Dose-Response-Relationship between Physical Activity and Cognition in Elderly
The health benefits of exercise are well established. However, the relationship between exercise volume and intensity and health benefits. The dose–response relationship, or exposure–response relationship, describes the change in . Environmental Health Perspectives. 23–7. Dose-Response Relationship of Physical Activity to Health Outcomes: There is an inverse and generally linear relationships for the rates of.
Description of Included Studies The sample sizes within the 13 included studies ranged from 20 to and observation periods from four to 48 weeks. Seven studies had a low-intensity placebo-treated control group CG 457151629 Treatment within the intervention groups differed.
Eight of 13 studies performed an intervention to improve aerobic fitness 241115162033 while six studies performed resistance training RT 2711151629 and two studies engaged in a mixed program including coordination exercises, too 20 Seven of 13 studies included healthy elderly participants 241115162033five included MCI patients 5728293031 and one study AD patients 3.
Detailed descriptions of the interventions and cognitive outcomes are presented in table 1. Squares indicate results for AD patients, triangles indicate results for MCI patients and circles indicate results for healthy elderly see fig. Executive Functions The following cognitive measures were assigned to the domain executive functions: We found heterogeneous results for seven studies with healthy elderly participants 2411151620 No effects were found in five groups.
Nine small and ten moderate ES were found at 5. The three studies with MCI patients 5730 showed no effects in two groups. Three large ES were found at We found a moderate and two large ES for one study with AD and mixed dementia patients at 3.
Processing Speed and Attention The following outcomes were assigned to the cognitive domain processing speed and attention: One large ES was found at A large ES was found at No effects as well as a moderate ES was found for one study with AD and mixed dementia patients 3 at 3. In three studies 42033 with healthy elderly no effects were found in four groups and four marginal ES were found at 8.
Five small and one moderate ES were found at 8. A small ES was found in one study with AD and mixed dementia patients 3 at 3. Discussion The purpose of this review was to verify the hypotheses of an evidence-based dose-response-relationship between cognitive functions and physical activity.
The results of the seven included studies with healthy elderly were heterogeneous in terms of ES and MET values. Most of the studies with healthy elderly were of low or medium quality, scoring two or three points in the risk of bias assessment see table 1 except for 20 An unclear randomization procedure, lack of double-blinding and a missing study protocol resulted in an increased risk for selection bias, performance and detection bias as well as reporting bias.
However, these results are based on only three studies of low two points 7medium three points 5 and high six points 30 methodological quality. Methodological quality of the other MCI studies was high four points 28 Only one study with AD patients fulfilled the inclusion criteria for this review.
What is the dose-response relationship between exercise training and blood pressure?
The study was of medium quality 3 points. However, negative results were also found on each level. Our findings also indicate that executive functions benefited more than the other cognitive functions from physical activity. This is in line with findings from other studies 46. These neuroprotective mechanisms lead to an enhanced synthesis of cerebral tissue Therefore, aerobic and strength exercise programs can lead to an increased brain reserve capacity, maintaining a healthy function for the aging brain and delaying the onset of clinical symptoms in MCI or AD 10 However, until now there is only modest evidence for aerobic and strength exercise programs on cognitive performance for people who already suffer from AD Previous studies found that even low-intensity exercise, such as coordination training can improve cognitive performance and alter brain structures and functions that are involved in cognitive processes and pathology 1819 Seven control groups of the included studies received a low-intensity placebo treatment, including stretching, postural and balance exercises as well as calisthenics and relaxation techniques.
These findings indicate that the amount and intensity of physical activity might not be the sole factor determining effects on brain function and structure, but rather supports the importance of the conducted type of the intervention.
Based on the 13 analyzed studies, aerobic exercise interventions demonstrated the largest ES, followed by strength and multicomponent exercise, while ES for low-intensity exercise were rather small. It remains to be elucidated, how different types of exercise e. Moreover, consensus on cognitive outcomes may help identifying a more detailed signature of exercise interventions that have optimal effects on the specific cognitive functions.
Limitations This review is limited by its focus on behavioral cognitive outcomes to elucidate the dose-response-relationship between physical activity and cognitive performance.
Moreover, the assignment of the cognitive outcomes to the specific cognitive domains was inconsistent within the analyzed studies, which have probably influenced our results.
Because of our selection criteria, mainly aerobic exercise interventions were included, raising the risk for selection bias.
A further limitation is the transformation of the physical intervention into MET. To get exact MET values, the metabolic rate of each subject is needed. Conclusion We could not determine a clear dose-response-relationship between the amount of physical activity per week and the cognitive domains executive functions, attention and processing speed, short- and long-term memory and verbal memory based on randomized controlled trials.
However, cognitive functions were improved by physical exercise at each intensity level. The amount and intensity of physical activity were probably not the key factors for determining the effects on brain structures and functions. Acknowledgement We thank Lisa M.
Stroehlein for reading and correcting the paper. Conflict of Interest The authors have no conflict of interest. Manipulating the exercise dose is done with the intent of eliciting a positive physiological response, which may be increased cardiovascular fitness, improved cholesterol profile or lowered blood pressure.
When designing exercise programs, fitness professionals should consider not only the optimal dose of exercise that will result in the greatest benefit, but also the potential risks associated with an increased amount of exercise.
In particular, the risk of musculoskeletal injury will be greater with an increasing volume and intensity of exercise. Scientific research has demonstrated that there is a dose-response relationship between exercise and multiple health outcomes see Table 1including cardiovascular fitness level, risk of coronary artery disease CAD and all-cause mortality, obesity, cholesterol profile, type 2 diabetes and colon cancer MacKinnon et al.
Exercise Programming: One Size Fits All?
Surgeon General have noted that the health benefits of a program are associated with the total weekly energy expenditure ACSM ; U. ACSM has recommended a target energy expenditure of — kcal per day. The lower end of this range corresponds to 1, kcal per week, while the upper end is equivalent to approximately 3, kcal per week ACSM Currently, PFTs are encouraged to design initial exercise programs to achieve the lower threshold 1, kcal per weekand then to progress gradually toward the higher end of the recommended range 3, kcal per week.
Absolute Energy Expenditure While there is compelling evidence based on the dose-response relationship between exercise volume and health benefits to support the absolute energy expenditure recommendations 1,— 3, kcal per week of ACSM and the U. Surgeon General, it is important to note that the number of calories burned during the same exercise session will be dissimilar among individuals of differing body weights. Table 2 illustrates Jack and Jill: While this exercise program yields a weekly energy expenditure of kcal for Jill, the same program leads to an energy expenditure of 1, kcal per week for Jack.
The primary reason for the difference in weekly energy expenditure is the variation in body weight. Is it correct to say that everyone, young or old, male or female, big or small, should follow the same absolute energy expenditure recommendation to achieve equivalent health benefits?
In our example, should an exercise professional encourage Jill to extend her daily exercise duration so as to increase her weekly energy expenditure to 1, kcal per week?
Conversely, should Jack be advised that his weekly energy expenditure is actually higher than the 1,kcal-per-week recommendation—and that he should therefore consider decreasing his daily exercise duration? This scenario places fitness professionals in an uncomfortable position."Dose Response Relationship" Explained in a Simple Way
They are faced with answering the question, Is an absolute weekly energy expenditure recommendation appropriate for everyone? We believe this approach introduces the possibility of under- or overestimating the energy expenditure requirements of individual exercise programs, thus diminishing the health outcomes for clients.
Fortunately, recent research findings have identified an improved approach to designing exercise programs and individualizing weekly energy expenditure goals. The unique aspect of STRRIDE was the investigation of separate doses of weekly energy expenditure relative to body weight and their effect on health outcomes, rather than the examination of different absolute weekly energy expenditure levels.
Each group was composed of approximately 40 male and female participants, aged 40—65 years.
- Dose–response relationship
- What is the dose-response relationship between exercise training and blood pressure?
- Exercise volume and intensity: a dose-response relationship with health benefits.
STRRIDE also examined the dose-response relationship between exercise intensity and various health outcomes, but further discussion of this aspect of the study—which involved a fourth group—is beyond the scope of this article.
In a dose-response manner comparing the control group, the low-amount group and the high-amount groupthere were greater improvements in each of the health outcomes during the course of the study with increasing volumes of exercise.
Cardiovascular fitness was higher in both the low-amount While high-density lipoprotein HDL cholesterol worsened in the sedentary group They support the dose-response relationship between increased amounts of energy expenditure and greater health benefits. The doses of energy expenditure prescribed are relative to individual differences in body weight. The specific doses used in the study provide guidelines for developing individual exercise prescriptions for future clients.
Customizing a Program How can you apply this information to customize exercise programs for clients with differences in body weight, gender and age? If we look at Table 3, it is apparent that based on differences in body weight, the relative weekly energy expenditure goals of the exercise programs for Jack and Jill are noticeably different.
The relative weekly energy expenditure goal for Jack is about 1, kcal per week, while Jill needs to achieve kcal per week. Although this approach yields different absolute weekly energy expenditure goals, the discrepancy between the two programs is accounted for by the differences in body weight. The dose-response relationship between exercise volume and health outcomes suggests that the major focus of exercise program design should be the total weekly energy expenditure.