Red Barn PT -- Valley Business News article by Elizabeth Deneen

Aging, Muscles, and Exercise

by Elizabeth K. Deneen MS, PT, GCS
as published by The Valley Business News, September 2002

By the time we reach our 70's, most of us will have lost 20 to 40 percent of our muscle tissue. The loss of skeletal muscle tissue is a normal phenomenon of aging and is referred to as sarcopenia (sar-ko-PEEN-ya). Its causes are not well identified, but researchers have linked hormonal changes, diet, and a sedentary lifestyle as factors. It seems clear, however, that an active lifestyle and exercising can delay the onset and severity of sarcopenia.

Every day of our life our muscles adjust to gravitational stress to keep us erect and moving. When stress due to gravity and movement decreases, the body responds quickly by reducing the nutrients and energy delivered to bone and muscle tissue. Studies of astronauts in space attest to the effects of weightlessness on the human body---without gravity, bone leaches out minerals (osteoporosis), and muscle tissue shrinks (sarcopenia)---the same conditions which affect the older population. A sedentary lifestyle, by reducing the metabolic demand on our skeletal muscles, has the some of the effects of weightlessness. In thinking about what happens to muscles as we age, some explanation of the different kind of skeletal muscles and how they work may be helpful.

There are different types of skeletal muscle fibers. Type I muscle fibers, described as "oxidative slow-twitch muscle fibers," generate muscle contractions of low-magnitude force. They contain a large numbers of mitochondria, cellular organelles specialized in the storage of oxygen used in the synthesis of adenosine triphosphate (ATP), the essential energy unit for muscle contraction. Type I muscle fibers are found in all muscle groups, but are present in greater numbers in certain muscles of your legs, the soleus muscle, for example, and around your spine and neck---muscles involved in posture, the muscles that literally keep the body from collapsing upon itself.

At the other extreme are type II muscle fibers, specialized in the short-duration, less frequent but powerful contractions used in activities like jumping, throwing, pushing and pulling. These fibers do not need oxygen for the synthesis of ATP and their contraction speed is fast---thus, they are known as "low-oxidative fast-twitch muscle fibers." They are found in the powerful muscles of the legs, and in your arms and torso. Other muscle fibers share in varying degrees the characteristics of these two types, performing intermediate functions and adapting to stress by changing their characteristics to more resemble either Type I or Type II fibers.

Type II muscle fibers are especially affected by aging. This may be the reason why at age 50 you do not feel anymore compel to jump over the fence when you see one. You would rather walk around it. You probably have also discovered that you can sustain activity with a low load output for a long period of time without feeling tired. That is because the motor recruitment of Type I muscle fibers has increased over the years.

Physical inactivity is a problem. Starting with grade school, we begin our chairbound lives. Increasingly, our jobs involve sitting at desks; we commute to work in comfortable car seats; we sit for dinner; and we recline in the sofa or lazy-boy to read or watch TV. If we don't supplement our routine with daily walks or some form of sport or exercise, we deprive our muscles of the necessary stress for maintenance of their normal function. We become astronauts in space. Not only are we are losing the ability to jump over the fence, but we prematurely develop problems with walking, getting up from chairs or bed---tasks called "activities of daily living" (ADL's) the performance of which is essential to our physical independence. Inactivity is so detrimental to people of any age that the Surgeon General has issued a report warning that inactivity is a major health risk. Fortunately, your muscles have the ability to adapt to stress and retain this ability even at very advanced age.

Getting started with exercise is usually easier than you think: begin with what you are able to do, and then push the limits gradually. If you can only walk 10 feet with a walker, start there, and the next day try one more step. What is often more difficult, however, is to stay motivated. For this reason, it is often helpful to seek professional guidance.

Four type of exercise are beneficial to older adults: endurance, resistance, flexibility, and balance. Endurance training improves lungs and cardiac function and tends to selectively develop your Type I muscle fibers. Exercising for endurance involves doing repetitive motion that are relatively easy to perform for a long period of time---for example, brisk walking, rowing, and bicycling. Endurance training should preferably be done every day for at least 30 minutes.

Resistance training increases your muscle strength reserve, prevents osteoporosis, improves your posture, and enhances the ability of frail persons to perform their ADL's. Strength build-up occurs when muscles are challenged to their maximum limit. Resistance training involves repeated lifting or pushing a load near your maximum effort (often, 3 sets of 8 repetitions 2 to 3 time per week for major muscle groups is enough). Resistance training stimulates your Type II muscle fibers. Research has yielded some astonishing results: very frail individuals can more than double their strength in a short period of time, and, when done properly, with very little risk of injury to the musculoskeletal system.

Flexibility exercise should always be part of an exercise program. Stretching helps your body stay limber, maintain healthy joints and increase your range of motion. Stretching is especially beneficial to people with neurological diseases such as Parkinson's, multiple sclerosis and stroke and for people confined to a wheelchair or a bed. There are many ways to stretch but to be effective stretching should be coordinated with breathing and the positions be held at least ½ minute.

Maintaining good balance is essential to prevent falls---the cause of so many hip and wrist fractures among older persons---Many exercises designed to improve balance resembles exercises designed to increase strength. Balance, however, is a complicated phenomenon, and although exercising may help, it is important to understand that the loss of balance can have multiple causes. Three organ systems influence balance: vision, proprioception (the ability to sense the spatial configuration of our body in the absence of vision) and the vestibular system of the inner ear, which registers information on the movement of the head. Any deficiencies in those organ systems will affect your balance. In addition, balance can be greatly affected by muscle weakness, loss of joint flexibility, medication, and alcohol.

Starting an exercise program on your own late in life may seem overwhelming, but help is available. A visit to your doctor is advised if you have underlying chronic conditions. If you are a beginner or if you have specific needs, physical therapy may be your answer. Physical therapists are licensed health professionals who will help you start with a safe exercise plan. For those with some experience, a home program or a group class may be more appropriate. Check with your local senior centers. Some health clubs also offer special classes for seniors. A good source of suggestions for home exercise is Exercise: a Guide From The National Institute On Aging, published by the National Institute on Aging, (publication # NIH 98-4258---you can order it by calling 1-800-222-2225.)

And don't forget that exercise doesn't have to be a chore. Many organizations offering sports and leisure activities welcome seniors. Join a dance or Tai Chi class, go swimming, golfing, bird watching, canoeing---you name it. You'll make a lot of new friends and probably have a lot of fun.