Comparison of combined aerobic and high-force eccentric resistance exercise with aerobic exercise only for people with type 2 diabetes mellitus

Slow-velocity eccentric-only resistance training improves symptoms of type 2 diabetic mellitus patients by regulating plasma MMP-2 and -9

OBJECTIVE

This study investigated the intervention effect of slow-velocity eccentric-only resistance training on type 2 diabetic mellitus (T2DM) patients based on the role of matrix metalloproteinase-2 and -9 (MMP-2 and -9) in regulating extracellular matrix homeostasis.

METHODS

50 T2DM patients were randomly divided into the slow-velocity eccentric-only resistance training group (E) and control group (C). The E group performed eccentric-only resistance training 3 times a week, every other day for 10 weeks, while the C group did not. Blood samples were collected before and after training, and subjects were tested for changes in clinical parameters, insulin resistance indices [fasting insulin, homeostatic model assessment insulin resistance (HOMA-IR)], MMP-2 and -9, and hydroxyproline, and muscle strength (12-RM), respectively.

RESULTS

After 10 weeks of training, the E group showed significant decreases in fasting glucose (P < .05), insulin (P < .05), insulin resistance indices (P < .05), hemoglobin A1c (HbA1c) (P < .01), triglycerides (P = .06) and MMP-2 (P < .05), while total cholesterol (P < .05), MMP-9 (P < .05), hydroxyproline (P < .01), Creatine Kinase (CK) (P < .05), and muscle strength (P < .001) significantly increased. There were no significant changes in the count of neutrophil, lymphocyte and platelet, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c). Compared with the C group, the E group showed a trend of a significant decrease in triglyceride (P < .05), lymphocyte count (P < .05), fasting glucose (P = .07), and plasma MMP-2 (P < .05), while MMP-9 (P < .05), hydroxyproline (P < .001), and muscle strength (P < .01) significantly increased. However, no significant changes were observed in insulin and insulin resistance indices, HbA1c, total cholesterol, HDL-c, LDL-c, CK, and other inflammatory indicators.

CONCLUSIONS

Slow-velocity eccentric-only resistance training was beneficial for T2DM, but the potential role of MMP-2 and -9 in regulating extracellular matrix homeostasis is very different in T2DM patients.

Evaluation of the Effectiveness of In-Hospital Exercise Rehabilitation in Middle-Aged and Elderly Patients with Type 2 Diabetes Mellitus Combined with Sarcopenia Effect of Lifestyle Management on Disease Status in Patients with Type 2 Diabetes Mellitus

OBJECTIVE

The aim of this study was to explore the effects of in-hospital exercise rehabilitation on glucose and lipid metabolism and healthy physical fitness in middle-aged and elderly patients with type 2 diabetes mellitus (T2DM) combined with sarcopenia, and to provide a reference for the effective implementation of exercise rehabilitation for middle-aged and elderly patients with T2DM combined with sarcopenia in healthcare institutions.

METHODS

This study retrospectively included 122 patients with T2DM combined with sarcopenia treated at the General Hospital of Ningxia Medical University from August 2017 to August 2020 and randomly divided into a control group and an experimental group. The control group was given conventional treatment and the experimental group was given exercise rehabilitation in the hospital for 12 weeks to compare the indexes related to glucose and lipid metabolism and healthy fitness in the two groups.

RESULTS

After the intervention, the experimental group showed significant decreases in fasting blood glucose (FBG), glycated hemoglobin (HbA1c), insulin resistance index (HOMA-IR), triglycerides (TG), total cholesterol (TC), low-density cholesterol (LDL-C) and body fat percentage (p < 0.05), while high-density cholesterol (HDL-C), grip strength, lower limb extension, lower limb flexion, peak oxygen uptake were significantly higher (p < 0.05) and were more significant at 12 weeks compared to the 6-week intervention (p < 0.05). However, there were no significant changes in any of the glucose metabolism indicators in the control group before and after the intervention. A two-way repeated measures ANOVA showed that at control baseline levels, HbA1c decreased significantly in the experimental group after both 6 and 12 weeks of intervention compared to the control group (p < 0.05). After 6 weeks of intervention, the experimental group showed a significant decrease in body fat percentage and a significant increase in grip strength. After 12 weeks of intervention, the experimental group showed an increase in glycemic control from 33.3% to 73.3%, a significant decrease in body fat percentage and a significant increase in grip strength, lower limb extension and lower limb flexion strength and peak oxygen uptake.

CONCLUSION

In-hospital exercise rehabilitation can effectively improve the glycemic and lipid profiles of patients with T2DM combined with sarcopenia and enhance their health fitness, with good clinical rehabilitation effects.

Effect of Eccentric Exercise on Metabolic Health in Diabetes and Obesity

There is a growing body of evidence showing the importance of physical activity against civilization-induced metabolic diseases, including type 2 diabetes (T2DM) and obesity. Eccentric contraction, when skeletal muscles generate force by lengthening, is a unique type of skeletal muscle activity. Eccentric contraction may lead to better power production characteristics of the muscle because eccentric contraction requires less energy and can result in higher tension. Therefore, it is an ideal tool in the rehabilitation program of patients. However, the complex metabolic effect (i.e., fat mass reduction, increased lipid oxidation, improvement in blood lipid profile, and increased insulin sensitivity) of the eccentric contraction alone has scarcely been investigated. This paper aims to review the current literature to provide information on whether eccentric contraction can influence metabolic health and body composition in T2DM or obesity. We also discussed the potential role of myokines in mediating the effects of eccentric exercise. A better understanding of the mechanism of eccentric training and particularly their participation in the regulation of metabolic diseases may widen their possible therapeutic use and, thereby, may support the fight against the leading global risks for mortality in the world.

The Health and Functional Benefits of Eccentric versus Concentric Exercise Training: A Systematic Review and Meta-Analysis

This review compared the effects of eccentric versus concentric exercise training in healthy people and people with metabolic disease. A systematic search on Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL, SPORTDiscus, Web of Science, SCOPUS and PubMed was conducted in February 2022. Randomised controlled trials conducted on sedentary healthy adults or those with an existing metabolic disease that compared eccentric versus concentric exercise training interventions of four weeks or longer that involved multiple joints and large muscle groups (e.g., walking, whole-body resistance training) were included in the review. The primary outcome was glucose handling, measured as HbA1c, HOMA, fasting glucose or insulin. Measures of cardiovascular health, muscle strength, and functional physical fitness were secondary outcomes. Nineteen trials involving 618 people were included. Results of meta-analyses showed that eccentric exercise had no benefit to glucose handling (HbA1c level; SMD - 0.99; 95% CI, -2.96 to 0.98; n = 74; P = 0.32) but resulted in significant increases in overall muscle strength (SMD 0.70; 95% CI 0.25 to 1.15; n = 224; P = 0.003) and decreases in blood pressure (Systolic Blood Pressure; MD -6.84; 95% CI, -9.84 to -3.84; n = 47, P = 0.00001, and Diastolic Blood Pressure; MD -6.39; 95% CI -9.62 to -3.15; n = 47, P = 0.0001). Eccentric exercise is effective for improving strength and some markers of cardiovascular health compared to traditional exercise modalities. Additional high-quality studies are necessary to validate these results. (PROSPERO registration: CRD42021232167).

Benefits of Eccentric Training with Emphasis on Demands of Daily Living Activities and Feasibility in Older Adults: A Literature Review

Aging is associated with a decline in physical capabilities and several other health-related conditions. One of the most common age-related processes is sarcopenia. Sarcopenia is usually accompanied with a decline in skeletal muscle mass and physical functioning. A decrease in these markers usually impacts basic daily living activities (DLAs), which become somewhat harder to accomplish for older individuals. Several research studies have examined the demands of DLA in older individuals with results indicating that activities such as walking, sitting, standing, stair climbing, stair descending, and running generate high demands on older adults. The forces that act on individuals are in most cases equal or multiple times higher relative to their body mass. For instance, it was reported that the GRF (ground reaction force) during stair descent ranged from 1.43 to 1.50 of BW (body weight) in an older population. Even higher demands were recorded during other related activities. These demands of DLA raise the question of appropriate rehabilitative or training management procedures. During the past decades, an eccentric form of resistance training gained popularity due to its effectiveness and lower metabolic demands, which seems to be an appropriate method to develop and maintain a basic level of strength capabilities in higher age. Multiple factors of eccentric training have been examined including modality of exercise, intensity, frequency, and safety of the elderly. Several modalities of eccentric exercise have been shown to be effective including traditional methods, as well as machine-based ones, with or without using some equipment. The studies included in this review varied in intensity from low to high; however, the most frequently used intensity was ≥50% of the maximal eccentric strength during two or three eccentric sessions per week. Importantly, the prevalence of injury of older adults appears to have been low to none, highlighting the safety of this approach. In summary, eccentric training prescriptions for older adults should consider the demands of DLA and the characteristics of the elderly for appropriate management of training recommendations.

Passive muscle stiffness is correlated with the intramuscular adipose tissue in young individuals

PURPOSE

We investigated the relationship between intramuscular adipose tissue (IntraMAT) and muscle stiffness (passive and mechanical) and lengthening in young individuals, hypothesizing that (1) passive muscle stiffness is negatively correlated with the IntraMAT content, and (2) the IntraMAT content is negatively correlated with mechanical changes in muscle stiffness and fascicle length during passive dorsiflexion.

METHODS

Twenty men and women (20.3 ± 1.3 years) participated in this study. Axial T1-weighted magnetic resonance imaging was performed at the thickest point of the medial gastrocnemius (MG) to measure the IntraMAT cross-sectional area (CSA) and muscle tissue CSA (units; cm²). The shear wave velocity (SWV) and fascicle length at the three ankle joint angles, namely 15° with plantarflexion (PF15), 0° with neutral position (NP), and 15° with dorsiflexion (DF15), were measured as parameters of muscle stiffness (unit; m/s) and lengthening (unit; cm) using ultrasound shear wave elastography and B-mode imaging. We further calculated the changes in SWV and fascicle length from PF15 to NP and from NP to DF15 as mechanical muscle stiffness and lengthening, respectively.

RESULTS

There was a relationship between IntraMAT CSA and absolute SWV at DF15 (r = - 0.47, P < 0.05). Further, a relationship was observed between IntraMAT CSA and change in SWV and fascicle length from NP to DF15 (r = - 0.47 and r = 0.59, P < 0.05); whereas no relationship was observed between changes in fascicle length and muscle SWV (r = - 0.23, P = 0.33).

CONCLUSION

These results may indicate biomechanical and/or physiological associations between IntraMAT CSA and passive muscle stiffness.

Effects of eccentric, concentric and eccentric/concentric training on muscle function and mass, functional performance, cardiometabolic health, quality of life and molecular adaptations of skeletal muscle in COPD patients: a multicentre randomised trial

Background

Chronic obstructive pulmonary disease (COPD) is the third cause of death worldwide. COPD is characterised by dyspnoea, limited exercise tolerance, and muscle dysfunction. Muscle dysfunction has been linked to dysregulation between muscle protein synthesis, myogenesis and degradation mechanisms. Conventional concentric cycling has been shown to improve several clinical outcomes and reduce muscle wasting in COPD patients. Eccentric cycling is a less explored exercise modality that allows higher training workloads imposing lower cardio-metabolic demand during exercise, which has shown to induce greater muscle mass and strength gains after training. Interestingly, the combination of eccentric and concentric cycling training has scarcely been explored. The molecular adaptations of skeletal muscle after exercise interventions in COPD have shown equivocal results. The mechanisms of muscle wasting in COPD and whether it can be reversed by exercise training are unclear. Therefore, this study aims two-fold: (1) to compare the effects of 12 weeks of eccentric (ECC), concentric (CONC), and combined eccentric/concentric (ECC/CONC) cycling training on muscle mass and function, cardiometabolic health, physical activity levels and quality of life in severe COPD patients; and (2) to examine the molecular adaptations regulating muscle growth after training, and whether they occur similarly in specific muscle fibres (i.e., I, IIa and IIx).

Methods

Study 1 will compare the effects of 12 weeks of CONC, ECC, versus ECC/CONC training on muscle mass and function, cardiometabolic health, levels of physical activity and quality of life of severe COPD patients using a multicentre randomised trial. Study 2 will investigate the effects of these training modalities on the molecular adaptations regulating muscle protein synthesis, myogenesis and muscle degradation in a subgroup of patients from Study 1. Changes in muscle fibres morphology, protein content, genes, and microRNA expression involved in skeletal muscle growth will be analysed in specific fibre-type pools.

Discussion

We aim to demonstrate that a combination of eccentric and concentric exercise could maximise the improvements in clinical outcomes and may be ideal for COPD patients. We also expect to unravel the molecular mechanisms underpinning muscle mass regulation after training in severe COPD patients.

Trial Registry: Deutshches Register Klinischer Studien; Trial registration: DRKS00027331; Date of registration: 12 January 2022. https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00027331.

A Short-Term Eccentric HIIT Induced Greater Reduction in Cardio-Metabolic Risk Markers in Comparison With Concentric HIIT in Sedentary Overweight Men

Background: Steady-state eccentric exercise training improves cardiometabolic risk (CMR) despite lesser cardiovascular demands compared with load-matched concentric training. Whether a high-intensity interval eccentric training is also effective reducing CMR is unknown. Aim: To compare the effects of a short-term high-intensity interval eccentric training (ECC-HIIT) with high-intensity interval concentric training (CONC-HIIT) on CMR in sedentary overweight men. Methods: Twenty men (age: 27.9 ± 5.3y, body massindex: 29.1 ± 3.1 kg·m-2) were randomly assigned to ECC-HIIT (n = 10) or CONC-HIIT (n = 10) delivered as six sessions, including 4 x 5:2 min work-to-rest ratio, at 80% peak concentric power output. Heart rate (HR), rate of perceived exertion (RPE) and muscle soreness weremonitored during training sessions. Training effects on lipid profile, insulin sensitivity (HOMA-IR), body composition, thigh circumference, isometric knee extensors maximal strength, resting systolic and diastolic blood pressure (SBP and DBP) were determined. Results: Average training HR and RPE were -29%and -50%lower in ECC-HIIT in comparison with CONC-HIIT. Muscle soreness was initially greater after ECC-HIIT compared with CONC-HIIT. Significant changes in total and low-density lipoprotein cholesterol (-7.0 ± 8.7%; p = .02 and -6.3 ± 14.4%; p = .03), SBP (-9.8 ± 7.8%; p = .002), and maximal thigh circumference (+2.5 ± 3.1%; p = .02) were observed following ECC-HIIT. No changes in any CMR marker were observed after CONC-HIIT. Moderate-to-large training effect sizes were obtained in thigh circumference, SBP, total cholesterol and low-density lipoprotein cholesterol in response to ECC-HIIT. Conclusion: A two-week ECC-HIIT was well-tolerated and induced rapid onset improvements in cholesterol and blood pressure compared to conventional CONC-HIIT in sedentary overweight men.

Eccentric-only versus concentric-only resistance training effects on biochemical and physiological parameters in patients with type 2 diabetes

Background

The benefits of resistance training for patients with type 2 diabetes (T2D) are well documented; however, the effects of exercise with different muscle contraction types such as eccentric versus concentric contractions on physiological outcomes for this population are not clear. This study compared eccentric-only (ECC) and concentric-only resistance training (CON) to test the hypothesis that ECC would be superior to CON to improve insulin sensitivity, lipid profile, body composition, muscle strength and physical function of patients with T2D.

Methods

Adults with T2D (50–79 years) were allocated to the ECC (n = 9) or CON group (n = 9). Resistance exercises (chest press, lateral pulldown, bicep curl, triceps extension, leg extension, leg curl, calf raise, abdominal crunch) consisting of 2–3 sets of 10 eccentric-only (5 s) or concentric-only contractions (1–2 s) was performed twice a week for 12 weeks. Changes in blood biomarkers, body composition, muscle strength and physical function from pre- to post-intervention were compared between groups.

Results

Overall rating of perceived exertion (RPE, 1–10 Borg scale) was lower (p < 0.05) for ECC (2.9 ± 1.2) than CON (5.4 ± 1.1). No significant changes in blood biomarkers were found for both groups. Lean mass increased [effect size (ES) = 0.148, ECC 3.2 ± 6.9%; CON 3.6 ± 2.3%], and fat mass decreased (ES = 0.545, ECC − 6.1 ± 12.4%; CON − 7.1 ± 16.4%) (p < 0.05) similarly. One-repetition maximal strength of each exercise increased (p < 0.05) for both ECC (12–37%) and CON (27–68%). Both groups improved (p < 0.05) 6-min walk distance (ES = 0.083, ECC 12.2 ± 2.3%; CON 12.5 ± 15.3%) and chair rise time (ES = 0.463, ECC − 13.4 ± 25.4%; CON − 20.0 ± 53.3%) but only ECC improved (p < 0.05) the timed up-and-go test (− 11.3 ± 13.6%, ES 0.014). No significant changes in balance tests were found for both groups.

Conclusion

These results did not fully support the hypothesis but showed that ECC was as effective as CON to improve body composition, muscle strength, and physical function with lesser RPE. Future studies should investigate whether larger differences between ECC and CON are evident when increasing the exercise frequency and matching the intensities of the two-exercise protocols.

Trial registration ACTRN12621001026819 (retrospectively registered on 5th Aug 2021).

Exercise Training to Decrease Ectopic Intermuscular Adipose Tissue in Individuals With Chronic Diseases: A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study was to evaluate the effect of exercise training on ectopic fat within skeletal muscle (intermuscular adipose tissue [IMAT]) in adult populations with chronic diseases.

METHODS

A literature search was conducted in relevant databases to identify randomized controlled trials (RCTs) from inception. Selected studies examined the effect of aerobic training (AET), resistance training (RT), or combined training (COM) on IMAT as assessed by noninvasive magnetic resonance imagery or computed tomography. Eligibility was determined using Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Data extraction was performed using the population (P), intervention (I), comparison (C), outcome (O), timing (T), and settings (S) approach. Methodological quality was analyzed by the Cochrane risk of bias assessment. Standardized effect sizes (ES) with 95% CIs were calculated. Heterogeneity among studies was quantified using I2 statistics. Subgroup and meta-regression analyses were included. Risk of publication bias was examined by the Egger regression test.

RESULTS

Nineteen RCTs included 962 adults (628 women; age range = 34.8-93.4 years) with different chronic conditions that participated in 10 AET, 12 RT, and 5 COM interventions. The quality of studies was deemed moderate. Overall, the effect of exercise on IMAT was small (ES = 0.24; 95% CI = 0.10 to 0.37; heterogeneity I2 = 0.0%) compared with no exercise or control interventions. Moderate-intensity AET and COM had larger ES compared with RT regardless of intensity. This effect was associated with exercise-induced body weight and fat mass losses. Subgroup analysis revealed larger ES in studies assessing IMAT by magnetic resonance imagery compared with computed tomography in adults and middle-aged individuals compared with older adults and in participants who were HIV+ compared with other diagnoses.

CONCLUSION

AET and COM of moderate intensity reduce IMAT in individuals from 18 to 65 years of age who are affected by chronic diseases. This effect is associated with exercise-induced body weight and fat mass losses. In older individuals who are frail and patients at an advanced disease stage, exercise may result in a paradoxical IMAT accumulation.

IMPACT

In people affected by chronic conditions, IMAT accumulation induces muscle mass and strength losses, decline in physical performance, inflammation, and metabolic alterations. The present study shows that moderate-intensity AET or COM prevent or reduce IMAT in these conditions. Thus, the deleterious effect of IMAT on skeletal muscle homeostasis may be reverted by a properly prescribed exercise regime. The findings of the present systematic review are critical for physical therapists and health care professionals because they emphasize the therapeutic role of exercise and provide recommendations for exercise prescription that ultimately may have a positive impact on the course of disease, recovery of functionality, and independence.

LAY SUMMARY

Aerobic exercise (eg, walking/jogging, cycling) alone or combined with resistance exercise (strength training with free-weights, kettle bells, or gym equipment) is effective in reducing fat streaks that infiltrate muscles and impair muscle function and growth, particularly in adults affected by chronic diseases.

Molecular Regulation of Skeletal Muscle Growth and Organelle Biosynthesis: Practical Recommendations for Exercise Training

The regulation of skeletal muscle mass and organelle homeostasis is dependent on the capacity of cells to produce proteins and to recycle cytosolic portions. In this investigation, the mechanisms involved in skeletal muscle mass regulation-especially those associated with proteosynthesis and with the production of new organelles-are presented. Thus, the critical roles of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) pathway and its regulators are reviewed. In addition, the importance of ribosome biogenesis, satellite cells involvement, myonuclear accretion, and some major epigenetic modifications related to protein synthesis are discussed. Furthermore, several studies conducted on the topic of exercise training have recognized the central role of both endurance and resistance exercise to reorganize sarcomeric proteins and to improve the capacity of cells to build efficient organelles. The molecular mechanisms underlying these adaptations to exercise training are presented throughout this review and practical recommendations for exercise prescription are provided. A better understanding of the aforementioned cellular pathways is essential for both healthy and sick people to avoid inefficient prescriptions and to improve muscle function with emergent strategies (e.g., hypoxic training). Finally, current limitations in the literature and further perspectives, notably on epigenetic mechanisms, are provided to encourage additional investigations on this topic.

Can Exercise-Induced Muscle Damage Be a Good Model for the Investigation of the Anti-Inflammatory Properties of Diet in Humans?

Subclinical, low-grade, inflammation is one of the main pathophysiological mechanisms underlying the majority of chronic and non-communicable diseases. Several methodological approaches have been applied for the assessment of the anti-inflammatory properties of nutrition, however, their impact in human body remains uncertain, because of the fact that the majority of the studies reporting anti-inflammatory effect of dietary patterns, have been performed under laboratory settings and/or in animal models. Thus, the extrapolation of these results to humans is risky. It is therefore obvious that the development of an inflammatory model in humans, by which we could induce inflammatory responses to humans in a regulated, specific, and non-harmful way, could greatly facilitate the estimation of the anti-inflammatory properties of diet in a more physiological way and mechanistically relevant way. We believe that exercise-induced muscle damage (EIMD) could serve as such a model, either in studies investigating the homeostatic responses of individuals under inflammatory stimuli or for the estimation of the anti-inflammatory or pro-inflammatory potential of dietary patterns, foods, supplements, nutrients, or phytochemicals. Thus, in this review we discuss the possibility of exercise-induced muscle damage being an inflammation model suitable for the assessment of the anti-inflammatory properties of diet in humans.

Effects of descending or ascending stair exercise on body composition, insulin sensitivity, and inflammatory markers in young Chinese women with obesity: A randomized controlled trial

We examined the effects of descending (DSE) or ascending (ASE) stair exercise on body composition, insulin sensitivity, and inflammatory markers in young Chinese women with obesity. Thirty-six participants were randomly assigned into three groups DSE, ASE and a control group. The DSE and ASE groups performed three sessions of stair walking per week for 12 weeks with a gradual increase in repetitions. Following the exercise interventions, body composition related variables obtained by Dual-energy X-ray absorptiometry scans significantly decreased. Abdominal fat decreased in the DSE group only. Moreover, Insulin sensitivity improved significantly 3.5-fold in the DSE group compared with ASE group (insulin: -33.2% vs. -9.8%, homoeostasis model assessment for insulin resistance: -35.6% vs. -10.8%). Pro-inflammatory factors showed significant decreases in tumour necrosis factor-α (TNF-α) (-39.9% vs. -23.2%) for both intervention groups. The reduction in TNF-α concentrations in the DSE group was significantly different compared to the other two groups. Interleukin-6 significantly decreased in both exercise protocols. Our results show that 12-weeks induced stair walking improved body composition parameters in Chinese females with obesity. The results also demonstrate the superiority of the DSE protocol for improving insulin sensitivity. These findings may be attributable to the decreases observed in TNF- α levels.

Technical feasibility of constant-load and high-intensity interval training for cardiopulmonary conditioning using a re-engineered dynamic leg press

Background

Leg-press devices are one of the most widely used training tools for musculoskeletal strengthening of the lower-limbs, and have demonstrated important cardiopulmonary benefits for healthy and patient populations. Further engineering development was done on a dynamic leg-press for work-rate estimation by integrating force and motion sensors, power calculation and a visual feedback system for volitional work-rate control. This study aimed to assess the feasibility of the enhanced dynamic leg press for cardiopulmonary exercise training in constant-load training and high-intensity interval training. Five healthy participants aged 31.0±3.9 years (mean ± standard deviation) performed two cardiopulmonary training sessions: constant-load training and high-intensity interval training. Participants carried out the training sessions at a work rate that corresponds to their first ventilatory threshold for constant-load training, and their second ventilatory threshold for high-intensity interval training.

Results

All participants tolerated both training protocols, and could complete the training sessions with no complications. Substantial cardiopulmonary responses were observed. The difference between mean oxygen uptake and target oxygen uptake was 0.07±0.34 L/min (103 ±17%) during constant-load training, and 0.35±0.66 L/min (113 ±27%) during high-intensity interval training. The difference between mean heart rate and target heart rate was −7±19 bpm (94 ±15%) during constant-load training, and 4.2±16 bpm (103 ±12%) during high-intensity interval training.

Conclusions

The enhanced dynamic leg press was found to be feasible for cardiopulmonary exercise training, and for exercise prescription for different training programmes based on the ventilatory thresholds.

Eccentric Muscle Contractions: Risks and Benefits

Eccentric contractions, characterized by the lengthening of the muscle-tendon complex, present several unique features compared with other types of contractions, which may lead to unique adaptations. Due to its specific physiological and mechanical properties, there is an increasing interest in employing eccentric muscle work for rehabilitation and clinical purposes. However, unaccustomed eccentric exercise is known to cause muscle damage and delayed pain, commonly defined as “Delayed-Onset Muscular Soreness” (DOMS). To date, the most useful preventive strategy to avoid these adverse effects consists of repeating sessions involving submaximal eccentric contractions whose intensity is progressively increased over the training. Despite an increased number of investigations focusing on the eccentric contraction, a significant gap still remains in our understanding of the cellular and molecular mechanisms underlying the initial damage response and subsequent adaptations to eccentric exercise. Yet, unraveling the molecular basis of exercise-related muscle damage and soreness might help uncover the mechanistic basis of pathological conditions as myalgia or neuromuscular diseases. In addition, a better insight into the mechanisms governing eccentric training adaptations should provide invaluable information for designing therapeutic interventions and identifying potential therapeutic targets.

Effects of aerobic versus resistance training on serum fetuin-A, fetuin-B, and fibroblast growth factor-21 levels in male diabetic patients

The aim of this study was to compare the effects of 8 weeks of aerobic versus resistance training programs on serum fetuin-A, fetuin-B, and fibroblast growth factor-21 (FGF-21) levels in males with type 2 diabetes mellitus. Participants (n = 34) were randomly assigned to a resistance training group (RTG; n = 12), an aerobic training group (ATG; n = 11), or a control group (n = 11). The ATG completed 30-45 min of aerobic running training at 65%-75% of the maximum heart rate. The RTG completed three sets of 10 repetitions maximum of leg press, bench press, knee extension, seated cable row, knee flexion, military press, and calf rise. Blood samples were taken before and after the training period to assess dependent variables. After 8 weeks, both the ATG and the RTG reduced fetuin-A (p < 0.05) and fetuin-B (p < 0.05), but increased FGF-21 (p < 0.05). Moreover, the RTG showed greater decrease than the ATG in fetuin-A (-18.3% vs. -7.9%), fetuin-B (-29.2% vs. -11.45%), and a lower increase in FGF-21 (42.2% vs. 25.1%), respectively. Aerobic and resistance exercise training significantly decreased serum fetuin-A, and fetuin-B, and increased FGF-21 levels in males with type 2 diabetes mellitus. However, more significant alterations in serum factors were observed from resistance training. Thus, resistance training may be considered a more suitable training strategy.

Impact of Underwater Treadmill Training on Glycemic Control, Blood Lipids, and Health-Related Fitness in Adults With Type 2 Diabetes

IN BRIEF A large number of adults with type 2 diabetes experience comorbidities that discourage physical activity and hinder regular participation in land-based exercise programs. An aquatic exercise program is an innovative exercise modality that incorporates combined aerobic and resistance exercise. The purpose of this study was to determine if an underwater treadmill walking program featuring gradual and progressive increases in walking speed and duration has a positive effect on glycemic control, metabolic health, cardiovascular function, body composition, and leg strength in middle-aged adults with type 2 diabetes.

Effects of 10-week walking and walking with home-based resistance training on muscle quality, muscle size, and physical functional tests in healthy older individuals

Background

Older individuals have been shown to present muscle atrophy in conjunction with increased fat fraction in some muscles. The proportion of fat and connective tissue within the skeletal muscle can be estimated from axial B-mode ultrasound images using echo intensity (EI). EI was used to calculate the index of muscle quality. Walking, home-based weight-bearing resistance training, and its combinations are considered simple, easy, and practical exercise interventions for older adults. The purpose of this study was to quantify the effects of walking and walking with home-based resistance training on muscle quality of older individuals.

Methods

Thirty-one participants performed walking training only (W-group; 72 ± 5 years) and 33 participants performed walking and home-based resistance training (WR-group; 73 ± 6 years). This study was a non-randomized controlled trial with no control group. All participants were instructed to walk 2 or 3 sets per week for 10 weeks (one set: 30-min continuous walking). In addition, the WR-group performed home-based weight-bearing resistance training. EI was measured as a muscle quality index using axial B-mode ultrasound images of the rectus femoris and vastus lateralis of the mid-thigh. We further averaged these parameters to obtain the EI of the quadriceps femoris (QF). Participants further performed five functional tests: sit-ups, supine up, sit-to-stand, 5-m maximal walk, and 6-min walk.

Results

QF EI was significantly decreased in both groups after training (W-group 69.9 ± 7.4 a.u. to 61.7 ± 7.0 a.u., WR-group 64.0 ± 9.5 a.u. to 51.1 ± 10.0 a.u.; P < 0.05), suggesting improved muscle quality. QF EI was further decreased in the WR-group compared with the W-group. The sit-up test in both groups and the sit-to-stand and 5-m maximal walk tests in the W-group were significantly improved after training.

Conclusion

These results suggest that training-induced stimulation is associated with a decrease in EI in some thigh regions. Furthermore, the addition of home-based resistance training to walking would be effective for a greater reduction of EI.

Eccentric cycling is more efficient in reducing fat mass than concentric cycling in adolescents with obesity

The benefits of eccentric (ECC) training on fat mass (FM) remain underexplored. We hypothesized that in obese adolescents, ECC cycling training is more efficient for decreasing whole-body FM percentage compared to concentric (CON) performed at the same oxygen consumption (VO₂ ). Twenty-four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile) were randomized to ECC or CON. They performed three cyclo-ergometer sessions per week (30 min per session) for 12 weeks: two habituation, 5 at 50% VO_2peak , and 5 at 70% VO_2peak . Anthropometric measurements, body composition, maximal incremental CON tests, strength tests, and blood samples were assessed pre- and post-training. Whole-body FM percentage decreased significantly after compared to pretraining in both groups, though to a larger extent in the ECC group (ECC: -10% vs CON: -4.2%, P < 0.05). Whole-body lean mass (LM) percentage increased significantly in both groups after compared to pretraining, with a greater increase in the ECC group (ECC: 3.8% vs CON: 1.5%, P <0.05). The improvements in leg FM and LM percentages were greater in the ECC group (-6.5% and 3.0%, P = 0.01 and P < 0.01). Quadriceps isometric and isokinetic ECC strength increased significantly more in the ECC group (28.3% and 21.3%, P < 0.05). Both groups showed similar significant VO_2peak improvement (ECC: 15.4% vs CON: 10.3%). The decrease in homeostasis model assessment of insulin resistance index was significant in the ECC group (-19.9%). In conclusion, although both ECC and CON cycling trainings are efficient to decrease FM, ECC induces greater FM reduction, strength gains, and insulin resistance improvements and represents an optimal modality to recommend for obese adolescents.

Eccentric Training Improves Body Composition by Inducing Mechanical and Metabolic Adaptations: A Promising Approach for Overweight and Obese Individuals

Skeletal muscle generates force by either shortening (concentrically) or lengthening (eccentrically). Eccentric (ECC) exercise is characterized by a lower metabolic demand and requires less muscle activity than concentric (CON) exercise at the same level of exerted force. However, the specific effect of ECC training vs. CON training on lean and fat mass remains underexplored. The first aim of this paper was to review the available evidence regarding the effects of ECC training on whole body and segmental lean and fat mass and, when possible, compare these with the effects of CON training. The second aim was to provide some insights into the main mechanical, physiological, and metabolic adaptations of ECC training that contribute to its effects on body composition. The third aim was to determine the beneficial effects of ECC exercise on health-related parameters in overweight and obese patients. ECC training is an effective modality to improve lean mass, but when matched for load or work, the difference between ECC and CON trainings seems unclear. A few studies reported that ECC training is also efficient at reducing fat mass. By increasing post-exercise resting energy expenditure, modifying metabolic substrate, and improving both blood lipid profile and insulin resistance, ECC training is a potential exercise modality for individuals with chronic conditions such as those who are overweight and obese. Further investigations using standardized experimental conditions, examining not only segmental but also whole body composition, are required to compare ECC and CON trainings.

Basic science and clinical use of eccentric contractions: History and uncertainties

The peculiar attributes of muscles that are stretched when active have been noted for nearly a century. Understandably, the focus of muscle physiology has been primarily on shortening and isometric contractions, as eloquently revealed by A.V. Hill and subsequently by his students. When the sliding filament theory was introduced by A.F. Huxley and H.E. Huxley, it was a relatively simple task to link Hill's mechanical observations to the actions of the cross bridges during these shortening and isometric contractions. In contrast, lengthening or eccentric contractions have remained somewhat enigmatic. Dismissed as necessarily causing muscle damage, eccentric contractions have been much more difficult to fit into the cross-bridge theory. The relatively recent discovery of the giant elastic sarcomeric filament titin has thrust a previously missing element into any discussion of muscle function, in particular during active stretch. Indeed, the unexpected contribution of giant elastic proteins to muscle contractile function is highlighted by recent discoveries that twitchin-actin interactions are responsible for the "catch" property of invertebrate muscle. In this review, we examine several current theories that have been proposed to account for the properties of muscle during eccentric contraction. We ask how well each of these explains existing data and how an elastic filament can be incorporated into the sliding filament model. Finally, we review the increasing body of evidence for the benefits of including eccentric contractions into a program of muscle rehabilitation and strengthening.

Exercise and Nutrition Strategies to Counteract Sarcopenic Obesity

As the population is aging rapidly, there is a strong increase in the number of individuals with chronic disease and physical limitations. The decrease in skeletal muscle mass and function (sarcopenia) and the increase in fat mass (obesity) are important contributors to the development of physical limitations, which aggravates the chronic diseases prognosis. The combination of the two conditions, which is referred to as sarcopenic obesity, amplifies the risk for these negative health outcomes, which demonstrates the importance of preventing or counteracting sarcopenic obesity. One of the main challenges is the preservation of the skeletal muscle mass and function, while simultaneously reducing the fat mass in this population. Exercise and nutrition are two key components in the development, as well as the prevention and treatment of sarcopenic obesity. The main aim of this narrative review is to summarize the different, both separate and combined, exercise and nutrition strategies so as to prevent and/or counteract sarcopenic obesity. This review therefore provides a current update of the various exercise and nutritional strategies to improve the contrasting body composition changes and physical functioning in sarcopenic obese individuals.

Aerobic exercise regulates blood lipid and insulin resistance via the toll‑like receptor 4‑mediated extracellular signal‑regulated kinases/AMP‑activated protein kinases signaling pathway

Diabetes mellitus is a complicated metabolic disease with symptoms of hyperglycemia, insulin resistance, chronic damage and dysfunction of tissues, and metabolic syndrome for insufficient insulin production. Evidence has indicated that exercise treatments are essential in the progression of type‑ІІ diabetes mellitus, and affect insulin resistance and activity of islet β‑cells. In the present study, the efficacy and signaling mechanism of aerobic exercise on blood lipids and insulin resistance were investigated in the progression of type‑ІІ diabetes mellitus. Body weight, glucose metabolism and insulin serum levels were investigated in mouse models of type‑ІІ diabetes mellitus following experienced aerobic exercise. Expression levels of inflammatory factors, interleukin (IL)‑6, high‑sensitivity C‑reactive protein, tumor necrosis factor‑α and leucocyte differentiation antigens, soluble CD40 ligand in the serum were analyzed in the experimental mice. In addition, expression levels of toll‑like receptor 4 (TLR‑4) were analyzed in the liver cells of experimental mice. Changes of oxidative stress indicators, including reactive oxygen species, superoxide dismutase, glutathione and catalase were examined in the liver cells of experimental mice treated by aerobic exercise. Expression levels and activity of extracellular signal‑regulated kinases (ERK) and AMP‑activated protein kinase (AMPK) signaling pathways were investigated in the liver cells of mouse models of type‑ІІ diabetes mellitus after undergoing aerobic exercise. Aerobic exercise decreased the expression levels of inflammatory factors in the serum of mouse models of type‑ІІ diabetes mellitus. The results indicated that aerobic exercise downregulated oxidative stress indicators in liver cells from mouse models of type‑ІІ diabetes mellitus. In addition, the ERK and AMPK signaling pathways were inactivated by aerobic exercise in liver cells in mouse models of type‑ІІ diabetes mellitus. The activity of ERK and AMPK, and the function of islet β‑cells were observed to be improved in experimental mice treated with aerobic exercise. Furthermore, blood lipid metabolism and insulin resistance were improved by treatment with aerobic exercise. Body weight and glucose concentration of serology was markedly improved in mouse models of type‑ІІ diabetes mellitus. Furthermore, TLR‑4 inhibition markedly promoted ERK and AMPK expression levels and activity. Thus, these results indicate that aerobic exercise may improve blood lipid metabolism, insulin resistance and glucose plasma concentration in mouse models of type‑ІІ diabetes mellitus. Thus indicating aerobic exercise is beneficial for improvement of blood lipid and insulin resistance via the TLR‑4‑mediated ERK/AMPK signaling pathway in the progression of type‑ІІ diabetes mellitus.

Investigation of cardiopulmonary exercise testing using a dynamic leg press and comparison with a cycle ergometer

BACKGROUND

Leg-press machines are widely employed for musculoskeletal conditioning of the lower-limbs and they provide cardiovascular benefits for resistance training in cardiac patients. The aim of this study was to assess the feasibility of a dynamic leg press (DLP) for incremental cardiopulmonary exercise testing (CPET) and to compare the results with those obtained using a cycle ergometer (CE).

METHODS

Twelve healthy participants aged 27±4 years (mean ± standard deviation) performed incremental cardiopulmonary exercise tests on a DLP and on a CE. To facilitate CPET, the DLP was augmented with force and angle sensors, a work rate estimation algorithm, and a visual feedback system. Gas exchange variables and heart rate were recorded breath-by-breath using a cardiopulmonary monitoring system.

RESULTS

Peak oxygen uptake and peak heart rate were significantly lower for the DLP than for the CE: peak oxygen uptake was 3.2±0.5 vs. 4.1±0.5 L/min (DLP vs. CE, p=6.7×10-6); peak heart rate was 174±14 vs. 182±13 bpm (DLP vs. CE, p=0.0016). Likewise, the sub-maximal cardiopulmonary parameters, viz. the first and second ventilatory thresholds, and ramp duration were significantly lower for the DLP.

CONCLUSIONS

The dynamic leg press was found to be feasible for CPET: the approach was technically implementable and all peak and sub-maximal cardiopulmonary parameters were able to be identified. The lower outcome values observed with the DLP can be attributed to a peripheral factor, namely the earlier onset of muscular fatigue.

Effects of Early Combined Eccentric-Concentric Versus Concentric Resistance Training Following Total Knee Arthroplasty

Objective

To investigate the effects of early combined eccentric-concentric (ECC-CON) or concentric (CON) resistance training following total knee arthroplasty (TKA).

Methods

Patients who underwent a primary TKA were randomly assigned to an ECC-CON group (n=16) or a CON group (n=18). All patients received early, progressive resistance training with five sessions per week for 2 weeks starting 2 weeks after TKA. Isometric knee flexor and extensor strength of the surgical and non-surgical knees, instrumental gait analysis for spatiotemporal parameters, 6-Minute Walk Test (6MWT), Timed Up and Go Test (TUG), Timed Stair Climbing Test (SCT) were used to evaluate performance-based physical function. The Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) and EuroQOL five dimensions (EQ-5D) questionnaire were used to evaluate self-reported physical function and self-reported quality of life. All patients underwent these evaluations before and 1 month after TKA.

Results

The ECC-CON group showed clinically meaningful improvements in extensor peak torque (PT) of the non-surgical knee, gait speed, and 6MWT from preoperative values. The CON group had an increase in H/Q ratio of the surgical knee and improvement in SCT-ascent postoperatively. Both groups showed significant improvements in WOMAC-Pain, function, and EQ-5D scores. Although extensor PT of the surgical knee did not reach the preoperative level in either group, the postoperative change was significantly less in the ECC-CON group than the CON group.

Conclusion

Early combined ECC-CON resistance training minimizes the loss in quadriceps strength of the surgical knee and improves endurance and gait speed after TKA.

The effects of supramaximal versus submaximal intensity eccentric training when performed until volitional fatigue

PURPOSE

Our purpose was to compare supramaximal versus submaximal intensity eccentric training performed until volitional fatigue.

METHODS

Thirty-two young adults (19 males) were randomized into one of three groups: (1) ECC110 performed eccentric (ECC) only contractions at 110% of concentric (CON) 1-repetition maximum (1RM); (2) ECC80 performed ECC only contractions at 80% of CON 1RM; (3) a control group. Training progressed from 3 to 6 sets of unilateral ECC training of the elbow flexors over 8 weeks, with each set performed until volitional fatigue. Elbow flexors muscle thickness (via ultrasound) and 1RM were assessed pre- and post-training. Rating of perceived exertion (RPE) and muscle soreness was self-reported.

RESULTS

Both ECC110 (+0.25 cm) and ECC80 (+0.21 cm) showed a greater post-training increase in muscle thickness compared to control (-0.01 cm) (p < 0.05), with no differences between ECC110 and ECC80. ECC80 (+1.23 kg) showed a greater post-training increase in strength compared to control (p < 0.05), while ECC110 (+0.76 kg) had no significant difference post-training vs. control (-0.01 kg). ECC80 had significantly lower average RPE scores than ECC110 (p < 0.05).

CONCLUSIONS

Both supramaximal intensity eccentric training and submaximal intensity eccentric training are effective for increasing muscle size, but submaximal eccentric training is perceived to require less exertion than supramaximal training. These findings suggest that submaximal eccentric training may be an ideal strategy to increase muscle size and strength in individuals whose needs warrant training at a lower level of exertion.

Finding the Optimal volume and intensity of Resistance Training Exercise for Type 2 Diabetes: The FORTE Study, a Randomized Trial

AIM

To compare different volumes and intensities of resistance training (RT) combined with aerobic training (AT) for improvements in glycemic control and cardiovascular health for persons with type 2 diabetes (T2DM).

METHODS

Participants with T2DM were stratified by HbA1c and randomized: "usual care" (RT1), which consisted of moderate intensity (50% 1-repetition maximum [1-RM]), low volumeRT (initiated half-way through program); higher intensity (75% 1-RM) and higher volume (initiated at program onset) RT (RT2); or moderate intensity but higher volume RT (RT3). RT sets and repetitions were adjusted to maintain similar work and volume between RT2 and RT3. Walking or cycling (60-80% aerobic capacity)was prescribed 5 times/week, and RT was prescribed 2 times/week. An ANCOVA, adjusted for baseline and gender, assessed changes post-6months in glycemic control (HbA1c- primary outcome), aerobic capacity and anthropometrics.

RESULTS

Sixty-two participants (52.3±1.2years, 48% female) were randomized (RT1, n=20; RT2, n=20; RT3, n=22). Only post-training fasting glucose, without significant HbA1c change, was different between groups (RT1-RT3=-1.7mmol/L, p=0.046). Pre-post differences were found in pooled HbA1c (7.4±0.2%[57±2.2mmol/mol] vs. 6.7±0.2%[50±2.2mmol/mol], p<0.001), aerobic capacity (21.5±0.8vs. 25.2±0.8ml/kg/min, p<0.001), body mass (84.0±2.7vs. 83.0±2.7kg, p=0.022[DXA]), body mass index (30.8±0.9vs. 30.3±0.8kg/m², p=0.02) and body fat (32.3±1.1vs. 31.3±1.2%, p<0.001). The trial was discontinued early; no HbA1c advantage was found with either RT2 or RT3 over RT1.

CONCLUSIONS

Combined AT+RT exercise improved glycemic control, cardiovascular risk factors and body composition after 6months for participants with T2DM, but differential effects between the prescribed intensities and volumes of RT were not found to effect HbA1c.

Low-Load High-Velocity Resistance Exercises Improve Strength and Functional Capacity in Diabetic Patients

This study investigated the effects of low-load high-velocity resistance exercises on neuromuscular and functional outcomes in patients with Type 2 diabetes (T2D) during the early-phase of resistance training. Thirty participants with T2D performed 18 training sessions (6 weeks - 3x week) in one of two groups: low-load high-velocity exercises (LLHV, n=15, 62.1±10.5 years) or recreational activities (RA, n=15 56.7 ± 19.4 years). LLHV performed resistance exercises with 3x 8reps as fast as possible with 50-60% 1RM. RA performed light activities. Strength, power, and functional tests were assessed. There was significant increasing in the knee extension peak-torque at 60°/s (7.6%) and 180°/s (12.2%), rate of force development in the LLHV group (P<0.05), whereas there were no changes in the RA group. Significant increases in functional test were observed in the LLHV group (P<0.01) with no changes in the RA group. In conclusion, the LLHV induced marked improvements in neuromuscular parameters, as well as in the functional capacity of participants with T2D.

Chronic eccentric arm cycling improves maximum upper-body strength and power

INTRODUCTION

Eccentric leg cycling (cycle ergometry adapted to impose muscle lengthening contractions) offers an effective exercise for restoring lower-body muscular function, maintaining health, and improving performance in clinical and athletic populations.

PURPOSE

We extended this model to the upper body and evaluated the effectiveness of a 7-week eccentric arm cycling (ECC_arm) intervention to improve upper-body muscular function. We also explored whether ECC_arm would alter arterial function.

METHODS

Participants performed ECC_arm (n = 9) or concentric arm cycling (CON_arm; n = 8) 3×/week while training intensity increased (5-20 min, 60-70% upper-body peak heart rate). Maximum elbow extensor strength, upper-body concentric power, and peripheral and central arterial stiffness were assessed before and after training.

RESULTS

During training, heart rates and perceived exertion did not differ between groups (~68% upper-body peak heart rate, ~12 Borg units, both P > 0.05), whereas power during ECC_arm was ~2× that for CON_arm (122 ± 43 vs. 59 ± 20 W, P < 0.01). Muscle soreness for ECC_arm was greater than CON_arm (P = 0.02), however, soreness was minimal for both groups (<0.50 cm). Following training, ECC_arm exhibited greater changes in elbow extensor strength (16 ± 10 vs. 1 ± 9%, P = 0.01) and upper-body power (6 ± 8 vs. -3 ± 7%, P < 0.01) compared to CON_arm. Peripheral and central arterial stiffness did not change for either group (both P > 0.05).

CONCLUSION

Upper-body eccentric exercise improved dynamic muscular function while training at low exertion levels. Results occurred with minimal soreness and without compromising arterial function. ECC_arm findings parallel eccentric leg cycling findings and indicate that eccentric cycle ergometry offers a robust model for enhancing upper-body muscular function. ECC_arm could have applications in rehabilitation and sport training.

Superior Effects of Eccentric to Concentric Knee Extensor Resistance Training on Physical Fitness, Insulin Sensitivity and Lipid Profiles of Elderly Men

It has been reported that eccentric training of knee extensors is effective for improving blood insulin sensitivity and lipid profiles to a greater extent than concentric training in young women. However, it is not known whether this is also the case for elderly individuals. Thus, the present study tested the hypothesis that eccentric training of the knee extensors would improve physical function and health parameters (e.g., blood lipid profiles) of older adults better than concentric training. Healthy elderly men (60–76 years) were assigned to either eccentric training or concentric training group (n = 13/group), and performed 30–60 eccentric or concentric contractions of knee extensors once a week. The intensity was progressively increased over 12 weeks from 10 to 100% of maximal concentric strength for eccentric training and from 50 to 100% for concentric training. Outcome measures were taken before and 4 days after the training period. The results showed that no sings of muscle damage were observed after any sessions. Functional physical fitness (e.g., 30-s chair stand) and maximal concentric contraction strength of the knee extensors increased greater (P ≤ 0.05) after eccentric training than concentric training. Homeostasis model assessment, oral glucose tolerance test and whole blood glycosylated hemoglobin showed improvement of insulin sensitivity only after eccentric training (P ≤ 0.05). Greater (P ≤ 0.05) decreases in fasting triacylglycerols, total, and low-density lipoprotein cholesterols were evident after eccentric training than concentric training, and high-density lipoprotein cholesterols increased only after eccentric training. These results support the hypothesis and suggest that it is better to focus on eccentric contractions in exercise medicine.

Eccentric Ergometer Training Promotes Locomotor Muscle Strength but Not Mitochondrial Adaptation in Patients with Severe Chronic Obstructive Pulmonary Disease

Eccentric ergometer training (EET) is increasingly being proposed as a therapeutic strategy to improve skeletal muscle strength in various cardiorespiratory diseases, due to the principle that lengthening muscle actions lead to high force-generating capacity at low cardiopulmonary load. One clinical population that may particularly benefit from this strategy is chronic obstructive pulmonary disease (COPD), as ventilatory constraints and locomotor muscle dysfunction often limit efficacy of conventional exercise rehabilitation in patients with severe disease. While the feasibility of EET for COPD has been established, the nature and extent of adaptation within COPD muscle is unknown. The aim of this study was therefore to characterize the locomotor muscle adaptations to EET in patients with severe COPD, and compare them with adaptations gained through conventional concentric ergometer training (CET). Male patients were randomized to either EET (n = 8) or CET (n = 7) for 10 weeks and matched for heart rate intensity. EET patients trained on average at a workload that was three times that of CET, at a lower perception of leg fatigue and dyspnea. EET led to increases in isometric peak strength and relative thigh mass (p < 0.01) whereas CET had no such effect. However, EET did not result in fiber hypertrophy, as morphometric analysis of muscle biopsies showed no increase in mean fiber cross-sectional area (p = 0.82), with variability in the direction and magnitude of fiber-type responses (20% increase in Type 1, p = 0.18; 4% decrease in Type 2a, p = 0.37) compared to CET (26% increase in Type 1, p = 0.04; 15% increase in Type 2a, p = 0.09). EET had no impact on mitochondrial adaptation, as revealed by lack of change in markers of mitochondrial biogenesis, content and respiration, which contrasted to improvements (p < 0.05) within CET muscle. While future study is needed to more definitively determine the effects of EET on fiber hypertrophy and associated underlying molecular signaling pathways in COPD locomotor muscle, our findings promote the implementation of this strategy to improve muscle strength. Furthermore, contrasting mitochondrial adaptations suggest evaluation of a sequential paradigm of eccentric followed by concentric cycling as a means of augmenting the training response and attenuating skeletal muscle dysfunction in patients with advanced COPD.

Moderate Load Eccentric Exercise; A Distinct Novel Training Modality

Over the last 20 years a number of studies have been published using progressive eccentric exercise protocols on motorized ergometers or similar devices that allow for controlled application of eccentric loads. Exercise protocols ramp eccentric loads over an initial 3 weeks period in order to prevent muscle damage and delayed onset muscle soreness. Final training loads reach 400-500 W in rehabilitative settings and over 1200 W in elite athletes. Training is typically carried out three times per week for durations of 20-30 min. This type of training has been characterizes as moderate load eccentric exercise. It has also been denoted RENEW (Resistance Exercise via Negative Eccentric Work by LaStayo et al., 2014). It is distinct from plyometric exercises (i.e., drop jumps) that impose muscle loads of several thousand Watts on muscles and tendons. It is also distinct from eccentric overload training whereby loads in a conventional strength training setting are increased in the eccentric phase of the movement to match concentric loads. Moderate load eccentric exercise (or RENEW) has been shown to be similarly effective as conventional strength training in increasing muscle strength and muscle volume. However, as carried out at higher angular velocities of joint movement, it reduces joint loads. A hallmark of moderate load eccentric exercise is the fact that the energy requirements are typically 4-fold smaller than in concentric exercise of the same load. This makes moderate load eccentric exercise training the tool of choice in medical conditions with limitations in muscle energy supply. The use and effectiveness of moderate load eccentric exercise has been demonstrated mostly in small scale studies for cardiorespiratory conditions, sarcopenia of old age, cancer, diabetes type 2, and neurological conditions. It has also been used effectively in the prevention and rehabilitation of injuries of the locomotor system in particular the rehabilitation after anterior cruciate ligament surgery.

Effects of aerobic exercise on functional capacity, anthropometric measurements and inflammatory markers in diabetic elderly women

This study investigated the effects of an aerobic training program on functional capacity [Timed Up and Go test (TUG), timed 10-m walk test (10MWT), five-repetition sit-to-stand test (5-STS), handgrip strength test (HGS) and one-legged stance test (OLS)], anthropometric measurements [body mass, body mass index (BMI), waist and hip circumferences and waist-to-hip ratio] and plasma levels of inflammatory markers [soluble tumor necrosis factor receptors 1 and 2, and interleukins 6 and 10] in 43 elderly women with type 2 diabetes mellitus. After the training, a significant improvement was observed in the performance of the participants on the TUG, 10MWT, 5-STS and HGS and in the anthropometric measures of body mass, BMI and hip circumference. None of the inflammatory markers showed a significant difference between pre- and post-training. The aerobic exercise program improved the functional capacity of diabetic elderly women, but was ineffective to change the levels of the inflammatory markers evaluated.

Muscle wasting and aging: Experimental models, fatty infiltrations, and prevention

Identification of cost-effective interventions to maintain muscle mass, muscle strength, and physical performance during muscle wasting and aging is an important public health challenge. It requires understanding of the cellular and molecular mechanisms involved. Muscle-deconditioning processes have been deciphered by means of several experimental models, bringing together the opportunities to devise comprehensive analysis of muscle wasting. Studies have increasingly recognized the importance of fatty infiltrations or intermuscular adipose tissue for the age-mediated loss of skeletal-muscle function and emphasized that this new important factor is closely linked to inactivity. The present review aims to address three main points. We first mainly focus on available experimental models involving cell, animal, or human experiments on muscle wasting. We next point out the role of intermuscular adipose tissue in muscle wasting and aging and try to highlight new findings concerning aging and muscle-resident mesenchymal stem cells called fibro/adipogenic progenitors by linking some cellular players implicated in both FAP fate modulation and advancing age. In the last part, we review the main data on the efficiency and molecular and cellular mechanisms by which exercise, replacement hormone therapies, and β-hydroxy-β-methylbutyrate prevent muscle wasting and sarcopenia. Finally, we will discuss a potential therapeutic target of sarcopenia: glucose 6-phosphate dehydrogenase.

Psoas Muscle Cross-sectional Area as a Measure of Whole-body Lean Muscle Mass in Maintenance Hemodialysis Patients

OBJECTIVE

We investigate whether psoas or paraspinous muscle area measured on a single L4-L5 image is a useful measure of whole lean body mass (LBM) compared to dedicated midthigh magnetic resonance imaging (MRI).

DESIGN

Observational study.

SETTING

Outpatient dialysis units and a research clinic.

SUBJECTS

One hundred five adult participants on maintenance hemodialysis. No control group was used.

INTERVENTION

Psoas muscle area, paraspinous muscle area, and midthigh muscle area (MTMA) were measured by magnetic resonance imaging.

MAIN OUTCOME MEASURE

LBM was measured by dual-energy absorptiometry scan.

RESULTS

In separate multivariable linear regression models, psoas, paraspinous, and MTMA were associated with increase in LBM. In separate multivariate logistic regression models, C statistics for diagnosis of sarcopenia (defined as <25th percentile of LBM) were 0.69 for paraspinous muscle area, 0.81 for psoas muscle area, and 0.89 for MTMA. With sarcopenia defined as <10th percentile of LBM, the corresponding C statistics were 0.71, 0.92, and 0.94.

CONCLUSIONS

We conclude that psoas muscle area provides a good measure of whole-body muscle mass, better than paraspinous muscle area but slightly inferior to midthigh measurement. Hence, in body composition studies a single axial MR image at the L4-L5 level can be used to provide information on both fat and muscle and may eliminate the need for time-consuming measurement of muscle area in the thigh.

High Intensity Interval Training Improves Glycaemic Control and Pancreatic β Cell Function of Type 2 Diabetes Patients

Physical activity improves the regulation of glucose homeostasis in both type 2 diabetes (T2D) patients and healthy individuals, but the effect on pancreatic β cell function is unknown. We investigated glycaemic control, pancreatic function and total fat mass before and after 8 weeks of low volume high intensity interval training (HIIT) on cycle ergometer in T2D patients and matched healthy control individuals. Study design/method: Elderly (56 yrs±2), non-active T2D patients (n = 10) and matched (52 yrs±2) healthy controls (CON) (n = 13) exercised 3 times (10×60 sec. HIIT) a week over an 8 week period on a cycle ergometer. Participants underwent a 2-hour oral glucose tolerance test (OGTT). On a separate day, resting blood pressure measurement was conducted followed by an incremental maximal oxygen uptake (V˙O_2max) cycle ergometer test. Finally, a whole body dual X-ray absorptiometry (DXA) was performed. After 8 weeks of training, the same measurements were performed. Results: in the T2D-group, glycaemic control as determined by average fasting venous glucose concentration (p = 0.01), end point 2-hour OGTT (p = 0.04) and glycosylated haemoglobin (p = 0.04) were significantly reduced. Pancreatic homeostasis as determined by homeostatic model assessment of insulin resistance (HOMA-IR) and HOMA β cell function (HOMA-%β) were both significantly ameliorated (p = 0.03 and p = 0.03, respectively). Whole body insulin sensitivity as determined by the disposition index (DI) was significantly increased (p = 0.03). During OGTT, the glucose continuum was significantly reduced at -15 (p = 0.03), 30 (p = 0.03) and 120 min (p = 0.03) and at -10 (p = 0.003) and 0 min (p = 0.003) with an additional improvement (p = 0.03) of its 1^st phase (30 min) area under curve (AUC). Significant abdominal fat mass losses were seen in both groups (T2D: p = 0.004 and CON: p = 0.02) corresponding to a percentage change of -17.84%±5.02 and -9.66%±3.07, respectively. Conclusion: these results demonstrate that HIIT improves overall glycaemic control and pancreatic β cell function in T2D patients. Additionally, both groups experienced abdominal fat mass losses. These findings demonstrate that HIIT is a health beneficial exercise strategy in T2D patients.

Exercise guidelines for gestational diabetes mellitus

The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide. This disease has many detrimental consequences for the woman, the unborn foetus and child. The management of GDM aims to mediate the effects of hyperglycaemia by controlling blood glucose levels. Along with pharmacology and dietary interventions, exercise has a powerful potential to assist with blood glucose control. Due to the uncertainty of risks and benefits of exercise during pregnancy, women tend to avoid exercise. However, under adequate supervision exercise is both safe and beneficial in the treatment of GDM. Therefore it is vital that exercise is incorporated into the continuum of care for women with GDM. Medical doctors should be able to refer to competently informed exercise professionals to aid in GDM treatment. It is important that exercise treatment is informed by research. Hence, the development of evidence-based guidelines is important to inform practice. Currently there are no guidelines for exercise in GDM. This review aims to assess the efficacy of exercise for the management of GDM in order to establish an exercise prescription guideline specific to the condition. It is recommended that women with GDM should do both aerobic and resistance exercise at a moderate intensity, a minimum of three times a week for 30-60 min each time.

Effects of passive static stretching on blood glucose levels in patients with type 2 diabetes mellitus

[Purpose] This study determined the effects of passive static stretching on blood glucose levels in patients with type 2 diabetes. [Subjects] Fifteen patients (8 males and 7 females) with type 2 diabetes were recruited and randomly assigned to the control group or passive static stretching group. [Methods] Glycated hemoglobin was measured before and after the 8-week training period. [Results] Glycated hemoglobin levels decreased significantly in the passive static stretching group, and there were significant differences in blood glucose levels between the 2 groups. [Conclusion] Passive static stretching of the skeletal muscles may be an alternative to exercise to help regulate blood glucose levels in diabetes patients.

Hip but not thigh intramuscular adipose tissue is associated with poor balance and increased temporal gait variability in older adults

BACKGROUND

Intramuscular adipose tissue (IMAT) of the lower extremity is a strong negative predictor of mobility function. Variability in temporal gait factors is another important predictor of mobility function. The purpose of this study was to examine the relationships between IMAT in the hip and thigh muscles, balance, and temporal gait variability in older adults.

METHODS

Forty-eight healthy community dwelling older adults (74 +/- 1 year) underwent a CT scan to quantify IMAT in the gluteus maximus (Gmax), gluteus medius/minimus (Gmed/min), hamstrings, vastus lateralis, and adductor muscles. Temporal Gait measures were collected on a GAITRite walkway and gait variability was determined by calculating intraindividual standard deviations. Individuals were divided by tertiles of temporal gait variability into categories of high, medium, and low variability. Differences in the IMAT of the hip abductors were calculated for those with high and low gait variability and partial correlations for gait variability and all muscle composition measures were determined for all variables with normalized gait speed as a covariate.

RESULTS

Gmed/min IMAT was greater in those with higher gait variability compared to those with lower gait variability (p<0.05). Gmed/min IMAT was related to stride width variability (r=0.30, p<0.05). Gmax IMAT was also related to time variability of swing (r=0.42), stance (r=0.26), double limb support (r=0.43), double support loading (r=0.44), and double support unloading (r=0.50) (all p<0.05).

CONCLUSION

Increased IMAT in the proximal hip muscles, particularly the hip abductors, was associated with increased gait variability and poorer balance. These findings may have implications for the assessment and treatment of balance and falls such that interventions for enhancing balance and mobility among older individuals should take into account the importance of gluteal muscle composition.

Adipose tissue content, muscle performance and physical function in obese adults with type 2 diabetes mellitus and peripheral neuropathy

AIMS

To determine leg intermuscular (IMAT) and subcutaneous (SQAT) adipose tissue and their relationships with muscle performance and function in obese adults with and without type 2 diabetes and peripheral neuropathy (T2DMPN).

METHODS

Seventy-nine age-matched obese adults were studied, 13 T2DM, 54 T2DMPN, and 24 obese controls. Leg fat (%IMAT, %SQAT) volumes were quantified using MRI. Ankle plantar flexion (PF) torque and power were assessed with isokinetic dynamometry. Physical function was assessed with 9-item Physical Performance Test (PPT), 6-minute walk distance, single-limb balance, and time to ascend 10 stairs. One-way ANOVAs determined group differences, and multiple regression predicted PPT score from disease status, % IMAT, and PF power.

RESULTS

T2DMPN participants had 37% greater IMAT volumes and 15% lower SQAT volumes than controls (p =. 01). T2DMPN and T2DM showed reduced PF torque and power compared to controls. T2DMPN participants had lower PPT score, 6-minute walk, single-limb balance, and stair climbing than controls (all p<.05). %IMAT volume correlated inversely, and %SQAT correlated directly, with PPT. Leg %IMAT and disease status predicted 49% of PPT score.

CONCLUSIONS

T2DMPN may represent a shift in adipose tissue accumulation from SQAT to IMAT depots, which is inversely associated with muscle performance and physical function.

The Relationship between Intramuscular Adipose Tissue, Functional Mobility, and Strength in Postmenopausal Women with and without Type 2 Diabetes

Objectives. To determine (1) whether intramuscular adipose tissue (IntraMAT) differs between women with and without type 2 diabetes and (2) the association between IntraMAT and mobility and strength. Methods. 59 women ≥ 65 years with and without type 2 diabetes were included. A 1-Tesla MRI was used to acquire images of the leg. Timed-up-and-go (TUG) and grip strength were measured. Regression was used to determine associations between the following: (1) type 2 diabetes and IntraMAT (covariates: age, ethnicity, BMI, waist : hip ratio, and energy expenditure), (2) IntraMAT and TUG (covariates: diabetes, age, BMI, and energy expenditure), and (3) IntraMAT and grip strength (covariates: diabetes, age, height, and lean mass). Results. Women with diabetes had more IntraMAT. After adjustment, IntraMAT was similar between groups (diabetes mean [SD] = 13.2 [1.4]%, controls 11.8 [1.3]%, P = 0.515). IntraMAT was related to TUG and grip strength, but the relationships became nonsignificant after adjustment for covariates (difference/percent IntraMAT [95% CI]: TUG = 0.041 seconds [-0.079-0.161], P = 0.498, grip strength = -0.144 kg [-0.335-0.066], P = 0.175). Conclusions. IntraMAT alone may not be a clinically important predictor of functional mobility and strength; however, whether losses in functional mobility and strength are promoted by IntraMAT accumulation should be explored.

Contraction induced muscle injury: towards personalized training and recovery programs

Skeletal muscles can be injured by their own contractions. Such contraction-induced injury, often accompanied by delayed onset of muscle soreness, is a leading cause of the loss of mobility in the rapidly increasing population of elderly people. Unlike other types of muscle injuries which hurt almost exclusively those who are subjected to intensive exercise such as professional athletes and soldiers in training, contraction induced injury is a phenomenon which may be experienced by people of all ages while performing a variety of daily-life activities. Subjects that experience contraction induced injury report on soreness that usually increases in intensity in the first 24 h after the activity, peaks from 24 to 72 h, and then subsides and disappears in a few days. Despite their clinical importance and wide influence, there are almost no studies, clinical, experimental or computational, that quantitatively relate between the extent of contraction induced injury and activity factors, such as number of repetitions, their frequency and magnitude. The lack of such quantitative information is even more emphasized by the fact that contraction induced injury can be used, if moderate and controlled, to improve muscle performance in the long term. Thus, if properly understood and carefully implemented, contraction induced injury can be used for the purpose of personalized training and recovery programs. In this paper, we review experimental, clinical, and theoretical works, attempting towards drawing a more quantitative description of contraction induced injury and related phenomena.

Impact of different training modalities on glycaemic control and blood lipids in patients with type 2 diabetes: a systematic review and network meta-analysis

AIMS/HYPOTHESIS

This study aimed to systematically review randomised controlled trials comparing the effects of aerobic exercise training (AET), resistance training (RT) and combined training (CT) on glycaemic control and blood lipids in patients with type 2 diabetes mellitus.

METHODS

Searches were performed in MEDLINE, EMBASE and the Cochrane Library. Inclusion criteria were: type 2 diabetes mellitus, adult, supervised training and a minimum intervention period of 8 weeks. Pooled effects were calculated by fixed/random effect pairwise and Bayesian fixed/random effects network meta-analyses.

RESULTS

A total of 14 trials enrolling 915 participants were included. AET was more effective than RT in improving HbA1c levels (mean difference [MD] -0.20% [-2.2 mmol/mol]; 95% CI -0.32, -0.08; p = 0.0007, 10 trials/515 participants) and fasting glucose (MD -0.9 mmol/l; 95% CI -1.71, -0.09; p = 0.03, 8 trials/245 participants). Compared with AET, CT resulted in a significantly more pronounced reduction in HbA1c (MD -0.17% [-1.87 mmol/mol]; 95% CI -0.31, -0.03; p = 0.02, 9 trials/493 participants). Compared with RT, the MD of the change in HbA1c (MD -0.62%, [-6.82 mmol/mol]; 95% CI -0.95, -0.30; p = 0.0002, 5 trials/362 participants], fasting glucose (MD -1.99 mmol/l; 95% CI -3.07, -0.90; p = 0.0003, 3 trials/99 participants) and triacylglycerols (MD -0.28 mmol/l; 95% CI -0.46, -0.10; p = 0.003, 4 trials/213 participants) were all in favour of CT. The exclusion of trials with a high risk of bias yielded only non-significant results.

CONCLUSIONS/INTERPRETATION

The present data suggest that CT might be the most efficacious exercise modality to improve glycaemic control and blood lipids. Interpretation with respect to clinical relevance is limited by the low quality of the studies included and the limited information on the clinically important outcomes or adverse effects of exercise.

Intermuscular fat: a review of the consequences and causes

Muscle's structural composition is an important factor underlying muscle strength and physical function in older adults. There is an increasing amount of research to support the clear disassociation between the loss of muscle lean tissue mass and strength with aging. This disassociation implies that factors in addition to lean muscle mass are responsible for the decreases in strength and function seen with aging. Intermuscular adipose tissue (IMAT) is a significant predictor of both muscle function and mobility function in older adults and across a wide variety of comorbid conditions such as stroke, spinal cord injury, diabetes, and COPD. IMAT is also implicated in metabolic dysfunction such as insulin resistance. The purpose of this narrative review is to provide a review of the implications of increased IMAT levels in metabolic, muscle, and mobility function. Potential treatment options to mitigate increasing levels of IMAT will also be discussed.

Eccentric exercise in rehabilitation: safety, feasibility, and application

This nonexhaustive mini-review reports on the application of eccentric exercise in various rehabilitation populations. The two defining properties of eccentric muscle contractions--a potential for high muscle-force production at an energy cost that is uniquely low--are revisited and formatted as exercise countermeasures to muscle atrophy, weakness, and deficits in physical function. Following a dual-phase implementation, eccentric exercise that induces rehabilitation benefits without muscle damage, thereby making it both safe and feasible in rehabilitation, is described. Clinical considerations, algorithms of exercise progression, and suggested modes of eccentric exercise are presented.

Intramuscular adipose tissue attenuates gains in muscle quality in older adults at high risk for falling. A brief report

OBJECTIVES

To examine the influence of intramuscular adipose tissue (IMAT) on muscle quality (MQ) changes in older adults after 12 weeks of exercise training.

DESIGN

Prospective cohort design.

SETTING

Academic health science center clinical exercise facility.

PARTICIPANTS

70 older (mean age 73.4 ± 6.3 years) adults with a history of falls.

INTERVENTION

Resistance, endurance and balance exercise three times weekly for 12 weeks.

MEASUREMENTS

Quadriceps strength was determined by maximum voluntary isometric contraction. An MRI of the thigh was used to determine cross-sectional area of lean tissue and IMAT. MQ was calculated as the force per unit area of lean tissue. Individuals were stratified into tertiles (Low IMAT, Middle IMAT, High IMAT) based on pre-IMAT levels. Changes in MQ, lean and IMAT were compared across groups.

RESULTS

No significant changes in lean or IMAT occurred in any group with training. MQ increased only in the Low IMAT group. The Middle and High IMAT groups did not demonstrate a significant change in MQ following 12 weeks of training. Low IMAT, pre = 2.7 [0.6] post= 3.0 [0.6]; Middle IMAT, pre =2.54 [0.8] post =2.75 [0.7]; High IMAT, pre =2.6 [0.6] to post =2.5 [0.6].

CONCLUSION

High levels of thigh IMAT appear to blunt the adaptive MQ response to training. High levels of thigh IMAT may be a potential reason why some older adults do not change their MQ following training. Future research should confirm these results and determine why IMAT impairs MQ and the adaptive response to training in older adults.

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.