Your Muscles: Secrets of Aging Gracefully


Inside Tufts HNRCA Laboratory of Nutrition, Exercise, Physiology and Sarcopenia-on the front lines of the fight against frailty.

At 711 Washington Street, in the heart of downtown Boston, you will find the worlds largest research center on nutrition and aging. With over 300 scientists, the Tufts Jean Mayer USDA Human Nutrition Research Center on Aging (HNRCA) has been advancing the knowledge of human nutrition since 1979. Step inside and take the elevator to the 13th floor. In the sunny hallway a scientist measures the gait speed of a woman, and in the research gym an elderly man walks on a treadmill, enjoying a breathtaking view of the city below.

Welcome to the Nutrition, Exercise, Physiology and Sarcopenia (NEPS) laboratory.

Sarcopenia: The Primary Suspect
The NEPS laboratory is investigating sarcopenia, the gradual loss of skeletal muscle in the later years of life. The condition goes hand in hand with decreased physical activity and increased likelihood for falls and fractures. Progressive sarcopenia is also an indicator for disability and loss of independence.

Skeletal muscles reach peak mass by the third decade of life, and with each subsequent decade muscle fibers decrease in size and number. This process speeds up in the later years of life; by age 80, up to 30% of muscle bulk may be lost.

Its clear that any new tool to fight sarcopenia is important. Sarcopenia affects 15% of people older than age 65, and 50% of people older than age 80. Since theres no stopping Father Time, the NEPS laboratory is committed to helping our bodies and its muscles age as gracefully as possible.

The Fat Blockade
Its clear that strength training increases muscle size and muscle strength. Whats perplexing is the diminished capacity to add muscle in later years. Why is it harder to develop muscle as we age?

The NEPS laboratory suspects that growth is hindered by molecular changes. Close examination has revealed two findings inside the muscle cells: a group of altered signaling proteins and an unusual amount of fat. Roger Fielding, PhD, director of the NEPS lab, reports, We are very excited about the observation of increased triglyceride in muscle and the byproducts of lipid storage in muscle.

The next challenge is nailing down the implications of fat inside aging muscle cells, and understanding why it accumulates in the cells. Fat infiltration could occur from increased storage of available lipids, or from a metabolic surge of production.

The bottom line is that extra fat inside aging muscle cells is bad news for most people. Still to be determined is whether eating less fat can translate into cleaner muscle cells and more muscle growth.

The LIFE Study
The NEPS laboratory is also participating in the Lifestyle Interventions and Independence for Elders (LIFE) Study-the largest research trial to date on physical activity in older adults. Spread across eight institutions in the United States, the trial is currently recruiting 1,600 older adults who will be followed for two to four years.>

The LIFE Study will determine if physical activity and health education can prevent major mobility disability, defined as the inability to walk a quarter of a mile or four blocks. Sara Folta, PhD, assistant professor in the John Hancock Research Center on Physical Activity, Nutrition and Obesity Prevention, is one of the Tufts co-investigators. Folta explains, Preventing disability is critical since being able to move around easily is closely tied with an older persons ability to lead a full, independent life. Disability is also linked to higher rates of morbidity, mortality, hospitalizations and a poorer quality of life.

Participants will be randomly assigned to a walking program or enrolled in Successful Aging health-education workshops with supervised stretching. The study will measure the effect on mobility disability and other factors such as cognitive function, heart health, prevention of falls and disability in common daily activities (eating, dressing and bathing).

The LIFE Studys focus on disability in participants in diverse geographic locations sets it apart from previous research. Folta notes, We expect that the results will impact both clinical practice and public health policy, and will therefore benefit both individuals and society.

Progress at Tufts is going well, with volunteer enrollment continuing through fall 2011. Recruitment continues across all study sites. To learn more about the LIFE Study, call (352) 273-5919 or toll-free (866) 386-7730 or visit Stay tuned for results in future years.

Muscular Vocabulary Sarcopenia means the age-related loss of muscle mass and strength; the word comes from the Greek, meaning poverty of flflesh. This condition of an overall weakening of the aging body caused by a change in body composition in favor of fat and at the expense of muscle was actually given its name by Healthletter Editor Irwin H. Rosenberg, MD, and fellow Tufts scientist William Evans, PhD. The ultimate price of this condition is loss of balance, reduced mobility and the frailty so often seen in the elderly. Besides naming this condition, Tufts University researchers such as those at the HNRCAs Nutrition, Exercise, Physiology and Sarcopenia Laboratory have gone on to show that sarcopenia is not a necessary or normal component of aging.

Muscle Power vs. Muscle Strength
Lifting a dumbbell fast or slow-does it really matter? Yes, says another research project from the NEPS lab.Recall the elements of physics, and remember that power is the combination of force and velocity. Muscle power measures both the muscles effort and its speed of contraction. In comparison, muscle strength measures only maximum brunt. Think of your last family reunion: Picking up that cute toddler requires a certain amount of muscle strength. But the difference between a slow raise (wow, theyve grown since last time!) and a fast swing up into the air is due to muscle power.

As it turns out, muscle power declines faster and earlier in life than muscle strength. Fielding says, Muscle power, more than muscle strength alone, is a stronger predictor of mobility function.

So why do we lose power before strength? It may be due to the quality of the muscle itself. Aging muscles have fewer fast twitch muscle fibers, the kind responsible for explosive, powerful movements, and instead rely more on slow twitch fibers involved in sustained movements.

High-speed exercises can potentially increase muscle power. At least thats what NEPS researchers argued when they started an exercise study in 57 older women. After 12 months, however, researchers found that women who performed high-speed leg exercises had improvements in leg power similar to women who performed only flexibility stretches. The results demonstrate the complex relationship between exercise and muscle power. Now ongoing research is examining the brains role in muscle response time and muscle contraction, yet another factor in muscle power.

To remain nimble, muscle power trumps muscle strength. Speedy exercises may help preserve power, but thats still under investigation.

Your Exercise Prescription

    Tufts NEPS lab endorses the 2008 Physical Activity Guidelines for Americans, established by the US Department of Health and Human Services. Follow these guidelines to reap the benefits of physical activity:

    • Aim for 150 minutes (2 hours and 30 minutes) each week of moderate-intensity aerobic physical activity. Think brisk walking.
      OR aim for 75 minutes each week of vigorous-intensity aerobic physical activity. Think jogging or bicycling.
      OR aim for an equivalent combination of moderate- and vigorous-intensity aerobic physical activity.
    • Perform aerobic activity in episodes of at least 10 minutes, preferably spread throughout the week.
    • Try muscle-strengthening activities at least two days per week.
    • Older adults at risk for falling should do exercises that maintain or improve balance.
    • Some older adults cannot do moderate-intensity aerobic activity due to chronic conditions. Be as physically active as your abilities allow and avoid inactivity.
    • Consult your health-care provider if you notice symptoms of chest pain, chest pressure, dizziness or joint pain.
    • If you have a chronic condition, speak with your doctor before starting any new exercise program-you may need a physical examination.

To learn more, see

More Protein = More Muscle?
Since protein is the building block for muscle tissue, will munching more protein prevent sarcopenia?To address the protein question, the NEPS researchers have asked a group of men and women ages 70-85 to take either a whey protein pill or a placebo pill with daily meals, in addition to visiting the NEPS gym for resistance strength-training exercises. Changes in muscle mass, function and size will be measured for six months to test the protective effect of protein.

Fielding notes, We expect that exercise does not have an isolated effect on muscle, but can be modulated by nutrition as well.

The Recommended Dietary Allowance (RDA) of daily protein for adults is 0.8 grams per kilogram of body weight, equaling 56 grams of protein for a 70-kilogram (154 pounds) person. These days most Americans are eating 1.2-1.5 grams of protein per kilogram of body weight per day-well above the RDA-making some skeptical that more protein will benefit aging muscle.

Before any changes can be made to the RDA, more substantial evidence from numerous research trials will be needed. For now, strive for an adequate amount of protein each day, but dont overdo it if your hunger for protein also means consuming lots of extra calories and saturated fat.

3 Ways to Prevent Sarcopenia

    So what have we learned from the years of research up on the 13th floor about how to prevent sarcopenia? You can help keep muscle loss at bay as you age with these tips from the NEPS laboratory:

  • 1. Avoid excess weight gain. Extra pounds are a strong predictor of physical disability, also taking a toll on bones, joints and your heart. Weight gain, by contributing fat to the muscle cell, may also inhibit muscle growth.
  • 2. Remain physically active. Fielding notes, We know that resistance exercise is the most potent stimulus of muscle growth in healthy adults. Maintain and increase that physical activity.
  • 3. Eat a varied, nutritious diet. Keep your muscles flexing and blood pumping by eating an adequate amount of protein along with a hearty helping of whole grains, fruits and vegetables.

– Rachel Perez

Rachel Perez is a dietetic intern and graduate student at Tufts Medical Center, Tufts University.


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