Nutrient Timing

By William J. Kraemer, Ph.D.

A popular concept in strength training related to nutrition is the importance of nutrient timing.  Getting macronutrients into the system before and after a conditioning session is important for optimal repair and remodeling of tissues. An increasing amount of research has focused on this concept over the past five years. While the specific recommendations can be variable, an important finding is that protein intake along with some carbohydrate both before and after the workout may be optimal for the recovery process.

The most important finding in this concept for recovery resides with complete protein and more importantly, the essential amino acids including branch chain amino acids.  Typically, 20 to 25 g of protein is consumed before the workout.  To stimulate protein synthesis, it appears that protein intake prior to the workout is more effective than after the workout. Additionally, as one gets older (e.g., over the age of 40) and digestive challenges become more prevalent, the amount of essential amino acids required appears to be increased.

Intakes of small amounts of carbohydrate before workouts allows for insulin signaling to help with protein synthesis.  Carbohydrate intake after a workout typically begins the replacement of muscle glycogen stores.  Typical carbohydrate intakes range from 25 to 50 grams. However, the key nutrient for the enhancement of recovery is protein, more specifically essential amino acids.

The demands for protein synthesis arise from the damage that can take place with exercise stress.  Exercise results in the breakdown of muscle or more specifically muscle fibers. Muscle fibers are made of contractile proteins that produce the forces of movement, and keeping these proteins in place is a host of what are called non-contractile proteins that also need repair if damaged.

So the first site of real recovery is at this level of muscle fibers which are used to perform the activity.  Now not all muscle fibers are used for every activity and therefore the damage to tissue can vary based on the intensity and duration of the exercise.  Lifting heavy weights in a weight training workout will create more muscle tissue damage. Therefore, the recovery and rebuilding process will be enhanced not only by providing the body with the needed intake of protein, but the timing of some of the protein intake will also be important.

Weight training sessions as well as long duration endurance events such as 10Ks, triathlons, marathons and other ultra-distance events produce significant repair requirements.  Endurance events produce some of the greatest damage to muscle fibers as a result of the long duration and repeated use of muscle, especially the slow twitch muscle fibers. Many times endurance athletes (who should also lift) forget to take in protein around their training sessions and competitions since they are so focused on the replacement of carbohydrate.

In summary, the demands of exercise and the resulting damage ranges on a continuum from low to high. But in each case, optimizing the intakes of carbohydrate and protein is an essential part of helping the body to recover. And on training and competition days, timing of a portion of the total intake of nutrients is also an important consideration.

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