High-intensity exercise and cognitive function in cognitively normal older adults: a pilot randomised clinical trial

The impact of exercise on blood-based biomarkers of Alzheimer's disease in cognitively unimpaired older adults

Physical activity is a promising preventative strategy for Alzheimer's disease: it is associated with lower dementia risk, better cognition, greater brain volume and lower brain beta-amyloid. Blood-based biomarkers have emerged as a low-cost, non-invasive strategy for detecting preclinical Alzheimer's disease, however, there is limited literature examining the effect of exercise (a structured form of physical activity) on blood-based biomarkers. The current study investigated the influence of a 6-month exercise intervention on levels of plasma beta-amyloid (Aβ42, Aβ40, Aβ42/40), phosphorylated tau (p-tau181), glial fibrillary acidic protein (GFAP) and neurofilament light (NfL) chain in cognitively unimpaired older adults, and as a secondary aim, whether blood-based biomarkers related to cognition. Ninety-nine community-dwelling older adults (69.1 ± 5.2) were allocated to an inactive control, or to moderate or high intensity exercise groups where they cycled twice weekly for six months. At baseline and six months (post-intervention), fasted blood was collected and analysed using single molecule array (SIMOA) assays, and cognition was assessed. Results demonstrated no change in levels of any plasma biomarker from pre- to post-intervention. At baseline, higher NfL was associated with poorer cognition (β = -0.33, SE = 0.13, adjusted p = .042). Exploratory analyses indicated higher cardiorespiratory fitness was associated with higher NfL and GFAP levels in apolipoprotein E (APOE) ε4 non-carriers compared to ε4 carriers (NfL, β = -0.43, SE = 0.19, p = .029; GFAP, β = -0.41, SE = 0.20, p = .044), though this association was mediated by body mass index (BMI). These results highlight the importance of considering BMI in analysis of blood-based biomarkers, especially when investigating differences between APOE ε4 carriers and non-carriers. Our results also indicate that longer follow-up periods may be required to observe exercise-induced change in blood-based biomarkers.

Association Between Physical Activity and Performance in Skill Learning Among Older Adults Based on Cognitive Function

BACKGROUND/OBJECTIVES

Most older adults experience cognitive and physical functioning problems; however, they require the ability to learn skills in response to age-related or social environmental changes for independent living. This study aimed to clarify the associations between age-related physical activity and performance in skill learning tasks based on cognitive function.

METHODS

Fifty-eight adults participated in this study and were divided into two groups: the control group (aged under 65 years) and older adult group (aged over 65). All the participants performed two-skill learning exercises based on cognitive function. Habitual exercise was measured using an accelerometer and a self-reported questionnaire.

RESULTS

At baseline, the scores on skill tasks were lower in the older adult group than in the control group and were associated with habitual exercise and motor performance. Skill acquisition, observed in both groups, was associated with age and self-reported physical activity. Retention of the acquired skill was not associated with habitual exercise, and it declined significantly in the older group.

CONCLUSIONS

Skill acquisition was maintained regardless of age; however, the ability to retain the acquired skills decreased among the older adults. Habitual physical activity was associated with skill acquisition but not the retention of the acquired skill. Significance/Implications: The study findings highlight the association between habitual exercise and motor skill learning in older adults, providing insight for practitioners in the rehabilitation and health care fields.

Effects of High-Intensity Interval Training on the Parameters Related to Physical Fitness and Health of Older Adults: A Systematic Review and Meta-Analysis

BACKGROUND

As a novel and time-efficient exercise form, high-intensity interval training (HIIT) has shown great potential in improving health-related physical fitness among diverse populations. However, empirical evidence on its efficacy among the elderly has not been well summarized. This systematic review and meta-analysis aimed to determine the effect of HIIT interventions on the parameters related to physical fitness and health of older adults, including resting heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiorespiratory fitness (CRF), body mass index (BMI), body fat percent (BF%), waist circumference (WC), muscular endurance (ME), muscular strength (MS), muscular power (MP), balance and flexibility, compared to non-exercise and other-exercise (e.g., moderate-intensity continuous training, resistance training) conditions.

METHODS

Literature published from January 2000 to May 2023 was collected through extensive searches across eight databases and relevant review papers. Randomized controlled trials (RCTs) featuring a minimum 2-week exercise intervention for older adults (≥ 60 years) were included. The pooled effect size of Hedges'g was estimated using random-effects models in R. Meta-regression was performed for both categorical (health status, duration of training programme, and frequency) and continuous moderators (mean age, male rate, and attrition rate).

RESULTS

Forty-four eligible RCTs with 1863 participants (52.1% female; 60.5-81.2 years) were included in the quantitative analysis. Compared to non-exercise condition, HIIT significantly improved resting HR (g = -0.36, 95%CI = [-0.67, -0.05], P = 0.032), SBP (g = -0.29, 95%CI = [-0.54, -0.03], P = 0.008), CRF (g = 0.77, 95%CI = [0.51, 1.04], P < 0.001), BF% (g = -0.26, 95%CI = [-0.41, -0.11], P = 0.006), MS (g = 0.47, 95%CI = [0.23, 0.71], P = 0.004), ME (g = 0.65, 95%CI = [0.10, 1.19], P = 0.036), and balance (e.g., timed-up-and-go) (g = -0.79, 95%CI = [-1.19, -0.40], P = 0.035). Compared to other-exercise condition, HIIT significantly improved resting HR (g = -0.11, 95%CI = [-0.21, -0.01], P = 0.029), SBP (g = -0.14, 95%CI = [-0.28, -0.01], P = 0.038), and CRF (g = 0.23, 95%CI = [0.07, 0.38], P = 0.008). No significant difference was found between HIIT and non-exercise condition for DBP, BMI and WC, as well as between HIIT and other-exercise condition for DBP, BMI, BF%, WC, ME, and balance (all P > 0.05). Meta-regression indicated that mean age moderated the HIIT effect on resting HR (b = -0.02, P = 0.014; HIIT vs. other-exercise condition) and SBP (b = 0.03, P = 0.048; HIIT vs. non-exercise), and attrition rate moderated the effect on CRF (b = 0.03, P = 0.007; HIIT vs. non-exercise).

CONCLUSION

This study supports the efficacy of HIIT in improving resting HR, SBP, CRF, BF%, MS, ME and balance among older adults. More empirical evidence is needed to determine the efficacy of HIIT for MP and flexibility in this population.

TRIAL REGISTRATION

PROSPERO CRD42022316246.

Cardiorespiratory Fitness Assessment for Exercise Research in Mild Cognitive Impairment Due to Alzheimer's Disease

PURPOSE

To analyze cardiorespiratory fitness (CRF) levels using the gold-standard, laboratory-based cardiopulmonary exercise test (CPET) in community-dwelling older adults (N = 145) with amnestic mild cognitive impairment (aMCI), specifically CPET feasibility, CRF prediction, and CRF status in comparison to published sedentary, cognitively normal, age- and sex-adjusted normative data.

METHOD

Peak oxygen consumption (VO2Peak [mL/kg/min]) was assessed by CPET, which was categorized as submaximal, near-maximal, or maximal tests. VO2Max predicted was compared to VO2Max measured to assess its utility. Data were analyzed with t tests.

RESULTS

Participants' mean age was 73.77 years (SD = 5.74 years), with 51.7% males, 91.7% Caucasian, 68.3% married, and 16.9 years (SD = 2.88 years) of education. Mean VO2Peak measured was 17.07 (SD = 4.92) for the total sample (18.29 [SD = 4.64] for males, 15.78 [SD = 4.91] for females). Sixteen (11.03%) CPETs were submaximal, 53 (36.55%) were near-maximal, and 76 (52.41%) were maximal. Mean VO2Max predicted was 28.59 (SD = 21.94) for the total sample (29.36 [SD = 22.3] for males, 27.76 [SD = 21.68] for females) and was significantly higher than VO2Max measured (p < 0.0001). Among participants with maximal CPETs, VO2Peak measured was significantly lower than sedentary normative data (p < 0.0001).

CONCLUSION

CPET was feasible for older adults with aMCI. VO2Max predicted overly inflates CRF estimates. Low levels of CRF in older adults with aMCI suggest aerobic exercise as an important intervention. [Journal of Gerontological Nursing, 50(9), 31-36.].

Association of Moderate and Vigorous Physical Activity With Cognitive Performance: Evidence From Brazil

OBJECTIVE

It is estimated that 2% of dementia cases worldwide could be prevented with increases in physical activity. However, there is little evidence of the association between vigorous physical activity (VPA) and cognitive performance. This study aimed to investigate the association of moderate physical activity (MPA) and VPA with cognitive performance in older adults from the Brazilian Longitudinal Study of Aging (ELSI-Brasil).

PATIENTS AND METHODS

Data from 7954 participants were analyzed. Mean age was 61.8 ± 9.2 years, 61.8% were women, and 44.3% were mixed races. Cognitive performance evaluated the memory, temporal orientation, and verbal fluency domains. A global composite z-score was derived from the tests. Physical activity was assessed by self-report. We used linear regression models to verify the association of MPA and VPA with cognitive performance.

RESULTS

Compared with participants who did not meet the guidelines for MPA (<150 min/wk), those who met the guidelines (150 to 299 min/wk) and those who performed more than 2x the recommended amount of MPA (300 min or more/wk) had better global cognitive performance (β = 0.163, 95% CI = 0.086, 0.241; P < 0.001; β = 0.180, 95% CI = 0.107, 0.253, P < 0.001, respectively). We found no association between VPA and cognitive performance.

CONCLUSION

There was no additional benefit of VPA for cognitive performance.

Cognitive and neuroscientific perspectives of healthy ageing

With dementia incidence projected to escalate significantly within the next 25 years, the United Nations declared 2021-2030 the Decade of Healthy Ageing, emphasising cognition as a crucial element. As a leading discipline in cognition and ageing research, psychology is well-equipped to offer insights for translational research, clinical practice, and policy-making. In this comprehensive review, we discuss the current state of knowledge on age-related changes in cognition and psychological health. We discuss cognitive changes during ageing, including (a) heterogeneity in the rate, trajectory, and characteristics of decline experienced by older adults, (b) the role of cognitive reserve in age-related cognitive decline, and (c) the potential for cognitive training to slow this decline. We also examine ageing and cognition through multiple theoretical perspectives. We highlight critical unresolved issues, such as the disparate implications of subjective versus objective measures of cognitive decline and the insufficient evaluation of cognitive training programs. We suggest future research directions, and emphasise interdisciplinary collaboration to create a more comprehensive understanding of the factors that modulate cognitive ageing.

Physical exercise, cognition, and brain health in aging

Exercise training is an important strategy to counteract cognitive and brain health decline during aging. Evidence from systematic reviews and meta-analyses supports the notion of beneficial effects of exercise in cognitively unimpaired and impaired older individuals. However, the effects are often modest, and likely influenced by moderators such as exercise training parameters, sample characteristics, outcome assessments, and control conditions. Here, we discuss evidence on the impact of exercise on cognitive and brain health outcomes in healthy aging and in individuals with or at risk for cognitive impairment and neurodegeneration. We also review neuroplastic adaptations in response to exercise and their potential neurobiological mechanisms. We conclude by highlighting goals for future studies, including addressing unexplored neurobiological mechanisms and the inclusion of under-represented populations.

Cognitive Fitness: Harnessing the Strength of Exerkines for Aging and Metabolic Challenges

Addressing cognitive impairment (CI) represents a significant global challenge in health and social care. Evidence suggests that aging and metabolic disorders increase the risk of CI, yet promisingly, physical exercise has been identified as a potential ameliorative factor. Specifically, there is a growing understanding that exercise-induced cognitive improvement may be mediated by molecules known as exerkines. This review delves into the potential impact of aging and metabolic disorders on CI, elucidating the mechanisms through which various exerkines may bolster cognitive function in this context. Additionally, the discussion extends to the role of exerkines in facilitating stem cell mobilization, offering a potential avenue for improving cognitive impairment.

The intensity paradox: A systematic review and meta-analysis of its impact on the cardiorespiratory fitness of older adults

AIM

The present systematic review and meta-analysis aimed to compare the effect of moderate- versus high-intensity aerobic exercise on cardiorespiratory fitness (CRF) in older adults, taking into account the volume of exercise completed.

METHODS

The databases MEDLINE (Ovid), EMBASE (Ovid), and CENTRAL (Cochrane Library) were searched to identify randomized controlled trials (RCTs). Two reviewers extracted data and assessed bias. Comprehensive Meta-Analysis software calculated overall effect size, intensity differences, and performed meta-regression analyses using pre-to-post intervention or change scores of peak oxygen uptake (V̇O2 peak). The review included 23 RCTs with 1332 older adults (intervention group: n = 932; control group: n = 400), divided into moderate-intensity (435 older adults) and high-intensity (476 older adults) groups.

RESULTS

Meta-regression analysis showed a moderate, but not significant, relationship between exercise intensity and improvements in V̇O2 peak after accounting for the completed exercise volume (β = 0.31, 95% CI = [-0.04; 0.67]). Additionally, studies comparing moderate- versus high-intensity revealed a small, but not significant, effect in favor of high-intensity (Hedges' g = 0.20, 95% CI = [-0.02; 0.41]). Finally, no significant differences in V̇O2 peak improvements were found across exercise groups employing various methods, modalities, and intensity monitoring strategies.

CONCLUSION

Findings challenge the notion that high-intensity exercise is inherently superior and indicate that regular aerobic exercise, irrespective of the specific approach and intensity, provides the primary benefits to CRF in older adults. Future RCTs should prioritize valid and reliable methodologies for monitoring and reporting exercise volume and adherence among older adults.

Dose-response effects of exercise on mental health in community-dwelling older adults: Exploration of genetic moderators

Background/Objective

(1) Examine the role of exercise intensity on mental health symptoms in a community-based sample of older adults. (2) Explore the moderating role of genetic variation in brain-derived neurotrophic factor (BDNF) and apolipoprotein E (APOE) on the effects of exercise on mental health symptoms.

Method

This study is a secondary analysis of a three-arm randomized controlled trial, comparing the effects of 6 months of high-intensity aerobic training vs. moderate-intensity aerobic training vs. a no-contact control group on mental health symptoms assessed using the Depression, Anxiety, and Stress Scale (DASS). The BDNF Val66Met polymorphism and APOE ε4 carrier status were explored as genetic moderators of exercise effects on mental health symptoms.

Results

The exercise intervention did not influence mental health symptoms. The BDNF Val66Met polymorphism did not moderate intervention effects on mental health symptoms. APOE ε4 carrier status moderated the effect of intervention group on perceived stress over 6 months, such that APOE ε4 carriers, but not non-carriers, in the high-intensity aerobic training group showed a decline in perceived stress over 6 months.

Conclusions

APOE ε4 carrier status may modify the benefits of high-intensity exercise on perceived stress such that APOE ε4 carriers show a greater decline in stress as a result of exercise relative to non-APOE ε4 carriers.

Effects of exercise interventions on cognitive functions in healthy populations: A systematic review and meta-analysis

Chronic exercise intervention is a non-pharmacological therapy suggested to improve cognitive function in various populations. However, few meta-analyses have assessed the cognitive benefits associated with all FITT-VP variables (exercise frequency, intensity, bout duration time, type, volume or total intervention length, and progression) in healthy populations by age. Thus, this meta-analysis assessed the effects of each FITT-VP variable on cognitive function in healthy children, adults, and older adults. This study followed PRISMA guidelines. After searching PubMed and the Web of Science, we included 54 randomized controlled trials to examined the effects of FITT-VP variables on five cognitive domains: global cognition, executive function, memory, attention, and information processing. Moderation analyses assessed the effects by age and by each exercise variables. Exercise benefitted overall cognition and all subcognitive domains. Aerobic and resistance exercise showed the greatest benefits on global cognition and executive function respectively, whereas mind-body exercise benefitted memory. Among all populations, older adults showed the greatest benefits of exercise on global cognition, executive function, and memory compared with controls. Additional studies are needed to assess the effects of exercise on attention and information processing. This meta-analysis offers new insights on the relationships between cognition and FITT-VP exercise variables in healthy populations.

Developing and validating a nomogram for cognitive impairment in the older people based on the NHANES

Objective

To use the United States National Health and Nutrition Examination Study (NHANES) to develop and validate a risk-prediction nomogram for cognitive impairment in people aged over 60 years.

Methods

A total of 2,802 participants (aged ≥ 60 years) from NHANES were analyzed. The least absolute shrinkage and selection operator (LASSO) regression model and multivariable logistic regression analysis were used for variable selection and model development. ROC-AUC, calibration curve, and decision curve analysis (DCA) were used to evaluate the nomogram's performance.

Results

The nomogram included five predictors, namely sex, moderate activity, taste problem, age, and education. It demonstrated satisfying discrimination with a AUC of 0.744 (95% confidence interval, 0.696-0.791). The nomogram was well-calibrated according to the calibration curve. The DCA demonstrated that the nomogram was clinically useful.

Conclusion

The risk-prediction nomogram for cognitive impairment in people aged over 60 years was effective. All predictors included in this nomogram can be easily accessed from its' user.

Mind body exercise improves cognitive function more than aerobic- and resistance exercise in healthy adults aged 55 years and older - an umbrella review

Exercise is often cited as a major factor contributing to improved cognitive functioning. As a result, the relationship between exercise and cognition has received much attention in scholarly literature. Systematic reviews and meta-analyses present varying and sometimes conflicting results about the extent to which exercise can influence cognition. The aim of this umbrella review was to summarize the effects of physical exercise on cognitive functions (global cognition, executive function, memory, attention, or processing speed) in healthy adults ≥ 55 years of age.Methods An umbrella review of systematic reviews with meta-analyses investigating the effect of exercise on cognition was performed. Databases (CINAHL, Cochrane Library, MEDLINE, PsycInfo, Scopus, and Web of Science) were searched from inception until June 2023 for reviews of randomized or non-randomised controlled trials. Full-text articles meeting the inclusion criteria were reviewed and methodological quality assessed. Overlap within included reviews was assessed using the corrected covered area method (CCA). A random effects model was used to calculate overall pooled effect size with sub-analyses for specific cognitive domains, exercise type and timing of exercise.Results Database searches identified 9227 reviews. A total of 20 met the inclusion criteria. They were based on 332 original primary studies. Overall quality of the reviews was considered moderate with most meeting 8 or more of the 16 AMSTAR 2 categories. Overall pooled effects indicated that exercise in general has a small positive effect on cognition (d = 0.22; SE = 0.04; p < 0.01). Mind-body exercise had the greatest effect with a pooled effect size of (d = 0.48; SE = 0.06; p < 0.001). Exercise had a moderate positive effect on global cognition (d = 0.43; SE = 0,11; p < 0,001) and a small positive effect on executive function, memory, attention, and processing speed. Chronic exercise was more effective than acute exercise. Variation across studies due to heterogeneity was considered very high.Conclusions Mind-body exercise has moderate positive effects on the cognitive function of people aged 55 or older. To promote healthy aging, mind-body exercise should be used over a prolonged period to complement other types of exercise. Results of this review should be used to inform the development of guidelines to promote healthy aging.Trial registration PROSPERO (CDR 42022312955).

Association of leisure activity changes and reversion from mild cognitive impairment to normal cognitive function among older adults: A prospective cohort study

Background

Older adults with mild cognitive impairment (MCI) have the possibility of reverting to normal cognitive function. Leisure activity engagement (LAE) plays a critical role in the progress of the cognitive function. A better understanding of the dynamic relationship between LAE and MCI reversion would inform the implementation of preclinical dementia interventions. This study aimed to investigate the association between change patterns of LAE and MCI reversion among older adults using the Chinese Longitudinal Healthy Longevity Survey (CLHLS) database.

Study design

Longitudinal population-based study.

Methods

Older adults with MCI at the baseline were enrolled in this study. Information about cognitive function, overall, cognitively stimulating, physically active/demanding, and socially engaged LAE was collected at baseline and follow-up. Adjusted hazard ratios (HRs) for reversion and 95% confidence intervals (CIs) were calculated by Cox hazard models with time as the underlying time metric. We also assessed potential effect modifications by creating a cross-product of the stratifying variable with LAE change patterns in the fully adjusted model.

Results

The restricted cubic spline showed that the association between LAE change scores and MCI reversion rate was statistically significant and nonlinear (p<0.01). Taking participants in the low-low group as a reference, participants in the low-medium, low-high, medium-medium, medium-high, high-medium, and high-high groups had increased possibilities of MCI reversion with HRs (95% CI) of 2.19 (1.57-3.06), 2.97 (2.13-4.13), 0.87 (0.64-1.19), 2.28 (1.71-3.03), 2.78 (2.10-3.69), 1.93 (1.43-2.59), and 2.74 (2.09-3.60), respectively. Further stratified models showed that the impact of LAE change patterns on MCI reversion varied in different ages (nonagenarian, octogenarian, and younger elderly) and gender.

Conclusions

Participants who maintained the highest LAE had the greatest possibility of MCI reversion. Meanwhile, a higher level of LAE maintenance was associated with the increased possibility of MCI reversion. These results provide a practical message to older adults about how dynamic changes in LAE are associated with improved cognitive function.

The Effect of Self-Paced Exercise Intensity and Cardiorespiratory Fitness on Frontal Grey Matter Volume in Cognitively Normal Older Adults: A Randomised Controlled Trial

OBJECTIVE

Exercise has been found to be important in maintaining neurocognitive health. However, the effect of exercise intensity level remains relatively underexplored. Thus, to test the hypothesis that self-paced high-intensity exercise and cardiorespiratory fitness (peak aerobic capacity; VO_2peak) increase grey matter (GM) volume, we examined the effect of a 6-month exercise intervention on frontal lobe GM regions that support the executive functions in older adults.

METHODS

Ninety-eight cognitively normal participants (age = 69.06 ± 5.2 years; n = 54 female) were randomised into either a self-paced high- or moderate-intensity cycle-based exercise intervention group, or a no-intervention control group. Participants underwent magnetic resonance imaging and fitness assessment pre-intervention, immediately post-intervention, and 12-months post-intervention.

RESULTS

The intervention was found to increase fitness in the exercise groups, as compared with the control group (F = 9.88, p = <0.001). Changes in pre-to-post-intervention fitness were associated with increased volume in the right frontal lobe (β = 0.29, p = 0.036, r = 0.27), right supplementary motor area (β = 0.30, p = 0.031, r = 0.29), and both right (β = 0.32, p = 0.034, r = 0.30) and left gyrus rectus (β = 0.30, p = 0.037, r = 0.29) for intervention, but not control participants. No differences in volume were observed across groups.

CONCLUSIONS

At an aggregate level, six months of self-paced high- or moderate-intensity exercise did not increase frontal GM volume. However, experimentally-induced changes in individual cardiorespiratory fitness was positively associated with frontal GM volume in our sample of older adults. These results provide evidence of individual variability in exercise-induced fitness on brain structure.

Getting Fit to Counteract Cognitive Aging: Evidence and Future Directions

Physical activity has shown tremendous promise for counteracting cognitive aging, but also tremendous variability in cognitive benefits. We describe evidence for how exercise affects cognitive and brain aging, and whether cardiorespiratory fitness is a key factor. We highlight a brain network framework as a valuable paradigm for the mechanistic insight needed to tailor physical activity for cognitive benefits.

Do Physical Activity, BMI, and Wellbeing Affect Logical Thinking?

We studied 6368 people (4544 women and 1824 men; aged 18–74 years). The research goal was to determine whether the Cognitive Reflection Test score (logical thinking compared with intuitive thinking) depends—and in what way it depends—on the healthy lifestyle components and emotional health-related components as well as age (18–74 years) and gender. We established that analytical vs. intuitive thinking depended on components of a healthy lifestyle, physical activity, sleep, eating habits, smoking and alcohol consumption, specificity of sporting activity, body mass index, and emotional health-related components (stress, depression, impulsivity, subjective health, emotional intelligence), as well as age and gender. We found that logical thinking was not associated with sleep, moderate-to-vigorous PA, impulsivity, subjective health, and components of a healthy lifestyle. However, logical thinking decreases with age, gender (higher in men than in women), BMI (decreases in both genders over the second degree of obesity), depression (the more severe depression in women, the worse their logical thinking), sedentary behavior (people who sat for longer periods had more difficulty solving problems), and in professional sportswomen (logical thinking is worse in professional sportswomen than in sedentary women, amateur sportswomen, or women who use gyms). Finally, we determined inverse correlations between logical thinking, emotional intelligence, and stress.

High-Intensity Interval Training in Older Adults: a Scoping Review

High-intensity interval training (HIIT) is an increasingly popular form of aerobic exercise which includes bouts of high-intensity exercise interspersed with periods of rest. The health benefits, risks, and optimal design of HIIT are still unclear. Further, most research on HIIT has been done in young and middle-aged adults, and as such, the tolerability and effects in senior populations are less well-known. The purpose of this scoping review was to characterize HIIT research that has been done in older adults including protocols, feasibility, and safety and to identify gaps in the current knowledge. Five databases were searched with variations of the terms, "high-intensity interval training" and "older adults" for experimental or quasi-experimental studies published in or after 2009. Studies were included if they had a treatment group with a mean age of 65 years or older who did HIIT, exclusively. Of 4644 papers identified, 69 met the inclusion criteria. The average duration of training was 7.9 (7.0) weeks (mean [SD]) and protocols ranged widely. The average sample size was 47.0 (65.2) subjects (mean [SD]). Healthy populations were the most studied group (n = 30), followed by subjects with cardiovascular (n = 12) or cardiac disease (n = 9), metabolic dysfunction (n = 8), and others (n = 10). The most common primary outcomes included changes in cardiorespiratory fitness (such as VO2peak) as well as feasibility and safety of the protocols as measured by the number of participant dropouts, adverse events, and compliance rate. HIIT protocols were diverse but were generally well-tolerated and may confer many health advantages to older adults. Larger studies and more research in clinical populations most representative of older adults are needed to further evaluate the clinical effects of HIIT in these groups.