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Whole-body vibration (WBV) has been employed for performance-enhancing purposes. WBV may positively affect muscular endurance and its underlying neural mechanisms due to an enhanced muscular blood circulation and oxygen uptake. However, the effects of WBV on endurance-related torque signal complexity have been understudied. This study aims to investigate the acute effects of WBV on i) maximal isometric torque production; ii) isometric knee extensors fatigability and iii) torque signal complexity during an isometric endurance task. Thirty adult males performed an isometric intermittent endurance protocol on their dominant lower limb after performing: static half squat with WBV (WBV), static half squat without WBV (HS), and no exercise protocol (CC). For each repetition the maximal torque was identified. The maximal torque of the first repetition was identified as the PeakT. The Mean torque (MTorque) and fatigue index (pFatigue) were calculated as the mean and the percentage decay in torque across the entire set of eighteen repetitions (MTorque0-100 %, pFatigue0-100 %), and across shorter blocks of six repetitions (MTorque0-33 %, pFatigue0-33 %; MTorque34-66 %, pFatigue34-66 %, and MTorque67-100 %, pFatigue67-100 %). Torque fluctuations were analysed computing Sample Entropy (SampEn) and the coefficient of variation (CV). PeakT was significantly higher in CC than in WBV (p < 0.01) and in HS (p < 0.01). PeakT was significantly higher in HS than in WB (p < 0.05). MTorque0-100 %, MTorque0-33 %, MTorque34-66 %, and MTorque67-100 % were significantly higher in CC than in WBV (all p-values <0.01) and in HS (p < 0.01). MTorque67-100 % was significantly higher in HS than in WB (p = 0.049). pFatigue34-66 % was significantly higher in WBV than in CC (p < 0.05) whereas pFatigue67-100 % was significantly higher in CC than in WB (p < 0.01) and in HS (p < 0.01). No effect of condition was observed for SampEn and CV. Acute WBV does not lead to beneficial effects on maximal torque production and isometric knee extensors fatigability. These acute detrimental effects may be related to long-term WBV-related adaptations.

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PURPOSE: To compare trunk flexor, extensor, and lateral flexor muscle endurance between women with moderate to severe disability due to chronic neck pain (CNP) and asymptomatic women. DESIGN: Observational case-control study. METHODS: Thirty women with CNP and Neck Disability Index scores ranging from 30% to 70% and 28 asymptomatic women were included. The visual analog scale was used to assess neck pain intensity at rest and during activity. To assess trunk muscles endurance, trunk flexor endurance test, Sorensen test, and side bridge endurance test were performed. RESULTS: Analysis of covariance indicated that neck pain group had lower body mass index-adjusted endurance times of trunk flexor, extensor, and lateral flexor muscles with large effect sizes (p < .001, η2 = 0.378-0.696). Trunk flexor endurance time showed a moderately negative correlation with neck pain intensity at rest and a weakly negative correlation with neck disability score (r = -460 and -365, p < .05). CONCLUSIONS: Women with moderate to severe disability due to CNP exhibited decreased trunk muscle endurance, which may be a predisposing factor for low back pain. Also, trunk flexor endurance was related to neck pain complaints. A holistic approach, addressing the entire spine rather than focusing solely on the cervical region, might be useful for managing CNP. CLINICAL IMPLICATIONS: The findings of reduced endurance in trunk muscles should consider incorporating interventions in the management of CNP to effectively address pain and disability.

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This study aimed to explore the impact of caffeine (CAF) encapsulated in transferrin-modified, sterically-stabilized liposomes (Tf-SSL) on the physical performance of rats, specifically forelimb grip strength, running, and swimming. The brain-targeted drug delivery system, Tf-SSL, was used for the administration of caffeine. 168 male Sprague-Dawley (SD) rats were randomly assigned to different groups, including swimming, running, running wheel, and strength groups. Each group was further subdivided into high, medium, and low dose free caffeine (HCAF, MCAF, LCAF) and Tf-SSL CAF groups, along with a control group (CON). The strength, swimming, and running groups underwent training for four weeks, three times per week. The running wheel group was placed in rearing cages for a one-week adaptation period. After the final training session, the resistance, swimming, running, and running wheel exercise capacities of the rats were tested. The rats were administered treatment via tail vein injection, while the blank CON group received 0.9 % saline solution without treatment throughout the entire process. The results demonstrated a Tf-SSL CAF group encapsulation rate of 70.58 ± 5.14 %. Increasing the concentration of supplemented caffeine led to enhanced forelimb grip strength in rats, with significant differences observed in HCAF alone group, medium-dose Tf-SSL CAF (MTf-SSL CAF), and high-dose Tf-SSL CAF (HTf-SSL CAF) groups compared to the CON group. In the running and swimming experiments, higher caffeine supplementation concentrations correlated with increased running and swimming time to exhaustion, and the MTf-SSL CAF group showed longer running and swimming time compared to the HCAF alone group. The results of rat striatal dopamine levels indicated that increased caffeine supplementation concentrations led to higher dopamine secretion, with significantly different striatal concentrations in the HCAF group, MTf-SSL CAF group, and HTf-SSL CAF group compared to the CON group. The running wheel experiment revealed that rats in the medium- and high-dose Tf-SSL CAF groups exhibited greater 6-h running distances than the HCAF group and CON group. In conclusion, caffeine supplementation improved the physical performance of rats, with the high concentration CAF group outperforming the low and medium concentration groups. Furthermore, Tf-SSL CAF demonstrated superior physical enhancement compared to caffeine supplementation alone.

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Background/Objectives: This study determined the effects of 60 min or 30 min Pilates program on cervicothoracic alignment, muscular strength, and endurance in university students with upper-crossed syndrome (UCS). Methods: Twenty-six university students with UCS were randomly allocated into 60 min Pilates (60 PG, n = 9), 30 min Pilates (30 PG, n = 9), and control (CG, n = 8) groups. The 60 and 30 PG students participated in the Pilates program, focusing on relaxation, stability, mobility, and strengthening of the cervical, thoracic, and scapular muscles for 60 or 30 min per session, twice a week, for 12 weeks. Cervicothoracic alignment was measured using BodyStyle to determine craniovertebral angle (CVA), forward shoulder angle (FSA), head position angle (HPA), head tilt angle (HTA), and kyphosis angle (KA). We measured the muscular strength and endurance of the shoulder on the dominant side. Results: After the intervention, CVA, HPA, HTA, and KA significantly improved in the 60 and 30 PG (all p < 0.01) but not in the CG (p > 0.05). There were no significant differences between the 60 and 30 PG at 4, 8, and 12 weeks. Shoulder strength differed between shoulder flexion and horizontal abduction (p < 0.01). Shoulder endurance differed between extension, flexion, and horizontal abduction (p < 0.05, p < 0.01, and p < 0.001, respectively). Conclusions: This study confirmed the effectiveness of the Pilates program in improving cervicothoracic sagittal alignment and shoulder muscular function in university students with UCS. Additionally, the effects of participating in 60 and 30 min Pilates programs were found to be equivalent. Therefore, encouraging busy university students to participate in at least 30 min of the Pilates program is important.

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Background: Caffeine is commonly used as an ergogenic aid to increase strength and endurance in athletes. The results of meta-analyses in this regard are still conflicting. Therefore, the current umbrella meta -analysis was conducted to determine the effects of caffeine supplementation on muscle strength and endurance as a clear and final conclusion. Methods: Relevant studies were searched in international databases including PubMed, Scopus, and Web of Science until August 15, 2022. Meta-analysis studies examining the effects of caffeine supplementation on muscle strength and endurance were included in this study. Random effects model was used to perform meta-analysis. Additional analyses including subgroup and sensitivity analyzes were performed. Findings: In general, 9 meta-analyses were included in the study. The results showed that caffeine supplementation led to a significant increase in muscle strength (SMD = 0.18, 95 % CI: 0.14, 0.21; p < 0.001) and muscle endurance (SMD = 0.30, 95 % CI 0.21, 0.38; p < 0.001). Conclusion: Meta -analysis showed the significant effects of caffeine consumption on muscle strength and muscle endurance. Due to the lack of evidence, further studies are needed in the women's population.

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Background: Exercise, especially high-intensity interval training (HIIT), can increase mitochondrial respiratory capacity and enhance muscular endurance, but its systemic burden makes it difficult to safely and continuously prescribe for patients with chronic kidney disease (CKD)-related cachexia who are in poor general condition. In this study, we examined whether HIIT using electrical stimulation (ES), which does not require whole-body exercise, improves muscle endurance in the skeletal muscle of 5/6 nephrectomized rats, a widely used animal model for CKD-related cachexia. Methods: Male Wistar rats (10 weeks old) were randomly assigned to a group of sham-operated (Sham) rats and a group of 5/6 nephrectomy (Nx) rats. HIIT was performed on plantar flexor muscles in vivo with supramaximal ES every other day for 4 weeks to assess muscle endurance, myosin heavy-chain isoforms, and mitochondrial respiratory function in Nx rats. A single session was also performed to identify upstream signaling pathways altered by HIIT using ES. Results: In the non-trained plantar flexor muscles from Nx rats, the muscle endurance was significantly lower than that in plantar flexor muscles from Sham rats. The proportion of myosin heavy chain IIa/x, mitochondrial content, mitochondrial respiratory capacity, and formation of mitochondrial respiratory supercomplexes in the plantaris muscle were also significantly decreased in the non-trained plantar flexor muscles from Nx rats than compared to those in plantar flexor muscles from Sham rats. Treatment with HIIT using ES for Nx rats significantly improved these molecular and functional changes to the same degrees as those in Sham rats. Furthermore, a single session of HIIT with ES significantly increased the phosphorylation levels of AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK), pathways that are essential for mitochondrial activation signaling by exercise, in the plantar muscles of both Nx and Sham rats. Conclusion: The findings suggest that HIIT using ES ameliorates muscle fatigue in Nx rats via restoration of mitochondrial respiratory dysfunction with activation of AMPK and p38 MAPK signaling. Our ES-based HIIT protocol can be performed without placing a burden on the whole body and be a promising intervention that is implemented even in conditions of reduced general performance status such as CKD-related cachexia.

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There are presently no acknowledged therapeutic targets or official drugs for the treatment of muscle fatigue. The alpha7 nicotinic acetylcholine receptor (α7nAChR) is expressed in skeletal muscle, with an unknown role in muscle endurance. Here, we try to explore whether α7nAChR could act as a potential therapeutic target for the treatment of muscle fatigue. Results showed that nicotine and PNU-282987 (PNU), as nonspecific and specific agonists of α7nAChR, respectively, could both significantly increase C57BL6/J mice treadmill-running time in a time- and dose-dependent manner. The improvement effect of PNU on running time and ex vivo muscle fatigue index disappeared when α7nAChR deletion. RNA sequencing revealed that the differential mRNAs affected by PNU were enriched in glycolysis/gluconeogenesis signaling pathways. Further studies found that PNU treatment significantly elevates glycogen content and ATP level in the muscle tissues of α7nAChR+/+ mice but not α7nAChR-/- mice. α7nAChR activation specifically increased endogenous glycogen-targeting protein orosomucoid (ORM) expression both in vivo skeletal muscle tissues and in vitro C2C12 skeletal muscle cells. In ORM1 deficient mice, the positive effects of PNU on running time, glycogen and ATP content, as well as muscle fatigue index, were abolished. Therefore, the activation of α7nAChR could enhance muscle endurance via elevating endogenous anti-fatigue protein ORM and might act as a promising therapeutic strategy for the treatment of muscle fatigue.

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Objectives: Low back pain (LBP) is common in elite athletes. Several peripheral and central factors have been identified to be altered in non-athletic LBP populations, however whether these alterations also exist in elite athletes with LBP is unknown. The aim of this study was to determine whether elite basketballers with a history of persistent LBP perform worse than those without LBP at a lumbar muscle endurance task, a lumbar extension peak-torque task, and a lumbar motor imagery task. Method: An observational pilot study. Twenty junior elite-level male basketballers with (n = 11) and without (n = 9) a history of persistent LBP were recruited. Athletes completed a lumbar extensor muscle endurance (Biering-Sorensen) task, two lumbar extensor peak-torque (modified Biering-Sorensen) tasks and two motor imagery (left/right lumbar and hand judgement) tasks across two sessions (48 hours apart). Performance in these tasks were compared between the groups with and without a history of LBP. Results: Young athletes with a history of LBP had reduced lumbar extensor muscle endurance (p < 0.001), reduced lumbar extension peak-torque (p < 0.001), and were less accurate at the left/right lumbar judgement task (p = 0.02) but no less accurate at a left/right hand judgement task (p = 0.59), than athletes without a history of LBP. Response times for both left/right judgement tasks did not differ between groups (lumbar p = 0.24; hand p = 0.58). Conclusions: Junior elite male basketballers with a history of LBP demonstrate reduced lumbar extensor muscle endurance and lumbar extension peak-torque and are less accurate at a left/right lumbar rotation judgement task, than those without LBP.

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At present, there are no official approved drugs for improving muscle endurance. Our previous research found acute phase protein orosomucoid (ORM) is an endogenous anti-fatigue protein, and macrolides antibiotics erythromycin can elevate ORM level to increase muscle bioenergetics and endurance parameters. Here, we further designed, synthesized and screened a new erythromycin derivative named HMS-01, which lost its antibacterial activity in vitro and in vivo. Data showed that HMS-01 could time- and dose-dependently prolong mice forced-swimming time and running time, and improve fatigue index in isolated soleus muscle. Moreover, HMS-01 treatment could increase the glycogen content, mitochondria number and function in liver and skeletal muscle, as well as ORM level in these tissues and sera. In Orm-deficient mice, the anti-fatigue and glycogen-elevation activity of HMS-01 disappeared. Therefore, HMS-01 might act as a promising small molecule drug targeting ORM to enhance muscle endurance.

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Peak oxygen uptake (VO2), evaluated as exercise tolerance, is a strong predictor of life prognosis regardless of health condition. Several previous studies have reported that peak VO2 is higher in those with a greater decrease in muscle oxygen saturation (SmO2) in the active muscles during incremental exercise. However, the skeletal muscle characteristics of individuals exhibiting a greater decrease in SmO2 during active muscle engagement in incremental exercise remain unclear. This study aimed to clarify the relationship among muscle strength, muscle endurance, and skeletal muscle oxygenation dynamics in active leg muscles during incremental exercise. Twenty-four healthy young men were included and categorized into the non-moderate-to-high muscular strength and endurance group (those with low leg muscle strength, endurance, or both; n = 11) and the moderate-to-high muscular strength and endurance group (those with both moderate-to-high leg muscle strength and endurance; n = 13). All participants underwent cardiopulmonary exercise testing combined with near-infrared spectroscopy to assess whole-body peak VO2 and the change in SmO2 at the lateral vastus lateralis from rest to each exercise stage as skeletal muscle oxygenation dynamics. A linear mixed-effects model, with the change in SmO2 from rest to each stage as the dependent variable, individual participants as random effects, and group and exercise load as fixed effects, revealed significant main effects for both group (P = 0.001) and exercise load (P < 0.001) as well as a significant interaction between the two factors (P < 0.001). Furthermore, multiple-comparison test results showed that the change in SmO2 from rest to 40%-100% peak VO2 was significantly higher in the moderate-to-high muscular strength and endurance group than in the non-moderate-to-high muscular strength and endurance group. Maintaining both muscle strength and endurance at moderate or higher levels contributes to high skeletal muscle oxygenation dynamics (i.e., greater decrease in SmO2) during moderate- or high-intensity exercise.

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(1) Background: Cardiac rehabilitation often emphasizes aerobic capacity while overlooking the importance of muscle strength. This study evaluated the impact of an enhanced remote strength training program (RCR-ST) on cardiac rehabilitation. (2) Methods: In this randomized prospective study (RCT registration number SMC-9080-22), 50 patients starting cardiac rehabilitation were assessed for muscle strength, aerobic capacity, and self-reported outcomes at baseline and after 16 weeks. Participants were divided into two groups: the RCR-ST group received a targeted resistance training program via a mobile app and smartwatch, while the control group received standard care with general resistance training advice. (3) Results: The RCR-ST group demonstrated significant improvements in muscle endurance, notably in leg extension and chest press exercises, with increases of 92% compared to 25% and 92% compared to 13% in the control group, respectively. Functional assessments (5-STS and TUG tests) also showed marked improvements in agility, coordination, and balance. Both groups improved in cardiorespiratory fitness, similarly. The RCR-ST group reported enhanced physical health and showed increased engagement, as evidenced by more frequent use of the mobile app and longer participation in the rehabilitation program (p < 0.05). (4) Conclusions: Incorporating a focused strength training regimen in remote cardiac rehabilitation significantly improves muscle endurance and patient engagement. The RCR-ST program presents a promising approach for optimizing patient outcomes by addressing a crucial gap in traditional rehabilitation protocols that primarily focus on aerobic training.

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This study aimed to explore the effects of acute ingestion of caffeine capsules on muscle strength and muscle endurance. We searched the PubMed, Web of Science, Cochrane, Scopus, and EBSCO databases. Data were pooled using the weighted mean difference (WMD) and 95% confidence interval. Fourteen studies fulfilled the inclusion criteria. The acute ingestion of caffeine capsules significantly improved muscle strength (WMD, 7.09, p < 0.00001) and muscle endurance (WMD, 1.37; p < 0.00001), especially in males (muscle strength, WMD, 7.59, p < 0.00001; muscle endurance, WMD, 1.40, p < 0.00001). Subgroup analyses showed that ≥ 6 mg/kg body weight of caffeine (WMD, 6.35, p < 0.00001) and ingesting caffeine 45 min pre-exercise (WMD, 8.61, p < 0.00001) were more effective in improving muscle strength, with the acute ingestion of caffeine capsules having a greater effect on lower body muscle strength (WMD, 10.19, p < 0.00001). In addition, the acute ingestion of caffeine capsules had a greater effect in moderate-intensity muscle endurance tests (WMD, 1.76, p < 0.00001). An acute ingestion of caffeine capsules significantly improved muscle strength and muscle endurance in the upper body and lower body of males.

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BACKGROUND: People with chronic pain might evade certain movements to prevent their experience of pain. Movement-evoked pain (MEP) might induce lower functionality during daily activities. HYPOTHESIS: (1) MEP after physical fitness tests would vary depending on the main musculature involved in the test; (2) physical and psychological factors would be associated with MEP in patients with NSCLBP. STUDY DESIGN: Cross-sectional design. LEVEL OF EVIDENCE: Level 3. METHODS: A total of 104 (69 women) patients aged 51.0 ± 10.3 years with NSCLBP participated. MEP was measured with a visual analog scale (VAS) at baseline and immediately after performing each physical fitness test, that is, the Biering-Sørensen, prone bridging, handgrip, chair-stand, and 8-foot time-up-and-go tests, measuring back extensor, back flexor, upper- and lower-body muscle strength, and motor agility, respectively. Global muscle strength was calculated with normalized index (z-score) procedure. Depression, anxiety, pain catastrophizing, and central sensitization were assessed with the Beck Depression Inventory II, State Trait Anxiety Inventory I, Pain Catastrophizing Scale, and Central Sensitization Inventory (CSI), respectively. RESULTS: Patients showed greater pain after completion of the Biering-Sørensen (mean difference 95% CI, 0.02, 1.11), prone bridging (0.15, 1.21), lower pain after handgrip (-1.46, -0.52), and the 8-foot time-up-and-go (-1.43, 0.46) tests (all P ≤ 0.04). Lower global muscular strength (ß between -0.18 and -0.30), and greater pain catastrophizing (ß = 0.16), and CSI scoring (ß between 0.18 and 0.27) were associated with greater MEP (all P ≤ 0.04). CONCLUSION: Greater MEP was observed after tests measuring core musculature strength than after tests measuring distal (limbs) strength and agility. Greater MEP was overall associated with lower muscle strength, greater pain catastrophizing, and central sensitization. CLINICAL RELEVANCE: Fitness testing might be implemented as a complementary tool for the monitoring of NSCLBP in clinical settings.

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This study examined the synergistic effects of combining Rhodiola rosea (RHO) and caffeine (CAF) supplementation on muscle endurance and explosiveness in SD rats and human subjects, encompassing individuals without prior exercise training experience and seasoned aerobic athletes. Male SD rats and healthy human volunteers were randomly divided into four groups: CAF, RHO, CAF + RHO, and a control group (CTR). Nutritional supplements were administered throughout the training period, and pre-and post-measurement data were collected. In both the rat model and human subjects, the RHO+CAF group demonstrated significantly greater effects compared to the use of RHO or CAF supplements individually. Rats in the RHO+CAF group demonstrated extended running and swimming times and an increase in erythropoietin (EPO) mRNA expression in comparison to the CTR. Blood parameters, such as serum EPO levels, were enhanced in the CAF + RHO group, while blood urea nitrogen (BUN) and lactate (LA) levels significantly decreased in both the RHO and CAF + RHO groups. Hepatic and muscle glycogen contents were also higher in these groups. The gene expression analysis in rats demonstrated an elevation in the mRNA levels of glucose transporter-4 (GLUT-4), peroxisome proliferator-activated receptor γ coactivator-1 alpha (PGC-1α), Monocarboxylate transporter 1 (MCT-1), and Heme Oxygenase-1 (HO-1) in both the RHO and RHO+CAF groups. For individuals without prior aerobic training experience, the RHO+CAF group showed significant improvements compared to the CTR group in maximal oxygen consumption (VO2max), 5 km run, countermovement jump (CMJ), standing long jump, and 30 m sprint. For individuals with years of aerobic training experience, the RHO+CAF group exhibited enhanced performance in the 5 km run, CMJ, and standing long jump compared to the CTR group. In conclusion, the continuous 30 days supplementation of RHO, combined with a single dose of CAF, demonstrated superior effects on muscle endurance and explosiveness in both animal and human studies when compared to the use of RHO or CAF individually.

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Low-load resistance training promotes muscle strength and hypertrophic adaptations when combined with blood flow restriction (BFR). However, the effect of BFR on muscle endurance remains unclear. The aim of this study was to clarify the effects of BFR on muscle performance and adaptation, with special reference to local muscle endurance. In experiment 1, eight healthy men performed unilateral elbow flexion exercise to failure at 30% of one-repetition maximum with BFR (at 40% of estimated arterial occlusion pressure) and free blood flow (FBF). During the exercise, muscle activity and tissue oxygenation were measured from the biceps brachii. In experiment 2, another eight healthy men completed 6 weeks of elbow flexion training with BFR and FBF. The number of repetitions to failure at submaximal load (Rmax), the estimated time for peak torque output to decay by 50% during repetitive maximum voluntary contractions (half-time), one-repetition maximum, isometric strength and muscle thickness of elbow flexors were measured pre- and post-training. Blood flow restriction resulted in fewer repetitions and lower muscle tissue oxygenation at the end of exercise than FBF, while the muscle activity increased similarly to repetition failure. Blood flow restriction also resulted in a smaller post-training Rmax, which was strongly correlated with the total exercise volume over the 6 week period. Despite the smaller exercise volume, BFR resulted in similar improvements in half-time, muscle strength and thickness compared with FBF. These results suggest that the application of BFR can attenuate muscle endurance adaptations to low-load resistance training by decreasing the number of repetitions during exercise, both acutely and chronically.

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PURPOSE OF REVIEW: Examine the current state of literature related to the impact of obesity in children and adolescents on health-related physical fitness and the resultant cardiometabolic disease risk. RECENT FINDINGS: Cardiorespiratory fitness of children and adolescents has declined over the past few decades which corresponds with an increase in obesity rates. Children with obesity are more likely to have low cardiorespiratory fitness which is associated with higher cardiometabolic disease risk and poorer mental health. The impact of obesity on muscular fitness in children and adolescents is more difficult to ascertain, but in general measures of physical function are lower in children with obesity which has also been associated with higher cardiometabolic disease risk. Components of health-related physical fitness are trending negatively in children and adolescents and appear to be related to the increase in prevalence of obesity. The resultant cardiometabolic disease risk has also risen which suggests a greater disease burden in the future. These disparaging findings highlight the need for aggressive interventions to improve physical fitness in children and adolescents.

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OBJECTIVE: Inspiratory muscle strength (IMS) appears to be reduced in subjects with chronic Chagas heart disease (CHD), especially in the presence of heart failure (HF). However, only one study about IMS and inspiratory muscle endurance (IME) in those with CHD without heart failure is available. This study aimed to compare IMS and IME in subjects with CHD in the presence and absence of HF. METHODS: This is a cross-sectional study in which 30 CHD adult patients were divided into CHD-CC group (initial phase of CHD, without HF; n = 15) and CHD-HF group (advanced phase of CHD, with HF; n = 15). We assessed IMS by maximum inspiratory pressure (MIP) and IME by incremental (Pthmax) and constant load (TLim) tests. Reduced IMS and IME were considered by predicted MIP values <70% and Pthmax/MIP <75%, respectively. RESULTS: Inspiratory muscle weakness (IMW) was more frequent in CHD-HF than in CHD-CC (46.7% vs. 13.3%; p = 0.05), and both groups had high frequencies of reduced IME (93.3% CHD-CC vs. 100.0% CHD-HF; p = 0.95). Age-adjusted logistic regression analysis using HF as a dependent variable showed that HF was associated with an increased chance of IMW compared with the CHD-CC group (OR = 7.47; p = 0.03; 95% CI 1.20-46.19). CONCLUSION: This study suggests that, in patients with CHD, HF is associated with IMW, and that reduction of IME is already present in the initial phase, similar to the advanced phase with HF.

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Introduction: Multi-ingredient pre-workout supplements (MIPS) are commonly used by individuals looking to enhance exercise performance and augment adaptations to training. However, the efficacy of commercially available MIPS is largely dependent on the ingredient profile, and new formulations should be investigated to determine their effectiveness. Therefore, the purpose of this study was to examine the effects of a commercially available MIPS product on performance during an upper body resistance exercise protocol. Methods: Twenty resistance-trained participants (10 men, 10 women) volunteered to complete this double-blind, placebo-controlled, crossover study consisting of 3 visits. Visit 1 consisted of body composition, 1-repetition maximum (1RM) testing, and familiarization. Visits 2 and 3 consisted of supplementation with either MIPS or placebo (PLA) 1 h prior to completion of an upper body resistance exercise workout during which power output, repetitions completed, rating of perceived exertion (RPE), and perceived recovery were recorded. Assessments of reaction time, isometric mid-thigh pull, and perceived levels of focus, energy, fatigue, and "muscle pump" were also completed before supplementation, 1 h after supplementation, and immediately after exercise. Results: Statistical analysis revealed significant main effects of trial for reaction time (p < 0.001) and bench press peak power (p = 0.026) indicating better performance during the MIPS trial. Furthermore, total number of repetitions completed significantly increased (p = 0.003) during the MIPS (96.90 ± 21.31 repetitions) trial compared to PLA (89.50 ± 18.37 repetitions). Additionally, overall session RPE was significantly lower (p = 0.002) during the MIPS (7.6 ± 1.2) trial compared to PLA (8.3 ± 0.9). Discussion: These findings suggest that acute supplementation with this MIPS improved upper body resistance exercise performance while reducing participant RPE. Further research should investigate the efficacy of chronic supplementation with this MIPS as the acute response provided an ergogenic benefit.

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BACKGROUND: Endurance capability in the muscles controlling the knee is poorly understood post anterior cruciate ligament (ACL) reconstruction, despite many sporting activities requiring notable muscle endurance. The hamstring muscles, when active, provide important anatomical support to protect the reconstructed graft. In the absence of good hamstring endurance, fatigue may predispose individuals to re-injury. OBJECTIVE: To assess whether ACL reconstruction (ACLR) with a hamstring graft leads to reduced hamstring endurance 9-13 months post-surgery. STUDY DESIGN: A cross-sectional inter-limb comparison study was undertaken with participants 9-13 months after an ACLR with a hamstring graft, and a group of age, sex, and activity-matched controls. There were 22 participants in each group. METHOD: Submaximal hamstring endurance was measured using a progressive fatigue test on an isokinetic dynamometer at a joint angular velocity of 120°/second. The dependant variable was the maximum number of repetitions performed. Statistical comparisons were made across injured, uninjured and control group limbs. RESULTS: There was a significant (p < 0.05) deficit in hamstring endurance observed between the injured leg (mean: 111 repetitions, SD 49) and uninjured leg (mean: 136 repetitions, SD 67) of the ACL group, but not between the uninjured and control group legs (mean: 124 repetitions, SD 50). CONCLUSION: The 18% deficit in submaximal hamstring endurance across the ACL-reconstructed individual's limbs is indicative of a notable loss in muscle performance at 9-13 months post-surgery. These results provide initial evidence for supporting further research examining the inclusion of hamstring endurance training in ACL rehabilitation programmes post-surgery.

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Background: Based on emerging evidence that brief periods of cessation from resistance training (RT) may re-sensitize muscle to anabolic stimuli, we aimed to investigate the effects of a 1-week deload interval at the midpoint of a 9-week RT program on muscular adaptations in resistance-trained individuals. Methods: Thirty-nine young men (n = 29) and women (n = 10) were randomly assigned to 1 of 2 experimental, parallel groups: An experimental group that abstained from RT for 1 week at the midpoint of a 9-week, high-volume RT program (DELOAD) or a traditional training group that performed the same RT program continuously over the study period (TRAD). The lower body routines were directly supervised by the research staff while upper body training was carried out in an unsupervised fashion. Muscle growth outcomes included assessments of muscle thickness along proximal, mid and distal regions of the middle and lateral quadriceps femoris as well as the mid-region of the triceps surae. Adaptions in lower body isometric and dynamic strength, local muscular endurance of the quadriceps, and lower body muscle power were also assessed. Results: Results indicated no appreciable differences in increases of lower body muscle size, local endurance, and power between groups. Alternatively, TRAD showed greater improvements in both isometric and dynamic lower body strength compared to DELOAD. Additionally, TRAD showed some slight psychological benefits as assessed by the readiness to train questionnaire over DELOAD. Conclusion: In conclusion, our findings suggest that a 1-week deload period at the midpoint of a 9-week RT program appears to negatively influence measures of lower body muscle strength but has no effect on lower body hypertrophy, power or local muscular endurance.

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