EXERCISE MODE AND COGNITION IN HEALTHY OLDER ADULTS – INTENSITY VS COMPLEXITY
Yael Netz – Wingate College, Israel
The research on physical activity and cognition has experienced enormous growth in the last decade. There are specific aspects involved in the relationship between exercise and cognition – some of them are mediators explaining this relationship, while others are moderators influencing this relationship. Cardiovascular fitness is the most discussed mediator. More specifically, cardiovascular fitness affects cerebral circulation, neurotrophic stimulation, high functional connectivity in neural networks, and greater gray matter volume in the prefrontal cortex. The moderators are the dose of exercise, the cognitive variables assessed, and the exercise mode which is the main topic of this lecture.
While the exercise mode may include specific skills such as yoga, Tai Chi, dance or exergames, in this lecture exercise modes will relate primarily to the basic movement components recommended by the American College of Sports Medicine: aerobic activity, strength training, flexibility, balance, and coordination. These components will be further categorized into physical training (aerobics, strength, flexibility) and motor training (balance and coordination).
Selected studies will be presented in the lecture, representing various aspects as well as the developmental progress of the research on exercise mode and cognition. Chronologically, types of physical training, mainly aerobic and strength, were explored first as enhancersof cognition, while motor training came later. A group of studies relating to aerobic versus light non-aerobic exercise will be presented first. The earliest in this group will be the study by Kramer et al. (1999), which focused on specific aspects of cognition (executive functions) with no brain cognition inquiry, followed by a few others concentrating on specific aspects of cognition and brain mediators, followed by the most recent study – Jonasson et al. (2017), focusing on a global cognitive score as related to the cortical (dlPFC, vlPFC, ACC) and subcortical (hippocampus) segments of the brain. Some studies assessing the acute effect of aerobic exercise on specific aspects of cognition, such as cognitive flexibility (Netz et al., 2007) or attention inhibition (Netz et al., 2016), will also be presented. The effect of strength training on executive functions (Anderson-Hanley et al., 2010) will then be discussed, followed by comparing aerobic exercise to strength training in enhancing information processing and executive functions (Coetsee & Terblanche, 2017).
Two studies comparing a mode of physical training to a mode of motor training will then be presented. One compares the effect of aerobic exercise to that of coordination training on perceptual speed and executive functioning (Voelcker-Rehage et al., 2011) and the other compares the effect of strength training to that of balance and coordination training on executive function and on inhibition and cognitive flexibility (Forte et al., 2013). Interestingly both studies report improvements in cognitive functioning as a result of both the physical training (aerobic or strength), as well as the motor training (coordination or balance and coordination), albeit through different pathways. The first (Voelcker-Rehage et al., 2011) demonstrates that different parts of brain (cortical as well as subcortical) are affected by aerobic exercise as compared to coordination training. Furthermore, different directions of brain network activation (increase vs. decrease) are observed following aerobic as compared to coordination training. The other (Forte et al., 2013) argues that the balance and coordination training enhances cognition directly, independent of motor fitness improvement, while the strength training enhances cognition through improvement in strength as a mediating mechanism.
Once motor training – mainly balance and coordination – was established as an enhancer of cognition, two studies took the research further and explored the differences between conventional motor training and motor training with an additional cognitive stimulator. One study (Schättin et al., 2016) showed that both balance exercises and exergames improved executive functions, but EEG measurements showed that theta relative power significantly decreased in favor of the exergame group. The other study (Falbo et al., 2016) assessed the effect of motor training (mainly balance and coordination) versus motor-cognitive (dual-task) training on executive functions. The conclusion was that the motor-cognitive training was more efficient in improving/preserving executive functions than the motor training alone. An additional study (Theill et al., 2013) showed that physical training (walking) performed simultaneously with cognitive training was, in a number of aspects, more beneficial in enhancing cognition than cognitive training by itself.
A systematic review of the beneficial effects of different types of exercise interventions on motor as well as cognitive functions (Levin et al., to be published), arguing that a combination of few exercise modes or a combination of physical-cognitive training is more efficient than a single mode of exercise in enhancing cognition, will also be presented.
In summary, while in the past only physical training (aerobic and strength training) were considered effective in enhancing cognition, later studies showed that motor training (balance and coordination) is no less efficient, and in some aspects is even more. However, the pattern of the mediating mechanisms of the effect of physical training and motor training is different. A model proposing the driving mechanism of each of the two types of training will be presented: in the physical training the driving mechanism is the movement intensity, while in the motor training it is the movement complexity. In the physical training, it is the improvement in cardiovascular fitness as a result of the training which affects functional connectivity in neural networks in a global manner. The motor training, on the other hand, directly affects specific networks that are related to specific motor tasks. Clearly, a combination of exercise modes, or physical/motor along with cognitive training, has been shown to be most efficient in improving or preserving cognition.
How does the information on exercise-cognition relationship affect the official recommendations for physical activity in old age? Fortunately, the implications are that if all training components traditionally recommended by official bodies – physical as well as motor training – are efficient in enhancing cognition, then we merely have to emphasize the inclusion of all exercise modes in our routine exercise regimen for physical as well as cognitive health. It is also recommended that more cognitive stimulations, such as dual-task activities involving both a movement-base as well as cognitive tasks, be implemented in the exercise routine.