Isotonic Muscle Research Articles

Novel Method to Assess Treatment Effcacy in Preclinical Peripheral Arterial Disease Studies

Background: Peripheral arterial disease (PAD), a condition caused by atherosclerotic narrowing or occlusion of blood vessels in the lower extremities, affects ~200 million adults globally and lacks effective treatment options to improve limb function. Cilostazol is the only approved pharmacological treatment option for PAD patients, but its effect on walking performance is modest and the drug is not widely used clinically. Over the past several decades, numerous therapies (drug, gene, and cell-based) have shown promise in the preclinical setting but failed to achieve primary outcomes in clinical trials. While the failure of therapeutic translation is complex, most preclinical studies have employed perfusion recovery as a primary outcome variable whereas most clinical trials in PAD patients employ the six-minute walk test. Although perfusion is an important contributor to limb function and walking performance, assessing preclinical therapeutics solely via perfusion recovery may be a flawed approach. Objective: To address the need for a more comprehensive method to assess the effcacy of preclinical PAD therapeutics, we aimed to develop a protocol to assess hindlimb function that incorporates assessment of muscle power and perfusion across a six-minute testing period. Methods: To assess muscle contractile performance, the tibialis anterior or plantarflexor muscles were carefully exposed and the distal tendon mounted to the force-length controller (Aurora Scientific) and the muscles were stimulated via the sciatic nerve in anesthetized C57BL6 mice. After obtaining isometric forces, a six-minute functional test was performed using repeated isotonic (shortening) contractions against a submaximal load (30% or 45% of the reference force). Muscle fatigue was measured as a change in power across the testing period. Throughout the test, laser Doppler flowmetry was used to measure muscle blood flow. Hindlimb ischemia was used as an experimental model of PAD. Results: In healthy mice without PAD, the test produced the expected dose-dependent relationship between fatigue and workload with contractions performed at 30% of the reference force having less fatigue compared to 45% of the reference force ( P=0.0051), without a significant difference in muscle blood flow between the conditions. Compared the mice that received a sham surgery, those subjected to hindlimb ischemia displayed significantly lower maximal isometric forces (1514 ± 118 mN vs. 880 ± 85 mN, P=0.0001) and power at 35% maximal force (280 ± 12 vs. 105 ± 46 watts/kg, P=0.0002). Whereas sham mice lost ~25% power across the six-minute test, HLI mice displayed a ~70% loss of power. Regarding muscle blood flow, sham mice increased blood flow ~250% whereas HLI mice were only able to increase blood flow to ~105% ( P<0.001). Conclusions: This newly developed protocol successfully combines isotonic muscle function and limb perfusion assessments in the hindlimb of mice and can detect differences between healthy and PAD mice. Future work is needed to fully evaluate the accuracy and sensitivity of this method to select therapeutics in preclinical PAD models. This study was supported by National Institutes of Health (NIH) grant R01-HL149704 (T.E.R.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Understanding Platysma Muscle Contraction Pattern and Its Relationship to Platysmal Banding: A Real-Time Ultrasound Study.

Addressing neck contouring with surgical and nonsurgical aesthetic procedures includes understanding the origin of platysmal banding. A theory was postulated to explain this phenomenon by isometric vs isotonic muscular contraction patterns. However, no scientific proof had been provided to date for its correctness. The aim of this study was to confirm the correctness of the platysmal banding theory based on isometric vs isotonic muscular contractions. Eighty platysma muscles from 40 volunteers (15 males and 25 females) were investigated (mean age 41.8; SD 15.2 years; mean BMI of 22.2; SD 2.3 kg/m2). Real-time ultrasound imaging was utilized to measure the increase in local muscle thickness inside and outside of a platysmal band as well as platysma mobility. Within a platysmal band, the local thickness of the muscle increases during muscular contractions by 0.33 mm (37.9%; P < .001). Outside of a platysmal band the thickness of the platysma muscle decreased by 0.13 mm (20.3%; P < .001). It was identified that within a platysmal band no gliding was detectable, whereas outside of a band an average muscle gliding of 2.76 mm was observed. The results confirm the correctness of the isometric vs isotonic platysma muscle contraction pattern theory: isotonic muscle contraction (gliding without increase in tension and therefore in muscle thickness) vs isometric muscle contraction (no gliding but increase in tension and therefore in muscle thickness). These 2 types of contraction patterns occur within the platysma simultaneously and are an indicator for zones of adhesion in the neck to guide surgical and nonsurgical aesthetic procedures.

Pattern Matching for Real-Time Extraction of Fast and Slow Spectral Components from sEMG Signals.

Previous studies have demonstrated the potential of surface electromyography (sEMG) spectral decomposition in evaluating muscle performance, motor learning, and early diagnosis of muscle conditions. However, decomposition techniques require large data sets and are computationally demanding, making their implementation in real-life scenarios challenging. Based on the hypothesis that spectral components will present low inter-subject variability, the present paper proposes the foundational principles for developing a real-time system for their extraction by utilizing a pre-defined library of components derived from an extensive data set to match new measurements. The model library was tailored to fulfill specific requirements for real-time system application and the challenges encountered during implementation are discussed in the paper. For system validation, four distinct data sets comprising isotonic and isometric muscle activations were utilized. The extracted during validation showed low inter-subject variability, suggesting that a wide range of physiological variations can be described with them. The adoption of the proposed system for muscle analysis could provide a deeper understanding of the underlying mechanisms governing different motor conditions and neuromuscular disorders, as it allows for the measurement of these components in various daily-life scenarios.

ACUTE EFFECT OF BLOOD FLOW RESTRICTED RESISTANCE EXERCISE ON IRISIN AND SEX HORMONES

Purpose: The relationship between exercise and irisin and sex hormone release is unclear and is of interest to current research. This study aimed to investigate the acute effect of blood flow restricted (BFR) resistance exercise on irisin and sex hormones.&#x0D; Material and Methods: The study included healthy males over 18 years of age. Participants' physical activity levels were determined using International Physical Activity Questionnaire (IPAQ). Participants underwent body composition analysis and isotonic muscle strength measurement and were randomly divided into 3 groups: low-intensity (20% of 1-RM) resistance exercise with BFR, high-intensity (70% of 1-RM) resistance exercise without BFR, and a control group. Blood samples were obtained 15 minutes post-exercise to assess acute irisin, testosterone, and estrogen responses.&#x0D; Results: The study included 17 healthy males. The average age was 26.1±2.9 years, mean physical activity was 1259.2±1003.1 MET/week, and mean 1-RM max (as measured with isotonic muscle strength test) was 41.1±7.5 kg. The descriptive characteristics of the three groups were statistically similar (p&gt;0.05). The acute post-intervention irisin and sex hormone levels were not statistically different between the groups (p&gt;0.05).&#x0D; Conclusion: Acute changes in irisin and sex hormone levels were not statistically different for low-intensity BFR and high-intensity non-BFR exercise.

Greater neuromuscular fatigue following low-load blood flow restriction than non-blood flow restriction resistance exercise among recreationally active men.

The purpose of this study was to examine the acute effects of low-load blood flow restriction (LLBFR) and low-load non-BFR (LL) on neuromuscular function after a bout of standardized fatiguing leg extension muscle actions. Fourteen men (mean age ± SD = 23 ± 4 yr) volunteered to participate in this investigation and randomly performed LLBFR and LL on separate days. Resistance exercise consisted of 75 isotonic unilateral leg extension muscle actions performed at 30% of one-repetition maximum. Before (pretest) and after (posttest) performance of each bout of exercise, strength and neural assessments were determined. There were no pretest to posttest differences between LLBFR and LL for maximal voluntary isometric contraction (MVIC) torque or V wave/M wave responses (muscle compound action potentials assessed during a superimposed MVIC muscle action), which exhibited decreases (collapsed across condition) of 41.2% and 26.2%, respectively. There were pretest to posttest decreases in peak twitch torque (36.0%) and surface electromyography amplitude (sEMG) (29.5%) for LLBFR but not LL and larger decreases in voluntary activation for LLBFR (11.3%) than for LL (4.5%). These findings suggested that LLBFR elicited greater fatigue-induced decreases in several indexes of neuromuscular function relative to LL. Despite this, both LLBFR and LL resulted in similar decrements in performance as assessed by maximal strength.NEW & NOTEWORTHY The application of blood flow restriction induces greater acute neuromuscular fatigue relative to nonrestricted conditions. Resistance exercise with blood flow restriction elicited a greater reduction in twitch responses. These neuromuscular differences might explain the more favorable adaptations achieved with blood flow restriction that are likely a function of metabolic stress and subsequent changes in efferent neural drive.

Effects of Cardiac Rehabilitation on Physical Fitness, Physical Function, and Self-reported Outcomes in Patients ≥80 yr: A RANDOMIZED CONTROLLED TRIAL.

The beneficial effects of exercise-based cardiac rehabilitation (CR) after an acute coronary syndrome (ACS) are well known, but patients ≥80 yr have been less studied. The aim was to evaluate the effects of CR on patients with ACS ≥80 yr on peak cardiorespiratory fitness (CRF), physical function, and patient-reported outcome measures (PROMs) compared with a control group. A total of 26 patients with ACS, median age 82 (81, 84) yr, were randomized to hospital-based CR combined with a home-based exercise program (CR group) or to a control group (C) for 4 mo. Outcomes were assessed at baseline and 4 mo and included the peak CRF (primary outcome), 6-min walk test (6MWT), muscle endurance, Timed Up and Go (TUG), Short Physical Performance Battery (SPPB), one-leg stand test, and PROMs. There were no significant differences between the groups in peak CRF. The CR group improved significantly in terms of the 6MWT ( P = .04), isotonic muscle endurance ( P < .001), one-leg stand test ( P = .001), SPPB total score ( P =.03), Activities-specific Balance Confidence ( P =.01), and anxiety ( P =.03), as compared with C. There were no significant intergroup differences in the TUG, the self-reported health question or depression. Patients with ACS ≥80 yr improved in walking distance, muscle endurance, physical function, and PROMs, but not in peak CRF, by participating in a CR program. These results suggest an increased referral to CR for this growing group of patients to enable preserved mobility and independence in daily living, but this needs to be confirmed in larger studies.

Technical innovation of Ervin G Erdös: A mechanical transducer for isotonic muscle contractions

I wrote on the renowned pharmacologist Professor Ervin G Erdös and his scientific opus in my reminiscence article written on the occasion of his death in 2019. When I attended the Fourth International Congress in Pharmacology in Basel in 1969, Dr Ervin G Erdös invited me to join his laboratory. Thus, in April 1970, I arrived in Oklahoma City as a Fulbright Fellow to work with him for two years. Later on, as a visiting scientist I frequently worked in his research laboratories in Dallas and Chicago and we shared research interests through visits across the Atlantic between the former Yugoslavia and the United States.

The Influence of Active Hamstring Stiffness on Markers of Isotonic Muscle Performance.

Background: Previous research demonstrates hamstring muscle-tendon stiffness (HMTS) influences isometric strength, landing biomechanics and architectural tissue properties. However, the influence on kinetics & kinematics during other modes of strength testing (isotonic dynamometry) has yet to be established. Purpose: Investigate how HMTS influences kinetics and kinematics during a novel isotonic muscle performance test which has never been done for the hamstrings. Previous work using dynamometry has been limited to isometric or isokinetic contractions, so the novelty arises from our custom isotonic protocol which allows quantitative assessment of the stretch-shortening cycle. Methods: Twenty-six recreationally active individuals (15 males, 11 females, 23.8 ± 2.5 years) completed baseline testing for anthropometry and maximum isometric hamstring strength (MVIC). At least 48 h later, subjects completed a measure of HMTS (damped oscillation technique) followed by an isotonic knee flexion test (eccentric velocity 180°/s; concentric torque 25% of MVIC). Separate linear regression models with examination of residuals were conducted between HMTS and each muscle performance variable. Standardized coefficients determined the magnitude of the relationships. Results: Significance was found for all outcome variables tested. HMTS and rate of torque development demonstrated the strongest relationship followed by isotonic concentric peak torque. The weakest relationship observed was with isometric peak torque. Conclusions: These findings build off previous work quantifying HMTS by showing HMTS more strongly relates to dynamic versus static muscle testing and identifies the potential clinical utility of isotonic dynamometry.

Dominant vs Nondominant Arm in Surgical Repair of Distal Biceps Tendon Rupture. A Case-Control Series of Isotonic Muscle Strength Evaluation

Dominant vs Nondominant Arm in Surgical Repair of Distal Biceps Tendon Rupture. A Case-Control Series of Isotonic Muscle Strength Evaluation

Rehabilitation physical training after anterior cruciate nanofibrous ligament reconstruction of sports knee joint

The anterior cruciate ligament (ACL) is an important stable structure of the knee joint. It has the physiological function of maintaining the stability of the knee joint at rest and during exercise. When the knee anterior cruciate ligament is damaged, due to the mechanical structure and proprioception of the knee joint Damage, resulting in decreased knee stability. This article studies rehabilitation physical fitness training after sports knee anterior cruciate nanofibrous ligament reconstruction. In this study, the isotonic muscle strength test system was first used to test the isokinetic strength of patients after anterior cruciate nanofibrous ligament reconstruction, and statistical analysis was used to study the recovery time and lower extremity muscle strength of patients after anterior cruciate nanofibrous ligament reconstruction. Relationship, and further study the true situation of muscle strength loss after anterior cruciate nanofibrous ligament reconstruction. The degree of recovery of muscle strength and motor function of patients in each period is clarified, so that a rehabilitation plan is formulated according to the degree of recovery, and the recovery of muscle strength and motor function around the knee joint of patients after anterior cruciate nanofiber ligament reconstruction is promoted. In this study, the drainage volume on the first postoperative day was (142.8 ± 61.5) ml, and the drainage volume on the second day was (45.13 ± 39.7) ml. Experimental data show that rehabilitation physical training after anterior cruciate nanofibrous ligament reconstruction has a repairing effect on ligament injury.

Minimal Clinically Important Difference for Quadriceps Muscle Strength in People with COPD following Pulmonary Rehabilitation

Quadriceps strength training is a key component of pulmonary rehabilitation (PR). Clinical interpretability of changes in muscle strength following PR is however limited due to the lack of cut-off values to define clinical improvement. This study estimated the minimal clinically important difference (MCID) for the isotonic and isometric quadriceps muscle strength assessed with the one-repetition maximum (1RM) and hand-held dynamometry (HHD) in people with chronic obstructive pulmonary disease (COPD) following PR. A secondary analysis of a real life non-randomised controlled study was conducted in people with COPD enrolled in a 12-week community-based PR programme. Anchor and distribution-based methods were used to compute the MCIDs. The anchors explored were the St. George’s respiratory questionnaire (SGRQ) and the six-minute walk test (6MWT) using Pearson’s correlations. Pooled MCIDs were computed using the arithmetic weighted mean (2/3 anchor, 1/3 distribution-based methods) and reported as absolute and/or percentage of change values. Eighty-nine people with COPD (84% male, 69.9 ± 7.9 years, FEV1 49.9 ± 18.9% predicted) were included. No correlations were found between changes in 1RM and the SGRQ neither between changes in HHD and the SGRQ and 6MWT (p > 0.05). Thus, anchor-based methods were used only in the MCID of the 1RM with the 6MWT as the anchor. The pooled MCIDs were 5.7Kg and 26.9% of change for the isotonic quadriceps muscle strength with 1RM and 5.2KgF for isometric quadriceps muscle strength assessed with HHD. The MCIDs found are estimates to improve interpretability of community-based PR effects on quadriceps muscle strength and may contribute to guide interventions.

Comparative study of diet variability on isotonic muscle contraction in adolescent students

Background: Isotonic muscle contraction creates force and helps to perform work like moving load. Various factors are found to affect performance of the skeletal muscle such as age, gender, height, weight, physical build, training, and race. Physical activity, exercise, and diet habits are day-to-day behavior that affects work done and health. Onset of fatigue is affected by motivation, degree of work, duration of work, and blood supply of exercising muscle. Only few studies have been conducted to show effect of gender and diet variation on work done and performance of skeletal muscle. Aim and Objective: This study aims to compare the effect of gender and diet variability on isotonic muscle contraction in adolescent students. Materials and Methods: This comparative study was conducted from May 2020 to April 2021. One hundred and fifty healthy adolescent male and female students aged 17–21 years were selected by convenience sampling. Approval from the Institutional Ethical Committee (IEC/HIMS/RR123/22-05-2020), informed consent from participants was taken. Subjects contract flexors of the right hand middle finger against resistance using Mosso’s Ergogram, till fingers get fatigued and can no longer lift load. Then, work done was calculated for flexor muscle. Data were statistically analyzed. Results: Work done using Mosso’s Ergography was higher in males when compared to females (P 0.05). Work done during intact blood supply was greater than during venous and arterial occlusion (P < 0.00001). Conclusion: Muscle performance was more in males due to height, weight, and hormonal effect. Work done during intact blood flow was better than during restricted blood flow. However, there was no statistically significant difference in work done between vegetarians and non-vegetarians.

Effects of Self-selected Resistance Training on Physical Fitness and Psychophysiological Responses in Physically Inactive Older Women: A Randomized Controlled Study.

This study aimed to investigate the effects of a 12-week self-selected resistance training (SSRT) program on physical fitness and psychophysiological responses among physically inactive older women. We randomly allocated 32 inactive older women (M age = 66.0 years, SD = 3.0) into either an SSRT (n = 16) or control group (n = 16). Participants performed SSRT three times per week over 12 weeks. We assessed maximal isotonic and isokinetic muscle strength, functional capacity, flexibility, cardiorespiratory fitness, and body composition at baseline and after the intervention. Affective responses and perceived exertion were evaluated after each exercise set throughout the training program. The SSRT group significantly improved their maximal muscle strength in all exercises (Cohen's d ranging from 1.4-3.3; all p's < .001), peak torque (knee flexors: d = 1.7; knee extensors: d = 1.6; all p < .001), flexibility (knee flexors: d = 1.7; single hip flexors: d = 1.6; all p < .001; bilateral hip flexors: d = 1.1, p = .001), fat-free mass (d = .9, p = .008), and cardiorespiratory fitness (d = .9, p = .014), compared to the control group. All components of functional capacity improved compared to the control group (Cohen's d ranging from .8 to 5.5; all p's ≤ .001). Participants perceived the exercise training sessions as pleasant and of low to moderate effort. Thus, a 12-week SSRT program was effective at improving physical fitness and inducing feelings of pleasure among inactive older women.

Reliability Of Muscle Power And Functional Performance In Healthy, Older Women

Functional performance measures in older adults are commonly used in studies investigating age-related declines in mobility. Surprisingly, there is a lack of literature on the clinimetric properties associated with these tests, especially in healthy, older adults. In addition, reliability of tests is commonly measured over 1-2 weeks, and does not address the question of longer-term reliability that might be more relevant for a typical training study. PURPOSE: The purpose of this study was to assess the longer-term reliability (over 9 weeks and 15 weeks) of an isotonic muscle power test (using an isokinetic dynamometer) and commonly-used functional measures (Short Physical Performance Battery, maximal gait, 30s chair stand test, stair climbing, and the 400-meter walk) in healthy, older women. METHODS: Participants were older women (n = 18) who were healthy and untrained (Age = 73.3 ± 3.4 years, Height = 159.6 ± 7.7 cm, Weight = 69.5 ± 12.7 kg, BMI = 27.3 ± 4.8). Test-retest measures (muscle power and function) took place at baseline, week 9, and week 15. Intraclass correlation coefficients (ICC) and the coefficient of variation of the typical error (CV) are reported for all time point comparisons. RESULTS: ICCs ranged from 0.83-0.97 for muscle power, and 0.64-0.93 for functional performance, indicating moderate to excellent reliability. CVs for upper-leg muscle power ranged from 5.7 - 10.5%, and lower-leg muscle power ranged from 9.9 - 20.0%, while CVs for functional tests ranged from 1.9 - 14.9%. For function, the stair-climb power test demonstrated the greatest reliability from baseline to week 15, with the CV = 8.94% and ICC = 0.94 (CI = 0.82-0.98). There were no changes in mean values for tests over time, with the exception of the chair stands which improved significantly from baseline to week 15 (p < 0.05). Although the chair stands were significantly different, these changes were smaller than what has previously been identified as clinically meaningful (eg. < 3.3 chair stands for the 30s chair stand test). CONCLUSIONS: Muscle power and functional tests demonstrated consistency over durations typically used in exercise studies. Conducting these tests under standardized conditions should enable researchers to confidently describe the impact of exercise interventions on muscle power and function in this population.

Dynamic contraction dependence on the instantaneous motor unit firing rates

The effect of voluntary muscle contraction is to regulate position change about a joint involving recruitment and rate coding of motor units (MU) to produce torque results in the shortening velocity component. Unlike isometric (static) muscle contractions, isotonic (dynamic) muscle contractions can involve feedback to slow the shortening velocity as the joint reaches the terminal position. During dynamic conditions of increasing velocity targets, evidence indicates that the neuromuscular initiation of movement is greater than at isometric conditions, possibly being enhanced by the motor neuron secondary firing rate range. Our objective was to further characterize voluntary neuromuscular control at the level of instantaneous motor unit action potential firings during dynamic shortening muscle contractions. During isometric and isotonic contractions, intramuscular fine‐wire electromyography (EMG) was used to record MU potentials from the anconeus and triceps brachii muscles in healthy younger men and women (range 20–35 years, n= 15). Isotonic contractions were normalized to the maximal isotonic velocity and were loaded at 20% of the maximal isometric voluntary contraction torque. For analysis, the EMG was digitally high‐pass filtered (1 kHz, 3rd order Butterworth) and MU action potential waveforms were determined and sorted by template matching (Spike2 Wavemark, version 7) with manual inspection. Torque, velocity and position were also measured and at each individual firing rate time‐point and these vectors were aligned. From this, 627 MU trains (mean±standard deviation 42±19, n= 15) during the isotonic contractions in the anconeus muscle and 226 MU trains (38±14, n= 6) in the long head of the triceps brachii muscle were measured. To explore a more comprehensive model related to firing rates, the torque, velocity and position were modelled by linear regression with the residuals of MU train number, participant, testing session, sex, muscle and target velocity removed. From the full model when comparing slope coefficients, there was no significant interactions between torque (β= 48.1x) and velocity (β= −28.5x) on firing rate dependence (p= 0.2). Position (β= 0.4x) had a smaller coefficient on firing rates as compared to torque and velocity and a significant interaction effect with torque (p&lt; 0.05), but not velocity (p= 0.4). These results indicate that a model of instantaneous firing rate dependence on torque, velocity and position requires a re‐examination, especially because the interaction of torque and velocity were significantly correlated (r= 0.5, p&lt; 0.05). Shortening velocity of muscles causing elbow joint extension must be first initiated by a rate of torque development, further supporting that a different conceptual approach may be necessary to understand MU output during dynamic contractions. It may be important in this task to model firing rates as the independent variable (time vector) that will affect succeeding dependent changes of torque, velocity and position.Support or Funding InformationSupported by NSERC.

The Role of Scarpa’s Fascia in the Human Body Wall

Humans have lost a cutaneous muscle layer called the panniculus carnosus that is found in a large survey of mammals and many non‐human primates. Humans have a tough fascial layer called Scarpa’s fascia in the same position as panniculus carnosus, which some researchers suggest is the remnant of this cutaneous muscle layer. In other mammals, panniculus carnosus shakes the skin, possibly to dislodge ectoparasites. However, in humans, it is possible that a tough fascia is more adaptive for passively maintaining the human orthograde posture than an isotonic muscle layer, and the loss of fur on the skin may require less movement to combat parasites. Interestingly, panniculus carnosus is generally associated with a fatty fascial layer termed panniculus adiposus. Traditionally, Camper’s fascia, a fatty layer just deep to the skin and superficial to Scarpa’s fascia has been assumed to be the representative of panniculus adiposus in human. However, our dissections demonstrate an undescribed fatty layer deep to Scarpa’s fascia. Based on comparative anatomy of the anterior abdominal wall across several groups of mammals, and the continuity of this fatty layer into the human perineum from the abdomen, we suggest that this undescribed deeper layer may be the evolutionarily conserved panniculus adiposus and not Camper’s fascia.Support or Funding InformationFunded by Midwestern University, University of Central Florida, and the American Association for Anatomy

A comparative study of combining intra-articular injection of platelet-rich plasma or sodium hyaluronate with isotonic muscle strength training in treating knee osteoarthritis

Objective To compare the efficacy of intra-articular injection of autologous platelet-rich plasma (PRP) with that of sodium hyaluronate for patients with knee osteoarthritis (KOA). Methods Fifty KOA patients were randomly divided into a PRP group (n=25) and a sodium hyaluronate group (n=25). Those in the PRP group were injected intra-articularly with 5 ml of autologous PRP every 2 weeks for 6 consecutive weeks, while the sodium hyaluronate group was given intra-articular injections of 2 ml of sodium hyaluronate once a week for 6 weeks. Both groups performed isokinetic strength training three times a week for 6 weeks. Before as well as 6 weeks, 3 months, 6 months and 12 months after the treatment, both groups were followed and evaluated using the Western Ontario and McMaster University osteoarthritis index (WOMAC). A Biodex System 4 isometric muscle strength testing system was used to evaluate the knees′ peak torque (PT) in flexion and extension, total power (TW), and average power (AP). Results Before the treatment there were no significant differences in pain, stiffness or average WOMAC score between the two groups. Afterward significant improvement was observed in the pain, stiffness and WOMAC scores of both groups. Compared with the sodium hyaluronate group, significantly greater decreases in the average WOMAC pain score were observed in the PRP group after the different intervals. That was also true of the average stiffness scores and the overall average WOMAC scores after 6 and 12 months. The flexor and extensor PT, TW and AP at the angular velocities of 60°/s and 90°/s also improved significantly in both groups after 6 weeks and 12 months, with the improvement of the PRP group significantly greater than that in the control group at the same time points. Conclusion Intra-articular injection of either autologous PRP or sodium hyaluronate can effectively alleviate the clinical symptoms of KOA when combined with isokinetic strength training. However, PRP is the more effective. Its use is worthy of clinical application and promotion. Key words: Knees; Osteoarthritis; Plasma; sodium hyaluronate; Isokinetic strength

Resistance training induced changes in strength and specific force at the fiber and whole muscle level: a meta-analysis

Considerable debate exists as to whether increases in strength that occur with resistance exercise are the result of increases in muscle size. Most studies have attempted to answer this question using assessments of whole muscle size and voluntary muscle strength, but examining changes at the individual muscle fiber level may also provide some insight. The purpose of this meta-analysis was to compare adaptations at the whole muscle and individual fiber level. A meta-analysis was conducted in February, 2018 including all previously published papers and was analyzed using a random effects model. There were no differences (p = 0.88) when comparing hypertrophy at the whole muscle (4.6%) and individual fiber level (7.0%), but significantly larger (p < 0.001) strength gains were observed at the whole muscle level (43.3%) relative to the individual fiber (19.5%). Additionally, there was an increase in the specific tension of type 1 muscle fibers (p = 0.013), but not type 2 muscle fibers (p = 0.23) which was driven by similar increases in strength (type 1: 17.5%, type 2A: 17.7%), despite differences in muscle size (type 1: 6.7%, type 2A: 12.1%). These results support the hypothesis that the neural adaptations play a large role in increasing isotonic whole muscle strength, but also demonstrate that an improvement in specific tension of type 1 muscle fibers is present. These results would suggest that some mechanism intrinsic to the muscle fiber, and independent of muscle growth, may also be contributing to strength increases in response to resistance exercise providing an avenue for future research.

Modeling Skeletal Muscle Stress and Intramuscular Pressure: A Whole Muscle Active-Passive Approach.

Clinical treatments of skeletal muscle weakness are hindered by a lack of an approach to evaluate individual muscle force. Intramuscular pressure (IMP) has shown a correlation to muscle force in vivo, but patient to patient and muscle to muscle variability results in difficulty of utilizing IMP to estimate muscle force. The goal of this work was to develop a finite element model of whole skeletal muscle that can predict IMP under passive and active conditions to further investigate the mechanisms of IMP variability. A previously validated hypervisco-poroelastic constitutive approach was modified to incorporate muscle activation through an inhomogeneous geometry. Model parameters were optimized to fit model stress to experimental data, and the resulting model fluid pressurization data were utilized for validation. Model fitting was excellent (root-mean-square error or RMSE <1.5 kPa for passive and active conditions), and IMP predictive capability was strong for both passive (RMSE 3.5 mmHg) and active (RMSE 10 mmHg at in vivo lengths) conditions. Additionally, model fluid pressure was affected by length under isometric conditions, as increases in stretch yielded decreases in fluid pressurization following a contraction, resulting from counteracting Poisson effects. Model pressure also varied spatially, with the highest gradients located near aponeuroses. These findings may explain variability of in vivo IMP measurements in the clinic, and thus help reduce this variability in future studies. Further development of this model to include isotonic contractions and muscle weakness would greatly benefit this work.

Detection of muscle activation through multi-electrode sensing using electrical stimulation

The need to assess muscle activation and intention recognition in the design of prosthetic or exoskeleton robots has recently increased in rehabilitation medical research. Assessment of the muscle activation has an important role in the control of wearable devices. Such application requires estimating a patient's intention through the detection of their muscle activation. Previously developed techniques, namely, bioelectrical impedance analysis, electrical impedance myography, electrical impedance tomography, and a surface electromyogram, have been used in the detection of muscle activation. However, these techniques tend to have difficulty in assessing the muscle activation. A biopsy needle can be used to sense the muscle activation in an invasive manner. We propose a new method for detecting the muscle activation using multi-electrode sensing with electrical stimulation, but without a biopsy needle. Electrical stimulation is applied to the skin of a subjects forearm. The signals reflected from their muscles are then measured using multiple electrodes placed on the skin. The forearm skin and its muscles can be modeled as muscle tissue circuits depending on the signal frequency. We verified the proposed method experimentally through isometric muscle contraction, isotonic muscle action, and a frequency response test using various frequencies of the electric stimulation signals. Experiments with eight healthy subjects showed promising results in the detection of muscle activation, which can be applied to prosthetic or exoskeleton robots.