**2.2 Working definitions**

230 Neuroimaging – Cognitive and Clinical Neuroscience

This of course has implications beyond executive dysfunction; disruption of cerebral white matter integrity in the middle-posterior cingulum regions could impact motor movement, learning, and reading comprehension. Early transcranial doppler studies concluded that aerobic exercise may be beneficial for maintenance of cerebral blood flow (Marks et al., 2000; Orlandi and Murri, 1996). A decade later, cerebral blood vessel morphology studies suggested physically active older adults have younger-looking cerebral vasculature (Bullitt

However, the retention and improvement of human brain plasticity via exercise is still not well understood. Despite animal studies demonstrating that exercise may promote neurogenesis, and human studies demonstrating a maintenance/increase in brain volume with exercise (Cotman et al., 2007; Ferris et al., 2007; van Praag et al., 1999), there is little information demonstrating the mechanism(s) for such changes. Furthermore, much of the evidence is equivocal as to whether these brain adaptations, presumably due to physical exercise, equates to improved cognitive function (Colcombe et al., 2003; Etnier and Nowell,

These aforementioned discrepancies may be due, at least in part, to the state of flux with research in this area. Numerous neuroimaging techniques are being used and the technology itself is rapidly changing. Cognitive tests commonly used for those with known cognitive deficits may not be sensitive enough to detect subtle cognitive changes in presumed healthy community dwelling elderly. Furthermore, researchers are using a variety of exercise paradigms, some of which are not reproducible due to lack of reporting standard exercise prescription procedures. Other factors such as age, gender, training status, and diet, known to be potential confounders in exercise and aging studies, are often overlooked. Finally, there is confusion in which term to use to simply identify the exercise paradigm itself. All of these factors make comparisons across studies difficult and the ability to draw definitive conclusions impossible (American College of Sports Medicine, 2010;

Therefore, the aims of this chapter are threefold: 1) Clarify the use of exercise, physical activity and related terms as profiling variables versus intervention modalities, 2) Review neuroimaging techniques currently being used to study the impact of exercise and physical activity on the aging human brain structure, and 3) Highlight the pros and cons for use of

Physical activity is associated with changes in brain structure. Regular exercise improves brain function. High aerobic fitness mediates cerebral white matter integrity. Do all these statements mean the same thing, or are there subtle differences in interpretation rendering

The terms "physical activity", "exercise", and "fitness" are often used interchangeably. But as with any discipline, these terms have distinct connotations and therefore should not be use as mere synonyms. To add to the terminology confusion, a myriad of additional phrases are incorporated in an attempt to better clarify the exercise paradigm. Typical terms include, but are not limited to: aerobic fitness, health fitness, physical fitness, calisthenics, circuit training, core training, resistance training, stretching and toning, strength training, and

et al., 2009, 2010).

2006; Heyn et al., 2004; Kharti et al., 2001).

Leasure and Jones, 2008; Lommatzsch et al., 2005).

**2. Is it physical activity, exercise, or fitness?** 

such methods with exercise paradigms.

the results difficult to compare?

**2.1 Defining "exercise"** 

Exercise scientists and physical educators continually find themselves clarifying the words that describe their work and this debate has raged for decades. For instance, the term *physical activity* is classically defined as any bodily movement that results in muscular contractions and increases energy expenditure above that which is used during rest (USDHHS/NHLBI, 2008). In contrast, the term *exercise* is defined as "*the regular or repeated use of a faculty or bodily orga*n" (Meriam Webster Free Dictionary, 2011). Thus, the term physical activity is often used due to its broader utility, but the term exercise should be used whenever the researcher's intent is to demonstrate the impact of *repeated exposure* to a *specific type* of physical activity. Therefore, exercise can be considered a structured sub-category of physical activity, with specific dosing parameters that result in health maintenance and/or improvement (Caspersen et al., 1985). The term *fitness,* in biological terms, simply means the ability of an organism to survive and reproduce. This generic term is most often used to connote one's health status and is expanded as needed (i.e., health fitness, physical fitness, aerobic fitness, brain fitness). The American College of Sports Medicine (1990) suggested the following definition be used for *physical fitness*: "fitness is the ability to perform moderate to vigorous levels of physical activity without undue fatigue and the capability of maintaining such ability throughout life." Obviously, this exercise science-based definition can be applied to the neurological system as well, suggesting that *brain fitness* can be defined as *the ability to perform daily cognitive tasks without undue mental fatigue or memory impairment and the capability to maintain cognitive abilities throughout life.* 
