Understanding heterogeneity of responses to, and optimizing clinical efficacy of, exercise training in older adults: NIH NIA Workshop summary

Advancements and Challenges in Exercise Training for Multiple Sclerosis: Comprehensive Review and Future Directions for Randomized Controlled Trials

Exercise training represents a health behavior for the treatment and management of the multi-faceted manifestations of multiple sclerosis (MS). This paper provides a comprehensive overview of evidence from randomized controlled trials (RCTs) regarding benefits, safety, participation, and guidelines for exercise training in MS, based on systematic reviews and meta-analyses. The paper then provides our opinions based on extensive experience regarding challenges for improving and expanding future RCTs that will advance our understanding of exercise training in MS. The comprehensive review of evidence from RCTs indicates that exercise training yields substantial improvements in aerobic and muscle fitness, mobility, fatigue and depression, quality of life, and participation outcomes. There is a non-significant increase in the risk of adverse events or serious adverse events with exercise training compared with control conditions or healthy populations. Rates of adherence and compliance with exercise training (i.e., participation) approximate 80% and 70%, respectively. The current prescriptive guidelines suggest 2-3 days per week of aerobic and resistance exercise training as the minimal dose for safely benefiting from exercise training in MS. We propose 10 important topics as avenues for expanding the body of research and improving its scope for evidence-based practice in MS. Overall, the research on exercise training in MS is strong, but it can get stronger. The expansion and advancement of evidence are critical for moving exercise training into the clinical armamentarium of MS disease treatment and management.

Randomized Controlled Trials of Rehabilitation in Multiple Sclerosis: Barriers and Unmet Needs

Randomized controlled trials (RCTs) provide the foundation of evidence-based practice for the application of rehabilitation as complementary of medications for filling in the gaps and enhancing outcomes in people with multiple sclerosis (MS). This paper identifies seven field-wide areas of relevance for RCTs of rehabilitation that are barriers for (a) knowledge translation and implementation, (b) impact among those who most need rehabilitation, and (c) the field and its value in comprehensive MS care. The seven field-wide areas include improving the quality of RCTs; implementing discovery models for informing selection of interventions; focusing on primary end-points in samples screened for presence of symptoms/dysfunction; exploring response heterogeneity as an avenue for precision medicine; quantifying adherence and compliance for guiding future prescriptions; understanding mechanisms of outcomes through experimental medicine; and extending research into under-researched populations. These field-wide areas represent unmet needs for (a) optimizing quality of life and full participation through evidence-based rehabilitation among all people with MS, (b) reducing burdens and strains among caregivers, and (c) minimizing the financial and societal impact of MS.

Underpowered studies in muscle metabolism research: Determinants and considerations

Biomedical research frequently employs null hypothesis testing to determine whether an observed difference in a sample is likely to exist in the broader population. Null hypothesis testing generally assumes that differences between groups or interventions are non-existent, unless proven otherwise. Because biomedical studies with human subjects are often limited by financial and logistical resources, they tend to have low statistical power, i.e. a low probability of statistically confirming a true difference. As a result, small but potentially clinically important differences may be overseen or ignored simply due to the absence of a statistically significant difference. This absence is often misinterpreted as 'equivalence' of treatments. In this educational paper, we will use practical examples related to the effects of exercise and nutrition on muscle protein metabolism to illustrate the most important determinants of statistical power, as well as their implications for both investigators and readers of scientific articles. Changes in muscle mass occur at a relatively slow rate, making it practically challenging to detect differences between treatment groups in a long-term setting. One way to make it 'easier' to differentiate between groups and hence increase statistical power is to have a sufficiently long study duration to allow treatment effects to become apparent. This is especially relevant when comparing treatments with relatively small expected differences such as the effect of modest changes in daily protein intake. Secondly, one could try to minimize the variance and response heterogeneity within groups, for example by using strict inclusion criteria and standardization protocols (e.g., meal provision), by using cross-over designs, or even within-subject designs where two interventions are compared simultaneously (e.g., studying an exercised limb vs a contralateral control limb) although this might limit the generalizability of the findings (e.g. such single-limb exercise training is not common in practice). In terms of data interpretation, investigators should obviously refrain from drawing strong conclusions from underpowered studies. Yet, such studies still provide valuable data for meta-analyses. Finally, because muscle protein synthesis rates are highly responsive to anabolic stimuli, acute metabolic studies are more sensitive to detect potentially clinically relevant differences in the anabolic response between treatments. Apart from further elaborating on these topics, this educational article encourages readers to more critically question null findings and scientists to more clearly discuss limitations that may have compromised statistical power.

Characteristics of the differential response to exercise in adults with restless legs syndrome

OBJECTIVE/BACKGROUND

Restless legs syndrome (RLS) is a prevalent, sensorimotor sleep disorder characterized by the irresistible urge to move that is temporarily relieved by movement. Despite evidence for the benefits of exercise in RLS, inter-individual variation in the response to exercise exists, whereby some people experience symptom improvement while others report exacerbations. The present study examined factors that may account for differences in perceived responses to exercise in RLS.

PATIENTS/METHODS

Participants (N = 527) completed a nationwide survey with items assessing RLS, physical activity, sedentary levels, and experiences with RLS responsiveness to exercise. Logistic regression analyses examined associations between individual characteristics (e.g., age, sex) and perceptions of improvement and exacerbation with exercise. Exploratory analyses examined characteristics associated with perceived positive responsiveness (i.e., exercise only improves RLS) or negative responsiveness (i.e., exercise only worsens RLS).

RESULTS

Ordinal logistic regression identified lower RLS severity (OR = 0.83, p = 0.044), higher prevalence of a condition that could cause secondary RLS (OR = 1.76, p = 0.005), lower prevalence of periodic limb movements (OR = 0.52, p = 0.001), and higher physical activity levels (OR = 1.47, p < 0.001) as significant, independent predictors of exercise improving RLS symptoms. Individual feature ordinal logistic regression identified female sex as significantly associated with exercise exacerbating symptoms (OR = 0.62, p = 0.008). Exploratory logistic regression identified people with higher BMI (OR = 0.69, p = 0.019) and higher RLS severity (OR = 0.70, p = 0.026) had lower odds of being positive responders to exercise.

CONCLUSIONS

The present study presents factors that might account for individual differences in the response to exercise. Overall, our results suggest that milder cases of RLS (lower severity, absence of PLMs), people with secondary forms of RLS, and those with a lower BMI may perceive exercise as more beneficial for symptoms. These should be considered in exercise-based management aimed at managing symptoms as the collective body of research supports the benefits of exercise in adults with RLS.

Heterogeneity of aerobic fitness changes with exercise training in progressive multiple sclerosis: Secondary, exploratory analysis of data from the CogEx trial

Background

There is heterogeneity of aerobic fitness (VO2peak) changes with a standardized exercise training stimulus in the general population (i.e. some participants demonstrate improvements, others no change, and some a reduction in VO2peak).

Objectives

This secondary, exploratory analysis of data examined the heterogeneity of VO2peak responses and possible correlates among persons with progressive multiple sclerosis (PMS) from the CogEx trial.

Methods

CogEx was a multi-site, multi-arm, randomized, double-blinded, and sham-controlled trial undertaken by 11 sites in six different countries. Participants were randomized into one of four conditions with different combinations of exercise training and cognitive rehabilitation including respective sham conditions. The analysis focuses primarily on VO2peak change for the pooled exercise training intervention conditions compared with the pooled sham exercise control conditions.

Results

Waterfall plots for change in VO2peak suggested greater heterogeneity with exercise training than sham, and the proportions of difference in VO2peak change (i.e. improvement/worsening) were significantly different between exercise training and sham conditions(p < 0.05). The multivariable analysis indicated that lower baseline VO2peak (p < 0.001) was the only statistically significant correlate of increases in VO2peak with exercise training.

Conclusion

Our results highlight the heterogeneity of change in VO2peak with exercise training that is correlated with initial aerobic capacity in PMS, and such results may inform hypothesis testing in future clinical trials of exercise training.

Sex-Specific Variations in Glycated Hemoglobin Responses to Structured Exercise in Type 2 Diabetes: Healthcare Implications of Walking and Strength Training on Glycemic Control

Type 2 diabetes mellitus (T2DM) affects one in ten individuals in the United States, with rates expected to rise significantly. This novel study aimed to evaluate the impact of a structured exercise program on glycated hemoglobin (HbA1c) levels among males and females with T2DM, and to compare the effects of different volumes of combined aerobic and resistance exercise. A total of 67 adult participants with T2DM were randomly assigned to two groups: Group 1 (exercise classes and walking sessions) and Group 2 (exercise classes only). After 10 weeks, 39 participants completed the intervention and 34 had complete HbA1c records. Results indicated a significant improvement in HbA1c levels overall, with males exhibiting a greater decrease compared to females. Minimal baseline differences were observed between the walking and non-walking groups and improvements in HbA1c were noted in both groups with no significant differences. These findings suggested potential sex-specific differences in response to structured exercise programs. The study highlighted the importance of tailored exercise interventions in healthcare while managing T2DM. Further research is necessary to optimize exercise prescriptions and evaluate long-term benefits, but the current evidence supports structured exercise as a valuable component of comprehensive diabetes care. This research underscores the need for personalized approaches in exercise regimens, contributing to the growing body of knowledge on sex-specific responses to T2DM interventions.

Prefrontal Cortex Oxygenation During Exercise in Older Adults with Motoric Cognitive Risk Syndrome

Motoric cognitive risk syndrome (MCR) is a pre-dementia syndrome characterized by subjective memory complaints and gait impairments that may be related to lower prefrontal cortex (PFC) function. Acute bouts of aerobic exercise are shown to improve PFC function, however, the acute effects of exercise on PFC oxygenation have not yet been examined in MCR. This study aims to characterize the PFC oxygenation responses during acute exercise in older adults with MCR. Nineteen older adults with MCR performed a submaximal cycling exercise protocol. Functional near-infrared spectroscopy (fNIRS) is used to measure concentrations of oxygenated (OxyHb) and deoxygenated (DeoxyHb) hemoglobin from the PFC. There is a trend for increased OxyHb concentrations and decreased DeooxyHb concentrations during exercise. Exercise also induced significant increases in ratings of perceived exertion (RPEs) and heart rate. A significant, positive correlation between PFC OxyHb and RPEs during the cycling exercise are also observed. The findings reveal that PFC oxygenation increases during exercise in an intensity-dependent manner and the subjective perception of exertion is associated with the magnitude of PFC oxygenation. These results suggest that moderate-intensity cycling exercise may have beneficial effects on increasing cerebral blood flow in the PFC of older adults with MCR.

Age, Race, Sex and Cardiorespiratory Fitness: Implications for Prevention and Management of Cardiometabolic Disease in Individuals with Diabetes Mellitus

Physical inactivity and poor cardiorespiratory fitness (CRF) are strongly associated with type 2 diabetes (DM2) and all-cause and cardiovascular morbidity and mortality. Incorporating physical activity promotion in the management of DM2 has been a pivotal approach modulating the underlying pathophysiology of DM2 of increased insulin resistance, endothelial dysfunction, and abnormal mitochondrial function. Although CRF is considered a modifiable risk factor, certain immutable aspects such as age, race, and gender impact CRF status and is the focus of this review. Results show that diabetes has often been considered a disease of premature aging manifested by early onset of macro and microvascular deterioration with underlying negative impact on CRF and influencing next generation. Certain races such as Native Americans and African Americans show reduced baseline CRF and decreased gain in CRF in randomized trials. Moreover, multiple biological gender differences translate to lower baseline CRF and muted responsivity to exercise in women with increased morbidity and mortality. Although factors such as age, race, and sex may not have major impacts on CRF their influence should be considered with the aim of optimizing precision medicine.

Influence of exercise prescription intervention based on WeChat on glycolipid metabolism and fitness of suboptimal-health teachers

Exercise is an effective means to promote health, but adherence is low. Due to the advantages of immediacy, economy and effectiveness, the use of WeChat social software has permeated into every aspect in daily life in China. To explore the influence of WeChat-based exercise prescription intervention mode on glycolipid metabolism and fitness of suboptimal-health teachers. 293 suboptimal-health teachers with senior professional titles were randomized to a control group (CG) or an experimental group (e.g.). The CG exercised on its own, while the e.g. adopted the exercise prescription intervention based on WeChat. The intervention period was 6 months. Finally, 264 cases were adhered to and completed, including 132 cases in the CG and 132 cases in the e.g.. The Suboptimal-Health Status Questionnaires-25 scores (SHSQ-25 scores), exercise adherence, subjective feelings, physical fitness, blood glucose and blood lipids were detected before and after intervention and compared between 2 groups. After the intervention, the SHSQ-25 scores in the e.g. was significantly decreased than those in the CG (P < .01). The complete exercise adherence in the e.g. was significantly higher than those in the CG (P < .01). After intervention, the subjective feelings of e.g. were significantly improved compared to CG (P < .05). The body shape, body function and physical quality in the e.g. was higher than those in the CG (P < .05). Total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) decreased significantly in the e.g. but not in the CG (P < .05). Fasting blood glucose (FBG) decreased significantly in the e.g. but not in the CG, with a significant difference between groups (P < .05). The subjects in the e.g. were very satisfied with WeChat management. WeChat-based exercise prescription intervention could improve SHS, exercise adherence, subjective feelings, physical fitness and glycolipid metabolism.

Understanding the variation in exercise responses to guide personalized physical activity prescriptions

Understanding the factors that contribute to exercise response variation is the first step in achieving the goal of developing personalized exercise prescriptions. This review discusses the key molecular and other mechanistic factors, both extrinsic and intrinsic, that influence exercise responses and health outcomes. Extrinsic characteristics include the timing and dose of exercise, circadian rhythms, sleep habits, dietary interactions, and medication use, whereas intrinsic factors such as sex, age, hormonal status, race/ethnicity, and genetics are also integral. The molecular transducers of exercise (i.e., genomic/epigenomic, proteomic/post-translational, transcriptomic, metabolic/metabolomic, and lipidomic elements) are considered with respect to variability in physiological and health outcomes. Finally, this review highlights the current challenges that impede our ability to develop effective personalized exercise prescriptions. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) aims to fill significant gaps in the understanding of exercise response variability, yet further investigations are needed to address additional health outcomes across all populations.

Effects of regular exercise on vascular function with aging: Does sex matter?

Vascular aging, featuring endothelial dysfunction and large elastic artery stiffening, is a major risk factor for the development of age-associated cardiovascular diseases (CVDs). Vascular aging is largely mediated by an excessive production of reactive oxygen species (ROS) and increased inflammation leading to reduced bioavailability of the vasodilatory molecule nitric oxide and remodeling of the arterial wall. Other cellular mechanisms (i.e., mitochondrial dysfunction, impaired stress response, deregulated nutrient sensing, cellular senescence), termed "hallmarks" or "pillars" of aging, may also contribute to vascular aging. Gonadal aging, which largely impacts women but also impacts some men, modulates the vascular aging process. Regular physical activity, including both aerobic and resistance exercise, is a first-line strategy for reducing CVD risk with aging. Although exercise is an effective intervention to counter vascular aging, there is considerable variation in the vascular response to exercise training with aging. Aerobic exercise improves large elastic artery stiffening in both middle-aged/older men and women and enhances endothelial function in middle-aged/older men by reducing oxidative stress and inflammation and preserving nitric oxide bioavailability; however, similar aerobic exercise training improvements are not consistently observed in estrogen-deficient postmenopausal women. Sex differences in adaptations to exercise may be related to gonadal aging and declines in estrogen in women that influence cellular-molecular mechanisms, disconnecting favorable signaling in the vasculature induced by exercise training. The present review will summarize the current state of knowledge on vascular adaptations to regular aerobic and resistance exercise with aging, the underlying mechanisms involved, and the moderating role of biological sex.

Financial Cost Analysis Associated with a Locomotor Exercise Randomized Controlled Trial in Chronic Stroke

Background

Post-stroke recovery trials pose distinct recruitment and retention challenges, and understanding the financial requirements of conducting randomized controlled trials is crucial to ensure sufficient resources for successful study execution. The purpose of this analysis was to quantify the costs at a single site with a large catchment area of the Moderate-Intensity Exercise Versus High-Intensity Interval Training to Recover Walking Post-Stroke, HIT Stroke Trial.

Methods

To determine cost, study expense reports were gathered and divided into four categories: oversight, recruitment, retention, and outcome assessments. Categories were then further divided into chronological order for initial contact and prescreening, consenting, initial screening, and baseline testing. The 12-week intervention was divided into 4-week blocks: intervention block 1, post 4-week outcome testing, intervention block 2, post 8-week outcome testing, intervention block 3, and post 12-week outcome testing.

Results

Total direct cost for site execution was $539,768 with cost per participant approximated as $35,984. Oversight costs accounted for 65.8% of the budget at $355,661. To achieve goals related to inclusive participant recruitment ($21,923) and retention ($28,009), our site costs totaled $49,932. Direct study-related costs included screening assessments ($5,905), baseline assessments ($15,028), intervention ($76,952), and outcome assessments ($36,288).

Conclusion

Clinical trials on walking rehabilitation and exercise, especially those involving multiple assessment visits, require intensive oversight. This cost analysis provides important and critical insight into the expenses required to successfully execute an exercise-based walking rehabilitation trial in the United States.

Hydrogen sulfide ameliorates endothelial dysfunction in aging arteries by regulating ferroptosis

Aging causes vascular endothelial dysfunction. We aimed to investigate the causes of vascular endothelial dysfunction during aging using plasma and renal arteries from patients who underwent nephrectomy and animal models. The results showed that the endogenous H2S-producing enzyme cystathione-γ-lyase (CSE) protein expression was downregulated in renal artery tissue, plasma H2S levels were reduced. Moreover, elevated lipid peroxidation and iron accumulation levels led to ferroptosis and endothelial diastolic function in the renal arteries was impaired in the elderly group. H2S enhanced the endogenous CSE expression in the elderly group, promoted endogenous H2S production, decreased lipid peroxide expression, and inhibited ferroptosis, which in turn improved vascular endothelial function in the elderly group. In animal models, we also observed the same results. In addition, we applied NaHS, Ferrostatin-1 (ferroptosis inhibitor) and erastin (ferroptosis inducer) to incubate renal arteries of SD rats. The results showed that NaHS enhanced ferroptosis related proteins expression, inhibited ferroptosis and improved vascular endothelial function. We demonstrated that endothelial dysfunction associated with aging is closely related to reduced endogenous H2S levels and ferroptosis in vascular endothelial cells. Notably, H2S reduced lipid peroxidation levels in vascular endothelial cells, inhibited ferroptosis in vascular endothelial cells, and improved endothelial dysfunction.