**10. Conclusions**

244 Neuroimaging – Cognitive and Clinical Neuroscience

*Directions: Query the participant regarding his/her extent of physical activity using the activity* 

1 = pleasure slow walking, routinely use stairs, occasionally heavy breathing or

**B. Regular participation modest/moderate physical activity ( e.g. golf, horseback riding, calisthenics, gymnastics, table tennis, bowling, weight lifting, yard work etc):** 

**C. Regular participation in heavy physical exercise (e.g. jogging, running, swimming, cycling, rowing, skipping rope, running in place, tennis, basketball, or handball etc.):**  4 = run less than 1 mile per week or spend less than 30 minutes per week in comparable

5 = run 1 to 5 miles per week or spend 30 to 60 minutes per week in comparable heavy

6 = run 5 to 10 miles per week or spend 1 to 3 hours per week in comparable heavy

7 = run over 10 miles per week or spend over 3 hours per week in comparable heavy

There are also scanner issues to deal with when a study design goes from a single acute scan to repeated scans over several months or years. Your scanner must be intra-reliable (i.e, a measure today will yield relatively the same results tomorrow). It is well known among neuroimaging technicians that scanners "drift" over time, therefore it is important to keep track of the drift so you can be sure changes that are seen months from the initial scan are corrected for the drift. Along these same lines, in order to get larger sample sizes, multiple sites may be needed. Therefore all the scanners used must be determined to be inter-reliable.

It is equally important to account for individual brain plasticity - the investigator must understand the normal brain changes over time independent of any treatment so that intervention changes seen can be distinguished from random occurrence or normal aging. Lastly, dehydration is an issue that only recently has begun to be accounted for in neuroimaging research studies. Care must be taken to ensure the research volunteers are euhydrated, otherwise, the question that may arise when a brain volume increase is reported: Is the increase in brain volume "true"? Or is it due to dehydration known to plague not only the elderly but also exercisers who exercise in a hot environment and may not have hydrated sufficiently? A simple way to account for hydration status is to obtain a urine sample and test it for urine specific gravity using either a dip stick (aka chem. strip) or a small handheld refractometer. A non-smelly light straw-colored urine would suggest the person was adequately hydrated. If a more precise objective measure is needed, the urine

specific gravity reading should be between 1.010 to 1.020 (Armstrong et al., 1998).

Table 3. Physical Activity Rating Scale (PARS; Baumgartner and Jackson, 1995).

This is generally accomplished with phantom testing.

**A. No regular participation in programmed recreational sport or physical activity:**  0 = avoid walking or exertion (always use elevator, drive whenever possible instead of

*descriptors below as well as established metabolic tables for physical activity.* 

walking.)

perspiration

2 = 10 to 60 minutes per week 3 = over one hour per week

heavy physical activity

physical activity

physical activity

physical activity

Aerobic fitness not only facilitates improved oxygen delivery and utilization in the cardiocerebral vascular systems, improved oxidative capacity has been shown to up-regulate expression of important neuronal growth factors such as insulin-like growth factor I (IGF-I), brain-derived neurotrophic factor (BDNF) and related protein precursors in animal models (Ding et al., 2006; van Praag et al., 2005). Furthermore, aerobic fitness may mediate improved cerebral white matter integrity via the intricate adaptations that take place on the neural-humoral level during exercise (Marks et al., 2010). Therefore, exercise outcome studies trials need to include not only structural imaging detailed in this paper, but also hormonal measurements and perfusion imaging.

In summary, the research questions that remain to be answered are: What is a sufficient exercise dose for the brain? How much, or how little, exercise is really needed to maintain brain structure and cognitive function? Will any type of physical activity do? Will the resultant health recommendations for the brain be complementary to the current guidelines for cardiovascular health?

To move the future of brain training research forward, we must continue to revisit the past ground-breaking cardiovascular research studies and modify them for the brain. Ancient physicians and philosophers like Hippocrates and Cicero espoused the benefits of exercising both the body and the mind, and here we are, 2,000 years later, scientifically documenting the neurobiological benefits of exercise. Several investigators have been using a few standard cardiovascular disease risk reduction guidelines with success in maintaining brain volume in older adults, but so many more exercise options remain to be explored. Hopefully it will not take another 50 years to firmly establish exercise guidelines for maintaining and enhancing brain health with exercise.
