Isometric Force Tests Research Articles

The reliability, variability and minimal detectable change of multiplanar isometric trunk strength testing using a fixed digital dynamometer

ABSTRACT Trunk strength plays a vital role in athletic performance, rehabilitation and general health, however, current assessment methods are expensive, non-portable or unreliable. This study aimed to investigate the within- and between-session reliability, variability, standard error of measurement and minimal detectable change (MDC) of trunk strength in the sagittal (flexion and extension) and frontal planes (left and right lateral flexion) using a fixed digital dynamometer. Eighteen participants (ten men and eight women) attended two sessions separated by 7 days. Participants were fitted with a trunk harness which was secured to an immovable base via a digital dynamometer. Three maximal voluntary isometric contractions were completed across four positions (prone, supine, left-side recumbent and right-side recumbent, respectively) on a glute-hamstring raise machine. All positions demonstrated excellent reliability and low variability within session (ICC: 0.95–0.98; CV: 5–7%) and between sessions (ICC: 0.98–0.99; CV: 4–6%), across all positions. The between-session MDC ranged from 8% (prone) to 13% (right-side recumbent), translating to absolute values between 2.9 and 3.2 kg across all positions. Maximal isometric force testing using a fixed digital dynamometer provides reliable measurements of multiplanar trunk strength, providing a practical method for use in clinical practice.

Test-retest reliability and construct validity of trunk extensor muscle force modulation accuracy.

Low back pain is associated with changes in trunk muscle structure and function and motor control impairments. Voluntary force modulation (FM) of trunk muscles is a unique and under-investigated motor control characteristic. One of the reasons for this paucity of evidence is the lack of exploration and publication on the reliability and validity of trunk FM protocols. The purpose of this study was to determine the within- and between-day test-retest reliability and construct validity for trunk extensor muscle FM. Twenty-nine healthy participants were tested under three FM conditions with different modulation rates. Testing was performed on a custom-built apparatus designed for trunk isometric force testing. FM accuracy relative to a fluctuating target force (20-50%MVF) was quantified using the root mean square error of the participant's generated force relative to the target force. Reliability and precision of measurement were assessed using the Intraclass Correlation Coefficient (ICC), standard error of measurement (SEM), minimal detectable difference (MDD95), and Bland-Altman plots. In a subset of participants, we collected surface electromyography of trunk and hip muscles. We used non-negative matrix factorization (NNMF) to identify the underlying motor control strategies. Within- and between-day test-retest reliability was excellent for FM accuracy across the three conditions (ICC range: 0.865 to 0.979). SEM values ranged 0.9-1.8 Newtons(N) and MDD95 ranged from 2.4-4.9N. Conditions with faster rates of FM had higher ICCs. NNMF analysis revealed two muscle synergies that were consistent across participants and conditions. These synergies demonstrate that the muscles primarily involved in this FM task were indeed the trunk extensor muscles. This protocol can consistently measure FM accuracy within and between testing sessions. Trunk extensor FM, as measured by this protocol, is not specific to any trunk muscle group but is the result of modulation by all the trunk extensor muscles.

Comparison of arterial storage conditions for delayed arterial ring testing

ObjectiveArterial ring testing is the gold standard for measuring arterial function. Increased arterial tone through arterial contraction and impaired endothelial relaxation (endothelial dysfunction) are key metrics of impaired arterial health in peripheral arterial disease (PAD). To allow for comparative testing of arteries during standard laboratory hours, storage buffers and conditions have been used to extend the functional life of arteries. Various storage conditions have been compared, but there has not been a robust comparison or validation in human arteries. The objective of this work is to optimize storage of arterial segments for endothelial cell (EC) testing in a murine model and to test EC function in human PAD arteries. We hypothesized that certain storage conditions would be superior to others. MethodsHealthy murine aortas were harvested from 10- to 14-week-old C57/Bl6J male and female mice and compared under different storage protocols (24 hours) to immediate arterial testing. The storage conditions tested were: Opti-MEM (37°C or 4°C), Krebs-HEPES with 1.8 mmol/L or 2.5 mmol/L calcium (4°C), or Wisconsin (WI) solution at 4°C. Vascular function was evaluated by isometric force testing. Endothelium-dependent and -independent relaxation were measured after precontraction with addition of methacholine or sodium nitroprusside, respectively. Arterial contraction was stimulated with potassium chloride or phenylephrine. Analysis of variance was used to determine significance compared with immediate testing with P < .05. Under institutional review board approval, 28 PAD arteries were collected at amputation and underwent vascular function testing as described. Disturbed flow conditions were determined by indirect (upstream occlusion) flow to the harvested tibial arteries. Stable flow arteries had in-line flow. Arterial calcification was quantified manually as present or not present. ResultsWe found that 4°C WI and 37°C Opti-MEM best preserved endothelium-dependent relaxation and performed similarly to immediately testing aortas (termed fresh for freshly tested) (P > .95). Other storage conditions were inferior to freshly tested aortas (P < .05). Vascular smooth muscle function was tested by endothelial-independent relaxation and contractility. All storage conditions preserved endothelial-independent relaxation and contractility similar to freshly tested arteries. However, 4°C WI and 37°C Opti-MEM storage conditions most closely approximated the maximum force of contraction of freshly tested arteries in response to potassium chloride (P > .39). For human arterial testing, 28 tibial arteries were tested for relaxation and contraction with 16 arteries with peripheral artery occlusive disease (PAD with disturbed flow) and 12 without peripheral artery occlusive disease (PAD with stable flow), of which 14 were calcified and 14 were noncalcified. Endothelial-dependent relaxation data was measurable in 9 arteries and arterial contraction data was measurable in 14 arteries. When comparing flow conditions, arteries exposed to disturbed flow (n = 4) had significantly less relaxation (2% vs 59%; P = .03) compared with stable flow conditions (n = 5). In contrast, presence the (n = 6) or absence of calcification (n = 3) did not impact arterial relaxation. Arterial contraction was not different between groups in either comparison by flow (n = 9 disturbed; n = 5 stable) or calcification (n = 6 present; n = 8 absent). ConclusionsIn healthy murine aortas, arterial storage for 24 hours in 4°C WI or 37°C Opti-MEM both preserved endothelium-dependent relaxation and maximum force of contraction. In human PAD arteries stored in 4° WI, flow conditions before arterial harvest, but not arterial calcification, led to differences in arterial relaxation in human PAD arteries. Arterial contractility was more robust (11/28 arteries) compared with arterial relaxation (7/28 arteries), but was not significantly different under flow or calcification parameters. This work defines ideal storage conditions for arterial ring testing and identifies that EC dysfunction from disturbed flow may persist in delayed ex vivo arterial testing.

Recovery During a Congested Schedule and Injury in Professional Football.

To analyze the relationships between the recovery kinetics experienced by professional football players and noncontact injury. A cohort of 46 professional football players (age 24.2 [4.7]y) from the same team (French Ligue 1) was monitored each day between matches when the team played twice a week. The recovery monitoring procedure was implemented after 38 matches and included some questionnaires: duration of sleep, Hooper scale (quality of sleep, level of stress, fatigue, and muscle soreness), perceived recovery status scale, creatine kinase concentrations, a countermovement jump, and an isometric force test. Noncontact injuries were collected during these periods. Noncontact injuries were associated with perceived fatigue and muscle soreness 2 days (relative risk [RR] = 1.89 and 1.48, respectively) and 3 days following the matches (RR = 2.08 and 2.08, respectively). An increase of sleep quantity during the 2 nights following a match was significantly associated with a lower RR (RR = 0.65), as well as a lower decrement score on the isometric force test on each of the 3 days after the matches (RR = 0.97, RR = 0.99, and RR = 0.97, respectively). No other association was reported for the variables sleep quality, stress, perceived recovery, creatine kinase concentrations, countermovement jump, and noncontact injuries. During a congested schedule, implementing a recovery monitoring protocol including questionnaires about fatigue, muscle soreness, quantity of sleep, and a physical test of isometric force could help practitioners prevent injuries.

Reliability, variability, and minimal detectable change of bilateral and unilateral lower extremity isometric force tests

Reliability, variability, and minimal detectable change of bilateral and unilateral lower extremity isometric force tests

Concurrent Validation and Reference Values of Gluteus Medius Clinical Test.

ContextThe hip abductor muscles, mainly the gluteus medius, are responsible for controlling hip adduction in a closed kinetic chain. Frontal plane knee alignment, assessed during functional activities such squatting, jumping and running, may overload joint structures, like the anterior cruciate ligament and patellofemoral joint. The hand-held dynamometer is reliable and effective for testing the muscular strength of the hip abductors.Objectives1. To assess the concurrent validity between the gluteus medius clinical test and a maximum isometric force test of the hip abductors using the hand-held dynamometer; (2) to determine the intra and inter-examiner reliability for the application of the gluteus medius clinical test; and (3) to describe reference values of gluteus medius clinical test on a population of youth athletes.DesignCross-sectional.MethodsThirty healthy individuals were recruited for validity and reliability testing. On the first day, participants performed the maximal isometric test of the hip abductors, measured via hand-held dynamometry. On the following week, the gluteus medius clinical test was performed. Intraclass correlation coefficients (ICC2,2) were computed for the reliability analysis, with a 95% confidence interval. To generate reference values, the gluteus medius clinical test was performed on 273 athletes.ResultsThe results of this study indicated a weak positive correlation (r = 0.436, p = 0.001) between tests, which indicates that they examine different domains of gluteus medius muscle function, likely endurance and muscle strength. The magnitude of computed ICCs (>0.95) indicates excellent intra- and inter-examiner reliability.ConclusionThe findings of the current study indicate that the gluteus medius clinical test is reliable and examines a domain of muscular function not fully captured by HHD. The clinical test developed in this study is low-cost and can be included for gluteus medius assessment.Level of evidenceLevel 3.

Efecto del entrenamiento con traje de electroestimulación de cuerpo entero en las adaptaciones neuromusculares en individuos desentrenados - Ensayo clínico aleatorizado, protocolo de estudio

Introduction. Electrostimulation is a method of training used in sports that has been shown to be effective in improving strength manifestations such muscle power. Currently, there is no known scientific literature in which a training program with electrostimulation suit is applied. Therefore, the aim of this study is to carry out a program to see the effects on neuromuscular adaptations in untrained subjects. Objective. to study the neuronal and muscular adaptations that occur in the active electrostimulation training applied with a full body suit on the extensor muscles of the arms and extensors of the leg. Material and methods. A randomized controlled study between groups. The experimental design of the study will allow us to analyze the neuromuscular adaptations that occur with the electrostimulation training applied with a full body suit and compare them to those of a traditional strength training. The dependent variables measured will be: electromyography activity in maximum isometric force test, maximum force value, force production rate, neural adaptation indicators. The program will be carried out during 24 sessions, twice a week, for 12 weeks. Expected results. We expect to achieve greater neuromuscular activation with the combination of electrostimulation applied with full body suit. Regardless of the results obtained, the final study will be published.

The resistance training effects of different weight level during menstrual cycle in female.

We examined the different effects of body mass index (BMI) level on resistance training during menstrual cycle. Thirty-six female subjects performed resistance training and subjects were divided into three groups: BMIunder, BMInorm, BMIover. Subjects completed 12 weeks of sub-maximal resistance training with 3 sets of 8–12 repetitions. Maximum isometric force test was measured before and after training in the follicular phase (FP) and the luteal phase (LP). Maximum isometric force of whole groups (BMIunder, BMInorm, BMIover) was significantly increased both FP and LP after 12-week resistance training. Maximum isometric force after training and absolute increase value in BMInorm and BMIover were no significantly different between FP and LP. However, significant different of maximum isometric force after training (FP, 79.08±11.60; LP, 84.05±12.38) and absolute increase value (FP, 9.63±5.47; LP, 15.13±6.06) were found between FP and LP just by BMIunder. We suggest that if muscle strength is measured in the FP (LP) before training and then they should be measured same phase, such as FP and LP after training and BMIunder can be influenced muscle strength in LP.

Gene Delivery for Limb-Girdle Muscular Dystrophy Type 2D by Isolated Limb Infusion.

In a previous limb-girdle muscular dystrophy type 2D (LGMD2D) clinical trial, robust alpha-sarcoglycan gene expression was confirmed following intramuscular gene (SGCA) transfer. This paved the way for first-in-human isolated limb infusion (ILI) gene transfer trial to the lower limbs. Delivery of scAAVrh74.tMCK.hSGCA via an intravascular route through the femoral artery predicted improved ambulation. This method was initially chosen to avoid safety concerns required for large systemic vascular delivery viral loads. ILI methods were adopted from the extensive chemotherapy experience for treatment of malignancies confined to the extremities. Six LGMD2D subjects were enrolled in a dose-ascending open-label clinical trial. Safety of the procedure was initially assessed in the single limb of a non-ambulant affected adult at a dose of 1 × 1012 vg/kg. Subsequently, ambulatory children (aged 8-13 years) were enrolled and dosed bilaterally with either 1 × 1012 vg/kg/limb or 3 × 1012 vg/kg/limb. The six-minute walk test (6MWT) served as the primary clinical outcome; secondary outcomes included muscle strength (maximum voluntary isometric force testing) and SGCA expression at 6 months. All ambulatory participants except one had pre- and post-treatment muscle biopsies. All four subjects biopsied had confirmed SGCA gene delivery by immunofluorescence, Western blot analysis (14-25% of normal), and vector genome copies (5.4 × 103-7.7 × 104 vg/μg). Muscle strength in the knee extensors (assessed by force generation in kilograms) showed improvement in two subjects that correlated with an increase in fiber diameter post gene delivery. Six-minute walk times decreased or remained the same. Vascular delivery of AAVrh74.tMCK.hSGCA was effective at producing SGCA protein at low doses that correlated with vector copies and local functional improvement restricted to targeted muscles. Future trials will focus on systemic administration to enable targeting of proximal muscles to maximize clinical benefit.

The relationship between the gross efficiency and the ability to repeat the given pressure force in trained cyclists

PurposeThe research aim was to determine the relationship between gross efficiency (E) and the ability to repeat the given pressure force (ARGPF).MethodsA group of 23 road cyclists performed an incremental exercise test on a cycle ergometer and a repeated isometric force test (RIFT) with lower and upper limbs. E was calculated on the basis of the estimated energy expenditure (EE) during the last 30 seconds of the submaximal work with the loads of E-100W, E-150W, E-200W, E-250W, E-300W. During RIFT, carried out on a kinesthesiometer with strain gauges, the subjects performed pressures with the force of 10 kg with upper limbs and 20 kg with lower limbs. RIFT was performed immediately before and after the incremental test; the data served to express ARGPF by means of the repeated given pressure force (RGPF) value.ResultsPost-exercise RGPF for the left lower limb significantly correlated with E at all incremental test loads (&lt;i&gt;r&lt;/i&gt;: 0.64, 0.72, 0.7, 0.63, 0.62, respectively, for 100 W, 150 W, 200 W, 250 W, and 300 W). Pre-exercise RGPF for the left upper limb significantly correlated with E at 100 W, 150 W, and 200 W loads (&lt;i&gt;r&lt;/i&gt;: 0.68, 0.72, 0.62, respectively). Both RGPF for limbs and E positively and statistically significantly correlated with the cyclists’ age.ConclusionsRoad cyclists with higher E presented greater variability of the repeated pressure force of the left limbs. Both characteristics show a strong relationship with the cyclists’ age, which may indicate that their development depends on training experience.

Movement Patterns and Muscle Damage During Simulated Rugby Sevens Matches in National Team Players.

Pereira, LA, Nakamura, FY, Moraes, JE, Kitamura, K, Ramos, SP, and Loturco, I. Movement patterns and muscle damage during simulated rugby sevens matches in national team players. J Strength Cond Res 32(12): 3465-3474, 2018-The aim of this study was to analyze the match performance (i.e., distance covered in different intensities), signs of muscle damage (assessed by means of creatine kinase [CK] activity and rate of force development [RFD]), and neuromuscular fatigue (using linear sprint and vertical jump performances) after 3 single-day simulated matches performed by rugby sevens players from the Brazilian National team. Ten male rugby sevens players (25.2 ± 3.6 years; 88.7 ± 7.1 kg; 182.2 ± 6.3 cm) participated in this study. On the day before the matches, the athletes performed a 40-m sprint, a vertical jump assessment, and a maximal isometric force test. In the morning of the match day, blood samples were collected to analyze the CK activity. Afterward, 3 simulated rugby sevens' matches were performed with 2-hour intermission periods. The match performance (encompassing total distance and distance covered in different velocity ranges and body loads [BLs]) was obtained from global positioning system units. The statistical analysis was performed using a mixed model approach and the effect sizes (ESs) of the differences. The statistical significance level was set at p ≤ 0.05. Players were capable of maintaining the match performance when comparing the first and last games. Large (ES > 0.8) and significant (p ≤ 0.05) reductions were demonstrated in the total distance and BL when comparing the second with the first halves. Decrements in the explosive force capacity (assessed by means of RFD) and the squat jump (SJ) were noticed (ES varying from 0.55 to 1.14; p ≤ 0.05). The CK activity increased after the matches (ES = 1.29; p ≤ 0.05). The rugby sevens players were able to maintain the physical performance across 3 successive matches simulating the first day of a tournament. The augmented CK activity and the decreases in the SJ and RFD suggest that increased levels of muscle damage were experienced on the day after the matches. Therefore, the technical staff are encouraged to implement recovery strategies and planned substitutions during multiday tournaments to reduce the impact of accumulated fatigue and muscle damage on subsequent match performance. In addition, specific training strategies aimed at better simulating the match demands need to be implemented in the players' training routines.

Efeito da potencialização pós-ativação no torque isométrico do tríceps braquial em adultos

Objetivo: Analisar o efeito de contraes voluntrias isomtricas mximas e da eletroestimulao no torque isomtrico e na ativao muscular do trceps braquial em adultos fisicamente ativos. Mtodos: Dezenove homens foram submetidos a testes de fora isomtrica (FI) como pr-teste, por meio de contrao voluntria isomtrica mxima durante 10 segundos e atividades condicionantes (ACs) randomizadas: isometrias durante 7, 10 e 12 segundos e eletroestimulao em 70 e 120Hz por 10 segundos cada. Aps as ACs, foram realizadas duas contraes voluntrias isomtricas mximas de 10 segundos com intervalo de 4 e 8 minutos, respectivamente. A atividade eltrica do trceps braquial (pores medial e lateral) foi registrada. Resultados: No foi verificado efeito em nenhuma das condies para o torque mximo ou mdio, bem como para atividade eltrica do trceps braquial (P0,05). Concluso: O intervalo adotado entre as ACs e o teste de FI no foi suficiente para induzir a melhoria do torque isomtrico.

How does functionality proceed in ACL reconstructed subjects? Proceeding of functional performance from pre- to six months post-ACL reconstruction.

This is the first study examining functionality of subjects with anterior cruciate ligament (ACL) tears and a subsequent reconstruction comprehensively by multiple test sessions from pre- to six months post-reconstruction. The purpose was to evaluate if a generally applied rehabilitation program restores functionality to levels of healthy controls. Subjects with unilateral tears of the ACL were compared to matched healthy controls throughout the rehabilitation. 20 recreational athletes were tested: T1 (preoperative), 6 weeks after tear; T2, 6 weeks, T3, 3 months, T4, 6 months post-reconstruction. At all test sessions, subjects self-evaluated their activity level with the Tegner activity score and their knee state with the Knee Injury and Osteoarthritis Outcome Score. Passive range of motion during knee flexion and extension and leg circumference were measured as functional clinical tests. Bilateral countermovement jumps, one-leg jumps for distance and isometric force tests in knee flexion and extension with 90° and 110° knee angle were conducted as functional performance tests. For determination of functionality, leg symmetry indices (LSIs) were calculated by dividing values of the injured by the uninjured leg. In the ACL group most LSIs decreased from T1 to T2, and increased from T2 and T3 to T4. LSIs of ACL subjects remained lower than LSIs of healthy controls at 6 months post-reconstruction in nearly all parameters. Self-evaluation of ACL subjects showed, additionally, that activity level was lower than the pre-injury level at 6 months post-reconstruction. Low LSIs and low self-evaluation indicate that knee joint functionality is not completely restored at 6 months post-reconstruction. The study shows that multiple comprehensive testing throughout the rehabilitation gives detailed images of the functional state. Therefore, the functional state of ACL reconstructed individuals should be evaluated comprehensively and continuously throughout the rehabilitation to detect persisting deficiencies detailed and adapt rehabilitation programs individually depending on the functionality.

Physical and physiological traits of a double world karate champion and responses to a simulated kumite bout: A case study

This study aimed at describing the changes in physical and physiological performance of a two-time World Karate Federation Champion athlete immediately prior to and after a bout simulation. The karateka was submitted to: (a) squat and countermovement jumps, jump squat and bench throw and maximal isometric force tests (half-squat and bench press, pre and post-match); (b) one simulated karate match. Improvements of 1.1% and 2.9% were observed in the squat jump and countermovement jumps, respectively, after the combat simulation. For jump squat, an increase in power production was observed after the simulation (0.6–7.4%). Conversely, for the bench throw a decrease in power was detected after the match (0.5–8.3%). The maximal isometric force increased for the half-squat (10.5%) and bench press exercises (1.6%). The investigated athlete presented quite different characteristics when compared to similarly highly trained peers, and these traits can probably explain his “outlier performance”.

Predicting race time in male amateur marathon runners.

The aim of the study was to analyze the relationship between anthropometry, training characteristics, muscular strength and effort-related cardiovascular response and marathon race time in male amateur runners. A total of 84 male amateur marathon runners aged between 23 and 70 years took part in this study (41.0±9.5 years). All of them competed in the 2013 edition of the Madrid Marathon with a finish time between 169.8 and 316 minutes (226.0±28.5 minutes). Age, running experience, number of marathon races finished, mean kilometers run weekly in the last three months, and previous personal best time in the 10 km, half marathon and marathon were recorded. Moreover, anthropometric characteristics, and the results from the Ruffier Test and a whole-body isometric force test were measured. After the marathon, the race time was registered. Training volume (r=-0.479; P=0.001), previous running milestones (marathon r=0.756; half-marathon r=0.812; 10-km r=0.732; P<0.001), cardiovascular fitness (r=0.371; P=0.001) and anthropometric variables (body mass, Body Mass Index, body fat percentage, skinfolds and lower leg volume) were correlated to marathon performance (P<0.05). Two regression models appeared from the data with r2>0.50. The best, including body fat percentage, heart rate change during the recovery after the Ruffier Test and the half-marathon race time, was strongly correlated with real marathon performance (r=0.77; P<0.001). A second regression model was proposed replacing the half-marathon performance with the 10-km race time, reducing the correlation to 0.73 (P<0.001). Marathon performance could be partially predicted by two different equations, including body fat percentage, recovery heart rate in the Ruffier Test and a half-marathon or 10-km performance.

Changes in Serum Free Amino Acids and Muscle Fatigue Experienced during a Half-Ironman Triathlon.

The aim of this study was to investigate the relationship between changes in serum free amino acids, muscle fatigue and exercise-induced muscle damage during a half-ironman triathlon. Twenty-six experienced triathletes (age = 37.0 ± 6.8 yr; experience = 7.4 ± 3.0 yr) competed in a real half-ironman triathlon in which sector times and total race time were measured by means of chip timing. Before and after the race, a countermovement jump and a maximal isometric force test were performed, and blood samples were withdrawn to measure serum free amino acids concentrations, and serum creatine kinase levels as a blood marker of muscle damage. Total race time was 320 ± 37 min and jump height (-16.3 ± 15.2%, P < 0.001) and isometric force (-14.9 ± 9.8%; P = 0.007) were significantly reduced after the race in all participants. After the race, the serum concentration of creatine kinase increased by 368 ± 187% (P < 0.001). In contrast, the serum concentrations of essential (-27.1 ± 13.0%; P < 0.001) and non-essential amino acids (-24.4 ± 13.1%; P < 0.001) were significantly reduced after the race. The tryptophan/BCAA ratio increased by 42.7 ± 12.7% after the race. Pre-to-post changes in serum free amino acids did not correlate with muscle performance variables or post-race creatine kinase concentration. In summary, during a half-ironman triathlon, serum amino acids concentrations were reduced by > 20%. However, neither the changes in serum free amino acids nor the tryptophan/BCAA ratio were related muscle fatigue or muscle damage during the race.

Improvement in muscle strength after an anterior cruciate ligament injury corresponds with a decrease in serum cytokines

The purpose of this communication was to identify if a decrease in serum cytokine concentrations associates with an improvement in muscle strength after an anterior cruciate ligament (ACL) injury. To establish groups with contrasting serum cytokine concentrations, subjects scheduled for ACL reconstructive surgery were separated into one of two groups (gender matched) based on their time from injury occurrence: (1) Early (<21-d from injury occurrence; n=22) or (2) Late (⩾21-d from injury occurrence; n=22). Before surgery, each subject provided a fasting blood sample and performed single-leg peak isometric force testing on the injured (INJ) and non-injured (NI) limbs. Compared to the NI limb, peak isometric force in the INJ limb was decreased (p<0.05) in both groups (Early, ∼35%; Late, ∼18%). The deficit in peak isometric force, however, was increased (p<0.05) in the Early compared to Late group. Similarly, serum granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-6, and IL-13 were increased (all p<0.05) in the Early group. These unique findings show a concurrent increase in muscular weakness and serum cytokine concentrations shortly after (<21-d) an ACL injury. Importantly, muscular weakness persisted thereafter (⩾21-d) but at an attenuated level and parallel to a decrease in circulating cytokine concentrations. We conclude that a decrease in serum cytokines associates with a reduction in muscular weakness after an ACL injury.

Muscle Anatomy and Dynamic Muscle Function in Osteogenesis Imperfecta Type I

Results of previous studies suggested that children and adolescents with osteogenesis imperfecta (OI) type I have a muscle force deficit. However, muscle function has only been assessed by static isometric force tests and not in more natural conditions such as dynamic force and power tests. The purpose of this study was to assess lower extremity dynamic muscle function and muscle anatomy in OI type I. The study was performed in the outpatient department of a pediatric orthopedic hospital. A total of 54 individuals with OI type I (6-21 years; 20 male) and 54 age- and sex-matched controls took part in this study. Calf muscle cross-sectional area and density were measured by peripheral quantitative computed tomography. Lower extremity muscle function (peak force per body weight and peak power per body mass) was measured by jumping mechanography through 5 tests: multiple two-legged hopping, multiple one-legged hopping, single two-legged jump, chair-rise test, and heel-rise test. Compared with age- and sex-matched controls, patients with OI type I had smaller muscle size (P = .04) but normal muscle density (P = .21). They also had lower average peak force and lower specific force (peak force/muscle cross-sectional area; all P < .008). Average peak power was lower in patients with OI type I but not significantly so (all P > .054). Children and adolescents with OI type I have, on average, a significant force deficit in the lower limb as measured by dynamic force tests. Nonetheless, these data also show that OI type I is compatible with normal muscle performance in some individuals.

Rosuvastatin improves vascular function of arteriovenous fistula in a diabetic rat model

This study investigates the pathogenesis of arteriovenous (AV) fistula failure in patients with diabetes mellitus (DM) and tests the vascular protective effect of rosuvastatin on the fistulous communication of diabetic rats. DM was induced in rats by a single injection of streptozotocin. One week later, a fistula was created in the descending aorta and the adjacent inferior vena cava (aortocaval [AC] fistula). Rats were then randomly assigned to receive placebo or rosuvastatin (15 mg/kg/d) in chow for 2 weeks. Blood flow in the aortic segments of the fistula was measured. Circulating CD34+/KDR+ endothelial progenitor cells (EPCs) were determined 2 weeks after creation of the AC fistulas using flow cytometry. Vascular function of the AC fistulas was assessed by isometric force testing. The expression of proinflammatory genes and generation of superoxide anions in the fistulas were examined. The number of EPCs was reduced in diabetic rats, and rosuvastatin significantly increased the number of circulating EPCs. Reduced blood flow and impaired endothelium-dependent relaxation in the AC fistula of animals with diabetes was significantly potentiated after treatment with rosuvastatin. Rosuvastatin also attenuated the expression of inducible nitric oxide synthase and nicotinamide adenine dinucleotide phosphate oxidase and generation of superoxide anions in the fistula tissues isolated from diabetic rats. We provide the first evidence demonstrating that rosuvastatin improves blood flow and endothelial function of AC fistulas in rats with DM by attenuating the activity of proinflammatory genes and generation of superoxide anions in the remodeled vasculature. Arteriovenous (AV) fistula is the most common vascular access for hemodialysis in patients with end-stage renal disease. Studies have shown that blood flow in the AV fistula is significantly reduced in patients with diabetes and the period for maturation of an AV fistula is longer in these patients. The underlying mechanisms of AV fistula failure in diabetes are still poorly understood and there are limited therapeutic approaches that can increase the lifespan of these fistulas. The present study demonstrates that oral administration rosuvastatin improves blood flow and endothelial function of AC fistulas in rats with diabetes, which results from attenuating the activity of proinflammatory genes in the remodeled vasculature, thereby reducing the generation of tissue superoxide anions. Our results may thus enhance our ability to prevent and manage vascular access failure in patients with diabetes with chronic renal disease.

Disturbed motor control of rhythmic movement at 2 h and delayed after maximal eccentric actions

The aim of this study was to examine the influence of exercise-induced muscle damage on elbow rhythmic movement (RM) performance and neural activity pattern and to investigate whether this influence is joint angle specific. Ten males performed an exercise of 50 maximal eccentric elbow flexions in isokinetic machine with duty cycle of 1:15. Maximal dynamic and isometric force tests (90°, 110° and 130° elbow angle) and both active and passive stretch reflex tests of elbow flexors were applied to the elbow joint. The intentional RM was performed in the horizontal plane at elbow angles; 60–120° (SA-RM), 80–140° (MA-RM) and 100–160° (LA-RM). All measurements together with the determination of muscle soreness, swelling, passive stiffness, serum creatine kinase were conducted before, immediately and 2 h as well as 2 days, 4 days, 6 days and 8 days post-exercise. Repeated maximal eccentric actions modified the RM trajectory symmetry acutely (SA-RM) and delayed (SA/MA/LA-RM) until the entire follow up of 8 days. Acutely lowered MA-RM peak velocity together with reduced activity of biceps brachii (BB) at every RM range, reflected a poorer acceleration and deceleration capacity of elbow flexors. A large acute drop of BB EMG burst amplitude together with parallel decrease in BB active stretch reflex amplitude, especially 2 h post-exercise, suggested an inhibitory effect originating most likely from groups III/IV mechano-nociceptors.