Mechanisms of mechanical overload-induced skeletal muscle hypertrophy: current understanding and future directions.

Mechanisms underlying mechanical overload-induced skeletal muscle hypertrophy have been extensively researched since the landmark report by Morpurgo (1897) of "work-induced hypertrophy" in dogs that were treadmill trained. Much of the preclinical rodent and human resistance training research to date supports that involved mechanisms include enhanced mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, an expansion in translational capacity through ribosome biogenesis, increased satellite cell abundance and myonuclear accretion, and postexercise elevations in muscle protein synthesis rates. However, several lines of past and emerging evidence suggest that additional mechanisms that feed into or are independent of these processes are also involved. This review first provides a historical account of how mechanistic research into skeletal muscle hypertrophy has progressed. A comprehensive list of mechanisms associated with skeletal muscle hypertrophy is then outlined, and areas of disagreement involving these mechanisms are presented. Finally, future research directions involving many of the discussed mechanisms are proposed.

Resistance-only and concurrent exercise induce similar myofibrillar protein synthesis rates and associated molecular responses in moderately active men before and after training.

Aerobic and resistance exercise (RE) induce distinct molecular responses. One hypothesis is that these responses are antagonistic and unfavorable for the anabolic response to RE when concurrent exercise is performed. This thesis may also depend on the participants' training status and concurrent exercise order. We measured free-living myofibrillar protein synthesis (MyoPS) rates and associated molecular responses to resistance-only and concurrent exercise (with different exercise orders), before and after training. Moderately active men completed one of three exercise interventions (matched for age, baseline strength, body composition, and aerobic capacity): resistance-only exercise (RE, n = 8), RE plus high-intensity interval exercise (RE+HIIE, n = 8), or HIIE+RE (n = 9). Participants trained 3 days/week for 10 weeks; concurrent sessions were separated by 3 h. On the first day of Weeks 1 and 10, muscle was sampled immediately before and after, and 3 h after each exercise mode and analyzed for molecular markers of MyoPS and muscle glycogen. Additional muscle, sampled pre- and post-training, was used to determine MyoPS using orally administered deuterium oxide (D2 O). In both weeks, MyoPS rates were comparable between groups. Post-exercise changes in proteins reflective of protein synthesis were also similar between groups, though MuRF1 and MAFbx mRNA exhibited some exercise order-dependent responses. In Week 10, exercise-induced changes in MyoPS and some genes (PGC-1ɑ and MuRF1) were dampened from Week 1. Concurrent exercise (in either order) did not compromise the anabolic response to resistance-only exercise, before or after training. MyoPS rates and some molecular responses to exercise are diminished after training.

Low baseline ribosome-related gene expression and resistance training-induced declines in ribosome-related gene expression are associated with skeletal muscle hypertrophy in young men and women.

Ribosomes are essential cellular machinery for protein synthesis. It is hypothesised that ribosome content supports muscle growth and that individuals with more ribosomes have greater increases in muscle size following resistance training (RT). Aerobic conditioning (AC) also elicits distinct physiological adaptations; however, no measures of ribosome content following AC have been conducted. We used ribosome-related gene expression as a proxy measure for ribosome content and hypothesised that AC and RT would increase ribosome-related gene expression. Fourteen young men and women performed 6 weeks of single-legged AC followed by 10 weeks of double-legged RT. Muscle biopsies were taken following AC and following RT in the aerobically conditioned (AC+RT) and unconditioned (RT) legs. No differences in regulatory genes (Ubf, Cyclin D1, Tif-1a and Polr-1b) involved in ribosomal biogenesis or ribosomal RNA (45S, 5.8S, 18S and 28S rRNAs) expression were observed following AC and RT, except for c-Myc (RT > AC+RT) and 5S rRNA (RT < AC+RT at pre-RT) with 18S external transcribed spacer and 5.8S internal transcribed spacer expression decreasing from pre-RT to post-RT in the RT leg only. When divided for change in leg-lean soft tissue mass (ΔLLSTM) following RT, legs with the greatest ΔLLSTM had lower expression in 11/13 measured ribosome-related genes before RT and decreased expression in 9/13 genes following RT. These results indicate that AC and RT did not increase ribosome-related gene expression. Contrary to previous research, the greatest increase in muscle mass was associated with lower changes in ribosome-related gene expression over the course of the 10-week training programme. This may point to the importance of translational efficiency rather than translational capacity (i.e. ribosome content) in mediating long-term exercise-induced adaptations in skeletal muscle.

The International Olympic Committee framework on fairness, inclusion and nondiscrimination on the basis of gender identity and sex variations does not protect fairness for female athletes.

The International Olympic Committee (IOC) recently published a framework on fairness, inclusion, and nondiscrimination on the basis of gender identity and sex variations. Although we appreciate the IOC's recognition of the role of sports science and medicine in policy development, we disagree with the assertion that the IOC framework is consistent with existing scientific and medical evidence and question its recommendations for implementation. Testosterone exposure during male development results in physical differences between male and female bodies; this process underpins male athletic advantage in muscle mass, strength and power, and endurance and aerobic capacity. The IOC's "no presumption of advantage" principle disregards this reality. Studies show that transgender women (male-born individuals who identify as women) with suppressed testosterone retain muscle mass, strength, and other physical advantages compared to females; male performance advantage cannot be eliminated with testosterone suppression. The IOC's concept of "meaningful competition" is flawed because fairness of category does not hinge on closely matched performances. The female category ensures fair competition for female athletes by excluding male advantages. Case-by-case testing for transgender women may lead to stigmatization and cannot be robustly managed in practice. We argue that eligibility criteria for female competition must consider male development rather than relying on current testosterone levels. Female athletes should be recognized as the key stakeholders in the consultation and decision-making processes. We urge the IOC to reevaluate the recommendations of their Framework to include a comprehensive understanding of the biological advantages of male development to ensure fairness and safety in female sports.

People with obesity exhibit losses in muscle proteostasis that are partly improved by exercise training.

This pilot experiment examines if a loss in muscle proteostasis occurs in people with obesity and whether endurance exercise positively influences either the abundance profile or turnover rate of proteins in this population. Men with (n = 3) or without (n = 4) obesity were recruited and underwent a 14-d measurement protocol of daily deuterium oxide (D2 O) consumption and serial biopsies of vastus lateralis muscle. Men with obesity then completed 10-weeks of high-intensity interval training (HIIT), encompassing 3 sessions per week of cycle ergometer exercise with 1 min intervals at 100% maximum aerobic power interspersed by 1 min recovery periods. The number of intervals per session progressed from 4 to 8, and during weeks 8-10 the 14-d measurement protocol was repeated. Proteomic analysis detected 352 differences (p < 0.05, false discovery rate < 5%) in protein abundance and 19 (p < 0.05) differences in protein turnover, including components of the ubiquitin-proteasome system. HIIT altered the abundance of 53 proteins and increased the turnover rate of 22 proteins (p < 0.05) and tended to benefit proteostasis by increasing muscle protein turnover rates. Obesity and insulin resistance are associated with compromised muscle proteostasis, which may be partially restored by endurance exercise.

Low energy availability reduces myofibrillar and sarcoplasmic muscle protein synthesis in trained females.

Low energy availability (LEA) describes a state where the energy intake is insufficient to cover the energy costs of both exercise energy expenditure and basal physiological body functions. LEA has been associated with various physiological consequences, such as reproductive dysfunction. However, the effect of LEA on skeletal muscle protein synthesis in females performing exercise training is still poorly understood. We conducted a randomized controlled trial to investigate the impact of LEA on daily integrated myofibrillar and sarcoplasmic muscle protein synthesis in trained females. Thirty eumenorrheic females were matched based on training history and randomized to undergo 10 days of LEA (25 kcal · kg fat-free mass (FFM)-1  · day-1 ) or optimal energy availability (OEA, 50 kcal · kg FFM-1  · day-1 ). Before the intervention, both groups underwent a 5-day 'run-in' period with OEA. All foods were provided throughout the experimental period with a protein content of 2.2 g kg lean mass-1  · day-1 . A standardized, supervised combined resistance and cardiovascular exercise training programme was performed over the experimental period. Daily integrated muscle protein synthesis was measured by deuterium oxide (D2 O) consumption along with changes in body composition, resting metabolic rate, blood biomarkers and 24 h nitrogen balance. We found that LEA reduced daily integrated myofibrillar and sarcoplasmic muscle protein synthesis compared with OEA. Concomitant reductions were observed in lean mass, urinary nitrogen balance, free androgen index, thyroid hormone concentrations and resting metabolic rate following LEA. These results highlight that LEA may negatively affect skeletal muscle adaptations in females performing exercise training. KEY POINTS: Low energy availability (LEA) with potential health and performance impairments is widespread among female athletes. We investigated the impact of 10 days of LEA on daily integrated myofibrillar and sarcoplasmic muscle protein synthesis in young, trained females. We show that LEA impairs myofibrillar and sarcoplasmic muscle protein synthesis in trained females performing exercise training. These findings suggest that LEA may have negative consequences for skeletal muscle adaptations and highlight the importance of ensuring adequate energy availability in female athletes.

The impact and utility of very low-calorie diets: the role of exercise and protein in preserving skeletal muscle mass.

PURPOSE OF REVIEW: Very low-calorie diets (VLCD) are used as a weight loss intervention, but concerns have been raised about their potential negative impact on lean mass. Here, we review the available evidence regarding the effects of VLCD on lean mass and explore their utility and strategies to mitigate reductions in skeletal muscle. RECENT FINDINGS: We observed that VLCD, despite their effects on lean mass, may be suitable in certain populations but have a risk in reducing lean mass. The extent of the reduction in lean mass may depend on various factors, such as the duration and degree of energy deficit of the diet, as well as the individual's starting weight and overall health. SUMMARY: VLCD may be a viable option in certain populations; however, priority needs to be given to resistance exercise training, and secondarily to adequate protein intake should be part of this dietary regime to mitigate losing muscle mass.

Important Concepts in Protein Nutrition, Aging, and Skeletal Muscle: Honoring Dr Douglas Paddon-Jones (1969-2021) by Highlighting His Research Contributions.

This review is a tribute to honor Dr Douglas Paddon-Jones by highlighting his career research contributions. Dr Paddon-Jones was a leader in recognizing the importance of muscle health and the interactions of physical activity and dietary protein for optimizing the health span. Aging is characterized by loss of muscle mass and strength associated with reduced rates of muscle protein synthesis (MPS) and the ability to repair and replace muscle proteins. Research from the team at the University of Texas Medical Branch in Galveston discovered that the age-related decline in MPS could be overcome by increasing the quantity or quality of dietary protein at each meal. Dr Paddon-Jones was instrumental in proposing and testing a "protein threshold" of ∼30 g protein/meal to optimize MPS in older adults. Dr Paddon-Jones demonstrated that physical inactivity greatly accelerates the loss of muscle mass and function in older adults. His work in physical activity led him to propose the "Catabolic Crisis Model" of muscle size and function losses, suggesting that age-related muscle loss is not a linear process, but the result of acute periods of disuse associated with injuries, illnesses, and bed rest. This model creates the opportunity to provide targeted interventions via protein supplementation and/or increased dietary protein through consuming high-quality animal-source foods. He illustrated that nutritional support, particularly enhanced protein quantity, quality, and meal distribution, can help preserve muscle health during periods of inactivity and promote health across the life course.

Limitations of the Food Compass Nutrient Profiling System.

Nutrient Profiling Systems provide frameworks to assess the healthfulness of foods based on food composition and are intended as inputs into strategies to improve diets. Many Nutrient Profiling Systems are founded on a reductionist assumption that the healthfulness of foods is determined by the sum of their individual nutrients, with no consideration for the extent and purpose of processing and its health implications. A novel Nutrient Profiling System called Food Compass attempted to address existing gaps and provide a more holistic assessment of the healthfulness of foods. We propose that the chosen algorithm is not well justified and produces results that fail to discriminate for common shortfall nutrients, exaggerate the risks associated with animal-source foods, and underestimate the risks associated with ultraprocessed foods. We caution against the use of Food Compass in its current form to inform consumer choices, policies, programs, industry reformulations, and investment decisions.

Short-term aerobic conditioning prior to resistance training augments muscle hypertrophy and satellite cell content in healthy young men and women.

Factors influencing inter-individual variability of responses to resistance training (RT) remain to be fully elucidated. We have proposed the importance of capillarization in skeletal muscle for the satellite cell (SC) response to RT-induced muscle hypertrophy, and hypothesized that aerobic conditioning (AC) would augment RT-induced adaptations. Fourteen healthy young (22 ± 2 years) men and women underwent AC via 6 weeks of unilateral cycling followed by 10 weeks of bilateral RT to investigate how AC alters SC content, activity, and muscle hypertrophy following RT. Muscle biopsies were taken at baseline (unilateral), post AC (bilateral), and post RT (bilateral) in the aerobically conditioned (AC + RT) and unconditioned (RT) legs. Immunofluorescence was used to determine muscle capillarization, fiber size, SC content, and activity. Type I and type II fiber cross-sectional area (CSA) increased following RT, and when legs were analyzed independently, AC + RT increased type I, type II, and mixed-fiber CSA, where the RT leg tended to increase type II (p = .05), but not type I or mixed-fiber CSA. SC content, activation, and differentiation increased with RT, where type I total and quiescent SC content was greater in AC + RT compared to the RT leg. Those with the greatest capillary-to-fiber perimeter exchange index before RT had the greatest change in CSA following RT and a significant relationship was observed between type II fiber capillarization and the change in type II-fiber CSA with RT (r = 0.35). This study demonstrates that AC prior to RT can augment RT-induced muscle adaptions and that these differences are associated with increases in capillarization.

Resistance training prescription for muscle strength and hypertrophy in healthy adults: a systematic review and Bayesian network meta-analysis.

OBJECTIVE: To determine how distinct combinations of resistance training prescription (RTx) variables (load, sets and frequency) affect muscle strength and hypertrophy. DATA SOURCES: MEDLINE, Embase, Emcare, SPORTDiscus, CINAHL, and Web of Science were searched until February 2022. ELIGIBILITY CRITERIA: Randomised trials that included healthy adults, compared at least 2 predefined conditions (non-exercise control (CTRL) and 12 RTx, differentiated by load, sets and/or weekly frequency), and reported muscle strength and/or hypertrophy were included. ANALYSES: Systematic review and Bayesian network meta-analysis methodology was used to compare RTxs and CTRL. Surface under the cumulative ranking curve values were used to rank conditions. Confidence was assessed with threshold analysis. RESULTS: The strength network included 178 studies (n=5097; women=45%). The hypertrophy network included 119 studies (n=3364; women=47%). All RTxs were superior to CTRL for muscle strength and hypertrophy. Higher-load (>80% of single repetition maximum) prescriptions maximised strength gains, and all prescriptions comparably promoted muscle hypertrophy. While the calculated effects of many prescriptions were similar, higher-load, multiset, thrice-weekly training (standardised mean difference (95% credible interval); 1.60 (1.38 to 1.82) vs CTRL) was the highest-ranked RTx for strength, and higher-load, multiset, twice-weekly training (0.66 (0.47 to 0.85) vs CTRL) was the highest-ranked RTx for hypertrophy. Threshold analysis demonstrated these results were extremely robust. CONCLUSION: All RTx promoted strength and hypertrophy compared with no exercise. The highest-ranked prescriptions for strength involved higher loads, whereas the highest-ranked prescriptions for hypertrophy included multiple sets. PROSPERO REGISTRATION NUMBER: CRD42021259663 and CRD42021258902.

Disuse-induced skeletal muscle atrophy in disease and nondisease states in humans: mechanisms, prevention, and recovery strategies.

Decreased skeletal muscle contractile activity (disuse) or unloading leads to muscle mass loss, also known as muscle atrophy. The balance between muscle protein synthesis (MPS) and muscle protein breakdown (MPB) is the primary determinant of skeletal muscle mass. A reduced mechanical load on skeletal muscle is one of the main external factors leading to muscle atrophy. However, endocrine and inflammatory factors can act synergistically in catabolic states, amplifying the atrophy process and accelerating its progression. In addition, older individuals display aging-induced anabolic resistance, which can predispose this population to more pronounced effects when exposed to periods of reduced physical activity or mechanical unloading. Different cellular mechanisms contribute to the regulation of muscle protein balance during skeletal muscle atrophy. This review summarizes the effects of muscle disuse on muscle protein balance and the molecular mechanisms involved in muscle atrophy in the absence or presence of disease. Finally, a discussion of the current literature describing efficient strategies to prevent or improve the recovery from muscle atrophy is also presented.

Aerobic conditioning alters the satellite cell and ribosome response to acute eccentric contractions in young men and women.

Satellite cells (SCs) and ribosomes are key determinants of the skeletal muscle adaptive response. Both are thought to increase acutely after resistance exercise and chronically with resistance training. However, the acute SC and ribosome exercise response with prior aerobic conditioning is unknown. Fourteen young men and women underwent 6 wk of single-legged aerobic conditioning followed by an acute bout of 300 eccentric contractions on each leg. Muscle biopsies were taken from the vastus lateralis of the aerobically conditioned (AC) and the control (CTL) legs before (Pre), 24 (24 h), and 48 (48 h) h post-contractions. Pre-eccentric contractions, 45S pre-rRNA and 5.8S internal transcribed spacer (ITS) expression were lower in the AC leg compared with the CTL leg. SC content (PAX7+ cells/100 fibers) in type I and mixed fibers showed a main effect of condition, where values were greater in the AC leg compared with the CTL. A main effect of condition for Pax7 and MyoD1 mRNA expression was observed where expression was greater in the AC leg compared with the CTL. AC had greater RNA concentration and mRNA expression of Ubf and Tif-1a compared with CTL. Only the AC leg increased (Pre-24h) 45S pre-rRNA, 5.8S ITS, and 28S ITS following eccentric contractions. We discovered that aerobic conditioning increased type-I SC abundance and the acute increase in ribosome content following eccentric contractions.

Dairy and Dairy Alternative Supplementation Increase Integrated Myofibrillar Protein Synthesis Rates, and Are Further Increased when Combined with Walking in Healthy Older Women.

BACKGROUND: The stimulation of muscle protein synthesis (MPS) by dietary protein is reduced with age. We hypothesized that twice-daily milk consumption would increase daily rates of MPS in older women relative to a nondairy milk alternative and that MPS would be enhanced by increased physical activity (PA). METHODS: Twenty-two older women were randomly assigned to 1 of 3 experimental groups: whole milk (WM; n = 7, 69 ± 3 y), skim milk (SM; n = 7, 68 ± 3 y), or an almond beverage (AB; n = 8, 63 ± 3 y). From days 1 to 3, participants consumed a standardized diet (0.8 g protein⋅kg-1 ⋅d-1) and performed their habitual PA (Phase 1, Baseline). From days 4 to 6, participants continued to perform habitual PA, but consumed an intervention diet consisting of the standardized diet plus twice-daily beverages (250 mL each) of either WM, SM, or AB (Phase 2, Diet Intervention). Finally, from days 7 to 9, the intervention diet was consumed, and PA via daily steps was increased to ∼150% of habitual daily steps (Phase 3, Intervention Diet + PA). Deuterated water was ingested throughout the study, and muscle biopsies were taken on days 1, 4, 7, and 10 to measure MPS. RESULTS: Daily MPS rates were not differentially affected by the addition of WM, SM, or AB to a standardized diet. There was, however, a significant effect of study phase such that, when collapsed across conditions, MPS was significantly increased from Phase 1 to Phase 2 (+0.133%⋅d-1; 95% CI: 0.035-0.231; P < 0.01) and further increased from Phase 2 to Phase 3 (+0.156%⋅d-1; 95% CI: 0.063-0.250; P < 0.01). CONCLUSIONS: Increasing PA through walking was sufficient to increase daily MPS rates in older women, irrespective of whether dietary protein intake is increased beyond the recommended intake of 0.8 g⋅kg-1 ⋅d-1. The trial was registered at clinicaltrials.gov as NCT04981652.

Transcriptomic links to muscle mass loss and declines in cumulative muscle protein synthesis during short-term disuse in healthy younger humans.

Muscle disuse leads to a rapid decline in muscle mass, with reduced muscle protein synthesis (MPS) considered the primary physiological mechanism. Here, we employed a systems biology approach to uncover molecular networks and key molecular candidates that quantitatively link to the degree of muscle atrophy and/or extent of decline in MPS during short-term disuse in humans. After consuming a bolus dose of deuterium oxide (D2 O; 3 mL.kg-1 ), eight healthy males (22 ± 2 years) underwent 4 days of unilateral lower-limb immobilization. Bilateral muscle biopsies were obtained post-intervention for RNA sequencing and D2 O-derived measurement of MPS, with thigh lean mass quantified using dual-energy X-ray absorptiometry. Application of weighted gene co-expression network analysis identified 15 distinct gene clusters ("modules") with an expression profile regulated by disuse and/or quantitatively connected to disuse-induced muscle mass or MPS changes. Module scans for candidate targets established an experimentally tractable set of candidate regulatory molecules (242 hub genes, 31 transcriptional regulators) associated with disuse-induced maladaptation, many themselves potently tied to disuse-induced reductions in muscle mass and/or MPS and, therefore, strong physiologically relevant candidates. Notably, we implicate a putative role for muscle protein breakdown-related molecular networks in impairing MPS during short-term disuse, and further establish DEPTOR (a potent mTOR inhibitor) as a critical mechanistic candidate of disuse driven MPS suppression in humans. Overall, these findings offer a strong benchmark for accelerating mechanistic understanding of short-term muscle disuse atrophy that may help expedite development of therapeutic interventions.

An intron variant of the GLI family zinc finger 3 (GLI3) gene differentiates resistance training-induced muscle fiber hypertrophy in younger men.

We examined the association between genotype and resistance training-induced changes (12 wk) in dual x-ray energy absorptiometry (DXA)-derived lean soft tissue mass (LSTM) as well as muscle fiber cross-sectional area (fCSA; vastus lateralis; n = 109; age = 22 ± 2 y, BMI = 24.7 ± 3.1 kg/m2 ). Over 315 000 genetic polymorphisms were interrogated from muscle using DNA microarrays. First, a targeted investigation was performed where single nucleotide polymorphisms (SNP) identified from a systematic literature review were related to changes in LSTM and fCSA. Next, genome-wide association (GWA) studies were performed to reveal associations between novel SNP targets with pre- to post-training change scores in mean fCSA and LSTM. Our targeted investigation revealed no genotype-by-time interactions for 12 common polymorphisms regarding the change in mean fCSA or change in LSTM. Our first GWA study indicated no SNP were associated with the change in LSTM. However, the second GWA study indicated two SNP exceeded the significance level with the change in mean fCSA (P = 6.9 × 10-7 for rs4675569, 1.7 × 10-6 for rs10263647). While the former target is not annotated (chr2:205936846 (GRCh38.p12)), the latter target (chr7:41971865 (GRCh38.p12)) is an intron variant of the GLI Family Zinc Finger 3 (GLI3) gene. Follow-up analyses indicated fCSA increases were greater in the T/C and C/C GLI3 genotypes than the T/T GLI3 genotype (P < .05). Data from the Auburn cohort also revealed participants with the T/C and C/C genotypes exhibited increases in satellite cell number with training (P < .05), whereas T/T participants did not. Additionally, those with the T/C and C/C genotypes achieved myonuclear addition in response to training (P < .05), whereas the T/T participants did not. In summary, this is the first GWA study to examine how polymorphisms associate with the change in hypertrophy measures following resistance training. Future studies are needed to determine if the GLI3 variant differentiates hypertrophic responses to resistance training given the potential link between this gene and satellite cell physiology.

Group-based nutrition interventions for community-dwelling older adults: a systematic review to inform community co-design.

Context: Many older adults fail to meet dietary recommendations for food quality and quantity, which is important to prevent disability and disease. Group and community-based nutrition interventions may help overcome psychosocial, environmental, and behavioural barriers to healthy eating. The EMBOLDEN project uses community co-design, integrating the best available evidence with local knowledge to develop a novel, group-based physical activity, system navigation, and nutrition intervention for older adults. This review synthesizes evidence on nutrition interventions to inform design decisions. Objective: To identify the effectiveness of group-based interventions to promote healthy eating among older adults, to inform the co-design of a targeted, community-based intervention. Study Design: Systematic review. Setting or Dataset: MEDLINE, CINAHL, EMBASE, PsycINFO, and Sociological Abstracts were searched for studies published in English from January 2010 to June 2020. Interventions delivered to groups in community-based settings were eligible; acute and long-term care settings were excluded. Population studied: Healthy, community-dwelling older adults age 55+. Studies were excluded if they targeted specific disease populations. Intervention: Group-based nutrition interventions (alone or in combination), including food access, didactic and/or interactive nutrition education, and education with embedded behaviour change techniques (e.g., goal setting). Weight loss interventions were excluded. Outcome Measures: Primary outcomes were dietary intake, nutritional risk, knowledge, and dietary habits. Results: Thirty-one studies involving 6,723 older adults were included. Studies had generally unclear or high risk of bias. Given heterogeneity across interventions and outcomes, meta-analysis was not possible. Interactive nutrition education may improve dietary intake and knowledge, yet behaviour change strategies likely result in a greater reduction in nutritional risk. Results were shared with EMBOLDEN's Guiding Council of older adults and local health/social service providers to co-design the intervention. Conclusions: Although group-based interventions demonstrate promise in promoting healthier eating among community-dwelling older adults, the available evidence is relatively low quality. Our analysis highlights an opportunity for primary care researchers to advance the science of health promotion and disease prevention nutrition initiatives for older adults.

The EMBOLDEN Co-design study: Partnering with older adults and communities to develop a community program to enhance mobility.

Context: Physical mobility and social participation are requisite for independence and quality of life as one ages. Barriers to mobility lead to social isolation, poor physical and mental health, all of which are precursors to frailty. To date, most mobility-enhancing interventions in older adults have been designed by researchers without citizen input and delivered in controlled settings; their translation to real-world contexts is often impractical and rarely occurs. Objectives: i) To engage older adults and community service providers to qualitatively explore priorities, needs, enablers and barriers to mobility and community participation faced by older adults, and ii) To co-design an evidence-informed, feasible, acceptable group intervention to support mobility and promote health among older adults facing health inequities. Study Design: Adapted experience-based co-design, conducted in collaboration with a Strategic Guiding Council comprised of older adults and service providers. Setting: Community-based. Population studied: Community-dwelling older adults (55+) and local health and social service providers. Outcome Measures: EMBOLDEN's Strategic Guiding Council and the research team collectively interpreted qualitative study findings, together with results of completed systematic reviews and an environmental scan, to determine priority design features of a community-based mobility-enhancing intervention to enable health and well-being in older adults in Hamilton, ON. Results: Eighteen diverse older adults and 16 service providers completed persona scenario interviews. These lived experience perspectives were analyzed, interpreted, and integrated with research and local evidence in the intervention co-design process. Priority design features for the intervention included duration, intensity, mode of delivery, characteristics of interventionists, and implementation strategies. Findings highlighted key strategies related to participant motivation, recruitment, and engagement, as well as important equity, diversity, and inclusion considerations. Conclusions: Partnering with diverse stakeholders is critical to identifying optimal design features of a community-based intervention to promote mobility. Ultimately, we aim to implement and evaluate a health promoting intervention that is sustainable, scalable, addresses health inequities, and effectively improves the lives of older adults.

Community-based physical activity and/or nutrition interventions to promote mobility in older adults: An umbrella review.

Background: Physical activity and a healthy diet are important in helping to maintain mobility and quality of life with aging. Delivery of physical activity and nutrition interventions in a group setting adds the benefits of social participation. Several published systematic reviews have explored a broad range of PA and/or nutrition interventions for older adults, making it challenging to bring together the best scientific evidence to inform program design and to inform multicomponent intervention development. This umbrella review aims to identify group-based physical activity and nutrition interventions for community-dwelling older adults that improve mobility. Methods: Five electronic databases (MEDLINE, Embase, CINAHL, Cochrane CENTRAL, Sociological Abstracts) were searched from inception to April 28, 2020. Eligibility criteria included systematic reviews exploring the effectiveness of physical activity and/or nutrition interventions, delivered in a group setting for community-dwelling older adults. Two reviewers independently performed eligibility screening, critical appraisal (using AMSTAR 2) and data extraction. The GRADE approach was used to assess the overall certainty of the evidence. Older adult/provider research partners informed data synthesis and results presentation. Results: In total, 54 systematic reviews (1 high, 21 moderate, 32 low/critically low quality) were identified; 46 included physical activity only, and eight included both physical activity and nutritional supplements. No reviews included nutrition interventions alone. Combined aerobic/resistance, general physical activity, and mind-body exercise all improved physical function and balance (moderate-high certainty). Aerobic/resistance training improved aerobic capacity (high certainty). Resistance training and general physical activity improved muscle strength (moderate certainty). Aerobic/resistance training and general physical activity are likely to reduce falls among older adults (moderate certainty). There was no evidence of benefit for nutritional supplementation with physical activity. Conclusions: Multicomponent group-based physical activity interventions can improve measures of mobility in community-dwelling older adults. We found no reviews focused on nutrition only, highlighting a gap in the literature.

Role of Resistance Training in Mitigating Risk for Mobility Disability in Community-Dwelling Older Adults: A Systematic Review and Meta-analysis.

OBJECTIVE: To examine the effects of community-based resistance training (RT) on physical function for older adults with mobility disability. DATA SOURCES: Four databases (PubM, PubMed, MEDLINE, Ovid, Cumulative Index to Nursing and Allied Health, Web of Science) were searched from inception to February 2, 2021. STUDY SELECTION: Randomized controlled trials that examined community-based RT for improving physical function in community-dwelling older adults were included. DATA EXTRACTION: Two reviewers independently conducted title and abstract screening, full-text evaluation, data extraction, and risk of bias quality assessment. DATA SYNTHESIS: Twenty-four studies (3656 participants; age range, 63-83 years) were included. RT programs ranged from 10 weeks to 18 months in duration. RT was more effective than control in improving 6-minute walk test distance (n=638; mean difference [MD], 16.1m; 95% CI, 12.27-19.94; P<.0001), lower extremity strength (n=785; standardized MD, 2.01; 95% CI, 1.27-2.75; P<.0001), and usual gait speed (n= 2106; MD, 0.05 m/s, 95% CI, 0.03-0.07; P<.001). In sensitivity analyses, benefits were maintained when studies with a high risk of bias were excluded. There was no effect of RT on fast gait speed or Short Physical Performance Battery score compared with control. CONCLUSIONS: RT improves walking distance, lower extremity strength, and usual gait speed in older adults with mobility disability. Improvements in physical function could increase independence in activities of daily living for this at-risk population.