Dr Jennifer Heisz is on a mission to help people understand the neuroscience of exercise (she's just written a book about it) and says there's just one thing she wishes everyone knew… that exercise gives us vitality. "Exercise helps us manage the things we struggle with daily. It helps us deal with stress, ease our depression, soothe our anxiety, stay sober, alleviate insomnia, keep dementia at bay, and it makes it easier for us to stay focused and be creative. All in all, it gives us the mental energy to fully engage with life.”
Exercise changes the brain in diverse and powerful ways. “One key thing that exercise increases is brain-derived neurotrophic factor (BDNF),” explains Heisz. "This acts as a fertiliser to grow new brain cells and help our existing brain cells function optimally."
She adds that in some cases, the power of exercise can even surpass that of genetics. Research from Heisz’s NeuroFitLab has shown that physical activity levels contribute to dementia risk as significantly as one’s genes. The researchers tracked over 1,600 people, and 25 per cent had a genetic risk factor for dementia, which is representative of the population at large. At the start of the study, no one had dementia. Five years on, those who were physically inactive were as equally likely to develop dementia as those who were genetically predisposed. In other words, being physically inactive completely negated a healthy set of genes.
WHICH EXERCISE OFFERS THE BIGGEST NEUROLOGICAL BENEFITS?
Heisz’s recent research has demonstrated HIIT improves memory, whereas moderate continuous training does not. “What makes HIIT so special is that the hard intervals push you above your anaerobic threshold and lactate accumulates,” she adds. “Although lactate was historically considered an inert by-product of metabolism, it turns out to be one of the most important promoters of neuroplasticity (our brain’s ability to adapt and adopt new behaviours). Lactate promotes angiogenesis (the growth of new blood vessels in the brain) to help ward off vascular dementia. Lactate also promotes hippocampal neurogenesis (the birth of new brain cells) to ward off Alzheimer’s disease.”
It turns out that the lactate from the muscles travels to the brain and may be one of the promoters of brain health.
What’s surprising about these new findings is how they contradict common perceptions about lactate. “We often hear fitness trainers talk about ‘flushing out lactate from the muscles’ as if lactate is a bad thing that we need to get rid of,” says Heisz. “But it turns out the lactate from the muscles travels to the brain, and may be one of the promoters of brain health.”
WHAT EXERCISE CAN ALLEVIATE DEPRESSION?
Research shows that when it comes to aerobic exercises for alleviating depression, duration matters most. “Increasing your workout duration by just 10 minutes will yield a greater antidepressant effect,” advises Heisz. “Resistance exercises also alleviate depression, but here intensity matters most. Increasing your workout intensity by just 10 per cent will yield a greater antidepressant effect.”
WHICH TYPES OF EXERCISE CAN LESSEN ANXIETY?
How people respond to exercise for anxiety relief depends on whether the person is anxiety sensitive, which literally means ‘the fear of fear itself’. Heisz explains: “People who are anxiety sensitive get even more anxious when they experience the somatic symptoms of anxiety, such as racing heart and rapid breathing. Unfortunately, these symptoms overlap with the physiological effects of high-intensity exercise.” Therefore, based on research, it’s recommended to start off at a moderate intensity and add in short bursts of higher intensity exercise if tolerated.
WHAT TYPE OF EXERCISE CAN ENCOURAGE BETTER SLEEP?
In general, the more you move during the day, the better you sleep at night. Studies show you can also schedule your exercise at the same time every day to help re-sync your biological clock. This will help you fall asleep faster. Pre-bedtime yoga sessions are shown to be particularly beneficial when it comes to improving sleep quality.
WHICH TYPES OF EXERCISE CAN IMPROVE FOCUS AND CREATIVITY?
When it comes to boosting focus and creativity, Heisz says short frequent movement breaks throughout the day are key. Research shows that interspersing five-minute HIIT breaks during a lecture improved students’ focus and learning. For creativity, a 10-minute self-paced walk has shown to be enough to help promote ‘outside-the-box’ thinking.
WOMEN PAY HEED…
Seventy per cent of those with neurodegenerative disorders are women, and women also have higher rates of mental illness and other diseases. Heisz explains that women tend to be more susceptible to stress-induced mental illnesses, such as anxiety and depression, and research has shown that exercise protects against stress-induced depression and anxiety in both men and women. Studies also demonstrate that women tend to benefit more from some of the cognitive benefits of exercise. This may be related to sex differences in the production of BDNF to exercise, but more research is needed in this area.
EXERCISE VERSUS OTHER TREATMENTS
While there are many mental health treatments on offer, Heisz believes that exercise really is hard to beat when it comes to mental health. Antidepressant medications work well for some, but not for all. “About one in three people have drug-resistant depression and these individuals often experience greater symptom relief from exercise than medication.” Some turn to alcohol, which can temporarily alleviate stress and anxiety, but you will pay for it later. “Alcohol disrupts our sleep, which makes it more difficult for us to think clearly and regulate our mood over the short term – and this can aggravate anxiety and depression over the long run.” Heisz explains the option of psychiatry can prove helpful, but it may not be feasible for all. It also can be difficult for some to find a therapist that they trust.
She adds: “Fortunately, with exercise, every workout has the potential to reset your brain by infusing it with all the neuro-chemicals the brain needs to thrive. Exercise can work well on its own, but also works well together with other therapies.”
Dr Jennifer Heisz is an Associate Professor in the Department of Kinesiology at McMaster University and Director of the NeuroFit Lab, which has attracted more than $1 million to support her research program on the effects of exercise for brain health. Heisz's research examines the effects of physical activity on brain function to promote mental health and cognition in young adults, older adults and individuals with Alzheimer’s disease. Heisz has recently authored the book, Move the Body, Heal the Mind.
