Knee Extensor Function Research Articles

Outcome of rectus femoris muscle flaps for groin coverage after vascular surgery

ObjectiveThe aim of this retrospective cohort study was to investigate the outcome of rectus femoris muscle flaps (RFFs) for deep groin wound complications in vascular surgery patients and to compare the outcome with a cohort of sartorius muscle flaps (SMFs) because the RFF is a promising alternative technique for groin coverage. MethodsAll RFFs and SMFs performed by vascular surgeons in a regional collaboration in The Southern Netherlands were retrospectively reviewed. Primary outcomes were muscle flap survival, overall and secondary graft salvage, and limb salvage. Secondary outcomes were 30-day groin wound complications and mortality, donor site and vascular complications, 1-year amputation-free survival, overall patient survival, impaired knee extensor function, and length of hospital stay. ResultsA total of 96 RFFs were performed in 88 patients (mean age, 68 years; 67% male) and compared with a cohort of 30 SMFs in 28 patients (mean age, 64 years; 77% male). At a mean follow-up of 29 months and 23 months, respectively, comparable flap survival (94% vs 90%), secondary graft salvage (80% vs 92%), and limb salvage (89% vs 90%) rates were found. The 30-day mortality rates were 12% and 17%, respectively, and the 1-year amputation-free survival was comparable between treatment groups (71% vs 68%). ConclusionsThis study presents a large series of RFFs for deep groin wound complications after vascular surgery. We demonstrate that muscle flap coverage using the rectus femoris muscle by vascular surgeons is an effective way to manage complex groin wound infections in a challenging group of patients, achieving similarly good results as the SMF.

How age and surface inclination affect joint moment strategies to accelerate and decelerate individual leg joints during walking

A joint moment also causes motion at other joints of the body. This joint coupling-perspective allows more insight into two age-related phenomena during gait. First, whether increased hip kinetic output compensates for decreased ankle kinetic output during positive joint work. Second, whether preserved joint kinetic patterns during negative joint work in older age have any functional implication. Therefore, we examined how age and surface inclination affect joint moment strategies to accelerate and/or decelerate individual leg joints during walking. Healthy young (age: 22.5 ± 4.1 years, n = 18) and older (age: 76.0 ± 5.7 years, n = 22) adults walked at 1.4 m/s on a split-belt instrumented treadmill at three grades (0%, 10%, −10%). Lower-extremity moment-induced angular accelerations were calculated for the hip (0% and 10%) and knee (0% and −10%) joints. During level and uphill walking, both age groups showed comparable ankle moment-induced ipsilateral (p = 0.774) and contralateral (p = 0.047) hip accelerations, although older adults generated lower ankle moments in late stance. However, ankle moment-induced contralateral hip accelerations were smaller (p = 0.001) in an older adult subgroup (n = 13) who showed larger hip extension moments in early stance than young adults. During level and downhill walking, leg joint moment-induced knee accelerations were unaffected by age (all p > 0.05). These findings suggest that during level and uphill walking increased hip flexor mechanical output in older adults does not arise from reduced ankle moments, contrary to increased hip extensor mechanical output. Additionally, results during level and downhill walking imply that preserved eccentric knee extensor function is important in maintaining knee stabilization in older age.

The Roles of Sex and Physical Activity in Gait and Knee Extensor Function With Age.

Older females experience higher rates of disability than males, potentially due to sex-specific differences in gait and muscle function. The authors evaluated the effects of age and physical activity (PA) on gait mechanics and knee extensor muscle function in males and females. Three groups of 20 individuals (each 10 females) participated: young (21-35y) and highly and less active older (55-70y) adults. Knee extensor strength and joint mechanics during preferred speed gait were collected before and after 30 minutes of walking. Age by sex and PA by sex interactions indicated older and less active older females had lower concentric knee extensor muscle power and larger hip extension moments than males. After 30minutes of walking, older less active adults had larger decreases in knee extensor power than their highly active older counterparts, and older adults of both sexes had decreases in ankle dorsiflexion moments while young adults did not. These results suggest that older, particularly less active, adults are susceptible to knee extensor muscle fatigue from moderate activity. For older adults, high levels of PA may be necessary to preserve gait mechanics in response to a bout of exercise. This new information may be important for targeting interventions in at-risk older adults.

Characterization of performance fatigability during a self-paced exercise

Pacing during a high-intensity cycling time trial (TT) appears to prevent premature task failure, but the performance fatigability during a self-paced exercise is currently unknown. Therefore, the current study characterized the time course of performance fatigability during a 4-km TT. Eleven male cyclists performed three separated TTs in a crossover, counterbalanced design. The TTs lasted until the end of the fast-start (FS; 600 ± 205 m), even-pace (EP; 3,600 ± 190 m), and end-spurt (ES; 4,000 m) phases. Performance fatigability was characterized by using isometric maximal voluntary contractions (IMVCs), whereas the muscle activation [i.e., voluntary activation (VA)] and contractile function of knee extensors [e.g., peak torque of potentiated twitches (TwPt)] were evaluated using electrically evoked contractions performed before and 1 min after each specific part of the trial. Gas exchange, power output (PO), and electromyographic activity (EMG) were also recorded. EMG/PO showed an abrupt increase followed by a continuous decrease toward the end of FS, resulting in a drop in IMVC (-12%), VA (-8%), and TwPt (-23%). EMG/PO was stable during EP, with no additional drop on IMVC, VA, or TwPt (-12%, -6%, and -22%, respectively). EMG/PO increased abruptly during the ES, but there was no change in IMVCs, VA, or TwPt (-13%, -8%, and -26%, respectively). These findings demonstrate that the performance fatigability during a self-paced exercise is characterized by a large drop in contractile function and muscle activation at the beginning of the trial (i.e., FS), without additional change during the middle and end phases (i.e., EP and ES).NEW & NOTEWORTHY The time course of performance fatigability throughout a self-paced exercise is currently unknown. The results showed that a large amount of muscle activation and contractile function impairments are attained early on a self-paced exercise (first ∼15% of the total time trial distance) and maintained throughout the test. This novel finding characterizes the performance fatigability from a contractile function and muscle activation perspective, which brings new insights for future studies focused on real-world exercise training and competition.

Post-exercise And Pre-sleep Protein-polyphenol Supplementation Improves Recovery Following Muscle-damaging Eccentric Exercise: Preliminary Findings.

PURPOSE: Eccentric contraction (EC) induced muscle damage is characterised by weakened force production, increased soreness and elevated plasma creatine kinase (CK). Recovery rate is likely to be dependent on muscle remodelling, which may be influenced by dietary protein and polyphenol availability. We investigated if consuming protein-polyphenol drinks post-exercise and before bed improved recovery of knee extensor function and reduced soreness following a bout of EC. METHODS: In a randomised, parallel groups, placebo controlled double blind design, 18 healthy males and females (22 ± 1 y; BMI: 24.0 ± 0.9 kg·m-2 (± SEM)) consumed a controlled isocaloric diet (1.2 g·kg-1 protein) for 7 days before and after a single bout of 300 maximal unilateral quadriceps EC, in combination with either post-exercise (20 g whey, casein and pea protein blend and 650 mg pomegranate extract) and pre-bed (20 g casein protein and 480 mg tart cherry extract) drinks (Beachbody LLC) (PRO; n = 9; 4 females), or isocaloric maltodextrin placebos (PLA; n = 9; 3 females). Total isokinetic work over 30 maximal knee extensions (TW), peak isometric torque (PT) and muscle soreness (visual analogue scale (VAS) and pressure pain threshold (PPT)) were measured relative to the contralateral control limb (%con) before and every 24 h for 7 d following EC, as was CK. Data were analysed using two-way ANOVAs. RESULTS: EC caused a maximum decline in TW in PLA after 48 h to 68 ± 6 %con (P < 0.001) which remained below baseline until 120 h (P < 0.05). Conversely, TW in PRO was reduced at 24 h only (to 89 ± 5 %con; P < 0.05) and was restored thereafter. PT decreased following EC (P < 0.001) and was significantly lower in PLA compared with PRO at 48 h (69 ± 5 vs 107 ± 13 %con, respectively) and 96 h (76 ± 7 vs 110 ± 14 %con, respectively). Muscle soreness in both groups peaked within 72 h of EC (P < 0.05), but vastus medialis PPT was attenuated at 72 h in PRO compared to PLA (102 ± 3 vs 88 ± 3 %con, respectively; P < 0.05). Plasma CK rose > 30-fold from 96 to 120 h (P < 0.01), and was similar between groups (P > 0.05). CONCLUSION: Consumption of commercially available post-exercise and before bed protein-polyphenol beverages accelerated recovery of skeletal muscle function following EC-induced muscle damage, potentially due to improved protein turnover and remodelling. Supported by a Beachbody LLC (USA) grant.

Acute and Delayed Neuromuscular Alterations Induced by Downhill Running in Trained Trail Runners: Beneficial Effects of High-Pressure Compression Garments.

Introduction: The aim of this study was to examine, from a crossover experimental design, whether wearing high-pressure compression garments (CGs) during downhill treadmill running affects soft-tissue vibrations, acute and delayed responses in running economy (RE), neuromuscular function, countermovement jump, and perceived muscle soreness.Methods: Thirteen male trail runners habituated to regular eccentric training performed two separate 40-min downhill running (DHR, –8.5°) sessions while wearing either CGs (15–20 mmHg for quadriceps and calves) or control garments (CON) at a velocity associated with ∼55% of VO2max, with a set of measurements before (Pre-), after (Post-DHR), and 1 day after (Post-1D). No CGs was used within the recovery phase. Perceived muscle soreness, countermovement jump, and neuromuscular function (central and peripheral components) of knee extensors (KE) and plantar flexors (PF) were assessed. Cardiorespiratory responses (e.g., heart rate, ventilation) and RE, as well as soft-tissue vibrations (root mean square of the resultant acceleration, RMS Ar) for vastus lateralis and gastrocnemius medialis were evaluated during DHR and in Post-1D.Results: During DHR, mean values in RMS Ar significantly increased over time for the vastus lateralis only for the CON condition (+11.6%). RE and cardiorespiratory responses significantly increased (i.e., alteration) over time in both conditions. Post, small to very large central and peripheral alterations were found for KE and PF in both conditions. However, the deficit in voluntary activation (VA) was significantly lower for KE following CGs (–2.4%), compared to CON (–7.9%) conditions. No significant differences in perceived muscle soreness and countermovement jump were observed between conditions whatever the time period. Additionally, in Post-1D, the CGs condition showed reductions in neuromuscular peripheral alterations only for KE (from –4.4 to –7.7%) and perceived muscle soreness scores (–8.3%). No significant differences in cardiorespiratory and RE responses as well as countermovement jump were identified between conditions in Post-1D.Discussion: Wearing high-pressure CGs (notably on KE) during DHR was associated with beneficial effects on soft-tissue vibrations, acute and delayed neuromuscular function, and perceived muscle soreness. The use of CGs during DHR might contribute to the enhanced muscle recovery by exerting an exercise-induced “mechanical protective effect.”

Quadriceps Lipid Content Has Sex-Specific Associations With Whole-Muscle, Cellular, and Molecular Contractile Function in Older Adults.

Increased adiposity is associated with reduced skeletal muscle function in older adults, but the mechanisms underlying this relationship remain unclear. To explore whether skeletal muscle properties track with adiposity, whole-muscle, cellular, and molecular function were examined in relation to adiposity measured at various anatomical levels in healthy older (60-80 years) men and women. Although women had greater absolute and relative body and thigh fat than men, quadriceps muscle attenuation, an index of intramuscular lipid content, was similar between sexes. At the whole-muscle level, greater quadriceps attenuation was associated with reduced knee extensor function in women, but not men. In women, decreased myosin heavy chain I and IIA fiber-specific force was associated with higher intramuscular lipid content, which may be explained, in part, by the reduced myofilament lattice stiffness found in myosin heavy chain IIA fibers. Longer myosin attachment times in myosin heavy chain I fibers from men and women were associated with greater amounts of adipose tissue, suggesting that fat deposits lead to slower myosin-actin cross-bridge kinetics. Our results indicate greater quantities of adipose tissue alter myofilament properties and cross-bridge kinetics, which may partially explain the adiposity-induced decrements in single-fiber and whole-muscle function of older adults, especially women.

Hip and Knee Kinetics During a Back Squat and Deadlift.

Choe, KH, Coburn, JW, Costa, PB, and Pamukoff, DN. Hip and knee kinetics during a back-squat and deadlift. J Strength Cond Res 35(5): 1364-1371, 2021-The back-squat and deadlift are performed to improve hip and knee extensor function. The purpose of this study was to compare lower extremity joint kinetics (peak net joint moments [NJMs] and positive joint work [PJW]) between the back-squat and deadlift. Twenty-eight resistance-trained subjects (17 men: 23.7 ± 4.3 years, 1.76 ± 0.09 m, 78.11 ± 10.91 kg; 11 women: 23.0 ± 1.9 years, 1.66 ± 0.06 m, 65.36 ± 7.84 kg) were recruited. One repetition maximum (1RM) testing and biomechanical analyses occurred on separate days. Three-dimensional biomechanics of the back-squat and deadlift were recorded at 70 and 85% 1RM for each exercise. The deadlift demonstrated larger hip extensor NJM than the back-squat {3.59 (95% confidence interval [CI]: 3.30-3.88) vs. 2.98 (95% CI: 2.72-3.23) Nm·kg-1, d = 0.81, p < 0.001}. However, the back-squat had a larger knee extensor NJM compared with the deadlift (2.14 [95% CI: 1.88-2.40] vs. 1.18 [95% CI: 0.99-1.37] Nm·kg-1, d = 1.44 p < 0.001). More knee PJW was performed during the back-squat compared with the deadlift (1.85 [95% CI: 1.60-2.09] vs. 0.46 [95% CI: 0.35-0.58] J·kg-1, d = 2.10, p < 0.001). However, there was more hip PJW during the deadlift compared with the back-squat (3.22 [95% CI: 2.97-3.47] vs. 2.37 [95% CI: 2.21-2.54] J·kg-1, d = 1.30, p < 0.001). Larger hip extensor NJM and PJW during the deadlift suggest that individuals targeting their hip extensors may yield greater benefit from the deadlift compared with the back-squat. However, larger knee extensor NJM and PJW during the back-squat suggest that individuals targeting their knee extensor muscles may benefit from incorporating the back-squat compared with the deadlift.

Effects of elevated H+ and Pi on the contractile mechanics of skeletal muscle fibres from young and old men: implications for muscle fatigue in humans.

The mechanisms responsible for the loss in muscle power and increased fatigability with ageing are unresolved. We show that the contractile mechanics of fibres from the vastus lateralis of old men were well-preserved compared to those of young men, but the selective loss of fast myosin heavy chain II muscle was strongly associated with age-related decrements in whole-muscle strength and power. We reveal that the combination of acidosis (H+ ) and inorganic phosphate (Pi ) is an important mediator of muscle fatigue in humans by inhibiting the low- to high-force state of the cross-bridge cycle and peak power, but the depressive effects of these ions on cross-bridge function were similar in fibres from young and old men. These findings suggest that the age-related loss in muscle power is primarily determined by the atrophy of fast fibres, but the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H+ and Pi . The present study aimed to identify the mechanisms responsible for the loss in muscle power and increased fatigability with ageing by integrating measures of whole-muscle function with single fibre contractile mechanics. After adjusting for the 22% smaller muscle mass in old (73-89years, n=6) compared to young men (20-29years, n=6), isometric torque and power output of the knee extensors were, respectively, 38% and 53% lower with age. Fatigability was ∼2.7-fold greater with age and strongly associated with reductions in the electrically-evoked contractile properties. To test whether cross-bridge mechanisms could explain age-related decrements in knee extensor function, we exposed myofibres (n=254) from the vastus lateralis to conditions mimicking quiescent muscle and fatiguing levels of acidosis (H+ ) (pH 6.2) and inorganic phosphate (Pi ) (30mm). The fatigue-mimicking condition caused marked reductions in force, shortening velocity and power and inhibited the low- to high-force state of the cross-bridge cycle, confirming findings from non-human studies that these ions act synergistically to impair cross-bridge function. Other than severe age-related atrophy of fast fibres (-55%), contractile function and the depressive effects of the fatigue-mimicking condition did not differ in fibres from young and old men. The selective loss of fast myosin heavy chain II muscle was strongly associated with the age-related decrease in isometric torque (r=0.785) and power (r=0.861). These data suggest that the age-related loss in muscle strength and power are primarily determined by the atrophy of fast fibres, but the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H+ and Pi .

Fitness, knee function and competition performance in professional alpine skiers after ACL injury

ObjectivesTo assess the fitness of elite alpine skiers during recovery from anterior cruciate ligament (ACL) reconstruction and changes in performance level after return to competition. DesignRetrospective cohort study. MethodsThe database of a specialized sports clinic was screened for professional alpine skiers with a history of ACL rupture and reconstruction. Strength and further functional tests as well as questionnaire data reflecting the athletes’ subjective perception of pain, function in activities of daily living and physical activity levels were extracted. The website of the International Ski Federation (FIS) was used to obtain FIS points reflecting the competition performance level prior to injury, after return to competition as well as one year later. ResultsQuestionnaire data revealed the highest patient satisfaction. Measurements performed 161.5±24.2days after surgery showed persistent muscle strength and power deficits, which primarily affected the knee extensor muscles and were more pronounced following reconstruction using quadriceps as compared to hamstring tendon grafts. FIS points increased immediately after return to competition (364.3±142.5days post-reconstruction) but dropped below pre-injury levels within the first year. ConclusionsACL injuries sustained by professional skiers entail muscle strength and power deficits that persist for more than five months after surgery. The rate of recovery of knee extensor muscle function may be slower following ACL reconstruction using quadriceps tendon grafts. On average, athletes returned to competition within one year after surgery and succeeded in surpassing their baseline performance level within the first year after return to competition.

The reliability of data produced by isokinetic dynamometry (IKD) of knee extension and flexion movement

To investigate the feasibility of using isolated knee performance to measure the f-v profile of human muscle in vivo, we were using isokinetic dynamometry (IKD) technique that span the entire f-v profile of skeletal muscle. With institutional ethics approval, eleven healthy males (mean ± SD: age, 24.9 ± 3.1 years; body mass, 80.2 ± 10.1 kg; height, 176.2 ± 7.1 cm) completed this study. The participants were physically active and were familiarized with the techniques and protocol prior to completing 4 experimental sessions (1 introductory session and 3 repeated experiment sessions). The sessions was used a protocol of knee extensor function on IKD at isometric mode and angular velocities of 60˚.s-1, 120˚.s-1, 240˚.s-1 and 450˚.s-1. IKD data were not significantly different across the 3 repeated trials, demonstrating there was no evidence of systematic bias. The average coefficient of variation (CV) of IKD was 9.3 ± 3.0% ranging from 7.0 to 15.7%. Therefore the isolated knee performance to measure the f-v profile of human muscle in vivo using the IKD was feasible.Keywords: f-v profile, isokinetic dynamometry, skeletal muscle

Burn survivors' pulmonary and muscular impairment, exercise tolerance and return-to-work following medical-vocational rehabilitation: A long-term follow-up.

To follow up the long-term outcome in return-to-work (RTW) rate in burn-injury patients, and to determine the degree of impairment in pulmonary and muscular function and exercise tolerance. A prospective, longitudinal follow-up study without a control group. Twenty-five burn-injury patients referred for medical-vocational rehabilitation. Return-to-work rate was followed after completed medical-vocational rehabilitation. Pulmonary function was evaluated with spirometry, diffusing capacity and radio spirometry. Exercise capacity was determined using a bicycle ergometer. Muscle functions evaluated in the arms and legs were: isokinetic torque, isometric strength, endurance and muscular strength utilization. Return-to-work rate was 87%. During bicycle exercise tests the patients, on average, reached their expected workloads. The dominating lung func-tion abnormality observed on lung scintigraphy was delayed wash-out time of inhaled radioactive xenon gas, suggesting airway obstruction. All tests of shoulder-flexor and knee-extensor muscle function showed large minimum-maximum differences. Mean isometric endurance of shoulder flexors was lower than mean of references, and isokinetic knee extensor torques were slightly lower. High return-to-work rates can be achieved after burn injury requiring hospital-ward care. Despite measurable impairments in muscle strength/endurance and pulmonary function in a substantial proportion of these patients, overall normal bicycle exercise capacity was observed except for a few cases.

Reliability of single- and paired-pulse transcranial magnetic stimulation for the assessment of knee extensor muscle function

This study examined inter-session and intra-session transcranial magnetic stimulation (TMS) reliability at two test stimulus intensities in the knee extensors. Strong and weak TMS was delivered via single- and paired- (3-ms and 100-ms inter-stimulus interval) pulses on the same day and different days. All stimuli were delivered during isometric contractions of the knee extensors at 20% of maximal voluntary force. Motor-evoked potentials (MEP) were assessed in quadriceps femoris muscles. Relative (intra-class correlation coefficient, ICC) and absolute (standard error of measurement, SEM) reliability and variability (coefficient of variation) were assessed. MEPs elicited by strong and weak single-pulse TMS had excellent relative reliability in all muscles as did weak short-interval and strong long-interval paired-pulse TMS (all ICC>0.75). Conversely, relative reliability of strong short-interval and weak long-interval paired-pulse TMS was lower (ICC: 0.34–0.83 and 0.22–0.97, respectively). MEP size variability was lower (P<0.05) and SEM comparable or lower in strong compared to weak TMS conditions. These results suggest single- and paired-pulse TMS at both strong and weak intensities are generally reliable in the knee extensors. Strong (or both strong and weak) single-pulse TMS is recommended. The results indicate using weak test pulses for short-interval and strong test pulses for long-interval paired-pulse TMS are recommended.

Influence of patellar position on the knee extensor mechanism in normal and crouched walking

Patella alta is common in cerebral palsy, especially in patients with crouch gait. Correction of patella alta has been advocated in the treatment of crouch, however the appropriate degree of correction and the implications for knee extensor function remain unclear. Therefore, the goal of this study was to assess the impact of patellar position on quadriceps and patellar tendon forces during normal and crouch gait. To this end, a lower extremity musculoskeletal model with a novel 12 degree of freedom knee joint was used to simulate normal gait in a healthy child, as well as mild (23 deg min knee flexion in stance), moderate (41 deg), and severe (67 deg) crouch gait in three children with cerebral palsy. The simulations revealed that quadriceps and patellar tendon forces increase dramatically with crouch, and are modulated by patellar position. For example with a normal patellar tendon position, peak patellar tendon forces were 0.7 times body weight in normal walking, but reached 2.2, 3.2 and 5.4 times body weight in mild, moderate and severe crouch. Moderate patella alta acted to reduce quadriceps and patellar tendon loads in crouch gait, due to an enhancement of the patellar tendon moment arms with alta in a flexed knee. In contrast, patella baja reduced the patellar tendon moment arm in a flexed knee and thus induced an increase in the patellar tendon loads needed to walk in crouch. Functionally, these results suggest that patella baja could also compromise knee extensor function for other flexed knee activities such as chair rise and stair climbing. The findings are important to consider when using surgical approaches for correcting patella alta in children who exhibit crouch gait patterns.

Effect of exercise training on neuromuscular function of elbow flexors and knee extensors of type 2 diabetic patients

Purpose: The effects of exercise training on neuromuscular function of arm and leg muscles in type 2 diabetic patients (T2D) was investigated. Methods: Eight T2D sedentary male patients (61.0±2.3years) and eight sedentary healthy age matched control subjects (H, 63.9±3.8years) underwent a 16-week supervised combined endurance and resistance exercise program. Before and after training, maximal isometric (MVIC), isokinetic (15, 30, 60, 120, 180, 240°s−1) torque and muscle endurance of the elbow flexors (EF) and knee extensors (KE) were assessed. Simultaneously, surface electromyographic signals from biceps brachii (BB) and vastus lateralis (VL) muscles were recorded and muscle fiber conduction velocity (MFCV) estimated. Results: Following training, maximal torque of the KE increased during MVIC and isokinetic contractions at 15 and 30°s−1 in the T2D (+19.1±2.7% on average; p<0.05) but not in the H group (+7±0.9%; p>0.05). MFCV recorded from the VL during MVIC and during isokinetic contractions at 15 and 30°s−1 increased (+11.2±1.6% on average; p<0.01), but in the diabetic group only. Muscular endurance was lower in T2D (20.1±0.7s) compared to H (26.9±1.3s), with an associated increase in the MFCV slope after training in the KE muscles only. Conclusion: The effect of a combined exercise training on muscle torque appears to be angular velocity-specific in diabetic individuals, with a more pronounced effect on KE muscles and at slow contraction velocities, along with an associated increase in the MFCV. MFCV appears to be a more sensitive marker than torque in detecting the early signs of neuromuscular function reconditioning.

080. Can Creatine Supplementation Improve Body Composition and Objective Physical Function in Rheumatoid Arthritis Patients? A Randomized Controlled Trial

OBJECTIVE: Rheumatoid cachexia (muscle wasting) in rheumatoid arthritis (RA) patients contributes to substantial reductions in strength and impaired physical function. The objective of this randomised control trial was to investigate the effectiveness of oral creatine (Cr) supplementation in increasing lean mass and improving strength and physical function in RA patients. METHOD: In a double-blind design, 40 RA patients, were randomised to either 12 weeks supplementation of Cr or placebo. Body composition (dual energy x-ray absorptiometry, DXA, and bioelectrical impedance spectroscopy, BIS), strength and objectively-assessed physical function were measured at: baseline, day 6, week 12 and week 24. Data analysis was performed by ANCOVA. RESULTS: Creatine supplementation increased appendicular lean mass (ALM; a surrogate measure of muscle mass) by 0.52 (± 0.13) kg (P = 0.004 versus placebo), and total LM by 0.60 (± 0.37) kg (P = 0.158). The change in LM concurred with the gain in intracellular water (0.64 ± 0.22 L, P = 0.035) measured by BIS. Despite increasing ALM, Cr supplementation, relative to placebo, failed to improve isometric knee extensor (P = 0.408), handgrip strength (P = 0.833), or objectively-assessed physical function (P's = 0.335 - 0.764). CONCLUSION: In patients with RA, creatine supplementation increased muscle mass, but not strength or objective physical function. No treatment-related adverse effects were reported suggesting that Cr supplementation may offer a safe and acceptable adjunct treatment for attenuating muscle loss; this treatment may be beneficial for patients suffering from severe rheumatoid cachexia. This article is protected by copyright. All rights reserved.

Muscle disuse alters skeletal muscle contractile function at the molecular and cellular levels in older adult humans in a sex-specific manner.

Physical inactivity that accompanies ageing and disease may hasten disability by reducing skeletal muscle contractility. To characterize skeletal muscle functional adaptations to muscle disuse, we compared contractile performance at the molecular, cellular and whole‐muscle levels in healthy active older men and women (n = 15) and inactive older men and women with advanced‐stage, symptomatic knee osteoarthritis (OA) (n = 16). OA patients showed reduced (P < 0.01) knee extensor function. At the cellular level, single muscle fibre force production was reduced in OA patients in myosin heavy chain (MHC) I and IIA fibres (both P < 0.05) and differences in IIA fibres persisted after adjustments for fibre cross‐sectional area (P < 0.05). Although no group differences in contractile velocity or power output were found for any fibre type, sex was found to modify the effect of OA, with a reduction in MHC IIA power output and a trend towards reduced shortening velocity in women, but increases in both variables in men (P < 0.05 and P = 0.07, respectively). At the molecular level, these adaptations in MHC IIA fibre function were explained by sex‐specific differences (P ≤ 0.05) in myosin–actin cross‐bridge kinetics. Additionally, cross‐bridge kinetics were slowed in MHC I fibres in OA patients (P < 0.01), attributable entirely to reductions in women with knee OA (P < 0.05), a phenotype that could be reproduced in vitro by chemical modification of protein thiol residues. Our results identify molecular and cellular functional adaptations in skeletal muscle that may contribute to reduced physical function with knee OA‐associated muscle disuse, with sex‐specific differences that may explain a greater disposition towards disability in women.

Arthroscopically Assisted Combined Anterior and Posterior Cruciate Ligament Reconstruction with Autologous Hamstring Grafts–Isokinetic Assessment with Control Group

ObjectiveThe aim of the study was to: 1) evaluate the differences in pre-post operative knee functioning, mechanical stability, isokinetic knee muscle strength in simultaneous arthroscopic patients after having undergone an anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) with hamstring tendons reconstruction, 2) compare the results of ACL/PCL patients with the control group.DesignControlled Laboratory Study.Materials and MethodsResults of 11 ACL/PCL patients had been matched with 22 uninjured control participants (CP). Prior to surgery, and minimum 2 years after it, functional assessment (Lysholm and IKDC 2000), mechanical knee joint stability evaluation (Lachman and “drawer” test) and isokinetic tests (bilateral knee muscle examination) had been performed. Different rehabilitation exercises had been used: isometric, passive exercises, exercises increasing the range of motion and proprioception, strength exercises and specific functional exercises.ResultsAfter arthroscopy no significant differences had been found between the injured and uninjured leg in all isokinetic parameters in ACL/PCL patients. However, ACL/PCL patients had still shown significantly lower values of strength in relative isokinetic knee flexors (p = 0.0065) and extensors (p = 0.0171) compared to the CP. There were no differences between groups regarding absolute isokinetic strength and flexors/extensors ratio. There was statistically significant progress in IKDC 2000 (p = 0.0044) and Lysholm (p = 0.0044) scales prior to (44 and 60 points respectively) and after the reconstruction (61 for IKDC 2000 and 94 points for Lysholm).ConclusionsAlthough harvesting tendons of semitendinosus and/or gracilis from the healthy extremity diminishes muscle strength of knee flexors in comparison to the CP, flexor strength had improved. Statistically significant improvement of the knee extensor function may indicate that the recreation of joint mechanical stability is required for restoring normal muscle strength. Without restoring normal muscle function and strength, surgical intervention alone may not be sufficient enough to ensure expected improvement of the articular function.

Eletroestimulação neuromuscular, exercícios contrarresistência, força muscular, dor e função motora em pacientes com osteoartrite primária de joelho

INTRODUÇÃO: A osteoartrite (OA) do joelho é um processo degenerativo e os sintomas são dor mecânica e períodos de dor inflamatória, rigidez articular e fraqueza muscular. Ela não tem cura. O objetivo do tratamento é aliviar os sinais e sintomas e, quando possível, retardar sua evolução. O fortalecimento muscular é indicado como tratamento da OA. OBJETIVO: Comparar a eficácia da eletroestimulação neuromuscular (EENM) e de exercícios contrarresistência (ECR) no ganho de força extensora de joelho, na diminuição da dor e na recuperação da função motora em pacientes com OA primária do joelho. MATERIAIS E MÉTODOS: Participaram da pesquisa 23 pacientes com diagnóstico de OA primária do joelho, segundo os critérios clínicos e radiológicos do American College of Rheumatology. Eles foram alocados aleatoriamente para um grupo de ECR (n = 9), um grupo de EENM (n = 8) e um grupo controle (n = 6), e foram submetidos aos procedimentos característicos de seu grupo três vezes por semana até completar 24 sessões. Foram avaliadas de forma cega a força extensora de joelho, a dor e a função motora. Foi utilizado o teste MANOVA 3 x 2 com medidas repetidas para P &lt; 0,05. RESULTADOS: Foi encontrada diferença significativa (P &lt; 0.05) somente nas comparações intragrupos para força extensora de joelho no grupo EENM e para dor nos grupos EENM e ECR. CONCLUSÃO: O fortalecimento da musculatura extensora de joelho pode auxiliar na diminuição da dor de pacientes com OA. A EENM, quando aplicada de acordo com o protocolo utilizado neste estudo, pode ser uma terapia interessante para o tratamento da OA do joelho.

The Effects of Kinesio Tape on Isokinetic Muscular Function of Horse Racing Jockeys

[Purpose] The purpose of this study was to conduct a scientific analysis of the effectiveness of Kinesio taping at preventing injury and improving horse racing jockey' performance, by studying the effects on isokinetic muscular function of Kinesio taping applied to the knee joint muscle. [Subjects] Eight horse racing jockeys were selected for this study. [Methods] Measurement of isokinetic muscular function of both flexor and extensor muscles was performed at the angular velocities of 60°/sec and 180°/sec using a Biodex system 3, before and after application of Kinesio taping to the rectus femoris, vastus medialis, vastus lateralis, and hamstring. [Result] At the angular velocities of 60°/sec and 180°/sec, significant differences were observed in both flexor and extensor peak torque, average power, and total work of the knee joint after application of Kinesio taping. [Conclusion] The application of Kinesio taping has a positive effect on the function of both knee flexors and extensors, and also kinetic ability. Therefore, its use would lead to a significant increase in the muscle function of horse racing jockeys.