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Part 2: How Aging Changes Your Response to Exercise, Training, & Nutrition

The following article is part two of a three part series on the importance of muscle strength as it relates to one’s health and longevity.  The first article discussed the relationship between muscle strength and maintaining healthy body functions as one ages, along with tips and advice for how to start an exercise-training program to increase muscle strength.  This second article will discuss how aging changes one’s response to exercise training and nutrition, and explain how diet and nutrient supplementation can be modified to improve exercise training adaptation. The third article will discuss the role of nitric oxide in muscle function and development, and explain the need to maintain adequate nitric oxide levels to bring about desired training adaptations. It is not exaggerating when I say that following the simple recommendations provided in these articles can have a profound effect on your quality of life.

Muscle Mass, Strength and Function with Aging

From birth until about 30 years of age, there is a continued development in strength, muscle mass and quality.  After age 35, a gradual decline in muscle mass and strength begins and is associated with a reduction in strength, power and speed of movement. This decline accelerates at about 50 years of age and then again at 70 years of age. After the age of 70, this decline continues to accelerate 25-30% per decade.

Aside from a loss in muscle mass and strength, other alterations in muscle occur with age include reductions in mitochondrial and capillary density. Mitochondria are the power plants of the cell.  They are responsible for aerobic (in the presence of oxygen) energy production in the form of adenosine triphosphate (ATP). ATP is the energy currency of the cell and is required to run all energy requiring metabolic processes in the body including muscle contraction. The capillaries surrounding the muscle fibers are where the transfer of oxygen and nutrients pass from the circulatory system into the muscle fiber, and where metabolic waste products are transferred out. As muscle mitochondrial and capillary density increases, the ability of the body to perform prolonged endurance exercise increases and efficiency of exercise recovery improves. Conversely, as mitochondrial and capillary density decrease, exercise endurance decreases. 

The decline in muscle mass and strength with age is genetically controlled. However, a decline in physical activity with age also contributes. If muscle is not physically challenged regularly, it will atrophy. Think “ if you don’t use it you loss it.”  This is why, as one ages, it is important to participate in a regular resistance exercise training program.  Another reason for the decline in muscle mass and strength is due to “anabolic resistance”.  Characteristics of anabolic resistance include a blunted protein synthesis response to resistance exercise and dietary protein including protein consumed immediately post exercise.

Therefore, with advancing age the amount of dietary protein necessary to maintain muscle mass increases.

Dr. John Ivy on connection between aging, protein, and muscle mass.


Dietary Protein Requirements

Dietary protein is a vital nutrient that supplies needed amino acids that are used to make enzymes, hormones, neurotransmitters, antibodies, and serve as the building blocks for repair and growth of all tissues of the body including muscle.  There are 20 amino acids that the body requires for these purposes.  Of these 20 amino acids, 11 can be produced in the body itself and are referred to as non-essential amino acids, while 9 are referred to as essential amino acids because they have to be obtained through dietary means.

Not all dietary proteins are equal in nutrient value.  As mentioned above, protein is made of amino acids and each protein has a unique amino acid profile.  Proteins can be classified as complete or incomplete proteins.

  • A complete protein is one that has an adequate proportion of all 9 essential amino acids necessary for the dietary needs of humans. Complete proteins are typically animal-based proteins such as meat, fish, milk, cheese and eggs. However, there are some plant sources of protein that are considered complete such as soy, quinoa, buckwheat, hemp, and spirulia.
  • An incomplete protein is one that lacks one or more of the essential amino acids or does not have an adequate proportion of one or more of the essential amino acids. However, just because a protein is incomplete does not mean that it is not beneficial. Meals are not generally made from a single food item, and combining the right combination of incomplete proteins can provide the necessary essential amino acids required by the body. Proteins that are combined to provide a complete amino acid profile are known as complimentary proteins.  Examples are brown rice and black beans or kale and almonds.

 As mentioned above, the RDA for protein is 0.36 g per lb. of body weight, and represents the quantity of protein that should be consumed daily to meet population needs and to prevent deficiency. However, factors including physical activity pattern, body type and age can have a significant influence on protein need.  For example, young individuals competing in sports who are likely involved in a rigorous training program require a greater amount of dietary protein than the RDA. Likewise, as individuals approach 45 to 50 years of age there is an increased requirement for dietary protein. In fact, once one reaches middle age, the requirement for dietary protein approximately doubles to between 0.55 to 0.68 g of protein per lb. of body weight

Increasing protein consumption in middle-age provides many benefits for both men and women.  It has been found to slow muscle loss with age, increase skeletal muscle mass and strength, and to enhance training adaptation when combined with a resistance or aerobic exercise training program. Consuming additional protein while lowering carbohydrate and fat consumption when dieting has also been found to reduce muscle loss while increasing fat loss in overweight individuals.


Timing Protein Consumption for Best Results

The timing of protein consumption is also an important consideration as it can have a significant impact on how effective whole body protein synthesis can be activated. Protein that is consumed at daily meals should be spread out evenly. That is, the protein at breakfast, lunch and dinner should be about the same volume.

Research indicates that consuming a moderate amount of protein at each meal stimulate muscle protein synthesis more effectively over a 24 hour period than skewing protein intake toward the evening meal.

In addition, eating a well balance breakfast consisting of an adequate amount of protein reduces appetite and is associated with a reduced caloric intake over the course of the day.

Consuming a protein snack such as Greek Yogurt, turkey breast, or low fat chocolate milk or a sports protein supplement before bedtime can also be beneficial.  During sleep there is usually a loss of muscle protein as muscle is broken and the amino acids released are converted by the liver to glucose in order to prevent blood glucose from falling. Recent research indicates that taking a protein supplement before bedtime will actually promote protein synthesis while sleeping and increase muscle mass. Moreover, subjects who participated in a 12-week resistance exercise training program and who received a pre-bedtime protein supplement were found to had significantly greater increases in muscle mass and 20% greater increase in total body strength than subjects that received a non-caloric placebo.

Post exercise is another important time to consume protein. Following a workout, the body is highly sensitive to certain nutrients. Consuming a protein supplement within 30 minutes post exercise has a much greater effect on stimulating muscle protein synthesis than at any other time. This is because after exercise the muscle is better able to take up amino acids from the blood due to an increase in amino acid transporters on the outer membrane of the muscle. Taking up more amino acids, particularly L-leucine, results in a greater activation of muscle protein synthesis. Stimulating protein synthesis post exercise accelerates muscle tissue repair, reduces muscle soreness and increases the rate of training adaptation.  For individuals preforming resistance exercise this translates to an increase in muscle mass and strength.  For individuals training aerobically, it translates to a greater increase in muscle mitochondria and capillarity.


Type of Protein Post Exercise

The type and quantity of protein consumed post exercise is also important. Proteins that are easily digested and high in L-leucine produce the highest rates of protein synthesis.  The single best protein for a post workout supplement is whey. In comparison tests against other quality proteins such as soy and casein, whey accelerated protein synthesis significantly faster. However, other vegetable proteins such as pea or rice are also beneficial. The amount of protein required to maximize protein synthesis post exercise is between 20 to 25 grams for adolescents and young adults. For middle aged and older individuals it appears to require as much as 35 to 40 grams of protein. However, it is possible to maximally stimulate muscle protein synthesis in older individuals with 20 to 25 grams of protein if about 2 to 3 grams of L-leucine is added to the supplement.



To summarize, individuals who are physically active, competing in sports or middle-aged or older should increase their daily protein intake to 0.55 to 0.68 g of protein per lb. of body weight.  Protein consumption should be evenly distributed across the 3 basic daily meals. Taking a protein snack or supplement containing 20 to 25 grams of protein 30 to 45 minutes before bedtime should also be considered as this will help to limit muscle loss while sleeping. If engaged in a regular exercise-training program, it is important to also consume a post exercise protein supplement as soon after the completion of each exercise session. This will limit muscle damage and soreness, promote muscle protein synthesis and enhance the rate of training adaptation. Protein supplementation post exercise should be about 20 grams for young individuals and 30 to 40 grams for middle-aged and older individuals. The amount of protein post exercise for older individuals can be reduced by adding 2 to 3 grams of L-leucine. If weight reduction is a goal, caloric restriction should be accompanied with an increase in protein consumption. This requires that the percentage of protein in the diet be increased to about 35% of total macronutrients.


Suggested Daily Protein Consumption

Distribution of Daily Protein Consumption Based on a 2,500 Caloric Diet with Protein encompassing 30% of the Total Macronutrients:

  • Basic 3 meals of the day
    • Breakfast – 40 grams
    • Lunch – 45 grams
    • Dinner – 55 grams
  • Post Exercise Workout
    • Within 30 minutes post exercise – 25 grams
  • Bedtime
    • Approximately 30 to 45 minutes before bedtime – 25 grams 

Total Daily Protein Consumption – 190 grams


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Author Dr. John Ivy

Dr. John Ivy, Executive Director of Sport & Nutrition Research

With a PhD in Exercise Physiology, Dr. John Ivy is our President of HumanN’s Science Advisory Board. He has authored over 180 scientific papers and several books, including the well-known and highly respected Nutrient Timing: The Future of Sports Nutrition. Working with notable sports greats, and Olympians in preparation for the 2008 and 2012 Summer Games, his contributions to sports nutrition and science are unparalleled. In addition to receiving a Citation Award from the American College of Sports Medicine and being named a Fellow in the American College of Sports Medicine, he is also one of the newest members of the University of Texas Department of Kinesiology and Health Education Hall of Honor.

Dr. Ivy’s research has pioneered our understanding of muscle metabolism and the role that properly formulated nutritional supplementation can play in improving exercise performance, recovery and training adaptation. His current research is centered around understanding the interactions of exogenous dietary nitrite/nitrate (NOx) on the endogenous NO/cGMP pathway and how dysfunctions in each system can affect cardiovascular health.

Dr. Ivy received his Ph.D. in Exercise Physiology from the University of Maryland, and trained in physiology and metabolism at Washington University School of Medicine as an NIH Post-Doctoral Fellow. He has served on the faculty at the University of Texas for over 30 years and as Chair of the Department of Kinesiology and Health Education for about half that time. Dr. Ivy is currently the Teresa Lozano Long Endowed Chair Emeritus at the University of Texas at Austin.

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