Exercising to improve muscle strength is not only good for keeping your body in shape, but it’s also good for the brain and may reduce the risk of developing Alzheimer’s disease. As part of Australia’s Alzheimer’s research project, they conducted The Study of Mental and Resistance Training (SMART) to determine whether strength training and/or computer brain training exercises could help people at risk for Alzheimer’s disease improve their brain function and minimize that risk. Although previous research has shown benefits of aerobic exercise (such as walking, biking, or jogging) for preventing Alzheimer’s disease, there has been much less research on resistance (strength) exercise.
Mild Cognitive Impairment (MCI)
The SMART trial studied 100 participants between the ages of 55 and 86 with mild cognitive impairment (MCI). MCI involves memory and thinking problems, but it does not affect the normal activities of everyday life. However, MCI may be an early sign of Alzheimer’s disease, a pre-dementia condition. Someone with MCI has about a 30 percent chance of progressing to Alzheimer’s over the course of 10 years.1 The SMART trial is part of the ongoing search for treatments that could restore and maintain brain function in people with MCI, to reduce their risk of developing Alzheimer’s disease.
Design of the SMART trial
To directly compare brain training, muscle strength training, and a combination of both, they divided participants into four groups:
- High-intensity progressive resistance exercise plus computerized cognitive training;
- High-intensity progressive resistance exercise plus placebo cognitive training (watching educational videos);
- Computerized cognitive training plus placebo exercise (mild activity designed not to increase strength – stretching and seated calisthenics);
- Placebo exercise plus placebo cognitive training.
The resistance exercise routine was high in intensity (about 80-90 percent of maximum strength) and progressive, meaning the weight was adjusted over time as participants’ strength increased. Cognitive training consisted of computer exercises aimed to improve memory, executive function, attention and speed of information processing. Participants completed their assigned activities twice a week.2
Strength training was linked to better cognitive scores
At the end of the six-month trial, there was evidence that the resistance training groups had improved in a variety of cognitive scores. Almost half of the participants in the resistance training groups improved their cognitive scores enough to be in the normal range (as opposed to the MCI range). The computerized cognitive training groups showed an improvement in memory (but not other cognitive scores) at the end of the trial. When the participants were tested again, a year after the trial had ended, those in the resistance training groups had held on to their cognitive improvements.3
The improvement in cognitive scores in the resistance-trained individuals was backed up by MRIs showing changes in the brain. The MRIs confirmed an increase in thickness in a region of the brain called the posterior cingulate cortex. This is an important finding because loss of gray matter in this region is a marker of Alzheimer’s disease.4
Muscle strength gains correlated with improvements in cognitive function.
The resistance training groups increased upper body, lower body, and whole-body strength, and aerobic capacity. The amount of strength gain – lower body strength in particular – correlated to the amount of cognitive gain – the stronger the participants got, the more their brain function improved.5
How does strength training work in the brain?
Future research will be needed to determine how resistance exercise accomplishes this improvement in brain function. Aerobic exercise improves blood flow in the brain, leading to more efficient delivery of oxygen and nutrients. It also promotes the production of brain-healthy molecules such as brain-derived neurotrophic factor (BDNF), which supports the growth of new brain cells, plus survival, repair, and enhanced connectivity between brain cells.6,7
Resistance exercise may work similarly. Improvements in inflammation and insulin sensitivity are probably also involved.7 In addition, increasing muscle strength may prevent an excessive drop in IGF-1 in older people. Of course, high IGF-1 (insulin-like growth factor 1) is undesirable, linked to cancer and premature death. However, in the elderly, IGF-1 may become too low, and this negatively affects brain function.8
In addition to brain function, resistance training has the benefit of increasing muscle mass and strength, which helps to prevent bone loss, frailty, and falls. Strength training has an advantage over aerobic exercise for older adults as it can be done seated. In addition, it is more accessible for people with conditions such as osteoarthritis that make walking and other aerobic activity difficult. Plus, resistance training can improve aerobic fitness. Even once brain function had started to decline, this strength exercise intervention made a difference.
Eating a Nutritarian diet is the most important thing a person can do to delay aging, live long and prevent dementia, but we also know that being fit, strong, and active is also important and effective for staying healthy as we push the envelope of human longevity.
References:
- Mitchell AJ, Shiri-Feshki M. Rate of progression of mild cognitive impairment to dementia – meta-analysis of 41 robust inception cohort studies. Acta Psychiatr Scand 2009, 119:252-265.
- Gates NJ, Valenzuela M, Sachdev PS, et al. Study of Mental Activity and Regular Training (SMART) in at-risk individuals: a randomised double blind, sham controlled, longitudinal trial. BMC Geriatr 2011, 11:19.
- Fiatarone Singh MA, Gates N, Saigal N, et al. The Study of Mental and Resistance Training (SMART) study-resistance training and/or cognitive training in mild cognitive impairment: a randomized, double-blind, double-sham controlled trial. J Am Med Dir Assoc 2014, 15:873-880.
- Suo C, Singh MF, Gates N, et al. Therapeutically relevant structural and functional mechanisms triggered by physical and cognitive exercise. Mol Psychiatry 2016, 21:1633-1642.
- Mavros Y, Gates N, Wilson GC, et al. Mediation of Cognitive Function Improvements by Strength Gains After Resistance Training in Older Adults with Mild Cognitive Impairment: Outcomes of the Study of Mental and Resistance Training. J Am Geriatr Soc 2016.
- Kandola A, Hendrikse J, Lucassen PJ, Yucel M. Aerobic Exercise as a Tool to Improve Hippocampal Plasticity and Function in Humans: Practical Implications for Mental Health Treatment. Front Hum Neurosci 2016, 10:373.
- Kirk-Sanchez NJ, McGough EL. Physical exercise and cognitive performance in the elderly: current perspectives. Clin Interv Aging 2014, 9:51-62.
- Tsai CL, Wang CH, Pan CY, Chen FC. The effects of long-term resistance exercise on the relationship between neurocognitive performance and GH, IGF-1, and homocysteine levels in the elderly. Front Behav Neurosci 2015, 9:23.
