Want to live longer? Move more, lift weights
*Active lifestyles may help nerves to heal after spinal injuries
Improving fitness does not require doing activities you do not like. That is the main message of research presented at EuroPrevent 2019. The largest study to date of cardiorespiratory fitness in healthy people found that moving more is linked to living longer, regardless of age, sex, and starting fitness level.
“People think they have to start going to the gym and exercising hard to get fitter,” said study author Dr. Elin Ekblom-Bak, of the Swedish School of Sport and Health Sciences in Stockholm. “But it doesn’t have to be that complicated. For most people, just being more active in daily life – taking the stairs, exiting the metro a station early, cycling to work – is enough to benefit health since levels are so low to start with. The more you do, the better.”
The study included 316,137 adults aged 18-74 years who had their first occupational health screening between 1995 and 2015 in Sweden. Cardiorespiratory fitness was measured using a submaximal cycle test and expressed as maximal oxygen uptake (VO2 max) in ml/minute/kg body weight. This is the maximum amount of oxygen the heart and lungs can provide the muscles during exercise. You can estimate your VO2 max using either submaximal cycle tests, treadmill tests, or walking tests.
Swedish national registries were used to obtain data on all-cause mortality and first-time cardiovascular events (fatal and non-fatal myocardial infarction, angina pectoris, or ischaemic stroke) during 1995-2015.
The risk of all-cause mortality and cardiovascular events fell by 2.8 per cent and 3.2 per cent, respectively, with each millilitre increase in VO2 max. Benefits of fitness were seen in men and women, in all age groups, and at all fitness levels. Previous studies have been too small to ascertain whether all of these subgroups profit from improving their cardiorespiratory fitness. There was no plateau of benefit in the total population, with some variation between sex- and age-subgroups.
“It is particularly important to note that an increase in fitness was beneficial regardless of the starting point,” said Dr Ekblom-Bak. “This suggests that people with lower levels cardiorespiratory fitness have the most to gain from boosting their fitness.”
Increasing fitness should be a public health priority and clinicians should assess fitness during health screening, said Dr. Ekblom-Bak. There are simple tests that could be used. “Our previous research has shown that fitness levels in the general population have dropped by 10 per cent in the last 25 years.2 In 2016-2017, almost every second man and woman had a low fitness level, so this is a huge problem. Fitness is needed for daily activities. Poor fitness is as detrimental as smoking, obesity and diabetes even in otherwise healthy adults, yet unlike these other risk factors it is not routinely measured.”
She advised, as a rough guide, that for every additional millilitre of VO2 max there will be an average three per cent risk reduction of all-cause mortality and cardiovascular events. “This is more motivational than just telling people they need to do better. People in the lower range of VO2 max will reduce their risk even more (nine per cent) while those at the upper end of VO2 max will reduce their risk by one per cent,” she said.
Also, you can prolong your life by increasing your muscle power. That was the main message of another study presented at EuroPrevent 2019, a congress of the European Society of Cardiology.
“Rising from a chair in old age and kicking a ball depend more on muscle power than muscle strength, yet most weight bearing exercise focuses on the latter,” said study author Professor Claudio Gil Araújo, director of research and education, Exercise Medicine Clinic – CLINIMEX, Rio de Janeiro, Brazil. “Our study shows for the first time that people with more muscle power tend to live longer.”
Power depends on the ability to generate force and velocity, and to coordinate movement. In other words, it is the measure of the work performed per unit time (force times distance); more power is produced when the same amount of work is completed in a shorter period or when more work is performed during the same period. Climbing stairs requires power – the faster you climb, the more power you need. Holding or pushing a heavy object (for example a car with a dead battery) needs strength.
Professor Araújo said: “Power training is carried out by finding the best combination of speed and weight being lifted or moved. For strength training at the gym most people just think about the amount of weight being lifted and the number of repetitions without paying attention to the speed of execution.
But for optimal power training results, you should go beyond typical strength training and add speed to your weight lifts.”
Muscle power gradually decreases after 40 years of age. “We now show that power is strongly related to all-cause mortality. But the good news is that you only need to be above the median for your sex to have the best survival, with no further benefit in becoming even more powerful,” said Professor Araújo.
Also, leading an active lifestyle may increase the likelihood of damaged nerves regenerating after a spinal cord injury.
The early-stage findings, published in the journal Science Translational Medicine, come from studies in mice and rats with spinal cord injuries, in which scientists uncovered a mechanism for nerve fibres repairing after they had been damaged.
An international team, led by researchers from Imperial College London, found that providing rodents with more space, an exercise wheel, toys and company before an injury helped to ‘prime’ their cells, making it more likely their damaged nerves would regenerate following spinal injury.
The researchers were also able to mimic the effects of an active lifestyle by using a drug that targets the same underlying pathways in the cells — ‘reprogramming’ the nerve cells to regenerate following a spinal injury.
The team says that while the work is still at an early stage the findings open a “realistic pathway” towards testing the links between pre-existing active lifestyle and recovery from spinal injury, and potentially to clinical trials of their drug treatment in human patients.
Professor Simone Di Giovanni, from the Department of Medicine at Imperial, whose team led the research, said: “Anecdotal evidence suggests that people with an active lifestyle may recover to a greater degree after spinal cord injury than those who are less active. Our studies support these findings. From what we have seen it’s almost as if the nerve cells are being ‘primed’ for regeneration and growth, which add to this enhanced recovery.”
The spinal cord is made up of bundles of nerve fibres. These are the long ‘tails’ (or axons) of nerve cells, which stretch up and down the spine. When the spinal cord is injured these fibres can become damaged, or in some cases severed completely, and so can no longer carry signals between the brain and body.
To date, injuries to the spine have been difficult to treat as while damaged bone and muscle may heal, regenerating the damaged nerve fibres within — reconnecting the brain and body — has remained a key challenge.
In the latest study, researchers discovered that stimulating nerve cells through environmental enrichment before an injury can help to promote regeneration of the nerve fibres, leading to more regrowth at the site of damage.
“We discovered that environmental enrichment such as housing mice in a larger cage than usual, with more mice in it, more toys, tunnels, swings, running wheels etc. increases the activity of neurons,” explained Professor Di Giovanni. “This leads to changes in gene expression which make the nerve more likely to regenerate. Essentially, by increasing the activity of neurons that sense enriched environmental stimuli we have been able to promote the regenerative potential of nerves after spinal cord injury.”
They found that when mice were generally given more environmental, physical or social stimuli, their nerve cells were altered, boosting their potential to regenerate compared to control mice which had a basic level of enrichment. When nerves from enriched animals were subsequently damaged, the effects of the active lifestyle led to more growth and sprouting of the nerve fibre at the site of injury.
Dr. Thomas Hutson, from the Department of Medicine at Imperial, who is first author on the publication said: “Although the findings that an active enriched lifestyle before injury can enhance the regenerative potential of nerve cells is exciting, humans that live enriched lives do not fully recover. This led us to further investigate the underlying cellular mechanisms to identify a therapeutic target that could be exploited after injury.”
The researchers identified a key molecule called CREB-Binding Protein (CBP) that may be effectively reprogramming the nerve cells, altering the expression of a number of genes in the cells and boosting their ability to regenerate.
Based on this, the team used a recently developed drug that activates CBP to reprogramme damaged nerve cells, mimicking the regenerative effect of environmental enrichment.
In trials with mice and rats, they found that giving the drug six hours after spinal injury (and once a week thereafter) promoted the regeneration and sprouting of damaged nerve fibres. Following injury and drug treatment, rats which were otherwise unable to walk properly regained significant mobility in their back legs, compared to control animals without treatment.
The researchers highlight that the study was limited as the findings are from rodents with relatively controlled spinal damage (compared to the variability in location and severity in human injuries), but add that pending safety studies and work in larger animal models, the drug has the potential to move to early stage clinical trials in future.
“The drug treatment that promoted regeneration and recovery in mice and rats after spinal cord injury offers an opportunity to be tested in patients,” said Professor Di Giovanni. “In principle, this kind of treatment is not very far from being tested in the clinic. Further studies are needed to show the drug is safe in humans, before it could be trialled. But in future it could potentially be combined with neurorehabilitation in clinical trials.”
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