A new study published in the Archives of Internal Medicine, a journal of the American Medical Association, found that among a group of senior women, aged 70-80, with mild cognitive impairment, those who engaged in 6 months of twice weekly resistance training (weight lifting) improved their brain functioning significantly, and more than those who instead engaged in 6 months of twice weekly walking exercise.
The new study, conducted by scientists from the Brain Research Center and the Department of Physical Therapy at the University of British Columbia, was published online in the April 23, 2012 issue of the Archives of Internal Medicine.
“Cognitive decline is a pressing health care issue. Worldwide, 1 new case of dementia is detected every 7 seconds,” the authors wrote in an introduction to their study. “Mild cognitive impairment—a well-recognized risk factor for dementia—represents a critical window of opportunity for intervening and altering the trajectory of cognitive decline in seniors,” they explained.
“Both aerobic training (AT) and resistance training (RT) [have been found to] enhance cognitive performance and functional plasticity in healthy, community-dwelling seniors and those with mild cognitive impairment,” the authors wrote, citing earlier studies.
“However, to our knowledge, no intervention study has compared the efficacy of both types of exercise on cognitive function and functional brain plasticity in seniors with mild cognitive impairment,” they stated. In the new study, they set out to do just that.
The study participants included a group of 86 community-dwelling women, 70 to 80 years old. At the beginning of the study, based on a cognitive assessment test, the participants were classified as having “probable mild cognitive impairment.”
The 86 women were randomly assigned to three groups. For a period of 6 months, one group (28 women) participated in twice-weekly supervised Resistance Training (RT) exercises, consisting of weight training, using a pressurized air system and free weights.
The second group (30 women) engaged in twice-weekly supervised Aerobic Training (AT) exercises, consisting of an outdoor walking program.
The third group (28 women), which served as the control group for the study, engaged in supervised twice-weekly Balance and Tone (BAT) Training, consisting of stretching, range of motion, and balance exercises, along with relaxation techniques.
Each of the twice-weekly exercise training sessions, for each of the groups, lasted 60 minutes.
Seventy-seven women completed the 6-month program. At the beginning and end of the program, the women underwent standard verbal and visual memory assessment tests, and tests that evaluated decision-making and problem-solving abilities. Almost one-third of the women also underwent MRI scans at the start and end of the study to measure brain activity changes in different regions of the brain.
The researchers found that, after 6 months, the Resistance Training (RT) group experienced “significant” cognitive improvement, compared to the control group (those in the Balance and Tone (BAT) classes). This included significantly improved performance on a cognitive test measuring “selective attention/conflict resolution,” and on the associative memory task test.
Compared with the BAT group, RT also led to functional changes in 3 regions of the cortex—the right lingual (P = .03) and occipital-fusiform (P = .02) gyri and the right frontal pole (P = .03)—during the encoding and recall of associations. In addition, there was a significant positive correlation between change in hemodynamic activity in the right lingual gyrus and change in behavioral associative memory performance (r = 0.51; P = .02).
Those who had MRI’s in the RT group also experienced changes in activity in three regions of the brain’s cortex associated with cognitive function, the researchers found. These included “functional changes in the right lingual (P = .03) and occipital-fusiform (P = .02) gyri and the right frontal pole (P = .03)—during the encoding and recall of associations,” the researchers reported. “In addition, there was a significant positive correlation between change in hemodynamic activity in the right lingual gyrus and change in behavioral associative memory performance (r = 0.51; P = .02),” they found. Similar changes were not found among those in the control BAT group.
The Aerobics Training (AT) (walking) group, showed significant improvements in physical functioning, compared to the control BAT group, This included “significantly improved general balance and mobility (P = .03) and cardiovascular capacity (P = .04) compared with the BAT group.”
However, the AT (walking) group did not appear to experience the same cognitive benefits as the RT (resistance/weight training) group.
“In senior women with subjective memory complaints, 6 months of twice-weekly RT improved selective attention/conflict resolution, associative memory, and regional patterns of functional brain plasticity compared with twice-weekly BAT exercises,” the authors wrote. “In contrast, 6 months of twice-weekly AT improved physical function. We provide novel evidence that RT can benefit multiple domains in those at risk for dementia,” they concluded.
“We also demonstrated that 6 months of RT twice-weekly significantly improved associative memory performance, co-occurring with positive functional changes in hemodynamic activity in regions involved in the memorization of associations. Impaired associative memory is a hallmark of early stages of Alzheimer disease,” the authors explained.
The associations found may even be stronger than appeared in the study results, the authors stated, because several of the women skipped classes.
“Most studies have looked at aerobic training, but this study compares both aerobic and strength training,” study co-author Teresa Liu-Ambrose, an assistant professor in the department of physical therapy and at the University of British Columbia and also a researcher at the university’s Center for Hip Health and Mobility and the Brain Research Center, told HealthDay News.
“Among people who don’t yet have dementia but are already at a high risk in terms of mild memory and executive function impairment, our study shows that strength training, but not aerobics training, does have benefits for cognition,” Author Liu-Ambrose said.
The study did not measure and cannot explain how (by what mechanisms) and why Resistance Training (RT) may improve cognitive functioning more than Aerobic (walking) Training (AT) does.
As one possible explanation, “It could be that resistance-training requires more learning and monitoring by its very nature,” Author Liu-Ambrose hypothesized to HealthDay. “If you’re lifting weights you have to monitor your sets, your reps, you use weight machines and you have to adjust the seat, etc. But with walking it’s much more natural for most, so there’s less cognitive involvement,” she suggested. “But at this point we don’t have a clear idea of what’s going on at the mechanistic level,” she said.
“In conclusion,” the authors wrote, “our study suggests that twice-weekly RT is a promising strategy to alter the trajectory of cognitive decline in seniors with mild cognitive impairment.”
They cautioned, however, that their findings may not necessarily apply to men or to women of a different age group than those studied.
Further research will be needed to confirm the specific effects of different types of exercises upon cognitive functioning in men and women, and also to better understand the mechanisms by which Resistance Training may have a stronger positive impact than other types of exercise.
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