No Sustained Effect of Aerobic or Resistance Training on Insulin Sensitivity in Nonobese, Healthy Older Women

Linking Physical Activity to Breast Cancer Risk via Insulin/Insulin-Like Growth Factor Signaling System, Part 1: The Effect of Physical Activity on the Insulin/Insulin-Like Growth Factor Signaling System

Physical activity may reduce the risk of developing breast cancer via its effect on the insulin/insulin-like growth factor (IGF) signaling system. A systematic review searched for randomized controlled trials (RCT), Mendelian randomization and prospective cohort studies that examined the effects of physical activity on insulin/IGF signaling [IGFs, their binding proteins (IGFBP), and markers of insulin resistance] in adult women. Meta-analyses were performed to generate effect estimates. Risk of bias was assessed, and the Grading of Recommendations Assessment, Development, and Evaluation system used to determine the overall quality of the evidence. Fifty-eight RCTs met our inclusion criteria, no observational or Mendelian randomization studies met the criteria for inclusion. Meta-analyses indicated that physical activity interventions (vs. control) reduced fasting insulin, the Homeostatic Model Assessment for Insulin Resistance and fasting glucose. Physical activity increased IGF-1, but there was no clear effect on IGFBP-3 or the ratio of IGF-1:IGFBP-3. Strong evidence was only established for fasting insulin and insulin resistance. Further research is needed to examine the effect of physical activity on C-peptide and HBA1c in women. Reductions in fasting insulin and insulin resistance following exercise suggest some biological plausibility of the first part of the physical activity-insulin/IGF signaling-breast cancer pathway. See related article by Drummond et al., p. 2116.

Can walking exercise programs improve health for women in menopause transition and postmenopausal? Findings from a scoping review

OBJECTIVE

Our goal was to explore the range and characteristics of published papers on therapeutic walking programs for menopausal women and to identify program features that resulted in successful outcomes including reduced symptoms and improved long-term wellness.

METHODS

We searched biomedical and exercise-related databases for articles published up to June 1, 2017, using keywords related to menopause and walking. Data were collected into EndNote X8 reference manager to identify and remove duplicates. The final selection included all articles that studied walking as a health intervention for women in menopause transition or postmenopausal.

RESULTS

A total of 3,244 papers were collected from the six databases. After removing duplicates and applying inclusion and exclusion criteria, 96 articles were charted, including 77 different walking programs. Walking interventions ranged from 4 weeks to 3 years with an average weekly frequency of 3.8 ± 1.8 and were applied to a variety of symptoms and their biological markers and risk factors. Overall, 91% of the programs showed a beneficial outcome in at least one menopause-related medical issue. Information on menopause-specific symptoms, especially vasomotor symptoms and sleep problems, was scarce.

CONCLUSION

The scoping review highlights the growing interest in walking programs as therapies for menopause and related symptoms and provides evidence of their possible benefit as a wellness option for women in menopause and beyond. Further research would be recommended to establish the therapeutic value of walking programs for women with specific focus on typical menopause symptoms at different stages of menopause. : Video Summary:http://links.lww.com/MENO/A587.

Association Between Hormone Therapy and Muscle Mass in Postmenopausal Women: A Systematic Review and Meta-analysis

IMPORTANCE

Hormone therapy (HT) has been suggested for protection against age-related muscle weakness in women. However, the potential for HT-associated health risks necessitates a better understanding of the direction and magnitude of the association between HT and health outcomes, such as lean body mass (LBM).

OBJECTIVE

To determine whether HT was associated with reduced LBM loss compared with not receiving HT among postmenopausal women aged 50 years and older.

DATA SOURCES

MEDLINE, Embase, AgeLine, CINAHL, and SportDiscus (searched from inception until April 25, 2018).

STUDY SELECTION

For this systematic review and meta-analysis, randomized clinical trials including postmenopausal women undergoing HT and control groups of women not receiving HT were selected by 2 reviewers. Studies were included if LBM or fat-free mass were measured as an outcome. Studies with participants from hospitals, long-term care facilities, or with specific diseases were excluded.

DATA EXTRACTION AND SYNTHESIS

Information regarding study characteristics and outcome measures were extracted by 1 reviewer and verified by another. Risk of bias was evaluated. Quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used to abstract data and assess data quality/validity. Data were pooled using a fixed-effects model.

MAIN OUTCOMES AND MEASURES

The primary study outcome was the overall absolute change in LBM (measured in kilograms), captured by dual-energy x-ray absorptiometry, dual-photon absorptiometry, or bioelectrical impedance analysis imaging.

RESULTS

Of 8961 studies that met selection criteria, 12 were included, with a total of 4474 recruited participants. Of the participants, mean (SD) age was 59.0 (6.1) years. Data on ethnicity were collected by 2 of the studies. Of the 22 HT intervention arms, 15 used estrogen-progesterone combination HT and 7 used estrogen-only HT. Control participants were women who received no HT at all or who received placebo. The median follow-up duration was 2 years (range, 6 months to 6 years). Seven treatment arms showed a loss of LBM, and 14 were protective. Overall, HT users lost 0.06 kg (95% CI, -0.05 to 0.18) less LBM compared with control participants, but the difference was not statistically significant (P = .26). The results were unchanged when stratified based on treatment type and dosage, duration of follow-up, time since menopause, study quality, and type of LBM measurement, with HT users losing between 0.06 kg more to 0.20 kg less LBM compared with control participants for all strata. The quality of evidence based on GRADE was low.

CONCLUSIONS AND RELEVANCE

This systematic review and meta-analysis did not show a significant beneficial or detrimental association of HT with muscle mass. Although muscle retention in aging women is of crucial importance, these findings suggest that interventions other than HT should be explored.

Insulin Sensitivity Following Exercise Interventions: Systematic Review and Meta-Analysis of Outcomes Among Healthy Adults

OBJECTIVE

Although exercise can improve insulin sensitivity, no adequate synthesis exists of exercise intervention studies with regard to their effect on insulin sensitivity. This comprehensive meta-analysis synthesized the insulin sensitivity outcomes of supervised exercise interventions.

METHOD

Extensive literature searching located published and unpublished intervention studies that measured insulin sensitivity outcomes. Eligible studies tested supervised exercise interventions among healthy adults. Primary study characteristics and results were coded. Random-effects meta-analyses of standardized mean differences included moderator analyses.

RESULTS

Data were synthesized across 2509 subjects (115 samples, 78 reports). The overall mean effect size for 2-group postintervention comparisons was 0.38 (95% confidence interval [CI] = 0.25-0.51, I (2) = 0%) and for 2-group pre-post comparisons was 0.43 (95% CI = 0.30-0.56, I (2) = 52%; higher mean insulin sensitivity for treatment than control subjects). The postintervention mean of 0.38 is consistent with treatment subjects ending studies with a mean fasting insulin of 6.8 mU/L if control participants' mean fasting insulin were 7.9 mU/L. Exploratory moderator analyses did not document different insulin sensitivity effect sizes across intervention characteristics or sample attributes.

CONCLUSION

This study documented that exercise is a valuable primary care and community health strategy for healthy adults to improve insulin sensitivity and lower the risk for diabetes conferred by insulin resistance.

Regional muscle glucose uptake remains elevated one week after cessation of resistance training independent of altered insulin sensitivity response in older adults with type 2 diabetes

BACKGROUND

Aging is associated with a decline in skeletal muscle size.Muscle is critical both for mobility and glucose disposal. While resistance exercise (RE) increases muscle mass and function in the elderly, its role in improving glucose utilization is less clear.

AIMS

To investigate whether muscle size was linked with insulin sensitivity (IS) in elders with diabetes following RE and if regional muscle glucose uptake differed from systemic glucose utilization.

METHODS

Seven (68.4 ± 5.9 yr) adults with diabetes participated. After 16 weeks of RE, within 24 h (post 1) and after 1 week of no exercise (post 2), lean tissue cross-sectional area (CSA) and IS via glucose infusion rate (GIR) were assessed along with a standardized 18-F fluorodeoxyglucose (FDG)-positron emission tomography uptake value (SUV).

RESULTS

CSA increased between pre-test (108.5 ± 35.3 cm2) and post 1 (116.8 ± 40.9 cm2), p=0.02 and did not differ at post 2 (116.0 ± 39.3 cm2). GIR during the 40 mU/m2/min insulin clamp differed between pretest (22.0 ± 15.8 mg/kg/min) and post 1 (67.9 ± 72.8 mg/kg/min), and post 1 and post 2 (25.0 ± 27.2 mg/kg/min) but not between pre-test and post 2. GIR results during the 200 mU/m2/min insulin clamps also differed between pre-test and post 1, and post 1 and post 2 but not between pre-test and post 2. FDG-SUV increased between pre-test (1.1 ± 0.2) and post 1 (1.4 ± 0.3), and remained stable between post 1 and post 2 (1.4 ± 0.4).

CONCLUSION

RE that increased muscle size and FDG-SUV improved IS 24 h but not 1 week after exercise training.

Exercise and type 2 diabetes: American College of Sports Medicine and the American Diabetes Association: joint position statement. Exercise and type 2 diabetes

Although physical activity (PA) is a key element in the prevention and management of type 2 diabetes mellitus (T2DM), many with this chronic disease do not become or remain regularly active. High-quality studies establishing the importance of exercise and fitness in diabetes were lacking until recently, but it is now well established that participation in regular PA improves blood glucose control and can prevent or delay T2DM, along with positively affecting lipids, blood pressure, cardiovascular events, mortality, and quality of life. Structured interventions combining PA and modest weight loss have been shown to lower T2DM risk by up to 58% in high-risk populations. Most benefits of PA on diabetes management are realized through acute and chronic improvements in insulin action, accomplished with both aerobic and resistance training. The benefits of physical training are discussed, along with recommendations for varying activities, PA-associated blood glucose management, diabetes prevention, gestational diabetes, and safe and effective practices for PA with diabetes-related complications.

Cardiovascular and metabolic effects of community based resistance training in an older population

Ageing is associated with decreases in strength and cardiovascular fitness, and increased cardiovascular risk factors. The aim of the current study was to determine the effectiveness of 16 weeks of community based resistance compared to flexibility training on strength, cardiovascular fitness and cardiovascular and metabolic parameters in a group of previously sedentary, healthy older men and women. A randomised controlled crossover intervention study. Forty nine healthy sedentary participants (23 males; age 66.7 ± 4.3 years; weight 78.6 ± 15.4 kg; mean ± SD) completed 16 weeks of supervised community-based resistance training and 16 weeks of flexibility training in a randomised order. Prior to and following each intervention, participants were assessed for muscle strength, cardiovascular fitness (VO(2 peak)), fasted blood lipids and blood glucose, insulin and insulin resistance. Resistance training resulted in significant increases in knee extension (+25.7 Nm; p < 0.001) and knee flexion strength (+8.9 Nm; p = 0.048) and decreases in fasting total cholesterol (-0.51 mmol L(-1); p = 0.001), HDL cholesterol (-0.12 mmol L(-1); p = 0.035), LDL cholesterol (-0.35 mmol L(-1); p = 0.022), glucose (-0.42 mmol L(-1); p < 0.001), insulin (-1.28 μU/mL; p = 0.049) and insulin resistance (-0.50 μU/mL; p = 0.004) compared to the flexibility protocol. No significant changes between the treatments were observed in VO(2peak) (+2.04 mL kg(-1)min(-1); p = 0.12). Community based resistance training is suitable for improving strength and reducing cardiovascular and metabolic risk factors in healthy older individuals.

Influence of resistance exercise on lean body mass in aging adults: a meta-analysis

PURPOSE

sarcopenia plays a principal role in the pathogenesis of frailty and functional impairment that occur with aging. There are few published accounts that examine the overall benefit of resistance exercise (RE) for lean body mass (LBM) while considering a continuum of dosage schemes and/or age ranges. Therefore, the purpose of this meta-analysis was to determine the effects of RE on LBM in older men and women while taking these factors into consideration.

METHODS

this study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Randomized controlled trials and randomized or nonrandomized studies among adults ≥ 50 yr were included. Heterogeneity between studies was assessed using the Cochran Q and the I statistics, and publication bias was evaluated through physical inspection of funnel plots as well as formal rank-correlation statistics. Mixed-effects meta-regression was incorporated to assess the relationship between RE dosage and changes in LBM.

RESULTS

data from 49 studies, representing a total of 1328 participants, were pooled using random-effect models. Results demonstrated a positive effect for LBM, and there was no evidence of publication bias. The Cochran Q statistic for heterogeneity was 497.8, which was significant (P < 0.01). Likewise, I was equal to 84%, representing rejection of the null hypothesis of homogeneity. The weighted pooled estimate of mean LBM change was 1.1 kg (95% confidence interval = 0.9-1.2 kg). Meta-regression revealed that higher-volume interventions were associated (β = 0.05, P < 0.01) with significantly greater increases in LBM, whereas older individuals experienced less increase (β = -0.03, P = 0.01).

CONCLUSIONS

RE is effective for eliciting gains in LBM among aging adults, particularly with higher-volume programs. Findings suggest that RE participation earlier in life may provide superior effectiveness.

Exercise and type 2 diabetes: the American College of Sports Medicine and the American Diabetes Association: joint position statement

Although physical activity (PA) is a key element in the prevention and management of type 2 diabetes, many with this chronic disease do not become or remain regularly active. High-quality studies establishing the importance of exercise and fitness in diabetes were lacking until recently, but it is now well established that participation in regular PA improves blood glucose control and can prevent or delay type 2 diabetes, along with positively affecting lipids, blood pressure, cardiovascular events, mortality, and quality of life. Structured interventions combining PA and modest weight loss have been shown to lower type 2 diabetes risk by up to 58% in high-risk populations. Most benefits of PA on diabetes management are realized through acute and chronic improvements in insulin action, accomplished with both aerobic and resistance training. The benefits of physical training are discussed, along with recommendations for varying activities, PA-associated blood glucose management, diabetes prevention, gestational diabetes mellitus, and safe and effective practices for PA with diabetes-related complications.

Increased strength and physical performance with eccentric training in women with impaired glucose tolerance: a pilot study

BACKGROUND

Menopause is associated with both a loss of muscle mass and a worsening of insulin sensitivity (IS). Although eccentric resistance exercise (ECC) can effectively improve muscle mass over time, a single bout of ECC can worsen IS. This study assessed the effect of repeated ECC on IS, muscle mass, and function in postmenopausal women with impaired glucose tolerance (IGT).

METHODS

Sixteen PM women (aged 56 years +/- 6.4) with IGT were randomly assigned to a 12-week, knee extensor ECC program (n = 10) or a nonexercise control group (CON) (n = 6). Participants underwent hyperinsulinemic-euglycemic clamps, dual-energy x-ray (DEXA) absorptiometry, quadriceps strength assessment, 6-minute walk (6MW) tests, and an assessment of steps taken per day before and after training.

RESULTS

ECC participants experienced greater increases in leg lean soft tissue mass (ECC, 0.41 kg; CON, -0.53 kg; p = 0.03), quadriceps strength (ECC, 9.3 kg force; CON, -2.9 kg force; p = 0.02), and 6MW distance (ECC, 56.4 meters; CON, 3.3 meters; p = 0.03) than CON participants and demonstrated a trend toward more steps taken per day posttraining (ECC, +1747 steps; CON, +339 steps; p = 0.10). IS was unchanged.

CONCLUSIONS

This novel exercise improves muscle mass and function without worsening IS in postmenopausal women with IGT. Because it can be performed at low levels of exertion and improves muscle mass and function without impairing IS, ECC should be used to ameliorate muscle loss in physically inactive postmenopausal women. The impact of longer-term ECC on IS should be investigated. Demonstrating that ECC does not worsen IS in this population is significant because it has promise to combat the muscle-mediated impairments common in aging women.

Resistance training and dietary protein: effects on glucose tolerance and contents of skeletal muscle insulin signaling proteins in older persons

BACKGROUND

Resistance training (RT) and dietary protein independently influence indexes of whole-body glucose control, though their synergistic effects have not yet been documented.

OBJECTIVE

This study assessed the influence of dietary protein intake on RT-induced changes in systemic glucose tolerance and the contents of skeletal muscle insulin signaling proteins in healthy older persons.

DESIGN

Thirty-six older men and women (age: 61 +/- 1 y) performed RT (3 times/wk for 12 wk) and consumed either 0.9 g protein . kg(-1) . d(-1) [lower-protein (LP) group; approximately 112% of the Recommended Dietary Allowance (RDA)] or 1.2 g protein . kg(-1) . d(-1) [higher-protein (HP) group; approximately 150% of the RDA]; the HP group consumed more total, egg, and dairy proteins.

RESULTS

After RT, body weight was unchanged; whole-body protein and water masses increased, and fat mass decreased with no significantly different responses observed between the LP and HP groups. The RT-induced improvement in oral glucose tolerance (decreased area under the curve, AUC) was not significantly different between the groups (LP: -28%; HP: -25%). The insulin (-21%) and C-peptide (-14%) AUCs decreased in the LP group but did not change significantly in the HP group. Skeletal muscle insulin receptor, insulin receptor substrate-1, and Akt contents were unchanged, and the amount of atypical protein kinase C zeta/lambda (aPKC zeta/lambda), a protein involved with insulin signaling, increased 56% with RT, independent of protein intake.

CONCLUSION

These results support the hypothesis that older persons who consume adequate or moderately high amounts of dietary protein can use RT to improve body composition, oral glucose tolerance, and skeletal muscle aPKC zeta/lambda content without a change in body weight.

Exercise and improved insulin sensitivity in older women: evidence of the enduring benefits of higher intensity training

Few studies have compared the relative benefits of moderate- vs. higher intensity exercise training on improving insulin sensitivity in older people while holding exercise volume constant. Healthy older (73 ± 10 yr) women ( N = 25) who were inactive, but not obese, were randomized into one of three training programs (9-mo duration): 1) high-intensity [80% peak aerobic capacity (V̇o2 peak); TH] aerobic training; 2) moderate-intensity (65% V̇o2 peak; TM) aerobic training; or 3) low-intensity (stretching) placebo control (50% V̇o2 peak; CTB). Importantly, exercise volume (300 kcal/session) was held constant for subjects in both the TH and the TM groups. V̇o2 peak was determined by using a graded exercise challenge on a treadmill. Total body fat and lean mass were determined with dual-energy X-ray absorptiometry. The rate of insulin-stimulated glucose utilization as well as the suppression of lipolysis were determined ∼72 h after the final exercise bout by using a two-step euglycemic-hyperinsulinemic clamp. We observed improved glucose utilization at the higher insulin dose with training, but these improvements were statistically significant only in the TH (21%; P = 0.02) compared with the TM (16%; P = 0.17) and CTB (8%; P = 0.37) groups and were observed without changes in either body composition or V̇o2 peak. Likewise in the TH group, we detected a significant improvement in insulin-stimulated suppression (%) of adipose tissue lipolysis at the low-insulin dose (38–55%, P < 0.05). Our findings suggest that long-term higher intensity exercise training provides more enduring benefits to insulin action compared with moderate- or low-intensity exercise, likely due to greater transient effects.