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Leucine: Maximize Your Strength

As an athlete, you work your tail off throughout the season to perform your best in that A race. The first part of your season consists of building a solid base – gaining strength in the gym that will transition to power on the bike or during a run. The second half of the season is devoted to speed and continued aerobic improvement.

For some athletes, performing their best means losing fat mass to get to a lean, healthy race weight. Without proper nutrition, however, you’ll not only lose fat but muscle mass as well. This could lead to substandard performance because of decreased strength and aerobic capacity. Not ideal.

No matter what your plan entails, the one piece that should never be left out is nutrition. Depending on what phase of training you’re in, your fueling may change to help promote muscle gain and muscle maintenance.

Muscle & Leucine

Skeletal muscle responds to exercise in a variety of ways. Endurance training alters muscle cells to be more fatigue resistant, be able to use fats for fuel, and have the capacity for more efficient use of carbohydrate fuels. Resistance-trained muscles use primarily chemical reactions for power rather than carbohydrates or fat, and these exercises increase muscle fibers to generate greater force.

In fact, resistance exercise is a potent stimulant of Muscle Protein Synthesis (MPS), or the building of muscle, and this process is further enhanced by specific nutrients. This is where leucine comes into play. Leucine is an essential amino acid that is theorized to be the limiting factor of MPS. Meaning that while all amino acids are necessary to build protein, if there isn’t enough leucine, muscle accretion is not nearly as great.

Leucine content of different protein sources differs dramatically (grams Leucine per 100g product):

  • Whey Protein Powder: 9.0 g

  • Pea Protein Powder: 8.4 g

  • Dried Egg White Powder: 6.83 g

  • Soy Protein Isolate Powder: 6.78 g

  • Casein Protein Powder: 6.65 g

  • Dry Nonfat Milk: 3.54 g

  • 2 Whole Eggs: 2.17 g

  • Dry Black Beans: 1.72 g

  • Ground Beef (95% Lean): 1.67 g

  • Whole Wheat Flour: 0.89 g

As you can see, whey protein powder (made from the liquid that is left behind when milk is curdled and the solids [casien] are removed) provides the highest concentration of leucine. The good news for vegans is that pea protein powder holds a very close second in leucine content with 8.4g per 100 grams.

Leucine: Amount & Timing for Muscle Gain

The above graph, created as a review of nine studies, shows resistance training-induced changes in lean muscle mass using different protein sources, with whey supplementation post-exercise creating the highest gains.

Along with the type of protein, the amount consumed also plays a key role. Studies have found that MPS plateaus with anything above a single dose of 20 grams of protein (about 8.5g of essential amino acids), consumed after resistance training. Any extra protein ingested at one time is burned as fuel and not used to build more muscle.

Timing your protein supplementation is also important for MPS. Consume 20 grams of high-quality protein within 1-2 hours after a workout for optimal gains, and/or 30-45 minutes before a workout.

However, I do not recommend taking in protein before a workout as much as I recommend carbs be taken at this time. Carbs give you the energy to perform your best; allowing you to have increased intensity, perform max lifting, and give you the fuel to get the most out of your workout. Protein does not provide the glucose your body needs to train hard — so I recommend taking in protein after and carbs before.

So what does this mean for YOU?

Training: Strength Phase

During the strength blocks of your training plan, when muscle accretion is an important factor, focus on having 20 grams of high-quality protein (preferably whey protein or pea protein powders, or another powder that has added leucine) within an hour of your resistance training session. This will help you make the most of your time in the gym.

Training: Speed & Aerobic Capacity

During the second half of your season, as time in the gym diminishes and time out on the road becomes more valuable, it’s equally important to focus on nutrition. During this time, fuel your workouts with a pre-workout carbohydrate snack, and refuel with a 4:1 or 3:1 ratio of carb: protein recovery drink.

To help maintain muscle mass during this time, have a protein shake before bed using whey or pea protein powder. Night time is when the body releases human growth hormone to help rebuild and repair muscles – this is your body’s anabolic (muscle building) time. Having some protein before bed may help with the muscle recovery and build process.


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