Mild aerobic training with blood flow restriction increases the hypertrophy index and MuSK in both slow and fast muscles of old rats: Role of PGC-1α

Blood Flow Restriction Enhances Recovery After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

PURPOSE

To conduct a systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating neuromuscular and clinical outcomes of blood flow restriction (BFR) training after anterior cruciate ligament reconstruction (ACLR) compared to non-BFR rehabilitation protocols.

METHODS

A systematic review was performed in accordance with the 2020 Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines by querying PubMed, MEDLINE, Scopus, the Cochrane Database for Systematic Review, and the Cochrane Central Register for Controlled Trials databases from inception through December 2023 to identify Level I-II RCTs evaluating outcomes of BFR training after ACLR compared to non-BFR rehabilitation. A meta-analysis was performed using random-effects models with standardized mean difference (SMD) for pain, muscle strength, and muscle volume, while mean difference (MD) was calculated for patient-reported outcome measures.

RESULTS

Eight RCTs, consisting of 245 patients, met inclusion criteria, with 115 patients undergoing non-BFR rehabilitation versus 130 patients undergoing BFR after ACLR. Mean patient age was 27.2 ± 6.7 years, with the majority of patients being male (63.3%, n=138/218). The length of the BFR rehabilitation protocol was most commonly between 8-12 weeks (range, 14 days - 16 weeks). The majority of studies set the limb/arterial occlusion pressure in the BFR group at 80%. When compared to non-BFR rehabilitation, BFR resulted in significant improvement in isokinetic muscle strength (SMD: 0.77, p=0.02, I2: 58%), IKDC score (MD: 10.97, p=<.00001, I2: 77%), and pain (SMD: 1.52, p=.04, I2: 87%), but not quadriceps muscle volume (SMD: 0.28, p=0.43, I2: 76%).

CONCLUSION

The use of BFR following ACLR led to improvements in pain, IKDC score and isokinetic muscle strength, with variable outcomes based on quadriceps strength, volume and thickness when compared to non-BFR rehabilitation.

Long-term high loading intensity of aerobic exercise improves skeletal muscle performance via the gut microbiota-testosterone axis

Exercise is reported to play a crucial role in skeletal muscle performance. However, the underlying mechanism is still unknown. Thus, we investigated the effect of high-intensity aerobic exercise on skeletal muscle performance. In this study, the male C57BL/6J mice were accepted by high-intensity aerobic exercise for 8 weeks to establish an exercise model. It was observed that high-intensity aerobic exercise markedly affected the expression of genes in skeletal muscle. Moreover, high-intensity aerobic exercise significantly improved skeletal muscle grip strength and serum testosterone levels. HE staining showed that the cross-sectional area (CSA) of the skeletal muscle was successfully increased after 8 weeks of high-intensity aerobic exercise. Additionally, we found that high-intensity aerobic exercise changed gut microbiota structure by altering the abundance of Akkermansia, Allobaculum, and Lactobacillus, which might be related to testosterone production. However, the beneficial effects disappeared after the elimination of the gut microbiota and recovered after fecal microbiota transplantation (FMT) experiments for 1 week. These results indicated that the beneficial effects of high-intensity aerobic exercise on skeletal muscle were partly dependent on the gut microbiota. Our results suggested that long-term high loading intensity of aerobic exercise could improve skeletal muscle performance, which was probably due to the gut microbiota-testosterone axis.

A Preclinical Systematic Review of the Effects of Chronic Exercise on Autophagy-Related Proteins in Aging Skeletal Muscle

Background: Exercise is one of the most effective interventions for preventing and treating skeletal muscle aging. Exercise-induced autophagy is widely acknowledged to regulate skeletal muscle mass and delay skeletal muscle aging. However, the mechanisms underlying of the effect of different exercises on autophagy in aging skeletal muscle remain unclear.

Methods: A systematic review was performed following an electronic search of SCOPUS, PubMed, Web of Science, ScienceDirect, and Google Scholar and two Chinese electronic databases, CNKI and Wan Fang. All articles published in English and Chinese between January 2010 and January 2022 that quantified autophagy-related proteins in aging skeletal muscle models.

Results: The primary outcome was autophagy assessment, indicated by changes in the levels of any autophagy-associated proteins. A total of fifteen studies were included in the final review. Chronic exercise modes mainly comprise aerobic exercise and resistance exercise, and the intervention types include treadmill training, voluntary wheel running, and ladder training. LC3, Atg5-Atg7/9/12, mTOR, Beclin1, Bcl-2, p62, PGC-1α, and other protein levels were quantified, and the results showed that long-term aerobic exercise and resistance exercise could increase the expression of autophagy-related proteins in aging skeletal muscle (p < 0.05). However, there was no significant difference in short term or high-intensity chronic exercise, and different types and intensities of exercise yielded different levels of significance for autophagy-related protein expression.

Conclusion: Existing evidence reveals that high-intensity exercise may induce excessive autophagy, while low-intensity exercise for a short period (Intervention duration <12 weeks, frequency <3 times/week) may not reach the threshold for exercise-induced autophagy. Precise control of the exercise dose is essential in the long term to maximize the benefits of exercise. Further investigation is warranted to explore the relationship between chronic exercise and different exercise duration and types to substantiate the delaying of skeletal muscle aging by exercise.

Regulation of mitochondrial dynamic equilibrium by physical exercise in sarcopenia: A systematic review

Background

Sarcopenia is a hallmark of the ageing process, which is characterized by the decline in muscle mass and strength. Growing evidence indicates that mitochondria dysfunction play core roles in this process. Meanwhile, physical exercise is regarded as one of the efficiency therapies to attenuate sarcopenia via regulating mitochondrial function during ageing. However, the specific mechanisms among exercise, mitochondrial function and sarcopenia are still unclear. The aim of this systematic review is to delineate the effects of physical exercise on mitochondria during ageing in order to explore potential target for rescuing sarcopenia.

Methods

A systematic literature search was performed in PubMed, Embase and Web of Science. Information was extracted from the included studies for review.

Results

In this review, 16 pre-clinical studies were included and 105 clinical studies that were not mechanistic research were excluded. 16 pre-clinical studies provided evidence that physical exercise could affect mitochondrial quality control to attenuate sarcopenia. Most of the included studies described the important role of mitochondrial dynamic equilibrium in sarcopenia and showed that effective physical exercise could influence mitochondrial biogenesis, fusion, fission and mitophagy to attenuate sarcopenia in aged animal.

Conclusions

This systematic review provides an up-to-date sequential overview and highlights the link in the potential mitochondria-related target and physical exercise in aged animal.

Translation of this article

Currently, there is no standard treatment method for sarcopenia. This systematic review revealed the underlying mechanisms for how physical exercise improved muscle performance via regulating mitochondrial dynamic equilibrium, which could provide scientific support for using exercise as a timely intervention for sarcopenia. Additionally, this systematic review allows a better understanding of mitochondrial dynamic equilibrium and exercise for future development of new therapeutic interventions to attenuate sarcopenia.

Protein signaling in response to ex vivo dynamic contractions is independent of training status in rat skeletal muscle

New Findings

What is the central question of this study?

Are myofibre protein signalling responses to ex vivo dynamic contractions altered by accustomization to voluntary endurance training in rats?

What is the main finding and its importance?

In response to ex vivo dynamic muscle contractions, canonical myofibre protein signalling pertaining to metabolic transcriptional regulation, as well as translation initiation and elongation, was not influenced by prior accustomization to voluntary endurance training in rats. Accordingly, intrinsic myofibre protein signalling responses to standardized contractile activity may be independent of prior exercise training in rat skeletal muscle.

Abstract

Skeletal muscle training status may influence myofibre regulatory protein signalling in response to contractile activity. The current study employed a purpose‐designed ex vivo dynamic contractile protocol to evaluate the effect of exercise‐accustomization on canonical myofibre protein signalling for metabolic gene expression and for translation initiation and elongation. To this end, rats completed 8 weeks of in vivo voluntary running training versus no running control intervention, whereupon an ex vivo endurance‐type dynamic contraction stimulus was conducted in isolated soleus muscle preparations from both intervention groups. Protein signalling response by phosphorylation was evaluated by immunoblotting at 0 and 3 h following ex vivo stimulation. Phosphorylation of AMP‐activated protein kinase α‐isoforms and its downstream target, acetyl‐CoA carboxylase, as well as phosphorylation of eukaryotic elongation factor 2 (eEF2) was increased immediately following the dynamic contraction protocol (at 0 h). Signalling for translation initiation and elongation was evident at 3 h after dynamic contractile activity, as evidenced by increased phosphorylation of p70 S6 kinase and eukaryotic translation initiation factor 4E‐binding protein 1, as well as a decrease in phosphorylation of eEF2 back to resting control levels. However, prior exercise training did not alter phosphorylation responses of the investigated signalling proteins. Accordingly, protein signalling responses to standardized endurance‐type contractions may be independent of training status in rat muscle during ex vivo conditions. The present findings add to our current understanding of molecular regulatory events responsible for skeletal muscle plasticity.

Blood Flow Restriction Training for the Intervention of Sarcopenia: Current Stage and Future Perspective

Sarcopenia is a geriatric syndrome that is characterized by a progressive and generalized skeletal muscle disorder and can be associated with many comorbidities, including obesity, diabetes, and fracture. Its definitions, given by the AWGS and EWGSOP, are widely used. Sarcopenia is measured by muscle strength, muscle quantity or mass and physical performance. Currently, the importance and urgency of sarcopenia have grown. The application of blood flow restriction (BFR) training has received increased attention in managing sarcopenia. BFR is accomplished using a pneumatic cuff on the proximal aspect of the exercising limb. Two main methods of exercise, aerobic exercise and resistance exercise, have been applied with BFR in treating sarcopenia. Both methods can increase muscle mass and muscle strength to a certain extent. Intricate mechanisms are involved during BFRT. Currently, the presented mechanisms mainly include responses in the blood vessels and related hormones, such as growth factors, tissue hypoxia-related factors and recruitment of muscle fiber as well as muscle satellite cells. These mechanisms contribute to the positive balance of skeletal muscle synthesis, which in turn mitigates sarcopenia. As a more suited and more effective way of treating sarcopenia and its comorbidities, BFRT can serve as an alternative to traditional exercise for people who have marked physical limitations or even show superior outcomes under low loads. However, the possibility of causing stress or muscle damage must be considered. Cuff size, pressure, training load and other variables can affect the outcome of sarcopenia, which must also be considered. Thoroughly studying these factors can help to better determine an ideal BFRT scheme and better manage sarcopenia and its associated comorbidities. As a well-tolerated and novel form of exercise, BFRT offers more potential in treating sarcopenia and involves deeper insights into the function and regulation of skeletal muscle.

The Effect of Blood Flow Restriction Exercise on Angiogenesis-Related Factors in Skeletal Muscle Among Healthy Adults: A Systematic Review and Meta-Analysis

Background

Blood flow restriction (BFR) exercise may be a potential exercise program to promote angiogenesis. This review aims to compare the effects of exercise with and without BFR on angiogenesis-related factors in skeletal muscle among healthy adults.

Methodology

Searches were made in Web of Science, Scopus, PubMed, and EBSCO databases from January 2001 to June 2021. Studies were screened, quality was evaluated, and data were extracted. The review protocol was registered at PROSPERO (PROSPERO registration number: CRD42021261367). Standardized mean differences (SMD) of vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR-2), hypoxia inducible factor 1α (HIF-1α), peroxisome proliferator-activated receptorγcoactivator-1α (PGC-1α) and endothelial nitric oxide synthase (eNOS) were analyzed using Revman 5.4 software with a 95% confidence interval (95% CI).

Results

Ten studies fulfilled the inclusion criteria with a total of 75 participants for BFR group and 77 for CON group. BFR exercise elicits greater expression of VEGF (heterogeneity test, P = 0.09, I2 = 44%; SMD, 0.93 [0.38, 1.48], P &lt; 0.05), VEGFR-2 (heterogeneity test, P = 0.81, I2 = 0%; SMD, 0.64 [0.08, 1.21], P &lt; 0.05), HIF-1α (heterogeneity test, P = 0.67, I2 = 0%; SMD, 0.43 [0.03, 0.82], P &lt; 0.05), PGC-1α (heterogeneity test, P = 0.02, I2 = 54%; SMD, 0.74 [0.21, 1.28], P &lt; 0.05) and eNOS (heterogeneity test, P = 0.88, I2 = 0%; SMD, 0.60 [0.04, 1.17], P &lt; 0.05) mRNA than non-BFR exercise. In the sub-group analysis, resistance exercise with BFR elicits greater expression of VEGF (heterogeneity test, P = 0.36, I2 = 6%; SMD, 1.66 [0.97, 2.35], P &lt; 0.05) and HIF-1α (heterogeneity test, P = 0.56, I2 = 0%; SMD, 0.51 [0.01, 1.02], P &lt; 0.05) mRNA than aerobic exercise with BFR.

Conclusion

Exercise with BFR elicited more angiogenesis-related factors mRNA expression than exercise without BFR, but not VEGF and PGC-1α protein expression. Therefore, BFR training may be a potential training program to improve vascular function.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42021261367].

Efficacy of low-load resistance training combined with blood flow restriction vs. high-load resistance training on sarcopenia among community-dwelling older Chinese people: study protocol for a 3-arm randomized controlled trial

BACKGROUND

Sarcopenia is accompanied by a decline in muscle mass, muscle strength, and muscle function. Resistance training is the most potential training method for the prevention and treatment of sarcopenia. However, the conventional high-load resistance training (CRT) recommended by the American College of Sports Medicine is a challenge for older people with sarcopenia. As a novel training method, low-load resistance training combined with blood flow restriction (LRT-BFR) may elicit similar muscle mass and muscle strength gains as CRT but with less effort. The objectives of this study are to assess and compare the efficacy and safety of 12-week LRT-BFR and CRT on muscle strength, muscle performance, body composition, pulmonary function, blood biomarkers, CVD risk factors, and quality of life in community-dwelling older Chinese people with sarcopenia.

METHOD

This is a 12-week, assessor-blinded, 3-arm randomized controlled trial with a non-exercise control group. Community-dwelling people over 65 years will be screened for sarcopenia according to the diagnostic criteria of the Asian Working Group for Sarcopenia (AWGS). Fifty-one subjects will be randomized into a LRT-BFR group (n = 17), a CRT group (n = 17), and a no-strength training control group (n = 17). The primary outcome is lower limb muscle strength. The secondary outcomes are body composition, upper limb muscle strength, pulmonary function, blood biomarkers, CVD risk factors, and quality of life. Post-intervention follow-up will be performed for 12 weeks. These indicators will be assessed at baseline (0 week), after the 12-week intervention (12 weeks), and at follow-up (24 weeks). The adverse events will also be reported. Data will be analyzed for all participants in an intent-to-treat plan.

DISCUSSION

This study is the first RCT that will systematically measure and compare the efficacy and safety of LRT-BFR and CRT in older people with sarcopenia on muscle strength, body composition, pulmonary function, blood biomarkers (inflammatory biomarkers, hormone, and growth factors), CVD risk factors, and quality of life. This study can provide an efficient and safe method to prevent the progression of sarcopenia in older people.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR2100042803 . Registered on 28 January 2021.

Blood flow restriction in human skeletal muscle during rest periods after high-load resistance training down-regulates miR-206 and induces Pax7

BACKGROUD

Blood flow restriction (BFR) with low-intensity resistance training has been shown to result in hypertrophy of skeletal muscle. In this study, we tested the hypothesis that BFR during the rest periods between acute, high-intensity resistance exercise sessions (70% of 1 repetition maximum, 7 sets with 10 repetitions) enhances the effects of the resistance training.

METHODS

A total of 7 healthy young men performed squats, and between sets BFR was carried out on one leg while the other leg served as a control. Because BFR was applied during rest periods, even severe occlusion pressure (approximately 230 mmHg), which almost completely blocked blood flow, was well-tolerated by the participants. Five muscle-specific microRNAs were measured from the biopsy samples, which were taken 2 h after the acute training.

RESULTS

Doppler data showed that the pattern of blood flow recovery changed significantly between the first and last BFR. microRNA-206 levels significantly decreased in the BFR leg compared to the control. The mRNA levels of RAC-β serine/threonine-protein kinase v22, nuclear respiratory factor 1, vascular endothelial growth factor, lupus Ku autoantigen protein p70 genes (p < 0.05), and paired box 7 (p < 0.01) increased in the BFR leg. The protein levels of paired box 7, nuclear respiratory factor 1, and peroxisome proliferator-activated receptor γ coactivator 1α did not differ between the BFR leg and the control leg.

CONCLUSION

BFR, during the rest periods of high-load resistance training, could lead to mRNA elevation of those proteins that regulate angiogenesis, mitochondrial biogenesis, and muscle hypertrophy and repair. However, BFR also can cause DNA damage, judging from the increase in mRNA levels of lupus Ku autoantigen protein p70.

Eight Weeks of High-Intensity Interval Static Strength Training Improves Skeletal Muscle Atrophy and Motor Function in Aged Rats via the PGC-1α/FNDC5/UCP1 Pathway

Background

Sarcopenia is a syndrome characterized by the loss of skeletal muscle mass and strength. Most studies have focused on dynamic resistance exercises for preventing muscular decline and maintaining the muscle strength of older individuals. However, this training mode is impractical for older people with osteoarthritis and a limited range of motion. The static strength training mode is more suitable for older people. Therefore, a determination of the effect and mechanism of static strength training on sarcopenia is critical.

Methods

In this study, we developed a training device designed to collect training data and evaluate the effects of static training on the upper limbs of rats. The expression of PGC-1α was locally blocked by injecting a siRNA at the midpoint of the biceps to determine whether PGC-1α signal transduction participates in the effects of high-intensity interval static training on muscle strength. Then, the rat’s motor capacity was measured after static strength training. Immunohistochemistry and Western blotting were applied to determine PGC-1α/FNDC5/UCP1 expression levels in the muscle and adipose tissue. The serum irisin level was also detected using an enzyme-linked immunosorbent assay (ELISA).

Results

Increased levels of serum irisin and local expression of FNDC5, PGC-1α, and UCP1 were observed in the biceps brachii and surrounding fatty tissue after static strength training. Static strength training showed an advantage in reducing body weight and white fat accumulation while increasing the muscle fiber volume, which resulted in a longer training time and shorter rest time.

Conclusion

Overall, these results indicated that high-intensity interval static training prevents skeletal muscle atrophy and improves the motor function of aged rats through the PGC-1α/FNDC5/UCP1 signaling pathway.

Modification of Neuromuscular Junction Protein Expression by Exercise and Doxorubicin

PURPOSE

Doxorubicin (DOX) is a highly effective antitumor agent widely used in cancer treatment. However, it is well established that DOX induces muscular atrophy and impairs force production. Although no therapeutic interventions exist to combat DOX-induced muscle weakness, endurance exercise training has been shown to reduce skeletal muscle damage caused by DOX administration. Numerous studies have attempted to identify molecular mechanisms responsible for exercise-induced protection against DOX myotoxicity. Nevertheless, the mechanisms by which endurance exercise protects against DOX-induced muscle weakness remain elusive. In this regard, impairments to the neuromuscular junction (NMJ) are associated with muscle wasting, and studies indicate that physical exercise can rescue NMJ fragmentation. Therefore, we tested the hypothesis that exercise protects against DOX-induced myopathy by preventing detrimental changes to key proteins responsible for maintenance of the NMJ.

METHODS

Female Sprague-Dawley rats were assigned to sedentary or exercise-trained groups. Exercise training consisted of a 5-d treadmill habituation period followed by 10 d of running (60 min·d, 30 m·min, 0% grade). After the last training bout, exercise-trained and sedentary animals were paired with either placebo (saline) or DOX (20 mg·kg i.p.) treatment. Two days after drug treatment, the soleus muscle was excised for subsequent analyses.

RESULTS

Our results indicate that endurance exercise training prevents soleus muscle atrophy and contractile dysfunction in DOX-treated animals. These adaptations were associated with the increased expression of the following neurotrophic factors: brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, nerve growth factor, and neurotrophin-3. In addition, exercise enhanced the expression of receptor-associated protein of the synapse and the acetylcholine receptor (AChR) subunits AChRβ, AChRδ, and AChRγ in DOX-treated animals.

CONCLUSION

Therefore, upregulating neurotrophic factor and NMJ protein expression may be an effective strategy to prevent DOX-induced skeletal muscle dysfunction.

Limb Blood Flow Restriction Plus Mild Aerobic Exercise Training Protects the Heart Against Isoproterenol-Induced Cardiac Injury in Old Rats: Role of GSK-3β

The present study was conducted to evaluate the effect of blood flow restriction (BFR) training on cardiac resistance to isoproterenol (ISO) induced heart injury in old rats and examined the hypothesis that BFR training may interfere with age-associated impairment of mitochondria by the inhibitory phosphorylation of GSK-3β at Ser9. Old male Wistar rats were divided into the following six groups: CTL (control), ISO (isoproterenol-treated), Sh + ISO (sham-operated plus ISO), BFR + ISO (blood flow restriction plus ISO), Sh-Ex + ISO (sham-operated subjected to exercise and ISO), and BFR-Ex + ISO (blood flow restriction along with exercise and ISO). 10 weeks of exercise training was considered. Then, cardiac injury was induced and physiological, histological, and biochemical parameters were recorded and assessed. Compared to CTL group, isoproterenol administration significantly reduced the systolic arterial pressure (SAP), left-ventricular systolic pressure (LVSP), and ± dp/dt max (P < 0.05). BFR training improved these parameters in the way that BFR-Ex + ISO group had higher SAP, LVSP and ± dp/dt max (P < 0.05) and lower LVEDP (left-ventricular end diastolic pressure) (P < 0.01) than untrained and Sh-Ex + ISO groups. The pS9-GSK-3β and pS9-GSK-3β/GSK-3β ratio were increased in the BFR-Ex + ISO group compared to CTL, ISO, Sh + ISO, and BFR + ISO groups (P < 0.05). The level of plasma cardiac Troponin-I and the severity of the injuries were significantly reduced in BFR-Ex + ISO group versus other cardiac damaged groups. In conclusion, our findings clearly confirmed the cardio-protective effect of BFR training against ISO-induced myocardial injury. Increased phosphorylated GSK-3β and angiogenesis in this model of exercise justify the resistance of old hearts facing stressful situations.

Sarcopenia disease in Iran: an overview

BACKGROUND

Sarcopenia is a geriatric disease with adverse clinical outcomes, high rate of mortality and a major challenge to healthy elderly. This study aimed to undertake a survey to identify gaps and highlight strengths in sarcopenia research in order to progress research in this area for the next years in Iran.

METHODS

This study included all studies published from the beginning until the first of 2019 in national and international journals by Iranian authors conducted in the field of sarcopenia. The databases including MEDLINE (via PubMed), Web of Science and SCOPUS were used as the sources of information. All relevant available academic studies, including review articles, original articles, case reports, conference abstracts, and letters were included in the analysis.

FINDINGS

A total of 48 articles obtained and then categorized into six groups. These groups were; about Pathophysiology, Epidemiology of sarcopenia, Screening of sarcopenia, Nutrition, Physical activity and Association of Sarcopenia and Other Diseases that briefly findings of each study had been described. These findings showed that the prevalence of sarcopenia was 16.5% to 32.5%, using different definitions. A study developed and validated a screening model for identifying people with sarcopenia. Lifestyle changes such as diet can be appropriate strategies for the prevention of sarcopenia and also, physical activity is considered to be one of the few effective strategies to improve sarcopenia and prevent its outcomes, especially if in combination with appropriate nutritional supplementation. Sarcopenia is associated with adverse outcomes and other serious areas such as metabolic disorders, cancers, cardiovascular diseases, nephrology, gastroenterology, psychiatry, other geriatric diseases (such as osteoporosis, etc) and death. Some studies about these areas have been done in Iran.

CONCLUSIONS

By this study, we found that studies on sarcopenia, the gaps of sarcopenia research in Iran, and highlighted the research priorities for future works. The outcome of the present research is to ultimately improve the health, quality of life and well-being of sarcopenic people.