Ask a child what an old person looks like, and they will likely stoop forward, walk slowly, feign inability to lift something heavy, and look tired and sad.
What they are unconsciously mimicking are the familiar symptoms of “frailty”- a syndrome that is easy to recognise, although somewhat harder to agree on with regards to its cause or most effective treatment. Although not all older adults become frail, these features associated with ageing are common enough that the stereotype is familiar to children everywhere.
We do know that frailty (most often defined as sarcopenia (loss of muscle), slowness, sedentariness, sleepiness, and strength loss) will affect up to one-half of the 1.6 billion older adults who will populate the world in 2050. Unfortunately, despite decades of research, we have no pharmacologic “magic bullet” to prevent or treat frailty, or slow its progression. We have no blood test to verify its presence, and even the measurements of its core features (muscle mass, muscle strength, gait speed, fatigue, physical activity level) require tools that are not part of the typical physician’s office or hospital visit, and therefore remain largely out of sight, out of mind.
Remarkably, however, we already have access to the specific antidote to the core features of frailty: loss of muscle mass and strength, which in turn contribute to the slowness of gait, inactivity, and fatigue. This antidote is called high intensity progressive resistance training or PRT.
The classic description of PRT is that of Milo of Croton from 540 BC, the most famous Olympic wrestler of all time. It is said that Milo built his incredible strength through a simple, but profound strategy. One day, a newborn calf was born near Milo's home. The wrestler decided to lift the small animal up and carry it on his shoulders. The next day, he returned and did the same. Milo continued this strategy for the next four years, hoisting the calf onto his shoulders each day as it grew, until he was no longer lifting a calf, but a four-year-old bull. Whether you believe this story to be true or mythological hyperbole, these are in fact the principles of progressive overload of muscle that have defined PRT up until the present day.
The first use in modern medicine began in 1945 when an army physician, Dr. Thomas L. DeLorme reasoned that such heavy lifting would prove beneficial for injured servicemen. DeLorme refined the system by 1948 to include 3 progressively heavier sets of 10 repetitions, and he referred to the program as "Progressive Resistance Exercise." It was quickly adopted as the standard in both military and civilian physical therapy programs and DeLorme's academic publications on progressive resistance exercise helped legitimize strength training and played a key role in laying the foundation for the science of resistance exercise. However, these principles were never applied to older adults wasting away from sarcopenia and frailty, perhaps due to a misplaced fear that it would be unsafe or ineffective once severe atrophy from disuse, chronic disease and extreme old age had set in.
In 1988, at the Harvard-affiliated Hebrew Rehabilitation Center on Aging, as a new faculty member, it seemed to me that the frail, aged care residents there might just benefit from an application of Milo’s basic principles of strength gain and DeLorme’s approach to rehabilitation. And so, we recruited 10 frail nursing home residents between 86 and 96 years of age into the first study of its kind- High Intensity Strength Training in Nonagenarians. In 8 short weeks, their muscle strength doubled or tripled, muscle size increased, and functional mobility improved. Two of them threw away their walking sticks. When the strength training stopped, they quickly lost the benefits gained.
Many other larger studies followed, and it was clear that this modality of exercise was the missing link in our approach to a variety of aged cohorts who also had wasting and muscle weakness as part of their clinical manifestation. These included older adults with renal failure, congestive heart failure, coronary artery disease, depression, diabetes, osteoarthritis and rheumatoid arthritis, cognitive impairment, hip fracture, and falls, among others. Muscle biopsy analyses in individuals up to 101 years of age showed a remarkable regenerative capacity in ageing skeletal muscle after PRT- including transformation of satellite cells into baby muscle cells, expression of molecular signals normally only seen in embryos and neonates, enlargement of mature muscle fibres, and marked increases in anabolic hormones such as insulin-like growth factor 1 (IGF-1).
In our experience, the older the individual, the more likely they are to exhibit clinically relevant improvements in strength after this kind of exercise. There is no age above which PRT is no longer effective or safe if applied according to standard principles of progressive overload while observing proper technique. Frailty is not a barrier to the application of robust exercise. Rather, it is one of the most important reasons to prescribe it.
Professor Maria Fiatarone Singh, MD, is from the University of Sydney, Faculty of Health Sciences and Sydney Medical School.
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