Perspective: Pragmatic Exercise Recommendations for Older Adults: The Case for Emphasizing Resistance Training

Effects of a ketogenic diet on motor function and motor unit number estimation in aged C57BL/6 mice

OBJECTIVE

Pathological, age-related loss of muscle function, commonly referred to as sarcopenia, contributes to loss of mobility, impaired independence, as well as increased risk of adverse health events. Sarcopenia has been attributed to changes in both neural and muscular integrity during aging. Current treatment options are primarily limited to exercise and dietary protein fortification, but the therapeutic impact of these approaches are often inadequate. Prior work has suggested that a ketogenic diet (KD) might improve healthspan and lifespan in aging mice. Thus, we sought to investigate the effects of a KD on neuromuscular indices of sarcopenia in aged C57BL/6 mice.

DESIGN

A randomized, controlled pre-clinical experiment consisting of longitudinal assessments performed starting at 22-months of age (baseline) as well as 2, 6 and 10 weeks after the start of a KD vs. regular chow intervention.

SETTING

Preclinical laboratory study.

SAMPLE SIZE

Thirty-six 22-month-old mice were randomized into 2 dietary groups: KD [n = 22 (13 female and 9 male)], and regular chow [n = 15 (7 female and 8 male)].

MEASUREMENTS

Measures included body mass, hindlimb and all limb grip strength, rotarod for motor performance, plantarflexion muscle contractility, motor unit number estimations (MUNE), and repetitive nerve stimulation (RNS) as an index of neuromuscular junction transmission efficacy recorded from the gastrocnemius muscle. At end point, muscle wet weight and blood samples were collected to assess blood beta-hydroxybutyrate levels.

STATISTICAL ANALYSIS

Primary analyses were two-way mixed effects ANOVA (diet and time × diet) to determine the effect of a KD on indices of motor function (grip, rotarod) and indices of motor unit (MUNE) and muscle (contractility) function.

RESULTS

Beta-hydroxybutyrate (BHB) was significantly higher at 10 weeks in mice on a KD vs control group (0.83 ± 0.44 mmol/l versus 0.42 ± 0.21 mmol/l, η2 = 0.265, unpaired t-test, p = 0.0060). Mice on the KD intervention demonstrated significantly increased hindlimb grip strength (diet, p = 0.0001; time × diet, p = 0.0030), all limb grip strength (diet, p = 0.0005; time × diet, p = 0.0523), and rotarod latency to fall (diet, p = 0.0126; time × diet, p = 0.0021). Mice treated with the KD intervention also demonstrated increased MUNE (diet, p = 0.0465; time × diet, p = 0.0064), but no difference in muscle contractility (diet, p = 0.5248; time × diet, p = 0.5836) or RNS (diet, p = 0.3562; time × diet, p = 0.9871).

CONCLUSION

KD intervention improved neuromuscular and motor function in aged mice. This pre-clinical work suggests that further research is needed to assess the efficacy and physiological effects of a KD on indices of sarcopenia.

Directed functional connectivity of the default-mode-network of young and older healthy subjects

Alterations in the default mode network (DMN) are associated with aging. We assessed age-dependent changes of DMN interactions and correlations with a battery of neuropsychological tests, to understand the differences of DMN directed connectivity between young and older subjects. Using a novel multivariate analysis method on resting-state functional MRI data from fifty young and thirty-one healthy older subjects, we calculated intra- and inter-DMN 4-nodes directed pathways. For the old subject group, we calculated the partial correlations of inter-DMN pathways with: psychomotor speed and working memory, executive function, language, long-term memory and visuospatial function. Pathways connecting the DMN with visual and limbic regions in older subjects engaged at BOLD low frequency and involved the dorsal posterior cingulate cortex (PCC), whereas in young subjects, they were at high frequency and involved the ventral PCC. Pathways combining the sensorimotor (SM) cortex and the DMN, were SM efferent in the young subjects and SM afferent in the older subjects. Most DMN efferent pathways correlated with reduced speed and working memory. We suggest that the reduced sensorimotor efferent and the increased need to control such activities, cause a higher dependency on external versus internal cues thus suggesting how physical activity might slow aging.

Ketogenic Diet Improves Motor Function and Motor Unit Connectivity in Aged C57BL/6 Mice

Objective

Pathological, age-related loss of muscle function, commonly referred to as sarcopenia, contributes to loss of mobility, impaired independence, as well as increased risk of adverse health events. Sarcopenia has been attributed to changes in both neural and muscular integrity during aging. Current treatment options are primarily limited to exercise and dietary protein fortification, but the therapeutic impact of these approaches are often inadequate. Prior work has suggested that a ketogenic diet (KD) might improve healthspan and lifespan in aging mice. Thus, we sought to investigate the effects of a KD on neuromuscular indices of sarcopenia in aged C57BL/6 mice.

Design

A randomized, controlled pre-clinical experiment consisting of longitudinal assessments performed starting at 22-months of age (baseline) as well as 2, 6 and 10 weeks after the start of a KD vs. regular chow intervention.

Setting

Preclinical laboratory study.

Sample size

Thirty-six 22-month-old mice were randomized into 2 dietary groups: KD [n = 22 (13 female and 9 male)], and regular chow [n = 15 (7 female and 8 male)].

Measurements

Measures included body mass, hindlimb and all limb grip strength, rotarod for motor performance, plantarflexion muscle contractility, motor unit number estimations (MUNE), and repetitive nerve stimulation (RNS) as an index of neuromuscular junction transmission efficacy recorded from the gastrocnemius muscle. At end point, blood samples were collected to assess blood beta-hydroxybutyrate levels.

Statistical Analysis

Two-way ANOVA mixed-effects analysis (time x diet) were performed to analyze grip, rotarod, MUNE, and muscle contractility data.

Results

Beta-hydroxybutyrate (BHB) was significantly higher at 10 weeks in mice on a KD vs control group (0.83 ± 0.44 mmol/l versus 0.42 ± 0.21 mmol/l, η2 = 0.265, unpaired t-test, p = 0.0060). Mice on the KD intervention demonstrated significantly increased hindlimb grip strength (time x diet, p = 0.0030), all limb grip strength (time x diet, p = 0.0523), and rotarod latency to fall (time x diet, p = 0.0021). Mice treated with the KD intervention also demonstrated significantly greater MUNE (time x diet, p = 0.0064), but no difference in muscle contractility (time x diet, p = 0.5836) or RNS (time x diet, p = 0.9871).

Conclusion

KD intervention improved neuromuscular and motor function in aged mice. This pre-clinical work suggests that further research is needed to assess the efficacy and physiological effects of a KD on indices of sarcopenia.

Immobility and the High Risk of Not Recovering Function in Older Adults: A Focused Ethnography

PURPOSE

The objective of the study was to explore the experiences of older adults with immobility posthospitalization.

DESIGN

We conducted a focused ethnography qualitative study.

METHODS

Data collection included in-depth interviews with 10 individuals ages 69-82 years who had been hospitalized for at least 1 week, field notes, and observations of mobility. An inductive approach was used to analyze the data.

FINDINGS

Older adults believe mobility is a central element in their life. Hospitalizations lasting 1 week or longer often result in a loss of the older adult's ability to function as before, a pattern that we identified as The Crushing Assault: Consequences of Immobility. Rehabilitation involves a Rocky Road to Regaining Mobility that is challenging but possible.

CONCLUSIONS

Immobility after hospitalization has unexpected and profound consequences that are life-changing and distressing for older adults at home. Recovering function is prolonged and difficult. An individualized training program that includes flexibility and progressive resistance exercises is recommended over longer periods and with extended medical follow-up.

CLINICAL RELEVANCE

Lingering problems with immobility at home are frequently overlooked. Active programming promoting preservation of function and an optimistic attitude as well as focusing on milestones to reach are key to optimal function.

[Strength training education for physicians increases its prescription]

INTRODUCTION

Medical prescriptions have traditionally been focused on aerobic exercise. However, an increasing number of authors are pointing towards strength training as the healthiest exercise modality. The purpose of this study is to assess whether physicians increase their knowledge as well as their confidence to prescribe strength training after attending a physical training course.

MATERIALS AND METHODS

A prospective cohort study of 160 physicians was conducted, 80 physicians out of the 160 attended a physical training course, whereas the remaining 80 physicians did not. Personal and professional data was collected, as well as data regarding the type of exercise they were practising or prescribing and the confidence and knowledge for their prescription. Finally, differences between the two groups and the impact of attending the course where analysed.

RESULTS

Both groups were homogeneous in gender, age, medical speciality and practice of physical exercise, with very low rates of strength training and prescription for both groups. It was established that the group attending the course acquired knowledge and confidence for prescribing strength training. Moreover, this group considered that strength training was the exercise modality which should be encouraged (P<.001).

CONCLUSIONS

Education in strength training for physicians by means of a theoretical-practical course increases knowledge and confidence for its prescription.

Resistance Circuit Training or Walking Training: Which Program Improves Muscle Strength and Functional Autonomy More in Older Women?

To evaluate the effects of two programs (resistance and walking training) on the functional autonomy and muscle strength (isometric and dynamic) of older women, 67 subjects were divided randomly into three groups: resistance training (RTG; Mean = 64.70 ± 6.74 years), walking (WG, Mean = 65.56 ± 7.82 years), and control (CG; Mean = 64.81 ± 4.34). The experimental groups underwent a 16-week intervention. Muscle strength (isometric and dynamic) and functional autonomy were assessed. The subjects participating in the RTG showed improvements in the comparison pre to post-test in the maximal forces of upper limb (MULS) (Δ% = 49.48%; p = 0.001) and lower limb (MLLS) (Δ% = 56.70%; p = 0.001), isometric biceps forces (BIS) (Δ% = 30.13%; p = 0.001) and quadriceps forces (QIS) (Δ% = 65.92%; p = 0.001), and in the general index (GI) of functional autonomy (Δ% = −18.32%; p = 0.002). The WG improved in all functional autonomy tests, except for the standing up from prone position test (SVDP). In strength tests, the WG obtained improvements only in the QIS (Δ% = 41.80%; p = 0.001) and MLLS (Δ% = 49.13%; p = 0.001) tests. The RTG obtained better results (p < 0.05) when compared to the WG and CG. The results allow us to infer that resistance exercise programs are more effective in increasing strength and functional autonomy, a fact that may mitigate the deleterious effects on health of aging.

Increased Lean Body Mass After Bodyweight-Based High Intensity Interval Training in Overweight and Obese Men

Purpose: The effects of 8 weeks of bodyweight exercise-based, high-intensity interval training (BWHIIT) on body composition and blood-based markers of metabolic health were investigated in overweight and obese, sedentary young men. Methods: In a parallel group, PRE-POST design, n = 30 men (age, 25.7 ± 4.3 y; body mass index, 27.7 ± 2.1 kg m^-2; 26.1 ± 5.2% body fat) were randomized to BWHIIT (n = 20) or a control group (CON; n = 10). BWHIIT consisted of supervised, group-based training sessions (~30 minutes) performed 3 times weekly. Each session consisted of 6 high-intensity bodyweight-based exercises, with each exercise being performed for 4 minutes in the manner of 8 sets of 20 seconds of exercise, 10 seconds of rest. Prior to commencing training (PRE), and 36 h after the final training session (POST), an overnight fasted blood sample was drawn, and body composition was assessed by dual-energy X-ray absorptiometry. Eighteen participants completed the intervention (CON, n = 9; BWHIIT, n = 9). Results: Lean body mass (LBM) was increased at POST in BWHIIT compared to CON (P = .011, η²_p = .359), with the mean (95% confidence limits) increase in LBM from PRE to POST within BWHIIT being 1.23 (0.55, 1.92) kg. Body mass and fat mass were unchanged in both groups from PRE to POST. BWHIIT had no effect on serum concentrations of total cholesterol, HDL-C, LDL-C, triglycerides, NEFA, hsCRP, or glucose. Conclusion: Eight weeks of bodyweight exercise-based high intensity interval training by overweight and obese sedentary young men increased LBM by ~2%, but fat mass and blood-based markers of metabolic health were unchanged.

Potential Benefits of a Minimal Dose Eccentric Resistance Training Paradigm to Combat Sarcopenia and Age-Related Muscle and Physical Function Deficits in Older Adults

The ability of older adults to perform activities of daily living is often limited by the ability to generate high mechanical outputs. Therefore, assessing and developing maximal neuromuscular capacity is essential for determining age-related risk for functional decline as well as the effectiveness of therapeutic interventions. Interventions designed to enhance neuromuscular capacities underpinning maximal mechanical outputs could positively impact functional performance in daily life. Unfortunately, < 10% of older adults meet the current resistance training guidelines. It has recently been proposed that a more “minimal dose” RT model may help engage a greater proportion of older adults, so that they may realize the benefits of RT. Eccentric exercise offers some promising qualities for such an approach due to its efficiency in overloading contractions that can induce substantial neuromuscular adaptations. When used in a minimal dose RT paradigm, eccentric-based RT may be a particularly promising approach for older adults that can efficiently improve muscle mass, strength, and functional performance. One approach that may lead to improved neuromuscular function capacities and overall health is through heightened exercise tolerance which would favor greater exercise participation in older adult populations. Therefore, our perspective article will discuss the implications of using a minimal dose, submaximal (i.e., low intensity) multi-joint eccentric resistance training paradigm as a potentially effective, and yet currently underutilized, means to efficiently improve neuromuscular capacities and function for older adults.

Effects of Three Different Exercise Strategies for Optimizing Aerobic Capacity and Skeletal Muscle Performance in Older Adults: A Pilot Study

This Brief Report describes a pilot study of the effect of 12 weeks of stationary bicycle high-intensity interval training, stationary bicycle moderate-intensity continuous training, and resistance training on cardiorespiratory, muscular, and physical function measures in insufficiently-active older adults (N=14; 66.4±3.9 years; 3 male, 11 female). After baseline testing, participants were randomly assigned to one of the exercise groups. High-intensity interval training and moderate-intensity continuous training had small-to-large effect sizes on cardiorespiratory/endurance and physical function measures, but very small effect sizes on muscular measures. Resistance training had small-to-large effect sizes on cardiorespiratory, muscular, and physical function measures. This pilot study should be interpreted cautiously, but findings suggest that resistance exercise may be the most effective of the three studied exercise strategies for older adults as it can induce beneficial adaptations across multiple domains. These effect sizes can be used to determine optimal sample sizes for future investigations.

Stretching for Recovery from Groin Pain or Injury in Athletes: A Critical and Systematic Review

Stretching is usually used as part of rehabilitation protocols for groin pain or injury, but its specific contribution to and within multimodal recovery protocols is unclear. Our goal was to systematically review the effects of stretching for the recovery from groin pain or injury. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed, with eligibility criteria defined according to PICOS: (Participants) athletes with groin pain or injuries; (Interventions) interventions with stretching as the differentiating factor; (Comparators) comparators not applying stretching; (Outcomes) symptom remission or improvement and/or time to return to sport and/or return to play; (Study design) randomized controlled trials. Searches were performed on 26 March 2021, in CINAHL, Cochrane Library, EBSCO, EMBASE, PEDro, PubMed, Scielo, Scopus, SPORTDiscus, and Web of Science, with no limitations regarding language or date, and no filters. Of 117 retrieved results, 65 were duplicates and 49 were excluded at the screening stage. The three articles eligible for full-text analysis failed to comply with one or more inclusion criteria (participants, intervention and/or comparators). We then went beyond the protocol and searched for non-randomized trials and case series, but no intervention was found where stretching was the differentiating factor. We found no trials specifically assessing the effects of stretching on recovery or improvement of groin pain or injury in athletes. Currently, the efficacy of these interventions is unknown, and more research is warranted.

Strength Training to Prevent Falls in Older Adults: A Systematic Review with Meta-Analysis of Randomized Controlled Trials

We performed a systematic review with meta-analysis of randomized controlled trials (RCTs) to assess the effects of strength training (ST), as compared to alternative multimodal or unimodal exercise programs, on the number of falls in older adults (≥60 years). Ten databases were consulted (CINAHL, Cochrane Library, EBSCO, EMBASE, PEDro, PubMed, Scielo, Scopus, SPORTDiscus and Web of Science), without limitations on language or publication date. Eligibility criteria were as follows: RCTs with humans ≥60 years of age of any gender with one group performing supervised ST and a group performing another type of exercise training, reporting data pertaining falls. Certainty of evidence was assessed with Grading of Recommendations, Assessment, Development and Evaluation (GRADE). Meta-analysis used a random effects model to calculate the risk ratio (RR) for number of falls. Five RCTs with six trials were included (n = 543, 76% women). There was no difference between ST and alternative exercise interventions for falls (RR = 1.00, 95% CI 0.77–1.30, p = 0.99). The certainty of evidence was very low. No dose–response relationship could be established. In sum, ST showed comparable RR based on number of falls in older adults when compared to other multimodal or unimodal exercise modalities, but evidence is scarce and heterogeneous, and additional research is required for more robust conclusions. Registration: PROSPERO CRD42020222908.

Strategies to Prevent Serious Fall Injuries: A Commentary on Bhasin et al. A Randomized Trial of a Multifactorial Strategy to Prevent Serious Fall Injuries. N Engl J Med. 2020;383(2):129-140

Every second of every day, an older adult suffers a fall in the United States (>30 million older adults fall each year). More than 20% of these falls cause serious injury (e.g., broken bones, head injury) and result in 800,000 hospitalizations and 30,000 deaths annually. Bhasin and colleagues recently reported results from a pragmatic, cluster-randomized trial designed to evaluate the effectiveness of a multifactorial intervention to prevent fall injuries. The intervention did not result in a significantly lower rate of a first adjudicated serious fall injury among older adults at increased risk for fall injuries as compared with enhanced usual care. In this commentary we briefly review and highlight these recent findings. Additionally, we argue that the findings should not be discounted just because of the lack of statistical significance. The approximately 10% reduction compared to enhanced usual care is, arguably, meaningful at both the individual and public health level, especially when one considers that the control group had better outcomes than expected based on prior work. Moreover, we encourage future research as well as practitioners to give strong consideration to the nuances of the exercise interventions for reducing falls and fall-related injuries particularly as it relates to exercise programming specifics, namely intensity and volume, to enhance neuromuscular function and also to neurorehabilitation approaches to enhance motor function (e.g., balance, motor planning, and coordination).

The influence of sex, training intensity, and frequency on muscular adaptations to 40 weeks of resistance exercise in older adults

The purpose of this investigation was to identify the influence that sex, training intensity, and frequency have on long-term resistance exercise (RE) outcomes in older adults.

METHODS

One-hundred eleven older adults (men: 41, women: 70) completed either: high-intensity RE 2d/week (HI-2D; n = 29), low-intensity RE 2d/week (LI-2D; n = 32), high-intensity RE 3d/week (HI-3D, n = 20), or low-intensity RE 3d/week (LI-3D, n = 30). HI protocols completed 3 sets of 8 repetitions with 80% one-repetition maximum (1-RM) while LI completed 3 sets of 16 repetitions with 40% 1-RM. Total and regional bone free lean body mass (BFLBM) were assessed via dual-energy x-ray absorptiometry and cross-sectional area (mCSA) of the rectus femoris.

RESULTS

mCSA was the only muscle quantity parameter to increase (p = 0.043). Significant trial effects for upper body, lower body, and specific strength were observed (all p < 0.001). Significant sex × time interactions (p < 0.001) were observed for upper and lower body strength, however, men and women displayed similar increases in lower body (45.7 ± 29.6 vs 46.4 ± 34.9%), upper body (33.1 ± 21.0 vs 33.4 ± 24.7%), and specific strength (36.5 ± 28.5 vs 40.1 ± 28.7%). A group × time interaction for lower body strength indicated that at 20-weeks HI-2D and LI-3D displayed greater lower body strength than LI-2D (both p < 0.009), and at 40-weeks HI-2D, HI-3D, and LI-3D displayed significantly greater lower body strength than LI-2D (all p < 0.038).

CONCLUSIONS

These observations indicate that older men and women display similar long-term RE outcomes. Additionally, regardless of frequency or intensity, the current prescriptions were effective for increasing strength, however these data suggest HI-2D > LI-2D and LI-3D > LI-2D but similar outcomes among HI-2D, HI-3D, and LI-3D. The variety of effective RE approaches provides flexibility among older adults for selecting a lifestyle intervention that would be most sustainable.