If we can predict lifespan, can we also modify it?
What is the best predictor of when you’ll die? That seems like a hard—not to mention morbid—question, but, incredibly, study after study is showing that simple tests of physical performance are highly predictive of future mortality.
My favorite recent example is a study from Brazil that tracked just over 2,000 subjects age 50 and up. A 10 point score system was developed to assess how easily they could get up off the floor based on a sitting-rising test (SRT):
Lower SRT scores were associated with higher mortality (p<0.001). A continuous trend for longer survival was reflected by multivariate-adjusted (age, sex, body mass index) hazard ratios of 5.44 (95% CI 3.1–9.5), 3.44 (95% CI 2.0–5.9), and 1.84 (95% CI 1.1–3.0) (p<0.001) from lower to higher SRT scores. Each unit increase in SRT score conferred a 21% improvement in survival. Conclusions: Musculoskeletal fitness, as assessed by SRT, was a significant predictor of mortality in 51–80-year-old subjects.
There was a clear relationship between how easy it was for the people to get off the floor and how long they lived.
A little deeper dive into the data shows that about 95 percent of the people who scored well (between eight and 10) survived over 14 years. Only about 60 percent of those who scored poorly (between zero and three) survived for 14 years, and the number of people who scored poorly increased with age.
And that’s not the only test out there that can predict lifespan. There is now evidence that poor grip strength predicts early mortality in young people.
All this led me to an interesting question. If we can predict lifespan, can we also modify it? The conventional answer is yes, we can. And it comes down to exercise. But a new look at the research and anecdotal evidence suggests otherwise. Staying active into old age may have less to do with aerobic fitness than athleticism.
Exercise Isn’t Enough
Ever since I started swimming seriously in the late 1990s, I noticed that competitive masters swimmers tended to look a bit better and less scrawny than their running counterparts and the same is true for cyclists. Why?
One reason is that most competitive swimmers keep interval training and the cyclists spend some time going uphill. Both of these activities require the generation of higher muscle forces than simply going out and running.
My thought is that far fewer masters runners do things that keep their strength up. In fact, a recent study in a large number of both male and female masters runners in their later 50s showed that over five years:
There was a significant loss of both isometric knee extension (about 5%/yr) and knee flexion (about 3.6%/yr) strength in both the men and women. However, there was no significant change in either isokinetic concentric or eccentric torque of the knee extensors. Our data demonstrated a significant decline in isometric knee extensor and knee flexor strength while there were no changes in LBM in this group of very active older men and women.
This data confirms a lot of casual observations, running alone won’t keep your legs strong. Endurance exercise isn’t enough.
Loss of Athleticism?
While the runners remained active, they lost out on something equally important: athleticism. When we are younger, most of us do different things, perhaps play multiple sports. All of this develops total body fitness and greater coordination. However, as we get older and settle into the work world it is easy to settle into a routine—including how we exercise—most days.
It’s unclear how much variety is needed to develop total body fitness. But it is interesting to note that the performance of elite mountain runners may decline more slowly with age than for runners as a whole. Is it the hill running? Going uphill is good for strength and downhill is good for balance and agility.
That’s not to say all is lost with aging. There is evidence that masters runners can improve their running economy by about six percent via strength training with their legs. This data is consistent with the idea that instead of focusing in on the same old activity or exercise program, moving into new territory may be of prime importance as we age.
When I look at the sitting-rising mortality data and the masters runners data, I am more convinced than ever that we need to go back to the future with our training starting in our 20s. And the data on CrossFit-like programs targeted toward runners is revealing: Athletes who undergo low volume explosive training paired with endurance training “produced significant gains in strength, power and endurance performance…” The very measures that together may increase lifespan.
Before CrossFit, sports like cyclocross and trail running stress these traits. But for everyone else, it means finding body weight strength and agility exercises that you can build into your exercise program: jumping rope, push-ups, sit-ups, climbers—and yes, burpees.
Michael J. Joyner, M.D., is a physiologist and anesthesiologist at the Mayo Clinic and a leading voice in the world of exercise physiology. Over the last 25+ years, he's published 100s of studies many of which have focused on how humans respond to exercise. Dr. Joyner also writes at Human Limits. The views expressed in this post are his own and do not reflect those of his employer.