you will store the extra as fat. Excess fat will slow you down during workouts. Too much protein can also dehydrate you, which can also negatively affect exercise. The best sources of protein are whole foods, such as lean poultry and beef, low-fat dairy and tofu. Supplemental protein in the form of bars and powders are convenient, but not necessary.

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