Even low-intensity and low-volume exercise training may improve insulin resistance in the elderly

Low-Intensity Exercise Training Additionally Increases Mitochondrial Dynamics Caused by High-Fat Diet (HFD) but Has No Additional Effect on Mitochondrial Biogenesis in Fast-Twitch Muscle by HFD

This study examines how the high-fat diet (HFD) affects mitochondrial dynamics and biogenesis, and also whether combining it with low-intensity endurance exercise adds to these effects. Six 8-week-old male Sprague–Dawley (SD) rats were put on control (CON; standard chow diet), HF (HFD intake), and HFEx (HFD + low-intensity treadmill exercise) for 6 weeks. As a result, no change in body weight was observed among the groups. However, epididymal fat mass increased significantly in the two groups that had been given HFD. Blood free fatty acid (FFA) also increased significantly in the HF group. While HFD increased insulin resistance (IR), this was improved significantly in the HFEx group. HFD also significantly increased mitochondrial biogenesis-related factors (PPARδ, PGC-1α, and mtTFA) and mitochondrial electron transport chain proteins; however, no additional effect from exercise was observed. Mitochondrial dynamic-related factors were also affected: Mfn2 increased significantly in the HFEx group, while Drp1 and Fis-1 increased significantly in both the HF and HFEx groups. The number of mitochondria in the subsarcolemmal region, and their size in the subsarcolemmal and intermyofibrillar regions, also increased significantly in the HFEx group. Taken overall, these results show that HFD in combination with low-intensity endurance exercise has no additive effect on mitochondrial biogenesis, although it does have such an effect on mitochondrial dynamics by improving IR.

The Effect of Exercise on Glucoregulatory Hormones: A Countermeasure to Human Aging: Insights from a Comprehensive Review of the Literature

Hormones are secreted in a circadian rhythm, but also follow larger-scale timetables, such as monthly (hormones of the menstrual cycle), seasonal (i.e., winter, summer), and, ultimately, lifespan-related patterns. Several contexts modulate their secretion, such as genetics, lifestyle, environment, diet, and exercise. They play significant roles in human physiology, influencing growth of muscle, bone, and regulating metabolism. Exercise training alters hormone secretion, depending on the frequency, duration, intensity, and mode of training which has an impact on the magnitude of the secretion. However, there remains ambiguity over the effects of exercise training on certain hormones such as glucoregulatory hormones in aging adults. With advancing age, there are many alterations with the endocrine system, which may ultimately alter human physiology. Some recent studies have reported an anti-aging effect of exercise training on the endocrine system and especially cortisol, growth hormone and insulin. As such, this review examines the effects of endurance, interval, resistance and combined training on hormones (i.e., at rest and after) exercise in older individuals. We summarize the influence of age on glucoregulatory hormones, the influence of exercise training, and where possible, examine masters' athletes' endocrinological profile.

Combined exercise is a modality for improving insulin resistance and aging-related hormone biomarkers in elderly Korean women

BACKGROUND

The functional decline of the endocrine and immune systems with aging causes changes in the regulation of the body's metabolism and defense functions. Although it is impossible to stop aging artificially, regular exercises reportedly delay aging and have positive effects on senile diseases. The improvements in insulin resistance values and aging-related hormones in elderly women after combined exercises have not been effectively elucidated.

OBJECTIVE

In this study, we aimed to examine the impact of combined exercise on insulin resistance and aging-related hormones in elderly women.

METHODS

Twenty elderly Korean women were randomly assigned to a "non-exercise" (n = 10) or combined exercise group (n = 10). The exercise group performed both anaerobic and aerobic exercises for 12 weeks, three times per week. Exercise intensity was increased gradually, from 40% to 70% of the heart rate reserve (HRR) every 3 weeks. Insulin resistance, growth hormone, IGF-1, DHEA-S, and estrogen were measured before and after the 12-week intervention.

RESULTS

The main effect was found in the glucose level for a time, which significantly decreased in the exercise group. The insulin level and HOMA-IR showed significant interaction effects and increased significantly in the control group. The GH level showed significant interaction effects and increased significantly in the exercise group. The IGF-1 level showed significant interaction effects, but not significantly within and between groups. The DHEA-S level revealed interaction effects and the main effect for a time and significantly increased in the exercise group. The estrogen level exhibited an interaction effect and increased significantly in the exercise group. After the 12-week combined exercise intervention, no significant difference was observed between groups.

DISCUSSION

This study has shown that 12-week combined exercise is useful for improving insulin resistance and GH, IGF-1, and DHEA-S levels in elderly women. Thus, this study provides evidence that combined exercise is a useful therapeutic method to decrease insulin resistance and stimulate the secretion of aging-related hormones in elderly women.

Associations of Physical Activity Intensities with Markers of Insulin Sensitivity

BACKGROUND

Objectively measured physical activity (PA) intensity has traditionally been categorized as light, moderate, and vigorous using laboratory calibrated cut points. The relative contribution of time spent across a spectrum of accelerometer-determined intensities on health outcomes is less clear.

PURPOSE

This study aimed to assess the relationship between objectively measured PA intensity on a continuous scale and markers of insulin sensitivity (IS).

METHODS

Participants at high risk of type 2 diabetes mellitus were recruited from primary care (Leicestershire, UK). PA was measured using an ActiGraph accelerometer. Fasting and postchallenge glucose and insulin levels were assessed using an oral glucose tolerance test. IS was calculated using the Matsuda-IS and the HOMA-IS indices. Log-linear regression modeling was used to assess the relationship between PA intensity, in increments of 500 counts per minute, with markers of IS. Models were controlled for known confounders.

RESULTS

Complete data were available for 569 participants. PA intensity was favorably associated with fasting and 2 h of insulin and IS, with the association increasing in magnitude with each increment of 500 counts per minute. Differences in HOMA-IS per 10 min of PA ranged from 12.4% (95% confidence interval = 3.7%-21.8%) to 26.8% (11.0%-44.7%) within the moderate-intensity PA category (from 2000-2499 to 3500-3999 counts per minute). For Matsuda-IS, these differences were 22.0% (10.3%-34.9%) and 34.7% (13.9%-59.3%), respectively. Significant associations for fasting insulin were no longer observed after controlling for body mass index, whereas differences associated with 2-h insulin and IS were attenuated but still significant.

CONCLUSION

PA of any intensity may positively influence glucose regulation and insulin sensitivity in individuals at high risk of type 2 diabetes mellitus in a dose-response manner. Further research is required to identify the intensity thresholds at which clinically relevant benefits occur in this population.

Resistance characteristics of innovative eco-fitness equipment: a water buoyancy muscular machine

This paper propose innovative eco-fitness equipment-a water buoyancy muscular machine (WBM machine) in which resistance is generated by buoyancy and fluid resistance. The resistance characteristics during resistance adjustment and under isometric, concentric, eccentric and isokinetic conditions were investigated and compared to a conventional machine with metal weight plates. The results indicated that the isometric, concentric and eccentric resistances could be adjusted by varying the water volume; the maximum resistances under isometric, concentric and eccentric conditions were 163.8, 338.5 and 140.9 N, respectively. The isometric resistances at different positions remained constant in both machines; however the isometric resistance was lower for WBM machine when at a position corresponding to a 5% total displacement. The WBM machine has lower resistance under eccentric conditions and higher resistance under concentric conditions. Although the conventional machine has an identical trend, the variation was minor (within 4 N). In the WBM machine, the eccentric resistance was approximately 30-45% of the concentric resistance. Concentric resistances increased with an increase in velocity in both machines; however, the eccentric resistances decreased with an increase in velocity. In summary, the WBM machine, a piece of innovative eco-fitness equipment, has unique resistance characteristics and expansibility.

The associations between increasing degrees of homeostatic model assessment for insulin resistance and muscular strengthening activities among euglycaemic US adults

PURPOSE

To examine the associations between the homeostatic model assessment for insulin resistance and self-reported muscular strengthening activity in a nationally representative sample of euglycaemic US adults.

METHODS

Sample included euglycaemic adults (⩾20 years of age (n = 2009)) from the 1999 to 2004 National Health and Nutrition Examination Survey. Homeostatic model assessment for insulin resistance was categorized into quartiles and was the primary independent variable of interest. No reported muscular strengthening activity was the dependent variable.

RESULTS

Following adjustment for covariates, those with homeostatic model assessment for insulin resistance values in fourth (odds ratio: 2.04, 95% confidence interval: 1.35-3.06, p < 0.001) quartile were found to have significantly greater odds of reporting no muscular strengthening activity. Following further adjustment for non-muscular strengthening activity specific aerobic leisure-time physical activity, results remained significant for the fourth (odds ratio: 2.30, 95% confidence interval: 1.50-3.52, p < 0.001) quartile. A significant trend was seen across quartiles of homeostatic model assessment for insulin resistance for increasing prevalence of no muscular strengthening activity (p < 0.001).

CONCLUSION

Having a higher homeostatic model assessment for insulin resistance value is associated with greater odds of reporting no muscular strengthening activity among euglycaemic US adults. This implies that subjects with an increasing degree of insulin resistance are more likely to not engage in muscular strengthening activity, an exercise modality that has been shown to reduce the risk of several cardiometabolic diseases and improve glycaemic status.

Relationship of visfatin level to pancreatic endocrine hormone level, HOMA-IR index, and HOMA β-cell index in overweight women who performed hydraulic resistance exercise

[Purpose] This study aimed to examine the correlation of visfatin level to pancreatic endocrine hormone level, homeostasis model assessment of insulin resistance (HOMA-IR) index, and HOMA β-cell index in hydraulic resistance exercise. Furthermore, it investigated the relationship between visfatin level and other variables affected by exercise in overweight women. [Subjects and Methods] The exercise group trained for 12 weeks, 70 minutes/day, 5 days/week. Visfatin level, pancreatic endocrine hormone level, HOMA-IR index, and HOMA β-cell index were measured before and after the intervention. Based on the blood insulin and glucose concentrations, HOMA-IR index, the indicator of insulin resistance, and HOMA β-cell index, the indicator of insulin secretion level, were assessed. [Results] Interaction effects on visfatin level, insulin level, HOMA-IR index, and HOMA β-cell index were observed. Interaction effects on glucagon and glucose levels were not observed between the intervention groups. The correlations of visfatin level to insulin, glucagon, and glucose levels, and HOMA-IR and HOMA β-cell indexes were not significant for any of the subjects. [Conclusion] Therefore, the 12-week resistance exercise affected body composition, visfatin level, insulin level, HOMA-IR index, and HOMA β-cell index. Finally, visfatin was not related to insulin, glucagon, and glucose levels, and HOMA-IR and HOMA β-cell indexes.

Objectively measured sedentary time and associations with insulin sensitivity: Importance of reallocating sedentary time to physical activity

OBJECTIVE

The aim of this study is to quantify associations between objectively measured sedentary time and markers of insulin sensitivity by considering allocation into light-intensity physical activity or moderate- to vigorous-intensity physical activity (MVPA).

METHODS

Participants with an increased risk of impaired glucose regulation (IGR) were recruited (Leicestershire, United Kingdom, 2010-2011). Sedentary, light-intensity physical activity and MVPA time were measured using accelerometers. Fasting and 2-hour post-challenge insulin and glucose were assessed; insulin sensitivity was calculated by HOMA-IS and Matsuda-ISI. Isotemporal substitution regression models were used. Data were analysed in 2014.

RESULTS

508 participants were included (average age=65years, female=34%). Reallocating 30min of sedentary time into light-intensity physical activity was associated a 5% (95% CI 1, 9%; p=0.024) difference in Matsuda-ISI after adjustment for measured confounding variables. Reallocation into MVPA was associated with a 15% (7, 25%; p<0.001) difference in HOMA-IS and 18% (8, 28%; p<0.001) difference in Matsuda-ISI. Results for light-intensity physical activity were modified by IGR status with stronger associations seen in those with IGR.

CONCLUSIONS

Reallocating sedentary time into light-intensity physical activity or MVPA was associated with differences in insulin sensitivity, with stronger and more consistent associations seen for MVPA.

The effect of 8 weeks aerobic exercise on insulin resistance in type 2 diabetes: a randomized clinical trial

Diabetes complications are the main reasons behind morbidity and mortality preventable by healthy diet and physical activity. There are few studies about the effect of aerobic exercises on insulin resistance in human. Also various training protocols are associated with different results. Since approaches to decrease insulin resistance may be followed by more effectiveness treatment, this study assessed the effect of aerobic exercise on insulin resistance in Type 2 Diabetes Mellitus. In this randomized clinical trial, 53 Type 2 diabetic women were randomly divided into two groups as exercise (n=27) and control (n=26). The exercise protocol included warm-up by stretching and flexibility exercises for 10 m, followed by walking for 30 m with maximum intensity 60% increase in heart rate and then stretching in the seated position for 10 m, 3 times a week for 8 weeks. Resistance to insulin was assessed using Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). Significant differences have been observed in insulin resistance, fasting glucose and plasma insulin between the groups after 8 weeks. There were significant differences in waist and hip circumference, BMI, plasma insulin and insulin resistance within the groups over time. In addition, the changes in waist and hip circumference, FBS, plasma insulin and insulin resistance had significant interaction with the time between the groups. The current exercise protocol has been effective in lowering plasma glucose (p = 0.05), insulin levels (p = 0.000) and insulin resistance (p = 0.02). It seems that aerobic exercises training promote the effectiveness of medical treatment in Type 2 Diabetes Mellitus.

Very short bouts of non-exercise physical activity associated with metabolic syndrome under free-living conditions in Japanese female adults

To assess the association between very short daily non-exercise physical activity (PA) lasting <5 min and metabolic syndrome (MS). A total of 42 females (50 ± 6 years) wore a pedometer with a one-axial accelerometer (Lifecorder, Kenz, Japan) to determine the time and the frequency of PA and the moderate to vigorous intensity PA (MVPA). In addition to the PA and the MVPA (PA(all) and MVPA(all)), the PA and MVPA were analyzed based on the bout duration, such as >32 s, >1 min, >3 min, and >5 min (PA(32S), PA(1M), PA(3M), PA(5M); MVPA(32S), MVPA(1M), MVPA(3M), MVPA(5M)). MS was defined according to the Japanese standard based on waist circumfluence, blood lipids, blood glucose, and blood pressure. The frequency of the MVPA(1M) was significantly lower in subjects with MS compared with that in subjects without MS (P < 0.05). The frequency of MVPA(32S) and MVPA(1M) was significantly associated with the HDL cholesterol (P < 0.05). The frequency of PA(3M) and PA(5M) was significantly associated with the fasting glucose level (P < 0.05). In contrast, we could not find any significant relationships between MS and the components of MS and the frequency of PA lasting <32 s. These results demonstrated that very short non-exercise PA, such as MVPA lasting >32 s to 3 min, has significantly associated with the components of MS. The specific advantages with regard to PA lasting <32 s remain unclear.

Effect of genetic testing for risk of type 2 diabetes mellitus on health behaviors and outcomes: study rationale, development and design

Abstract

Trial Registration

ClinicalTrials.gov: NCT00849563

Aging, resistance training, and diabetes prevention

With the aging of the baby-boom generation and increases in life expectancy, the American population is growing older. Aging is associated with adverse changes in glucose tolerance and increased risk of diabetes; the increasing prevalence of diabetes among older adults suggests a clear need for effective diabetes prevention approaches for this population. The purpose of paper is to review what is known about changes in glucose tolerance with advancing age and the potential utility of resistance training (RT) as an intervention to prevent diabetes among middle-aged and older adults. Age-related factors contributing to glucose intolerance, which may be improved with RT, include improvements in insulin signaling defects, reductions in tumor necrosis factor-α, increases in adiponectin and insulin-like growth factor-1 concentrations, and reductions in total and abdominal visceral fat. Current RT recommendations and future areas for investigation are presented.

The role of physical activity in type 2 diabetes prevention: physiological and practical perspectives

Lifestyle changes that include a nutritionally balanced diet and increased physical activity (PA) are effective intervention options for persons with prediabetes who want to prevent progression to type 2 diabetes mellitus. Although nutritional counseling is standard practice for patients in a clinical setting, an individualized PA prescription, including recommendations on the type, frequency, duration, and intensity, is much less likely to occur. This is surprising because lifestyle modifications including a PA program are at least as effective in diabetes prevention as any single pharmacological agent. The success of regular PA in improving glycemic control in persons with either prediabetes or type 2 diabetes likely results from adaptations that occur in several organs and tissues, including adipose, skeletal muscle, liver, and pancreas. Increased insulin sensitivity is an important link between increased PA, body composition, and metabolic health, and it is at this link where increases in PA and energy expenditure exert much of their effect on preventing metabolic disorders and improving symptoms of existing disease. In addition to improving insulin sensitivity, regular PA has several cardioprotective effects, especially for persons with metabolic dysfunction, and has been shown to elicit minimal adverse events in these populations. Effective PA prescription is contingent on an understanding of the underlying physiological adaptations and the differing responses to diverse modes and intensities of PA. This article highlights recent findings on the beneficial role of regular PA for improving and/or maintaining insulin sensitivity in persons with prediabetes. We also provide an evidence-informed prescription for the type, intensity, and duration of both resistance and aerobic PA in persons with prediabetes.

Resistance exercise plus to aerobic activities is associated with better lipids' profile among healthy individuals: the ATTICA study

BACKGROUND

The influence of different types of exercise on risk factors for cardiovascular diseases has rarely been investigated. The aim of the present work was to evaluate the effect of adding resistance exercise to aerobic activities on lipid-lipoprotein profile, in a representative sample of men and women from the province of Attica, Greece.

METHODS

We randomly enrolled 1514 and 1528 healthy men and women, respectively, stratified by city, age and gender distribution. Participants were classified as inactive (INA), sufficiently active (SA) and highly active for either aerobic activities (HAA) alone or a combination of aerobic plus resistance exercise (HAC). The main outcome measures are lipid-lipoprotein profile [total, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, apolipoprotein-A1, apolipoprotein-B] and anthropometric indices.

RESULTS

From those participating in aerobic activities, 480 (31.7%) men and 502 (32.9%) women were classified as SA, 100 men (6.6%) and 93 women (6.1%) as HAA and 90 men (5.9%) and 49 women (3.2%) as HAC. After various adjustments were made, men from the HAC group had an average of 23% lower plasma triacylglycerol concentration (P = 0.04) and 10% lower LDL-cholesterol (P = 0.01) when compared with the HAA group. Moreover, women from the HAC group had 13% lower LDL-cholesterol when compared with HAA group (P = 0.051).

CONCLUSION

These data suggest that combining aerobic and resistance-type activities may confer a better effect on lipoprotein profile in healthy individuals than aerobic activities alone.

Insulin resistance syndrome and glucose dysregulation in the elderly

The incidence of insulin resistance in the geriatric population is growing as this population grows. The management of hyperglycemia and its associated risk factors depends on an expanding understanding of the underlying pathophysiology and progression of disease and of the currently available and future therapeutics, which are continually evolving. There is a major need for studies in the long-term care setting to determine the appropriate standard of care in prevention and treatment of metabolic dysregulation.

Individualizing recommendations for weight management in the elderly

PURPOSE OF REVIEW

This review provides current strategies for weight management in the elderly population as it can be different from young adults due to multiple factors: co-morbidities, polypharmacy, limitation of functional activities, social issues.

RECENT FINDINGS

The recommendations for weight management for all age groups include exercise, diet, pharmacotherapy and surgery. In the elderly population, because of changes in age-related body composition, reduced energy requirement and expenditure, the standard young adult recommendations cannot be applied directly. The goal of weight management in the elderly differs from the young adult. The preferred method is maintenance of weight rather than aggressive weight loss with achieving a healthy, functional, and good quality of life.

SUMMARY

The growing prevalence of obesity in the elderly population is becoming a major health problem and can affect functional status, can contribute to frailty and decline in activity, as well as worsening co-morbid medical problems. Practical recommendations for weight management in the elderly are challenging because of the obesity paradox in the elderly, and the lack of substantial research in this population. Individualized recommendations should be considered for elderly patients with a focus on the underlying medical problems, functional status and living environments.

Exercise training and blood lipids in hyperlipidemic and normolipidemic adults: a meta-analysis of randomized, controlled trials

OBJECTIVE

To determine the effectiveness of exercise training (aerobic and resistance) in modifying blood lipids, and to determine the most effective training programme with regard to duration, intensity and frequency for optimizing the blood lipid profile.

DESIGN

Trials were identified by a systematic search of Medline, Embase, Science Citation Index (SCI), published reviews and the references of relevant trials. The inclusion criteria were limited to randomized, controlled trials of aerobic and resistance exercise training which were conducted over a minimum of four weeks and involved measurement of one or more of the following: total cholesterol (TC), high density lipoprotein (HIDL-C), low density lipoprotein (LDL-C) and triglycerides (TG).

SUBJECTS

A total of 31 trials ( 1833 hyperlipidemic and normolipidemic participants) were included.

RESULTS

Aerobic exercise training resulted in small but statistically significant decreases of 0.10 mmol/L (95% CI: 0.02, 0.18). 0.10 (95% CI: 0.02, 0.19), 0.08 mmol/L (95% CI: 0.02, 0.14), for TC, LDL-C, and TG, respectively, with an increase in HDL-C of 0.05 mmol/L (95% CI: 0.02, 0.08). Comparisons between the intensities of the aerobic exercise programmes produced inconsistent results; but more frequent exercise did not appear to result in greater improvements to the lipid profile than exercise three times per week. The evidence for the effect of resistance exercise training was inconclusive.

CONCLUSIONS

Caution is required when drawing firm conclusions from this study given the significant heterogeneity with comparisons. However, the results appear to indicate that aerobic exercise training produced small but favourable modifications to blood lipids in previously sedentary adults.