Fitter bodies = fitter brains. True at all ages?

The results of recent­ly pub­lished stud­ies sug­gest that fit­ter chil­dren also have fit­ter brains. It looks like exer­cis­ing your body pro­motes brain health. Is this true at all ages? How does it work? How much exer­cise should we do?

Phys­i­cal activ­i­ty and brain health in children

An emerg­ing lit­er­a­ture sug­gests that phys­i­cal activ­i­ty and high lev­els of aer­o­bic fit­ness dur­ing child­hood  may enhance cog­ni­tion. In the 2 most recent stud­ies by Kramer and col­leagues (2010), the cog­ni­tive per­for­mance and the brains of high­er-fit and low­er-fit 9- and 10-year-old chil­dren were examined.

In one study, fit­ter chil­dren did bet­ter than less fit chil­dren in a task requir­ing to ignore irrel­e­vant infor­ma­tion and attend to rel­e­vant cues. Fit­ter chil­dren also had larg­er basal gan­glia (more specif­i­cal­ly dor­sal stria­tum) than less fit chil­dren. The basal gan­glia play a key role in cog­ni­tive con­trol (e.g. prepar­ing, ini­ti­at­ing, inhibit­ing, switch­ing responses).

In anoth­er study, fit­ter chil­dren did bet­ter than less fit chil­dren in a task requir­ing to mem­o­rize infor­ma­tion. Fit­ter chil­dren also had larg­er hip­pocampi than less fit chil­dren. The hip­pocam­pus is a struc­ture in the brain that is key to the for­ma­tion of new memories.

These stud­ies sug­gest that phys­i­cal fit­ness in chil­dren is relat­ed or asso­ci­at­ed with a) bet­ter cog­ni­tive per­for­mance and b) larg­er brain struc­tures (usu­al­ly the ones respon­si­ble for the per­for­mance dif­fer­ence). The results do not show a cau­sa­tion rela­tion­ship between phys­i­cal fit­ness and cog­ni­tive per­for­mance but as we exam­ine the results com­ing from the adult pop­u­la­tion, it seems like­ly that the causal effect is here.

Phys­i­cal activ­i­ty and brain health in adults

In 2003, Col­combe and Kramer, ana­lyzed the results of 18 sci­en­tific stud­ies pub­lished between 2000 and 2001. These were not cor­re­la­tion stud­ies. Researchers ran­domly assigned par­tic­i­pants to either an aer­o­bic train­ing group or a con­trol group. Cog­ni­tive per­for­mance in both groups was assessed before and after the train­ing peri­od. The results of this meta-analy­sis clear­ly showed that fit­ness train­ing increased cog­ni­tive per­for­mance in healthy adults between the ages of 55 and 80. Giv­en the design of the stud­ies, results sug­gest a causal rela­tion between more phys­i­cal exer­cise and bet­ter cog­ni­tive performance.

Anoth­er meta-analy­sis pub­lished in 2004 by Heyn and col­leagues showed sim­i­lar ben­e­fi­cial effects of fit­ness train­ing for peo­ple over 65 years old who had cog­ni­tive impair­ment or dementia.

In 2006, Col­combe and col­leagues ran­domly assigned 59 old­er adults to either a car­dio­vas­cu­lar exer­cise group, or a non­aer­o­bic exer­cise con­trol group (stretch­ing and ton­ing exer­cise). Par­tic­i­pants exer­cised 3h per week for 6 months. Col­combe et al. scanned the par­tic­i­pants’ brains before and after the train­ing peri­od. After 6 months, the brain vol­ume of the aer­o­bic exer­cis­ing group increased in sev­eral areas com­pared to the oth­er group. Vol­ume increase occurred prin­ci­pally in frontal and tem­po­ral areas of the brain involved in exec­u­tive con­trol and mem­ory processes.

More recent stud­ies con­firm that aer­o­bic exer­cise is relat­ed to the size of regions respon­si­ble for mem­o­ry process­es (such as the hip­pocam­pus) in elder­ly humans (Erick­son et al., 2009).

How does it work?

As you know neu­ro­plas­tic­i­ty is the brain’s abil­i­ty to reor­ga­nize itself through­out life. This reor­ga­ni­za­tion occurs through the gen­er­a­tion of new neu­rons (neu­ro­ge­n­e­sis) and new con­nec­tions (synaps­es) between neu­rons. Neu­ro­plas­tic­i­ty is trig­gered by our expe­ri­ences, by what hap­pens in our life.

It seems that phys­i­cal exer­cise trig­gers some neu­ro­plas­tic changes in the brain.

Numer­ous ani­mal stud­ies have shown that phys­i­cal exer­cise has a mul­ti­tude of effects on the brain: neu­ro­ge­n­e­sis, cre­ation of synaps­es, increase in var­i­ous neu­ro­trans­mit­ters and nerve growth fac­tor lev­els, and angio­gen­e­sis (the for­ma­tion of new blood vessels).

In human stud­ies,  researchers sus­pect that the increased brain vol­umes observed fol­low­ing fit­ness train­ing may be due to an increased num­ber of blood ves­sels and an increased num­ber of con­nec­tions between neurons.

Neu­ro­plas­tic­i­ty slows down as we age but does not dis­ap­pear. Clear­ly the brain can ben­e­fit from phys­i­cal exer­cise at all ages.

The guide­lines

Aer­o­bic exer­cise, at least thir­ty to six­ty min­utes per day, three days a week, has been shown to have a pos­i­tive impact on brain func­tions. As point­ed out in the Sharp­Brains Guide to Brain Fit­ness, the exer­cise does not have to be stren­u­ous: Walk­ing has been shown to have pos­i­tive effects too.

As we all know it is not always easy to inte­grate phys­i­cal exer­cise in our busy lives. Two things may help:

·       Set a goal that you can achieve. Do some­thing you enjoy for even only 15 min­utes a day; you can always add more time and vari­ety later.

·       Sched­ule exer­cise into your dai­ly rou­tine. It will become a habit faster if you do.