Maximal Isometric Knee Extension Research Articles

Effects of whole-body electromyostimulation on function, muscle mass, strength, social participation, and falls-efficacy in older people: A randomized trial protocol.

Resistance training has a positive impact on functional capacity and muscle mass in the elderly. However, due to physical limitations or a simple aversion against regular exercise, a majority of the elderly do not reach the recommended exercise doses. This led us to evaluate the effect of whole-body electromyostimulation (WB-EMS), a novel, time-efficient, and smooth training technology on physical function, fat-free mass, strength, falls-efficacy, and social participation of the elderly. The present study is a randomized, parallel group clinical trial approved by the Ethics Committee of our Institution. Sixty-six volunteers (age ≥ 60 years) will be recruited from the geriatric outpatient department in a tertiary hospital and primary care units and randomized into two groups: WB-EMS group or active control group (aCG). The WB-EMS or aCG protocol will consist of 16 sessions for 8 consecutive weeks, twice per week. The primary outcomes will be maximal isometric knee extension (IKE), functional lower extremity strength, fat-free mass, gait speed, and risk of falls measured before and after intervention. The secondary outcomes will be social participation and falls-efficacy assessed before and after the intervention and at three and six months of follow-up. Participant's satisfaction with and awareness of electrical stimulation therapy will also be assessed immediately after the 8-week intervention. Patients receiving WB-EMS exercises are believed to have better outcomes than those receiving conventional, more time-consuming resistance exercises. Hence, innovative, time-efficient, joint-friendly, and highly individualized exercise technologies (such as WB-EMS) may be a good choice for the elderly with time constraints, physical limitations, or little enthusiasm, who are exercising less than the recommended amounts for impact on muscle mass, strength, and function.

Quadriceps Oxygenation During Exercise in Patients With Anterior Cruciate Ligament Reconstruction.

The causes of persistent muscle weakness after anterior cruciate ligament reconstruction (ACLR) are not well known. Changes in muscle oxygenation have been proposed as a possible mechanism. To investigate changes in quadriceps muscle oxygenation during knee extension in ACLR-involved and ACLR-uninvolved limbs. Case-control study. Laboratory. A total of 20 individuals: 10 patients with primary, unilateral ACLR (7 women, 3 men; age = 22.90 ± 3.45 years, height = 170.81 ± 7.93 cm, mass = 73.7 ± 15.1 kg) and 10 matched control individuals (7 women, 3 men; age = 21.50 ± 2.99 years, height = 170.4 ± 10.7 cm, mass = 68.86 ± 9.51 kg). Each participant completed a single data-collection session consisting of 5-second isometric contractions at 25%, 50%, and 75% of the volitional maximum followed by a 30-second maximal isometric knee-extension contraction. Oxygenated hemoglobin (O2Hb) measures in the reconstructed thigh were continuously recorded (versus the uninvolved contralateral limb as well as the nondominant thigh of healthy control individuals) using 3 wearable, wireless near-infrared spectroscopy units placed superficially to the vastus medialis, vastus lateralis, and rectus femoris muscles. Relative changes in oxygenation were ensemble averaged and plotted for each contraction intensity with associated 90% CIs. Statistical significance occurred where portions of the exercise trials with CIs on the O2Hb graph did not overlap. Effect sizes (Cohen d, 90% CI) were determined for statistical significance. We observed less relative change in O2Hb in patients with ACLR than in healthy control participants in the rectus femoris at 25% (d = 2.1; 90% CI = 1.5, 2.7), 50% (d = 2.8; 90% CI = 2.6, 2.9), and 75% (d = 2.0; 90% CI = 1.9, 2.2) and for the vastus medialis at 75% (d = 1.5; 90% CI = 1.4, 1.5) and 100% (d = 2.6; 90% CI = 2.5, 2.7). Less relative change in O2Hb was also noted for the vastus medialis in ACLR-involved versus ACLR-uninvolved limbs at 100% (d = 2.62; 90% CI = 2.54, 2.70). Quadriceps muscle oxygenation during exercise differed between patients with ACLR and healthy control individuals. However, not all portions of the quadriceps were affected uniformly across contraction intensities.

Effectiveness of the PROMUFRA program in pre-frail, community-dwelling older people: A randomized controlled trial

This study evaluated the effect of PROMUFRA program on physical frailty, kinanthropometric, muscle function and functional performance variables in pre-frail, community-dwelling older people. Participants (n = 50, 75 ± 7 years) were randomly assigned to two groups: intervention group (IG), and control group (CG). The IG performed multi-component exercise program, focused on high-intensity resistance training (HIRT) combined with self-massage for myofascial release (SMMR) for 12 weeks (2 d.wk−1). Two measurements were performed, at baseline and post-3 months. Participants (n = 43) were analyzed and significant differences were found in group-time interaction for muscle mass (p = 0.017), fat mass (p = 0.003), skeletal muscle mass index (p = 0.011), maximum isometric knee extension (p = 0.042), maximum dynamic knee extension (p = 0.001), maximum leg press (p < 0.001), Barthel Index (p = 0.039) and EuroQol 5-dimensions-3-levels (p = 0.012). We conclude that PROMUFRA program is an effective training method to achieve healthy improvements for the pre-frail community.

Early vs. late rate of torque development: Relation with maximal strength and influencing factors

We re-examined the relationship between rate of torque development (RTD) and maximal voluntary contractions (MVC) torque, and investigated some possible neuromuscular determinants of early (≤100 ms) and late (≥200 ms) RTD. Seventeen healthy men performed maximal explosive isometric knee extensions at five joint angles, from which MVC torque, RTD at different time intervals (50–250 ms), and early quadriceps EMG activity (EMG50) were evaluated. Quadriceps muscle thickness (MT) was quantified by longitudinal ultrasonography. The relationship between MVC torque, EMG50 and MT against RTD was assessed with Pearson’s and repeated measures correlation coefficients. Moderate-to-strong correlation coefficients were observed between MVC torque and RTD (r = 0.50–0.88, p < 0.001), with stronger relationships for late RTD than for early RTD. Weak-to-strong correlation coefficients were observed amongst RTD and EMG50 (r = 0.37–0.83, p < 0.001), with stronger relationships for early RTD than for late RTD. Only late RTD was significantly correlated with MT, though only moderately (r = 0.50–0.52, p < 0.05). These findings suggest that early and late knee extension RTD are potentially governed by different neuromuscular factors. Neuromuscular activation seems to have a greater influence on early RTD than on late RTD, and vice versa for muscle mass.

Lower Limb Strength Profile in Elderly with Different Pathologies: Comparisons with Healthy Subjects.

Sarcopenia and muscle strength reduction are a frequent disorder in non-communicable chronic diseases. The aims of this study are: (a) to verify if the absolute and relative to body weight muscle strength of lower limb is affected by the presence of pathology; (b) to verify if the trends are different among knee and ankles joints. One-hundred and forty-five elderly were recruited (16 liver transplant recipients, 48 kidney transplant recipients, 52 elderly with obesity, 30 healthy elderly). Muscular strength of lower limb was evaluated. Evaluation protocol included maximal isometric knee extension, maximal isokinetic knee extension and flexion, maximal isokinetic ankle (both right and left) extension and flexion. A statistically significant interaction between measurement and group membership was found for absolute strength measure (F (4.23, 170.56) = 3.316, p = 0.011, partial η2 (η2p) = 0.076), and relative strength measure(F (4.44, 174.72) = 16.407, p < 0.01, partial η2 (η2p) = 0.294). Elderly patients living with kidney transplants showed the lower level of absolute muscular strength, while relative muscular strength is mainly lacking in the elderly with obesity. The strength profile of elderly subjects is affected by obesity, liver transplantation, and kidney transplantation.

Associations of combined genetic and epigenetic scores with muscle size and muscle strength: a pilot study in older women.

BackgroundInter‐individual variance in skeletal muscle is closely related to genetic architecture and epigenetic regulation. Studies have examined genetic and epigenetic relationships with characteristics of ageing muscle separately, while no study has combined both genetic and epigenetic profiles in ageing muscle research. The aim of this study was to evaluate the association between combined genetic and methylation scores and skeletal muscle phenotypes in older women.MethodsForty‐eight older Caucasian women (aged 65–79 years) were included in this study. Biceps brachii thickness and vastus lateralis anatomical cross‐sectional area (ACSAVL) were measured by ultrasonography. Maximum isometric elbow flexion (MVCEF) and knee extension (MVCKE) torques were measured by a customized dynamometer. The muscle‐driven genetic predisposition score (GPSSNP) was calculated based on seven muscle‐related single nucleotide polymorphisms (SNPs). DNA methylation levels of whole blood samples were analysed using Infinium MethylationEPIC BeadChip arrays. The DNA methylation score was calculated as a weighted sum of methylation levels of sarcopenia‐driven CpG sites (MSSAR) or an overall gene‐wise methylation score (MSSNP, the mean methylation level of CpG sites located in muscle‐related genes). Linear regression models were built to study genetic and epigenetic associations with muscle size and strength. Three models were built with both genetic and methylation scores: (1) MSSAR + GPSSNP, (2) MSSNP + GPSSNP, and (3) gene‐wise combined scores which were calculated as the ratio of the SNP score to the mean methylation level of promoters in the corresponding gene. Additional models with only a genetic or methylation score were also built. All models were adjusted for age and BMI.ResultsMSSAR was negatively associated with ACSAVL, MVCEF, and MVCKE and explained 10.1%, 35.5%, and 40.1% of the variance, respectively. MSSAR explained more variance in these muscular phenotypes than GPSSNP, MSSNP, and models including both genetic and methylation scores. MSSNP and GPSSNP accounted for less than 8% and 5% of the variance in all muscular phenotypes, respectively. The genotype and methylation level of CNTF was positively related to MVCKE (P = 0.03) and explained 12.2% of the variance. The adjusted R 2 and Akaike information criterion showed that models with only a MSSAR performed the best in explaining inter‐individual variance in muscular phenotypes.ConclusionsOur results improve the understanding of inter‐individual variance in muscular characteristics of older women and suggest a possible application of a sarcopenia‐driven methylation score to muscle strength estimation in older women while the combination with a genetic score still needs to be further studied.

Sirolimus for treatment of patients with inclusion body myositis: a randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial.

Inclusion body myositis is the most frequent myositis in patients older than 50 years. Classical immunosuppressants are ineffective in treating inclusion body myositis, and to date there are no recommendations for pharmacological approaches to treatment. When used after organ transplantation, sirolimus can block the proliferation of effector T cells, while preserving T regulatory cells, and induce autophagy, all of which are processes that are impaired in inclusion body myositis. In this pilot study, we aimed to test the efficacy of sirolimus in patients with inclusion body myositis. This randomised, double-blind, placebo-controlled, proof-of-concept, phase 2b trial was done at a single hospital in Paris, France. The study included men and women (aged 45-80 years) who had a defined diagnosis of inclusion body myositis according to established criteria. Eligible participants were randomly assigned (1:1) to receive once-daily oral sirolimus 2 mg or placebo. Centralised balanced block randomisation (blocks of four) was computer generated without stratification. The study comprised a 15-day screening period (days -15 to 0) and a 52-week treatment period (day 0 to month 12). The primary endpoint was the relative percentage change from baseline to month 12 in maximal voluntary isometric knee extension strength. Secondary endpoints included the following assessments at months 6 and 12: 6-min walking distance, isometric muscle strength for hand grip (finger flexors), knee flexion and elbow flexion and extension, forced vital capacity, muscle replacement with fat measured by quantitative nuclear MRI, Inclusion Body Myositis Weakness Composite Index (IBMWCI), Inclusion Body Myositis Functional Rating Scale (IBMFRS), Health Assessment Questionnaire without Disability Index (HAQ-DI), and analyses of T-cell subpopulations by mass cytometry. The primary analysis was done on the intention-to-treat population. The trial is registered at ClinicalTrials.gov, NCT02481453. Between July 15, 2015, and May 13, 2016, we screened 285 patients, 44 of whom were randomly allocated to sirolimus (22 patients) or placebo (22 patients). We observed no difference in the primary outcome of relative percentage change from baseline to month 12 of the maximal voluntary isometric knee extension strength (median difference 3·78, 95% CI -10·61 to 17·31; p=0·85). For secondary outcomes, differences between the groups were not significant for changes in strength of other muscle groups (grip, elbow flexion and extension, or knee flexion), IBMWCI, IBMFRS, and lower limb muscle fat fraction. However, we observed significant differences in favour of sirolimus between the study groups for HAQ-DI, forced vital capacity, thigh fat fraction, and 6-min walking distance. Ten (45%) of 22 patients in the sirolimus group had a serious adverse event compared with six (27%) of 22 patients in the placebo group. Four (18%) patients in the sirolimus group stopped their treatment because of adverse events (severe mouth ulcers, aseptic pneumonia, renal insufficiency, and peripheral lower limb oedema), which resolved after treatment discontinuation. Canker sores were the most frequent side-effect and were mainly mild or moderate in ten patients. We found no evidence for efficacy of sirolimus for treating inclusion body myositis based on maximal voluntary isometric knee extension strength and other muscle strength measures, and the side-effects of treatment were substantial for some patients. However, we believe there was enough evidence of benefit in certain secondary outcomes to pursue a multicentre phase 3 trial to further assess the safety and efficacy of sirolimus. Institut national de la santé et de la recherche médicale, Direction générale de l'offre de soins, and Association Française contre les Myopathies.

Quadriceps Strength And Rate Of Torque Development Are Associated With Countermovement Jump Knee Kinetics Post-aclr

Quadriceps neuromuscular dysfunction is ubiquitous after anterior cruciate ligament reconstruction (ACLR) and can impair knee function during athletic activities. While peak quadriceps strength is often measured, time-dependent metrics such as rate of torque development may be important to sports performance. PURPOSE: To determine the relationships between quadriceps strength, rate of torque development, time since surgery, and knee joint kinetics during jumping in collegiate athletes up to 2 years post-ACLR. METHODS: 31 Division I athletes (age 20.3±1.3, BMI 26.1±3.9 kg/m2, 17 female) performed countermovement jumps (CMJ) on force plates while whole body kinematics were recorded and completed maximal and rapid voluntary isometric knee extension (KE) contractions. Sagittal plane KE impulses were computed for concentric (CON) and landing (LAND) CMJ phases; KE peak torque (PT) and rate of torque development from 20-80% of peak torque (RTD) were extracted from isometric KE efforts. Limb symmetry indices (LSI) were computed and clinically relevant cutoffs of 90% LSI were investigated. A mixed effects model accounted for repeated measurements and assessed the relationships of PT, RTD, and time from surgery with CON and LAND. All possible pairwise interactions were tested. RESULTS: Among 31 athletes, 81 tests were completed 4-24 months post-surgery. PT and RTD were significantly correlated with CON (PT: p=.001, RTD: p=.044) and LAND (PT: p=.009, RTD: p=.008). No significant pairwise interactions between PT, RTD, and time from surgery were detected. Among 24 instances of PT LSI ≥ 90%, mean CON and LAND LSI were 87.3% and 94.2%, respectively. In comparison, among 15 occurrences of RTD LSI ≥ 90%, mean CON and LAND LSI were 93.0% and 102.2%. Among the 22 assessments completed ≥ 1 year post-surgery, mean CON and LAND LSI were 82.4%, and 83.3%, respectively. However, when CON and LAND LSI were ≥ 90%, mean PT was 94.5-94.7% and mean RTD was 85.1-85.3%. CONCLUSIONS: Both peak and rapid knee extensor torque development are strongly associated with symmetrical sagittal plane CMJ knee mechanics. CMJ knee kinetic asymmetries did not resolve over time, independent from quadriceps function. Restoring maximal and rapid quadriceps torque capacity appears to be an important step in recovering symmetrical CMJ mechanics post-ACLR.

Does Muscle Glycogen Content Account For The Contralateral Force Deficit During Unilateral Fatigue?

Performing unilateral contractions to exhaustion has been shown to lead to force deficits of both the exercised and unexercised limbs. It has been proposed that the contralateral force deficits are of neural origin, and not due to peripheral mechanisms of fatigue (e.g. glycogen depletion). While this proposed model appears likely, it remains speculative as the absence of peripheral factors to contralateral force deficits have not been verified. PURPOSE: Therefore, the purpose of the study was to quantify the changes in muscle glycogen content and maximal force of both limbs in response to unilateral fatigue. METHODS: Nineteen healthy subjects performed two maximal voluntary isometric (MVC) knee extensions of each leg before (PRE) and after (POST) a fatiguing protocol of the right leg. The fatiguing protocol consisted of repeated 56 second long ramp contractions of the right leg at 30% MVC until failure. During the plateau phase of each contraction, ultrasound images were taken at the midpoint of the rectus femoris (RF). The echo intensity, which has been shown to be sensitive to acute changes in muscle glycogen content, was analyzed from each image of the RF muscle. RESULTS: A two way repeated measures ANOVA showed a significant time × limb interaction (p < 0.001) for MVCs. Follow-up paired sample t-tests indicated that both limbs showed significant force loss. However, the right leg (-33%, from 773.36±191.79 to 517.13±136.72, p < 0.001) demonstrated a much larger force deficit than the left leg (-9.7%, from 803.07±215.32 to 725.04±198.44, p = 0.002). For echo intensity, the right leg demonstrated a significant change (8.8%, from 48.64±7.70 to 52.58±8.68, p = 0.009) from PRE to POST. However, the left leg did not change (1.34%, from 53.93±7.65 to 54.65±7.72, p = 0.621). It is worth noting the increase in echo intensity, such as seen with the right leg, represents a decrease in tissue density (e.g. decreased muscle glycogen content). CONCLUSION: Our findings suggest peripheral fatigue mechanisms, such as muscle glycogen content, were not responsible for the decreased force in the contralateral limb. This absence of peripheral, intracellular changes supports the original proposal that the contralateral force deficit is of a central, neural origin.

Mechanical and Material Tendon Properties in Patients With Proximal Patellar Tendinopathy.

IntroductionThe effect of chronic patellar tendinopathy on tissue function and integrity is currently unclear and underinvestigated. The aim of this cohort comparison was to examine morphological, material, and mechanical properties of the patellar tendon and to extend earlier findings by measuring the ability to store and return elastic energy in symptomatic tendons.MethodsSeventeen patients with chronic (>3 months, VISA-P < 80), inferior pole patellar tendinopathy (24 ± 4 years; male = 12, female = 5) were carefully matched to controls (25 ± 3 years) for training status, pattern, and history of loading of the patellar tendon. Individual knee extension force, patellar tendon stiffness, stress, strain, Young’s modulus, hysteresis, and energy storage capacity, were obtained with combined dynamometry, ultrasonography, magnetic resonance imaging, and electromyography.ResultsAnthropometric parameters did not differ between groups. VISA-P scores ranged from 28 to 78 points, and symptoms had lasted from 10 to 120 months before testing. Tendon proximal cross-sectional area was 61% larger in the patellar tendinopathy group than in the control group. There were no differences between groups in maximal voluntary isometric knee extension torque (p = 0.216; d < −0.31) nor in tensile tendon force produced during isometric ramp contractions (p = 0.185; d < −0.34). Similarly, tendon strain (p = 0.634; d < 0.12), hysteresis (p = 0.461; d < 0.18), and strain energy storage (p = 0.656; d < 0.36) did not differ between groups. However, patellar tendon stiffness (−19%; p = 0.007; d < −0.74), stress (−27%; p< 0.002; d < −0.90) and Young’s modulus (−32%; p = 0.001; d < −0.94) were significantly lower in tendinopathic patients compared to healthy controls.DiscussionIn this study, we observed lower stiffness in affected tendons. However, despite the substantial structural and histological changes occurring with tendinopathy, the tendon capacity to store and dissipate energy did not differ significantly.

Hamstring to quadriceps strength ratio and cross-sectional area of the quadriceps and hamstrings muscles assessed using extended field-of-view ultrasonography

ABSTRACT This study examined whether the association between hamstring (H) and quadriceps (Q) strength with size depends on the region and the muscle used to examined cross-sectional area (CSA). Maximum isometric contraction knee extension and flexion torque was obtained from 20 young participants while Q and H CSA was recorded using extended field of view ultrasonography at four sections along the thigh. Stepwise linear regression models using the maximum CSA of individual muscles showed a significant association of quadriceps (R2 = 0.793) and hamstring (R2 = 0.275) CSA with MVC torque (p < 0.05). The association was lower when maximum or section-specific muscle group CSAs were used as indices of size. The H:Q CSA ratio showed a significant association (R2 = 0.275, p < 0.05) and a moderate correlation (r = 0.48) with H:Q torque ratio. These results indicated that the association between muscle CSA and strength differs between the knee extensors and flexors. Amongst the various indices of muscle size, the combination of maximum CSA values of each muscle displayed the greatest relationship between strength and CSA. The H:Q CSA ratio can explain a significant but small part of the H:Q isometric strength ratio.

Quantitative Analysis of Patellar Tendon After Total Knee Arthroplasty Using Echo Intensity: A Nonrandomized Controlled Trial of Alpine Skiing

BackgroundDespite the knee extensor weakness, less attention has been paid to the evaluation of patellar tendon after total knee arthroplasty (TKA). We previously observed patellar tendon hypertrophy after TKA. The purpose of this study is to reanalyze these ultrasound data to detect whether brightness mode ultrasound imaging reflects pathological changes of the patellar tendon after TKA. MethodsTwenty-eight participants with post unilateral TKA were assigned to an intervention group or control group. The intervention group underwent a 12-week skiing program. Patellar tendon mechanical properties were obtained by combining isometric dynamometry, ultrasound imaging, and electromyography in operated knee and nonoperated knee. Luminosity ratio (LR) was measured using echo intensity in a relaxed and maximally loaded phase. ResultsBaseline comparisons revealed significant effects of the surgical side (P < .001) and loading phase (P = .017), but no interaction between leg and phase (P < .149). LR of the operated knee was significantly lower than LR of the nonoperated knee in relaxed (P < .001) and maximally loaded phases (P = .003). In addition, there was a significant correlation between LR of maximum phase and isometric knee extension torque (r2 = 0.156, P = .038). However, LR was not related to patellar tendon stiffness, Young’s modulus, or strain. There was a significant time effect in knee extension torque, but no time effects on LR and tendon force. ConclusionPatellar tendon LR is decreased along with degenerative change after TKA. Ultrasound imaging provides a promising metric to acquire in vivo patellar tendon pathological assessment after TKA.

Long-term assessment of morphological, functional, and quantitative parameters of skeletal muscle in older patients after unilateral total hip arthroplasty.

Total hip arthroplasty (THA) is performed for pain relief in patients with osteoarthritis of the hip joint. After THA, patients may recover muscle mass and physical function. Muscle quality is the main parameter used to indicate intramuscular fat content, and it is related with muscle function in older individuals. However, how THA affects muscle quality, as determined by echo intensity (EI), is not well understood. The purpose of this study was to determine the long-term characteristics of EI, muscle quantity, muscle function, and physical functions in the patients with THA surgery. In order to achieve the purpose, we performed two comparison. First, we compared muscle EI, quantity and function in operated leg with unoperated legs in the same patients and with the legs of healthy adults (i.e., both unoperated legs). Second, we compared physical functional tests between THA patient and age and body composition matched controls. Twenty-two older individuals (age: 67.1±5.3years, height: 160.9±7.1cm, body mass: 62.6±16.1kg) who underwent unilateral THA several (5.2±3.1) years ago (THA group) and 22 healthy controls with matching age and body composition (age: 68.3±4.4years, height: 160.3±7.9cm, body mass: 61.7±7.8kg) (CON group) participated in this case-control study. EI, an index of muscle quality, and muscle thickness (MT), an index of muscle quantity, were measured from B-mode transverse images of the rectus femoris obtained through ultrasound. The maximal isometric knee extension torque was measured in both the operated and unoperated legs in the THA group and in the right leg in the CON group (control leg); physical function tests, such as sit-to-stand, walking speed, hip adduction, and abduction torque assessments, were performed in both groups. MT and maximal isometric knee extension torque in operated leg were not different with unoperated, and control legs; the EI in the operated leg was significantly higher than that in the control leg (106.9±16.9 vs. 92.4±21.0a.u., P<0.05). The THA group demonstrated slower walking speed and lower hip abduction torque than the CON group (walking speed: 1.3±0.2 vs. 1.5±0.2m/s; hip abduction torque 1.2±0.3 vs. 1.5±0.5Nm/kg, P<0.05). Several years after THA, the operated legs completely recovered the same level of muscle quantity as that in healthy participants but with lower muscle quality and hip joint function. These defects may be associated with locomotive dysfunction in older THA patients.

Effect of pulsed ultrasound versus placebo on muscle soreness perception and muscular performance

The purpose of this study was to compare the analgesic effect of pulsating ultrasound treatment and placebo on delayed onset of muscle soreness produced by an eccentric exercise bout. In addition, the effect of pulsed ultrasound on muscular performance following an eccentric exercise bout was studied. Eighteen untrained subjects were randomly assigned to: 1) ultrasound (A) [N = 6] over the areas of concentrated muscle soreness, i.e. proximal vastus lateralis and distal vastus medialis; 2) placebo ultrasound (B) [N = 6]; and 3) no therapeutic intervention (C) [N = 6]. Baseline data were recorded for maximum isometric knee extension contraction (MVC), maximum knee extension torque (MT), knee extension work (W), and soreness perception (SP). All values were subsequently reassessed 24 and 48 hours after intense muscular activity. Immediately following the 24 hour reassessment the A group received ultrasound treatment, the B group received placebo ultrasound, while the C group received no treatment. Percent deviation from baseline of SP, MVC, MT and W were significantly less for A than B and C (p less than 0.05) at 48 hours post muscle soreness bout. These data indicate that pulsed ultrasound accelerates restoration of normal muscle performance, and thus is effective in decreasing delayed onset of muscle soreness. The mechanism for decreasing soreness perception in the muscle is unknown, but may be related to decreasing intramuscular pressure and/or decreasing the inflammatory response.

Effect of age and sex on strength and spatial electromyography during knee extension

BackgroundMultichannel surface electromyography (EMG) is a method to examine properties of motor unit (MU) activity using multiple electrodes arranged on a two-dimensional grid. This technique can be used to examine alterations in EMG activity distribution due to contraction intensity as well as due to physiological differences such as age or sex. Therefore, the purpose of this study was to compare strength and high-density surface EMG (HDsEMG) features during isometric and isokinetic knee extensions between older and younger men and women.MethodsTwenty younger (ages 19–25 years) and twenty older (ages 64–78) men and women performed submaximal and maximal isometric (at a joint angle of 90°) and isokinetic knee extensions, while HDsEMG was recorded from the vastus lateralis. Spatial distribution was estimated using the root mean square (RMS), and 2-dimensional (2D) maps were developed to examine spatial features. Coefficient of variation (CV) and modified entropy were used to examine alterations in muscle heterogeneity and pattern. Peak torque and HDsEMG parameters were compared across age and gender.ResultsYounger males and females produced significantly higher mean torque than the older group (p < 0.001) for all contractions. Both age- and sex-related significant differences (p < 0.05) were found for EMG spatial features suggesting neuromuscular differences. Modified entropy was significantly higher and CV was lower for young females compared to young males (p < 0.05) across both isometric and isokinetic contractions.ConclusionsWe found that isometric and isokinetic knee extension strength, spatial distribution, and intensity differ as a function of age and sex during knee extensions. While there were no differences detected in entropy between age groups, there were sex-related differences in the younger age category. The lack of age-related differences in entropy was surprising given the known effects of aging on muscle fiber composition. However, it is often reported that muscle coactivation increases with age and this work was limited to the study of one muscle of the knee extensors (vastus lateralis) which should be addressed in future work. The findings suggest while both age and sex affect muscle activation, sex had a greater effect on heterogeneity. The results obtained will help to develop improved rehabilitation programs for aging men and women.

Body mass index moderates the association between gait kinetics, body composition, and femoral knee cartilage characteristics.

This study compared femoral cartilage characteristics between age- and sex-matched individuals with (n = 48, age = 22.8 ± 3.5 years; body mass index [BMI] = 33.1 ± 4.1 kg/m2 ) and without obesity (n = 48 age = 22.0 ± 2.6 years; BMI = 21.7 ± 1.7 kg/m2 ) and evaluated the associations between body composition, quadriceps function, and gait kinetics with femoral cartilage characteristics. Medial and lateral femoral cartilage thickness, medial:lateral thickness ratio and medial and lateral cartilage echo intensity were measured using ultrasound imaging. Body composition was assessed using air displacement plethysmography. Quadriceps function was assessed via maximal isometric knee extension. Three-dimensional gait biomechanics were recorded to extract peak external knee flexion and adduction moments, and peak loading rate of the vertical ground reaction force. Cartilage outcomes were compared between groups using one-way multivariate analysis of variance. Stepwise moderated regression evaluated the association between body composition, quadriceps function, and gait kinetics with femoral cartilage outcomes in individuals with and without obesity. Medial (75.24 vs 65.84; P < .001, d = 1.02) and lateral (58.81 vs 52.22; P < .001, d = 0.78) femoral cartilage echo intensity were higher in individuals with compared with those without obesity. A higher body fat percentage was associated with higher medial and lateral cartilage echo intensity (ΔR2 = 0.09-0.12) in individuals with obesity. A higher knee adduction moment was associated with a larger medial:lateral thickness ratio (ΔR2 = 0.09) in individuals without obesity. No associations were found between quadriceps function and cartilage outcomes. These findings suggest that high body fat in adults with obesity is associated with cartilage echo intensity. The obese body mass index was also associated with a lack of a positive relationship between cartilage thickness and joint loading during walking.

Practice day may be unnecessary prior to testing knee extensor strength in young healthy adults

ABSTRACT A practice session is common prior to strength testing. However, the benefits of practice have not been previously reported. The purpose of this study was to determine the effect of a practice session on peak torque, mean torque and between trial variability across three test days. We hypothesized that peak and mean torque would be higher and less variable the second and third test days than the first. Twenty-five healthy, young participants completed 3 maximal voluntary isometric and isokinetic knee extensions on three separate days. No difference in isometric torque was found between days 1 and 2, but there was a significant decrease in isokinetic torque (8.45 Nm). There was a significant decrease in both mean isometric and isokinetic torque from day 1 to day 3 (12.67 and 13.59 Nm). Contrary to our hypothesis, no benefit from a practice session was found. Healthy, young adults are able to produce peak knee extensor torques on the first day of testing and do not demonstrate any benefit from additional testing. Thus, a practice day preceding isometric and isokinetic knee extensor strength testing may not be necessary when testing healthy, young participants, and may, in fact, negatively impact subsequent strength measurements.

Routine monitoring of isometric knee extension strength in patients with muscle impairments using a new portable device: cross-validation against a standard isokinetic dynamometer

Objective: Muscle strength is a critical clinical hallmark in both health and disease. The current study introduces a novel portable device prototype (MyoQuad) for assessing and monitoring maximal voluntary isometric knee extension torque (MVIT). Approach: Fifty-six patients with inclusion body myositis were studied. Knee extension weakness is a key feature in this inflammatory muscle disease. Cross-validation with an isokinetic dynamometer (Biodex System 3 Pro) was performed. Between-day reproducibility and ability to monitor changes in muscle strength over time compared to the gold standard method as a reference, were also investigated. Main results: The measurement was feasible even in the weakest patients. Agreement between methods was excellent (standard error of measurement (SEM) was 3.8 Nm and intra-class correlation coefficient (ICC) was 0.973). Least significant difference (LSD) was 4.9 and 5.3 Nm for the MyoQuad and the Biodex, respectively Measurements using the MyoQuad exhibited excellent between-day reproducibility (SEM was 2.4 Nm and ICC was 0.989 versus 2.6 Nm and 0.988 using the Biodex). Changes in MVIT at 6 and 12 months were similar between methods (timepoint × method interaction was not significant; all p > 0.19); strength changes classified according to LSD at 6 and 12 months were consistent between methods (>70% consistent classification)). Significance: The measurement of MVIT using the MyoQuad offers a cost-effective, portable and immediate alternative for the routine measurement of maximal voluntary isometric strength of the quadriceps. The MyoQuad offers a comfort and stability that cannot be provided by standard hand-held dynamometers. These results support quantitative muscle strength assessment using fixed yet flexible dynamometry within clinical routine and multicenter trials.

Impact of daily protein and energy intake and distribution on muscle mass and strength in Danish older individuals-The CALM study

AbstractThe importance of dietary protein for the maintenance of muscle mass and strength is heavily discussed. However, adequate energy intake is an underlying assumption but often not considered. In this study, we investigated the impact of daily intake and meal distribution of both protein and energy on muscle mass and strength. In a cross-sectional study, a total of 184 older individuals (gender: 86F/98M, age: 70.2 ± 3.9 yrs, BMI: 25.4 ± 3.7 kg/m2; means ± SD) were recruited. Participants underwent a 3-day weighed dietary record, Dual-energy X-ray Absorptiometry (DXA) scan, hand-grip strength, and Maximal Voluntary Isometric knee-extension Contraction (MVIC). Participants were divided into two categories: lower (LOW; &lt; 0.83 g/adjusted(a)BW/day) or higher (HIGH; ≥ 1.1 g/aBW/day) protein intake levels analysed by gender to characterize a daily protein and energy intake pattern. Main meal protein and energy intake distributions were calculated, and correlations were made. Further, energy intake at breakfast and lunch divided by total energy intake (energy ratio) was correlated with appendicular skeletal muscle index (ASMI), hand-grip strength, and MVIC were determined using the LOW/HIGH-protein-intake categorization. Further, gender-specific ASMI, hand-grip strength and knee extension were compared based on the following four distinct daily protein intake ranges: &lt; 0.66; ≥ 0.66- &lt; 0.83; ≥ 0.83- &lt; 1.1; ≥ 1.1 g/aBW/day. A positive correlation appeared between protein and energy intake in all main meals (r ≥ 0.57, p &lt; 0.0001). In the LOW category, positive correlations were found between energy ratio and ASMI (r = 0.16, p = 0.048), hand-grip strength (r = 0.40, p = 0.0009), and MVIC (r = 0.36, p = 0.0019), whereas no associations were found in the HIGH category. ASMI, hand grip, and MVIC were similar regardless of the protein intake ranges, though with women being lower than men (p &lt; 0.05) in all outcomes. These results show that total daily protein intake did not affect muscle mass and strength in our cohort. However, our data demonstrate that greater energy intake in breakfast and lunch relative to total energy intake is associated with higher muscle mass and strength, particularly when protein intake is lower than 0.83 g/aBW/day, indicating the potential importance of meal energy content at lower intakes of protein.

Preliminary effect and feasibility of physiotherapy with strength training and protein-rich nutritional supplement in combination with anabolic steroids in cross-continuum rehabilitation of patients with hip fracture: protocol for a blinded randomized controlled pilot trial (HIP-SAP1 trial)

BackgroundA 2014 Cochrane review evaluating the effect of anabolic steroids after hip fracture concluded that the quality of the studies was insufficient to draw conclusions on the effects and recommended further high-quality trials in the field. Therefore, the aim of this pilot trial is to determine the preliminary effect and feasibility of a 12-week multimodal intervention consisting of physiotherapy (with strength training), protein-rich nutritional supplement and anabolic steroid on knee-extension muscle strength and function 14 weeks after hip fracture surgery.MethodsWe plan to conduct a randomized, placebo-controlled pilot trial with 48 patients operated for acute hip fracture. The patients are randomized (1:1) to either (1) physiotherapy with protein-rich nutritional supplement plus anabolic steroid or (2) physiotherapy with protein-rich nutritional supplement plus placebo. Outcome assessments will be carried out blinded at baseline (3–10 days after surgery) and at 14 weeks after entering the trial. Primary outcome is the change from baseline to follow-up in maximal isometric knee-extension muscle strength in the fractured limb. Secondary outcomes are physical performance test, patient-reported outcomes, and measures of body composition.DiscussionIf the trial is found feasible and the results show an indication of anabolic steroid being a relevant addition to further enhance the recovery of muscle strength and function in an enhanced recovery after surgery program, this trial will constitute the basis of a larger confirmatory trial.Trial registrationClinicalTrials.gov, NCT03545347. Preregistered on 4 June 2018.