Quadriceps Cross-sectional Area Research Articles

Effects of different strength training frequencies during reduced training period on strength and muscle cross-sectional area

This study investigated the effects of different reduced strength training (RST) frequencies on half-squat 1 RM and quadriceps cross-sectional area (QCSA). Thirty-three untrained males (24.7 ± 3.9 years; 1.73 ± 0.08 m; 74.6 ± 8.4 kg) underwent a 16-week experimental period (i.e. eight weeks of strength training [ST] followed by additional eight weeks of RST). During the ST period, the participants performed 3–4 sets of 6–12 RM, three sessions/week in half-squat and knee extension exercises. Following ST, the participants were randomly allocated to one of three groups: reduced strength training with one (RST1) or two sessions per week (RST2), and ceased training (CT). Both RST1 and RST2 groups had their training frequency and total training volume-load (i.e. RST1 = 50.3% and RST2 = 57.1%) reduced, while the CT group stopped training completely. Half-squat 1 RM (RST1 = 27.9%; RST2 = 26.7%; and CT = 28.4%) and QCSA (RST1 = 6.1%; RST2 = 6.9%; and CT = 5.8%) increased significantly (p < .05) in all groups after eight weeks of ST. No significant changes were observed in 1 RM and QCSA for RST1 and RST2 groups after the RST period, while the CT group demonstrated a decrease in half-squat 1 RM (22.6%) and QCSA (5.4%) when compared to the ST period (p < .05). In conclusion, different RST frequencies applied were able to maintain muscle mass and strength performance obtained over the regular ST period. Thus, it appears that RST frequency does not affect the maintenance of muscle mass and strength in untrained males, as long as volume-load is equated between frequencies.

The knee extensor moment arm is associated with performance in male sprinters.

Although large knee extensor torque contributes to superior sprint performance, previous findings have indicated that the quadriceps cross-sectional area (CSA), a pivotal morphological regulator of knee extensor torque, is not correlated with performance in sprinters. We hypothesized that the knee extensor moment arm (MA), another main morphological regulator of knee extensor torque, may affect sprint performance. To test this hypothesis, we examined the relationship between knee extensor MA and sprint performance. The quadriceps CSA and knee extensor MA in 32 well-trained male sprinters and 32 male non-sprinters were measured using magnetic resonance imaging. Knee extensor MA, but not quadriceps CSA, was greater in sprinters than in non-sprinters (P = 0.013). Moreover, knee extensor MA, but not the quadriceps CSA, was correlated with the personal best time in a 100-m race in sprinters (r = -0.614, P < 0.001). Furthermore, among 24 sprinters who participated in the 60-m sprint test, knee extensor MA was correlated with sprinting velocities in the acceleration (r = 0.717, P < 0.001) and maximum speed (r = 0.697, P < 0.001) phases. The present study demonstrates that the knee extensor MA is greater in sprinters than in non-sprinters, and this morphological structure in sprinters is associated with sprint performance. Therefore, for the first time, we provided evidence that a greater knee extensor MA in sprinters may be an advantageous for achieving superior sprint performance.

Test-Retest Reliability of Muscle Thickness, Echo-Intensity and Cross Sectional Area of Quadriceps and Hamstrings Muscle Groups Using B-mode Ultrasound

Ultrasound muscle images have been extensively used as tools for investigating, diagnosing and monitoring thigh muscles. However, there is a lack of information examining ultrasound reliability of quadriceps and hamstrings images for research and clinical use. Objectives: To determine the reliability of muscle thickness (MT), echo intensity (EI) and cross sectional area (CSA) of quadriceps and hamstrings muscle groups. Methods: Single transverse images of the rectus femoris (RF), vastus intermedius (VI), vastus medialis (VM), vastus lateralis (VL), biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) muscles were scanned in the right and left legs of ten healthy collegiate men (age 23.4 ± 2.2 yrs, mass 71.7 ± 11.7 kg, height 1.73 ± 0.06 m) between two sessions with one day interval. Intraclass correlation coefficients (ICCs), standard error of measurement (SEM), and minimum difference to be considered “real” (MD) were measured for MT, EI, and CSA. Results: A range of 0.97-0.99, 0.83-0.88, and 0.86-0.97 (ICC); 0.72-1.38, 2.73-3.41, and 0.36-1.04 (SEM); and 2.01-3.82, 7.56-9.46, and 0.99-2.89 (MD) were found for quadriceps muscles, and 0.93-0.99, 0.74-0.90, and 0.89-0.96 (ICC); 0.73-1.94, 3.29-4.98, and 0.69-1.08 (SEM); and 2.03-5.38, 9.13-13.81, and 1.91-2.98 (MD) were found for hamstrings muscles. Conclusions: These results suggest that ultrasound imaging of both quadriceps and hamstrings muscle architecture is a reliable technique for assessing thigh musculoskeletal tissue. The anatomical sites, as well as ultrasound adjustments, images, and results utilized here may assist future researchers and clinicians as reference tools when measuring quadriceps and hamstrings musculature.

Creatine Loading Does Not Preserve Muscle Mass or Strength During Leg Immobilization in Healthy, Young Males: A Randomized Controlled Trial

BackgroundA short period of leg immobilization leads to rapid loss of muscle mass and strength. Creatine supplementation has been shown to increase lean body mass in active individuals and can be used to augment gains in muscle mass and strength during prolonged resistance-type exercise training.ObjectiveOur objective was to investigate whether creatine loading can attenuate the loss of muscle mass and strength during short-term leg immobilization.MethodsHealthy young men (n = 30; aged 23 ± 1 years; body mass index [BMI] 23.3 ± 0.5 kg/m−2) were randomly assigned to either a creatine or a placebo group. Subjects received placebo or creatine supplements (20 g/d) for 5 days before one leg was immobilized by means of a full-leg cast for 7 days. Muscle biopsies were taken before creatine loading, prior to and immediately after leg immobilization, and after 7 days of subsequent recovery. Quadriceps cross-sectional area (CSA) (computed tomography [CT] scan) and leg muscle strength (one-repetition maximum [1-RM] knee extension) were assessed before and immediately after immobilization and after 1 week of recovery. Data were analyzed using repeated measures analysis of variance (ANOVA). Data are presented consistently as mean ± standard error of the mean (SEM).ResultsThere was a significant overall increase in muscle total creatine content following the 5-day loading phase (p = 0.049), which appeared driven by an increase in the creatine group (from 90 ± 9 to 107 ± 4 mmol/kg−1 dry muscle) with no apparent change in the placebo group (from 88 ± 4 to 90 ± 3 mmol/kg−1; p = 0.066 for time × treatment interaction). Quadriceps muscle CSA had declined by 465 ± 59 and 425 ± 69 mm2 (p < 0.01) in the creatine and placebo group, respectively, with no differences between groups (p = 0.76). Leg muscle strength decreased from 56 ± 4 to 53 ± 4 kg in the creatine and from 59 ± 3 to 53 ± 3 kg in the placebo group, with no differences between groups (p = 0.20). Muscle fiber size did not change significantly over time in either group (p > 0.05). When non-responders to creatine loading were excluded (n = 6), responders (n = 8; total creatine content increasing from 70 to 106 mmol/kg−1) showed similar findings, with no signs of preservation of muscle mass or strength during immobilization. During the subsequent recovery phase, no differences in muscle mass or strength were found between the two groups (p > 0.05).ConclusionCreatine supplementation prior to and during leg immobilization does not prevent or attenuate the loss of muscle mass or strength during short-term muscle disuse.NIH Clinical Trial Registration Number: NCT01894737 (http://www.clinicaltrials.gov/).

Differential Effects of 2 Rehabilitation Programs Following Anterior Cruciate Ligament Reconstruction.

The muscular function restoration related to the type of physical rehabilitation followed after anterior cruciate ligament reconstruction (ACLR) using autologous hamstring tendon graft in terms of strength and cross-sectional area (CSA) remain controversial. To analyze the CSA and force output of quadriceps and hamstring muscles in subjects following either an Objective Criteria-Based Rehabilitation (OCBR) algorithm or the usual care (UCR) for ACL rehabilitation in Spain, before and 1 year after undergoing an ACLR. Longitudinal clinical double-blinded randomized controlled trial. Sports-medicine research center. 40 recreational athletes (30 male, 10 female [24 ± 6.9 y, 176.55 ± 6.6 cm, 73.58 ± 12.3 kg]). Both groups conducted differentiated rehabilitation procedures after ACLR. Those belonging to OCBR group were guided in their recovery according to the current evidence-based principles. UCR group followed the national conventional approach for ACL rehabilitation. Concentric isokinetic knee joint flexor-extension torque assessments at 180°/s and Magnetic Resonance Imaging (MRI) evaluations were performed before and 12 months after ACLR. Anatomical muscle CSA (mm2) was assessed, in Quadriceps, Biceps femoris, Semitendinous, Semimembranosus, and Gracilis muscles at 50% and 70% femur length. Reduced muscle CSA was observed in both treatment groups for Semitendinosus and Gracilis 1 year after ACLR. At 1-year follow-up, subjects allocated to the OCBR demonstrated greater knee flexor and extensor peak torque values in their reconstructed limbs in comparison with patients treated by UCR. Objective atrophy of Semitendinosus and Gracilis muscles related to surgical ACLR was found to persist in both rehabilitation groups. However, OCBR after ACLR lead to substantial gains on maximal knee flexor strength and ensured more symmetrical anterior-posterior laxity levels at the knee joint.

A pilot study examining the impact of exercise training on skeletal muscle genes related to the TLR signaling pathway in older adults following hip fracture recovery.

These pilot data demonstrate that 3 mo of exercise training in older adults recovering from hip fracture surgery was able to mitigate skeletal muscle gene expression related to inflammation and ceramide metabolism while also improving surgical limb lean tissue, strength, and physical function.

Mechanisms of Chronic Muscle Wasting and Dysfunction after an Intensive Care Unit Stay. A Pilot Study.

Critical illness survivors often experience permanent functional disability due to intensive care unit (ICU)-acquired weakness. The mechanisms responsible for long-term weakness persistence versus resolution are unknown. To delineate cellular mechanisms underlying long-term weakness persistence in ICU survivors. We conducted a nested, prospective study of critically ill patients mechanically ventilated for 7 days or longer. The patients were recruited from the RECOVER program and serially assessed over 6 months after ICU discharge. Twenty-seven of 82 patients consented to participate; 15 and 11 patients were assessed at 7 days and 6 months after ICU discharge, respectively. We assessed motor functional capacity, quadriceps size, strength, and voluntary contractile capacity and performed electromyography, nerve conduction studies, and vastus lateralis biopsies for histologic, cellular, and molecular analyses. Strength and quadriceps cross-sectional areas were decreased 7 days after ICU discharge. Weakness persisted to 6 months and correlated with decreased function. Quadriceps atrophy resolved in 27% patients at 6 months. Muscle mass reconstitution did not correlate with resolution of weakness, owing to persistent impaired voluntary contractile capacity. Compared with Day 7, increased ubiquitin-proteasome system-mediated muscle proteolysis, inflammation, and decreased mitochondrial content all normalized at 6 months. Autophagy markers were normal at 6 months. Patients with sustained atrophy had decreased muscle progenitor (satellite) cell content. Long-term weakness in ICU survivors results from heterogeneous muscle pathophysiology with variable combinations of muscle atrophy and impaired contractile capacity. These findings are not explained by ongoing muscle proteolysis, inflammation, or diminished mitochondrial content. Sustained muscle atrophy is associated with decreased satellite cell content and compromised muscle regrowth, suggesting impaired regenerative capacity.

Effects of high‐intensity interval cycling performed after resistance training on muscle strength and hypertrophy

Aim of the study was to investigate whether high-intensity interval cycling performed immediately after resistance training would inhibit muscle strength increase and hypertrophy expected from resistance training per se. Twenty-two young men were assigned into either resistance training (RE; N=11) or resistance training plus high-intensity interval cycling (REC; N=11). Lower body muscle strength and rate of force development (RFD), quadriceps cross-sectional area (CSA) and vastus lateralis muscle architecture, muscle fiber type composition and capillarization, and estimated aerobic capacity were evaluated before and after 8weeks of training (2 times per week). Muscle strength and quadriceps CSA were significantly and similarly increased after both interventions. Fiber CSA increased significantly and similarly after both RE (type I: 13.6±3.7%, type IIA: 17.6±4.4%, type IIX: 23.2±5.7%, P<0.05) and REC (type I: 10.0±2.7%, type IIA: 14.8±4.3% type IIX: 20.8±6.0%, P<0.05). In contrast, RFD decreased and fascicle angle increased (P<0.05) only after REC. Capillary density and estimated aerobic capacity increased (P<0.05) only after REC. These results suggest that high-intensity interval cycling performed after heavy-resistance exercise may not inhibit resistance exercise-induced muscle strength/hypertrophy after 2months of training, while it prompts aerobic capacity and muscle capillarization. The addition of high-intensity cycling after heavy-resistance exercise may decrease RFD partly due to muscle architectural changes.

One Week of Bed Rest Leads to Substantial Muscle Atrophy and Induces Whole-Body Insulin Resistance in the Absence of Skeletal Muscle Lipid Accumulation.

Short (<10 days) periods of muscle disuse, often necessary for recovery from illness or injury, lead to various negative health consequences. The current study investigated mechanisms underlying disuse-induced insulin resistance, taking into account muscle atrophy. Ten healthy, young males (age: 23 ± 1 years; BMI: 23.0 ± 0.9 kg · m(-2)) were subjected to 1 week of strict bed rest. Prior to and after bed rest, lean body mass (dual-energy X-ray absorptiometry) and quadriceps cross-sectional area (CSA; computed tomography) were assessed, and peak oxygen uptake (VO2peak) and leg strength were determined. Whole-body insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. Additionally, muscle biopsies were collected to assess muscle lipid (fraction) content and various markers of mitochondrial and vascular content. Bed rest resulted in 1.4 ± 0.2 kg lean tissue loss and a 3.2 ± 0.9% decline in quadriceps CSA (both P < 0.01). VO2peak and one-repetition maximum declined by 6.4 ± 2.3 (P < 0.05) and 6.9 ± 1.4% (P < 0.01), respectively. Bed rest induced a 29 ± 5% decrease in whole-body insulin sensitivity (P < 0.01). This was accompanied by a decline in muscle oxidative capacity, without alterations in skeletal muscle lipid content or saturation level, markers of oxidative stress, or capillary density. In conclusion, 1 week of bed rest substantially reduces skeletal muscle mass and lowers whole-body insulin sensitivity, without affecting mechanisms implicated in high-fat diet-induced insulin resistance.

Low-intensity Resistance Training With Blood Flow Restriction Increases Muscle Function And Mass In Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovia involvement and gradual degradation of peripheral joints. Strengthening exercises are widely recommended for improving muscle function and mass in RA. High-intensity resistance training (~75% 1RM) has been shown effective for both muscle mass and strength gains; however, patients with RA are often unable to exercise at such intensities. Alternatively, low-intensity resistance training (~30% 1RM) combined with partial blood flow restriction (LIO) has been alleged to induce similar gains in muscle function which could be beneficial for RA, as lower loads represent less stress to the affected joints. PURPOSE: To investigate the effects of a LIO training program on muscle strength, mass and functionality in patients with RA. METHODS: Twenty-three female patients with RA were divided into three groups: LIO (30% 1RM associated with partial blood-flow restriction), high-intensity training (HI: 80% 1RM), and control. LIO and HI underwent a 12-week, twice-a-week supervised training program and all patients were assessed for lower-limb 1RM (leg press and knee extension), functionality (timed-stands [TST] and timed-up-and-go test [TUG]), and quadriceps cross sectional area (CSA) at baseline and after the intervention. Absolute changes were tested by ANOVA. RESULTS: HI and LIO resulted in similar increases in leg-press (39.9 and 32.1%, respectively) and knee-extension 1RM (26.8 and 19.8%, respectively), which were significantly greater than control (all p<0.05). Functionality was significantly (all p<0.05) improved in both HI (TST: 10.7%; TUG: -12.3%) and LIO (TST: 9.6%; TUG: -7.3%) when compared with control (TST: -0.9%; TUG: 0.8%). In addition, quadriceps CSA was also significantly (all p<0.05) improved in both trained groups (HI: 12.8%; LIO: 7.7%) when compared with control (-2.0%). CONCLUSIONS: LIO was as effective as conventional HI in improving lower-body strength and muscle mass as well as functionality in RA patients. Importantly, LIO may be more advantageous than HI as lower training loads may be both safer and more enjoyable to these patients while maintaining training effectiveness. We conclude that LIO constitute a promising alternative adjunctive therapy for RA management.

Effects of Periodized Strength Training Regimens on Functional and Morphological Adaptations of Skeletal Muscle

It has been suggested that periodized strength training (ST) regimens optimize the training-induced adaptations. PURPOSE: The purpose of current study was to investigate the effects of different periodized and non-periodized regimens on functional performance and morphological skeletal muscle adaptations. METHODS: Thirty-four participants (age=24.6 ±5.4 years) were random allocated into four groups: control (C), non-periodized (NP), traditional periodized (TP) and daily undulating periodized (UP). Experimental groups underwent 12 weeks of ST twice a week, and performed half-squat and knee extensors exercises (i.e. 2-4 sets, 4-12 repetitions). Maximum dynamic strength (1RM) and quadriceps cross-sectional area (CSA) were evaluated at baseline and after six and 12 weeks of training. RESULTS: Training groups had similar total volume load over the experimental period (NP 92.598 ± 15.340kg; TP: 92.973kg ± 10.760kg; UP 108.367 ± 18.316kg [p>0.05]). Only NP and UP increased 1RM after six weeks (17.0 ± 8.7%, p<0.0001; 12.9 ± 9.9%, p<0.01, respectively). After 12 weeks, NP, TP and UP increased 1RM values (19.5 ± 13.2%; p<0.0001; 17.9 ± 13.7%; p<0.0001; 20.4 ± 9.0%; p<0.0001 respectively). All experimental groups increased quadriceps CSA after six (5.1 ± 2.7%, p < 0.0001) and 12 weeks (9.5 ± 4.5% p < 0.0001) of training. Furthermore, only GPL significantly increased quadriceps CSA between six and 12 weeks (6.4%, p<0.0001). CONCLUSION: Even though experimental groups presented differences in the time-course of functional performance and morphological adaptations, overall between-group effects suggest similar efficiency of the training regimens for healthy male individuals.

Anatomical and neuromuscular variables strongly predict maximum knee extension torque in healthy men.

This study examined the relative influence of anatomical and neuromuscular variables on maximal isometric and concentric knee extensor torque and provided a comparative dataset for healthy young males. Quadriceps cross-sectional area (CSA) and fascicle length (l f) and angle (θ f) from the four quadriceps components; agonist (EMG:M) and antagonist muscle activity, and percent voluntary activation (%VA); patellar tendon moment arm distance (MA) and maximal voluntary isometric and concentric (60°s(-1)) torques, were measured in 56men. Linear regression models predicting maximum torque were ranked using Akaike's Information Criterion (AICc), and Pearson's correlation coefficients assessed relationships between variables. The best-fit models explained up to 72% of the variance in maximal voluntary knee extension torque. The combination of 'CSA+θ f+EMG:M+%VA' best predicted maximum isometric torque (R (2)=72%, AICc weight=0.38) and 'CSA+θ f+MA' (R (2)=65%, AICc weight=0.21) best predicted maximum concentric torque. Proximal quadriceps CSA was included in all models rather than the traditionally used mid-muscle CSA. Fascicle angle appeared consistently in all models despite its weak correlation with maximum torque in isolation, emphasising the importance of examining interactions among variables. While muscle activity was important for torque prediction in both contraction modes, MA only strongly influenced maximal concentric torque. These models identify the main sources of inter-individual differences strongly influencing maximal knee extension torque production in healthy men. The comparative dataset allows the identification of potential variables to target (i.e. weaknesses) in individuals.

Exercise Responses to Gravity-Independent Flywheel Aerobic and Resistance Training.

Although several exercise systems have been developed to mitigate the physiological deconditioning that occurs in microgravity, few have the capacity to positively impact multiple physiological systems and still meet the volume/mass requirements needed for missions beyond low Earth orbit. The purpose of this study was to test the gravity-independent Multi-Mode Exercise Device (M-MED) for both resistance (RE) and aerobic (AE) training stimuli. Eight men and nine women (mean age 22.0 ± 0.4 yr) completed 5 wk of training on the M-MED: RE 4 × 7 squats 2 d/wk, and AE 4 × 4-min rowing bouts at ∼90% Vo2max 3 d/wk. Pre- and post-training data collection included an aerobic capacity test, MR imaging, strength testing, and vastus lateralis muscle biopsy. Vo2max increased 8%, 3RM strength 18%, and quadriceps femoris cross-sectional area (CSA) 10%. Knee extensor strength increased at all isokinetic speeds tested. Subjects also demonstrated improved fatigue resistance in knee extension. At the cellular and molecular level, the biopsy revealed increases in mixed myofiber CSA (13%), citrate synthase activity (26%), total RNA concentration (24%), IGF-I mRNA (77%), and Type IIa myosin heavy chain (MHC) mRNA (8%), and a concomitant decrease in Type IIx MHC mRNA (-23%). None of the changes were gender-specific. Both the functional outcomes and biomarker changes indicate that a very low volume of M-MED exercise results in robust adaptation in the cardiovascular and musculoskeletal systems. The M-MED has the potential to provide a wide range of countermeasure exercises and should be considered for testing in ground-based spaceflight simulation.

Relationships between maximal strength, muscle size, and myosin heavy chain isoform composition and postactivation potentiation.

The purpose of this study was to examine the relationships between maximal voluntary postactivation potentiation (PAP) and maximal knee extensor torque, quadriceps cross-sectional area (CSA) and volume, and type II myosin heavy chain (MHC) isoform percentage in human skeletal muscle. Thirteen resistance-trained men completed a test protocol consisting of 2 isokinetic knee extensions at 180°·s(-)(1) performed before and 1, 4, 7, and 10 min after the completion of 4 maximal knee extensions at 60°·s(-)(1) (i.e., a conditioning activity (CA)). Magnetic resonance imaging and muscle microbiopsy procedures were completed on separate days to assess quadriceps CSA and volume and MHC isoform content. Maximal voluntary PAP response was assessed as the ratio of the highest knee extensor torques measured before and after the CA. There were large to very large correlations between maximal voluntary PAP response and maximal knee extensor torque (r = 0.62) and quadriceps CSA (r = 0.68) and volume (r = 0.63). Nonetheless, these correlations were not statistically significant after adjusting for the influence of type II MHC percentage using partial correlation analysis. By contrast, the strongest correlation was observed for type II MHC percentage (r = 0.77), and this correlation remained significant after adjusting for the other variables. Maximal voluntary PAP response is strongly correlated with maximal knee extensor torque and quadriceps CSA and volume, but is mostly clearly associated with the type II myosin isoform percentage in human skeletal muscle.

Short-term muscle disuse lowers myofibrillar protein synthesis rates and induces anabolic resistance to protein ingestion.

Disuse leads to rapid loss of skeletal muscle mass and function. It has been hypothesized that short successive periods of muscle disuse throughout the lifespan play an important role in the development of sarcopenia. The physiological mechanisms underlying short-term muscle disuse atrophy remain to be elucidated. We assessed the impact of 5 days of muscle disuse on postabsorptive and postprandial myofibrillar protein synthesis rates in humans. Twelve healthy young (22 ± 1 yr) men underwent a 5-day period of one-legged knee immobilization (full leg cast). Quadriceps cross-sectional area (CSA) of both legs was assessed before and after immobilization. Continuous infusions of l-[ring-(2)H5]phenylalanine and l-[1-(13)C]leucine were combined with the ingestion of a 25-g bolus of intrinsically l-[1-(13)C]phenylalanine- and l-[1-(13)C]leucine-labeled dietary protein to assess myofibrillar muscle protein fractional synthetic rates in the immobilized and nonimmobilized control leg. Immobilization led to a 3.9 ± 0.6% decrease in quadriceps muscle CSA of the immobilized leg. Based on the l-[ring-(2)H5]phenylalanine tracer, immobilization reduced postabsorptive myofibrillar protein synthesis rates by 41 ± 13% (0.015 ± 0.002 vs. 0.032 ± 0.005%/h, P < 0.01) and postprandial myofibrillar protein synthesis rates by 53 ± 4% (0.020 ± 0.002 vs. 0.044 ± 0.003%/h, P < 0.01). Comparable results were found using the l-[1-(13)C]leucine tracer. Following protein ingestion, myofibrillar protein bound l-[1-(13)C]phenylalanine enrichments were 53 ± 18% lower in the immobilized compared with the control leg (0.007 ± 0.002 and 0.015 ± 0.002 mole% excess, respectively, P < 0.05). We conclude that 5 days of muscle disuse substantially lowers postabsorptive myofibrillar protein synthesis rates and induces anabolic resistance to protein ingestion.

Bedside assessment of quadriceps muscle by ultrasound after admission for acute exacerbations of chronic respiratory disease.

Hospitalization represents a major event for the patient with chronic respiratory disease. There is a high risk of readmission, which over the longer term may be related more closely to the underlying condition of the patient, such as skeletal muscle dysfunction. We assessed the risk of hospital readmission at 1 year, including measures of lower limb muscle as part of a larger clinical trial. Patients hospitalized with an exacerbation of chronic respiratory disease underwent measures of muscle function including quadriceps ultrasound. Independent factors influencing time to hospital readmission or death were identified. Patients were classified into four quartiles based on quadriceps size and compared. One hundred and ninety-one patients (mean age, 71.6 [SD, 9.1] yr) were recruited. One hundred and thirty (68%) were either readmitted or died. Factors associated with readmission or death were age (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01-1.08; P = 0.015), Medical Research Council (MRC) dyspnea grade (OR, 4.57; 95% CI, 2.62-7.95; P < 0.001), home oxygen use (OR, 12.4; 95% CI, 4.53-33.77; P < 0.001), quadriceps (rectus femoris) cross-sectional area (Qcsa) (OR, 0.34; 95% CI, 0.17-0.65; P = 0.001), and hospitalization in the previous year (OR, 4.82; 95% CI, 2.42-9.58; P < 0.001). In the multivariate analyses, home oxygen use (OR, 4.80; 95% CI, 1.68-13.69; P = 0.003), MRC dyspnea grade (OR, 2.57; 95% CI, 1.44-4.59; P = 0.001), Qcsa (OR, 0.46; 95% CI, 0.22-0.95; P = 0.035), and previous hospitalization (OR, 3.04; 95% CI, 1.47-6.29; P = 0.003) were independently associated with readmission or death. Patients with the smallest muscle spent more days in hospital than those with largest muscle (28.1 [SD, 33.9] vs. 12.2 [SD, 23.5] d; P = 0.007). Smaller quadriceps muscle size, as measured by ultrasound in the acute care setting, is an independent risk factor for unscheduled readmission or death, which may have value both in clinical practice and for risk stratification.

Does vitamin-D intake during resistance training improve the skeletal muscle hypertrophic and strength response in young and elderly men? - a randomized controlled trial.

IntroductionRecent studies have shown that vitamin-D intake can improve skeletal muscle function and strength in frail vitamin-D insufficient individuals. We investigated whether vitamin-D intake can improve the muscular response to resistance training in healthy young and elderly individuals, respectively.MethodsHealthy untrained young (n = 20, age 20–30) and elderly (n = 20, age 60–75) men were randomized to 16 weeks of daily supplementary intake of either 48 μg of vitamin-D + 800 mg calcium (Vitamin-D-group) or 800 mg calcium (Placebo-group) during a period and at a latitude of low sunlight (December-April, 56°N). During the last 12 weeks of the supplementation the subjects underwent progressive resistance training of the quadriceps muscle. Muscle hypertrophy, measured as changes in cross sectional area (CSA), and isometric strength of the quadriceps were determined. Muscle biopsies were analyzed for fiber type morphology changes and mRNA expression of vitamin-D receptor (VDR), cytochrome p450 27B1 (CYP27B1) and Myostatin.ResultsIn the vitamin-D groups, serum 25(OH)D concentration increased significantly and at week 12 was significantly different from placebo in both young men (71.6 vs. 50.4 nmol/L, respectively) and elderly men (111.2 vs. 66.7 nmol/L, respectively). After 12 weeks of resistance training, quadriceps CSA and isometric strength increased compared to baseline in young (CSA p < 0.0001, strength p = 0.005) and elderly (CSA p = 0.001, strength p < 0.0001) with no difference between vitamin-D and placebo groups. Vitamin-D intake and resistance training increased strength/CSA in elderly compared to young (p = 0.008). In the young vitamin-D group, the change in fiber type IIa percentage was greater after 12 weeks training (p = 0.030) and Myostatin mRNA expression lower compared to the placebo group (p = 0.006). Neither resistance training nor vitamin-D intake changed VDR mRNA expression.ConclusionNo additive effect of vitamin-D intake during 12 weeks of resistance training could be detected on either whole muscle hypertrophy or muscle strength, but improved muscle quality in elderly and fiber type morphology in young were observed, indicating an effect of vitamin-D on skeletal muscle remodeling.Trial registrationClinicalTrials with nr. NCT01252381Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0029-y) contains supplementary material, which is available to authorized users.

Effects of exercise intensity and occlusion pressure after 12 weeks of resistance training with blood-flow restriction.

We compared the effects of different protocols of blood-flow restriction training (BFRT) with different occlusion pressures and/or exercise intensities on muscle mass and strength. We also compared BFRT protocols with conventional high-intensity resistance training (RT). Twenty-six subjects had each leg allocated to two of five protocols. BFRT protocols were performed at either 20 or 40 % 1-RM with either 40 or 80 % occlusion pressure: BFRT20/40, BFRT20/80, BFRT40/40, and BFRT40/80. Conventional RT was performed at 80 % 1-RM (RT80) without blood-flow restriction. Maximum dynamic strength (1-RM) and quadriceps cross-sectional area (CSA) were assessed at baseline and after 12 weeks. Regarding muscle mass, increasing occlusion pressure was effective only at very low intensity (BFRT20/40 0.78 % vs. BFRT20/80 3.22 %). No additional increase was observed at higher intensities (BFRT40/40 4.45 % vs. BFRT40/80 5.30 %), with no difference between the latter protocols and RT80 (5.90 %). Exercise intensity played a role in CSA when comparing groups with similar occlusion pressure. Muscle strength was similarly increased among BFRT groups (~12.10 %) but to a lesser extent than RT80 (21.60 %). In conclusion, BFRT protocols benefit from higher occlusion pressure (80 %) when exercising at very low intensities. Conversely, occlusion pressure seems secondary to exercise intensity in more intense (40 % 1-RM) BFRT protocols. Finally, when considering muscle strength, BFRT protocols seem less effective than high-intensity RT.

Skeletal muscle contractility and fatigability in adults with cystic fibrosis

BackgroundRecent discovery of cystic fibrosis transmembrane conductance regulator expression in human skeletal muscle suggests that CF patients may have intrinsic skeletal muscle abnormalities potentially leading to functional impairments. The aim of the present study was to determine whether CF patients with mild to moderate lung disease have altered skeletal muscle contractility and greater muscle fatigability compared to healthy controls. MethodsThirty adults (15 CF and 15 controls) performed a quadriceps neuromuscular evaluation using single and paired femoral nerve magnetic stimulations. Electromyographic and mechanical parameters during voluntary and magnetically-evoked contractions were recorded at rest, during and after a fatiguing isometric task. Quadriceps cross-sectional area was determined by magnetic resonance imaging. ResultsSome indexes of muscle contractility tended to be reduced at rest in CF compared to controls (e.g., mechanical response to doublets stimulation at 100Hz: 74±30Nm vs 97±28Nm, P=0.06) but all tendencies disappeared when expressed relative to quadriceps cross-sectional area (P>0.5 for all parameters). CF and controls had similar alterations in muscle contractility with fatigue, similar endurance and post exercise recovery. ConclusionsWe found similar skeletal muscle endurance and fatigability in CF adults and controls and only trends for reduced muscle strength in CF which disappeared when normalized to muscle cross-sectional area. These results indicate small quantitative (reduced muscle mass) rather than qualitative (intrinsic skeletal muscle abnormalities) muscle alterations in CF with mild to moderate lung disease.

Potential Risks And Distribution Pattern Of Intramuscular Fat In Obese Children

PURPOSE: The purpose of this study was to assess relationship between IMF and physiological and biochemical variables. METHODS: Thirty-seven obese boys and girls participated in this study (age, 10.4 ± 2.1 years; height, 146.2 ± 13.4 cm; weight, 56.1 ± 16.5 kg; percentage of overweight, 41.1 ± 16.8%). This study was conducted a part of treatment of the subjects and was approved by the institutional review board of local committees. Computed tomography (CT) images were taken at the mid-thigh and umbilicus levels. Using the CT images, IMF index of the quadriceps femoris (QF), hamstrings (HM) and adductor (AD) muscle groups based on mean grey scale level of the interested muscle groups and visceral fat cross-sectional area (CSA) were calculated. For the mid-thigh CT image, skeletal muscle CSA and subcutaneous fat was also calculated. Plasma triglyceride, FFA, HDL-cholesterol, total-cholesterol, AST, ALT, glucose and HbA1c were measured from fasting blood drop. RESULTS: IMF index of QF, HM and AD was significantly different in all comparisons: HM was the lowest (1066 ± 6), meaning largest IMF depot, and QF was the highest (1080 ± 3), meaning smallest IMF depot. Stepwise regression analysis revealed that QF CSA, visceral fat CSA, and triglyceride were extracted to predict IMF index in QF (R=0.707, P < 0.01). For IMF index in HM, visceral fat CSA, age, triglyceride, percentage of overweight, and sex were extracted (R=0.806, P < 0.01). Interestingly, percentage of overweight was the only extracted variable to predict IMF index in AD (R=0.529, P < 0.01). CONCLUSIONS: These results suggest that muscle-specific IMF deposition pattern was observed in obese children and that intramuscular fat in each muscle group may have physiological and biochemical specific roles.