The Runner’s High
In several previous brain blogs I’ve described some of the many long-term brain benefits of regular exercise. These have mainly focused on the benefits that regular exercise offers to older people in terms of reducing the rate of age-related cognitive decline (ARCD). Actually the brain benefits of taking regular exercise extend way beyond merely slowing ARCD and what's more, they're applicable to everyone, young and old.
Do It For Your Brain’s Sake
People who exercise regularly have lower rates of anxiety and depression. They even boast greater cortical thickness in parts of the prefrontal cortex and the medial temporal lobe. Specifically brain scanning studies have demonstrated that the right hippocampus, fundamental both to creating memories and knowing where we are in space, are a little larger in those who exercise regularly versus those who are mostly sedentary. This increase in tissue thickness is thought to be indicative of a denser meshwork of synaptic connections reflecting a greater complexity of neuronal network. In other words several brain areas fundamentally involved in memory and cognition are able to perform better. What’s more regular exercise leads to improvements in mood and even helps you sleep better. And there is little better than a good night’s sleep for helping brains to reach peak performance.
Exercise also leads to increased levels of nerve growth factors such as BDNF (brain-derived neurotrophic factors) known to promote birth and survival of new brain cells, synapses and improved blood supply. So this is a likely mechanism for the changes in the thickness of various brain regions in people who take regular exercise and quite possible the long term benefits in cognitive ability and mental health.
In Sort Your Brain Out Adrian and I urge people to move away from thinking about exercise as a pastime that should be motivated by the desire to improve the appearance of our bodies and more as something vital to brain health. When people are feeling stressed out their motivation levels towards hitting the gym are often at rock bottom levels. This is a huge shame because exercise is exactly what would make them feel much better.
Athletes often speak of the “runner’s high.” This has long been explained as a result of endorphins released in the brain in response to moderate to intense exercise. It makes good theoretical sense because endorphins, the brain’s natural opiates, have the twin effect of numbing pain and making us feel good. The trouble is that up until 2008 there was little if any hard evidence to back this notion up. Yet further doubt was cast on the whole endorphin hypothesis when a study demonstrated that the runner’s high still occurred even when the effect of any released endorphins was blocked with a drug called naloxone.
Looking elsewhere for a mechanism through which the runner’s high might be achieved researchers started to focus on a possible role for endocannabinoids. Similar in structure to the hundreds of cannabinoid chemicals found in the Cannabis sativa plant smoked recreationally in pursuit of a mood-enhancing effect, endocannabinoids are naturally produced throughout the brain.
Subsequently, elevated endorphin levels were observed in a brain scanning study that compared brains that had recently completed a 2-hour endurance run compared to other brains that hadn’t (Boecker et al, 2008). So consensus now is that the anxiety reducing effects of exercise are mediated by a combination of endocannabinoid and endorphin release in the brain.
What Purpose Might the Runner’s High Serve?
From an evolutionary perspective pain signals clearly should be switch on and off-able because they can be helpful or disabling depending on the context. Pain signals from damaged body parts helps us to avoid worsening the injury when at rest or engaging in gentle exercise, clearly an advantage when the priority is to allow a twisted ankle, strained knee or inflamed muscle to heal properly. But in the context of evading a predator or attempting to catch prey, such pain signals could lead to the huge potential disadvantage should it lead to getting caught and killed by the predator, or failing to catch the very food that might keep us, and our dependents, alive. The benefit of the analgesic / hedonic effect is that if a person is running to save their skin, then switching off the pain signal and inducing a light high to further compensate for any residual pain resulting in an unimpeded getaway makes perfect sense. Better to endure minor tissue damage if it is the only way to ensure you’ll live to see another day.
Little and Often
There is a huge amount of evidence to support the concept that regular exercise is extremely good for body and brain. The trouble is, we all know this but few actually get around to taking regular exercise. In my view the main reason for this is partly feeling overwhelmed by their busy lives but also probably involves exercising in the wrong way: when people do finally get around to exercising they often overdo it. Spending the whole of the next day aching all over will do little to incentivise them to take the trouble to exercising again any time soon.
I would argue that little and often is the best policy. Even at the frantic pace of modern life everyone can fit in 20-30mins of exercise a day. That way, even if some weeks you only hit 50% of your target, you’ll still be getting your heart rate and breathing rate up, flooding the brain with highly oxygenated blood, endorphins, endocannabinoids and BDNF, 3-4 times per week – exactly the recommended dose!
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