Does Brawn Affect Brain?
Strength training is increasingly promoted for its many health-related benefits, including a lower risk of all causes of mortality, fewer cardiovascular events (i.e., heart attacks, strokes), improved body composition, better glucose metabolism and insulin sensitivity, and lower blood pressure in persons with prehypertension and hypertension (Garber et al. 2011). Garber and colleagues also consider it a suitable intervention for preventing and/or managing osteoporosis, osteoarthritis and metabolic syndrome.
Surprisingly, much less research has focused on the mental health benefits of resistance training in women and men. Recently, O’Connor, Herring and Caravalho completed an extensive literature review on this topic, admitting only studies that met certain criteria for quality research. Highlights from their findings are summarized here.
According to O’Connor and colleagues, 15% of the U.S. population reports frequent anxiety symptoms lasting 15–30 days a month. Anxiety is generally manifested in feelings of nervousness, fear, apprehension and worry. It is normal to experience anxiety in relation to interviews, tests, new challenges or performances. However, with prolonged and heightened symptoms, anxiety is associated with sleep disruptions, mental distress, bodily pain, poor health and limitations to physical activity.
From the seven resistance training studies on this topic that met the criteria for inclusion in the review, O’Connor, Herring and Caravalho conclude that resistance training is a meaningful intervention for people suffering from anxiety. Interestingly, two of the seven studies compared the effects of high-intensity resistance training (exercises performed at 80% of 1-repetition maximum [1-RM]) with the effects of moderate-intensity training (50%–60% of 1-RM) and found that the latter was more effective in reducing anxiety.
Cognition refers to the brain’s processing ability to obtain knowledge through thought, experience and the senses. Cognition research attempts to determine how we transform events and experiences into stored memory, which can be recovered and used to complete mental and physical tasks. Highly associated with cognition is executive function. Executive function is the “command and control” conductor of cognitive skills. This brain control center manages all of the tasks in a person’s life, such as writing an article, doing a research project, preparing for class and organizing a trip.
A great amount of research on exercise and cognitive function has been completed with older adults as subjects, as it’s been felt that exercise might offer this population consequential benefits in this area (Colcombe & Framer 2003). O’Connor, Herring and Caravalho note that seven randomized controlled studies show that resistance training improves several aspects of cognition in healthy older adults. Uniquely, one of the most profound effects is a marked improvement in memory and memory-related tasks. Additionally, it appears that improved executive function is a major benefit, both of resistance training (Anderson-Hanley, Nimon & Westen 2010) and of cardiovascular exercise (Colcombe & Framer 2003).
Faced with life’s challenges and losses, most people feel sad or depressed at one time or another. However, intense sadness may lead to feelings of hopelessness and helplessness, resulting in mood disturbances, fatigue, lack of motivation, insomnia (or excessive sleep called “hypersomnia”), restlessness, agitation and/or body weight fluctuations.
O’Connor, Herring and Caravalho point out that the 18 training studies examining the effect of resistance training on persons with depression symptoms have mixed results. Several studies show a significantly positive effect, while others show little change. Perhaps further investigation is needed to determine if there is an optimal dose of resistance training for persons suffering from depression. Four studies have investigated the effect of resistance training on adults diagnosed as clinically depressed. The results are unanimous: Resistance training participation is linked to large reductions in depression.
According to O’Connor and colleagues, 25% of the U.S. population experiences persistent fatigue symptoms. In addition, the occurrence of chronic fatigue is elevated among people with lasting medical illnesses, especially those with psychological disorders.
For some people, fatigue is a reason to make frequent visits to their primary practitioner; for some it is an excuse for not exercising. Impressively, 94% of the 70 randomized studies on exercise and fatigue show that exercise is clinically beneficial (i.e., significant) and even more beneficial than drug or cognitive-behavioral interventions (O’Connor, Herring & Caravalho 2010). In fact, a strength training–only intervention results in the largest improvements in chronic fatigue.
Self-esteem is a person’s self-opinion. It is a personality characteristic tied in with self-worth, self-respect and self-integrity. High self-esteem is strongly associated with positive physical and mental well-being. Resistance training has been shown to improve self-esteem in healthy adults (both younger and older), in populations with cancer or depression and in people undergoing cardiac rehabilitation.
O’Connor and colleagues note that we spend 30% of our lives sleeping and that insufficient sleep is very problematic for our physical and mental health. Consistent sleep deprivation (less than 6 hours a night) is associated with cognitive impairment, mental illness, hypertension, obesity, cardiovascular disease, stroke, daytime sleepiness, motor vehicle accidents and a diminished quality of life.
The research indicates that physically active people usually have healthy sleep patterns and a lower risk for sleep apnea. Furthermore, depressed persons with sleep disorders show a 30% improvement in sleep from a regular resistance training intervention. These results appear to become most effective after 8–10 weeks of consistent resistance training.
Resistance Training and Mental Health
The mechanisms by which resistance training improves mental health are speculative at this time. The researchers propose that a complex network of neurophysiological adaptations occur that directly and indirectly effect mental processes. For instance, many of the physical health benefits of resistance training cited earlier can have a direct and indirect effect on a person’s mental well-being.
In addition, resistance training may improve central nervous system functioning, which could have a positive effect on mental health. Van Praag (2009) posits that improved cognition from exercise is likely to stem from multifactorial adaptations involving new nerve-cell generation in the brain, an increase in neurotransmitters (chemical substances that transmit nerve impulses across a synapse) and generation of new brain blood vessels, resulting in more efficient oxygen delivery and waste product removal.
The evidence is quite impressive when one considers how resistance training can positively affect several major mental health issues (see Figure 1). In addition, the research is convincing that resistance training can appreciably improve cognitive function. An exercise professional’s bottom line message to clients is clear: For a mental lift, you should weight-lift!