Alleviation of peripheral sensitization by quadriceps insertion of cog polydioxanone filaments in knee osteoarthritis rats.

A recently established therapeutic strategy, involving the insertion of biodegradable cog polydioxanone filaments into the quadriceps muscles using the Muscle Enhancement and Support Therapy (MEST) device, has demonstrated significant efficacy in alleviating knee osteoarthritis (OA) pain. This study investigated changes in peripheral sensitization as the potential mechanism underlying MEST-induced pain relief in monoiodoacetate (MIA) induced OA rats. The results revealed that MEST treatment potently reduces MIA-induced sensitization of L3/L4 dorsal root ganglion (DRG) neurons, the primary nociceptor pathway for the knee joint. This reduction in DRG sensitization, as elucidated by voltage-sensitive dye imaging, is accompanied by a diminished overexpression of TRPA1 and NaV1.7, key nociceptor receptors involved in mechanical pain perception. Importantly, these observed alterations strongly correlate with a decrease in mechanically-evoked pain behaviors, providing compelling neurophysiological evidence that MEST treatment alleviates OA pain by suppressing peripheral sensitization.

Effect of isometric quadriceps exercise on local microcirculation of the infrapatellar fat pad in female patients with knee osteoarthritis.

OBJECTIVE: To elucidate the local microcirculation of the infrapatellar fat pad (IFP) in patients with knee osteoarthritis (KOA) by determining the changes in IFP hardness and hemoglobin concentration during isometric quadriceps exercise (IQE). DESIGN: In this observational cross-sectional study, patients diagnosed with bilateral KOA were included in the KOA group (30 knees), healthy older adults in the control group (20 knees), and younger adults in the young group (20 knees). Ultrasonography was performed at rest and during IQE to measure IFP hardness based on shear wave velocity. Near-infrared spectroscopy was performed to measure oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (cHb) in the IFP before (Baseline), during (IQE task), and after IQE (Post). IFP hardness and O2Hb, HHb, and cHb concentration were analyzed using a linear mixed model for the groups and measurement points. RESULTS: During IQE, IFP hardness changes were significantly less in the KOA group than in the other groups (KOA: 95 % confidence intervals (CIs) [-0.854, 0.028]; control: 95 % CI [-0.941, -0.341]; and young: 95 % CI [-2.305, -1.706]). In the KOA group, O2Hb concentration exhibited no significant changes at Post compared with Baseline; however, significant changes were observed in the other groups (KOA: 95 % CI [-1.176, 0.423]; control: 95 % CI [-1.452, -0.276]; and young: 95 % CI [-4.062, -2.102]). CONCLUSIONS: During IQE, changes in hardness and hemoglobin concentration in the IFP were not significant in the KOA group, suggesting impaired local microcirculation of the IFP.

Quadriceps muscle contraction causes medial patellofemoral ligament elongation by intermeshed fibers of vastus medialis oblique muscle.

The first aim of this study was to compare the medial patellofemoral length between contracted and relaxed quadriceps muscle and second to assess the importance of the intermeshed vastus medialis oblique fibers. After a priori power analysis (α = 0.05, power [1-ß] = 0.95), 35 healthy males aged 18-30 were prospectively examined with a 3.0-T magnetic resonance imaging (MRI) scanner in 10-15° of knee flexion. Two axial MRI sequences (25 s each) were made with relaxed and contracted quadriceps. Two blinded, independent raters measured twice medial patellofemoral ligament length (curved line) and attachment-to-attachment length (straight line). Mean medial patellofemoral ligament length and attachment-to-attachment length with relaxed quadriceps was: 65.5 mm (SD = 3.7), 59.7 mm (SD = 3.6), and after contraction, it increased to 68.7 mm (SD = 5.3), 61.2 mm (SD = 4.7); p < 0.01 and <0.001, respectively. Intraclass correlation coefficients for intra- and inter-rater reliabilities ranged from 0.55 (moderate) to 0.97 (excellent). Mean medial patellofemoral ligament length elongation after quadriceps contraction was significantly greater (3.2 mm, SD = 3.9) than mean attachment-to-attachment length elongation (1.6 mm, SD = 2.8); p < 0.001. Contraction of quadriceps muscle causes elongation of the medial patellofemoral ligament to the extent greater than the elongation of distance between its attachments. This confirms that medial patellofemoral ligament elongation after quadriceps contraction results not only from movement of its patellar attachment but also directly from intermeshed vastus medialis oblique fibers pulling medial patellofemoral ligament in a different direction creating a bow-like construct in agreement with the "pull-and-guide mechanism" proposed in the literature.

Post-activation potentiation after isometric contractions is strongly related to contraction intensity despite the similar torque-time integral.

Post-activation potentiation (PAP) is defined as an enhanced contractile response of a muscle following its own contractile activity and is influenced by the intensity and duration of the conditioning contraction. The aim of this study was to determine if the combination of intensity and duration, that is, torque-time integral (TTI) is a determinant of PAP amplitude. We compared PAP amplitude following low-to-maximal voluntary conditioning contraction intensities with and without similar TTI in the knee extensors. Twelve healthy males completed two experimental sessions. Femoral nerve stimulation was applied to evoke single twitches on the relaxed quadriceps before and after isometric conditioning contractions of knee extensors. In one session, participants performed conditioning contractions without similar TTI (6 s at 100, 80, 60, 40 and 20% maximal voluntary contraction (MVC)), while they performed conditioning contractions with similar TTI in the other session (6 s at 100%, 7.5 s at 80%, 10 s at 60%, 15 s at 40%, and 30 s at 20% MVC). In both sessions, PAP amplitude was related to conditioning contraction intensity. The higher the conditioning contraction intensity with or without similar TTI, the higher PAP. Significant correlations were found (i) between PAP and conditioning contraction intensity with (r2 = 0.70; P < 0.001) or without similar TTI (r2 = 0.64; P < 0.001), and (ii) between PAP with and without similar TTI (r2 = 0.82; P < 0.001). The results provide evidence that TTI has a minor influence on PAP in the knee extensors. This suggests that to optimize the effect of PAP, it is more relevant to control the intensity of the contraction rather than the TTI.

Age and dietary restriction modulate mitochondrial quality in quadriceps femoris muscle of male mice.

Dietary restriction (DR) is a potential intervention for ameliorating ageing-related damages. Mitochondrial quality control is the key mechanism for regulating cellular functions in skeletal muscle. This study aimed to explore the effect of age and DR on the homeostasis of mitochondrial quality control in skeletal muscle. To study the effect of age on mitochondrial homeostasis, young (3 months old) male C57BL/6J mice were fed ad libitum (AL) until 7 (Young), 14 (Middle), and 19 months (Aged) of age. For the DR intervention, 60% of AL intake was given to the mice at 3 months of age until they reached 19 months of age (16 months). The quadriceps femoris muscle was collected for further analysis. Significant changes in the skeletal muscle were noticed during the transition between middle age and the elderly stages. An accumulation of collagen was observed in the muscle after middle age. Compared with the Middle muscle, Aged muscle displayed a greater expression of VDAC, and lower expressions of mitochondrial dynamic proteins and OXPHOS proteins. The DR intervention attenuated collagen content and elongated the sarcomere length in the skeletal muscle during ageing. In addition, DR adjusted the abnormalities in mitochondrial morphology in the Aged muscle. DR downregulated VDAC expression, but upregulated OPA1 and DRP1 expressions. Taken together, greater pathological changes were noticed in the skeletal muscle during ageing, especially in the transition between middle age and the elderly, whereas early-onset DR attenuated the muscular ageing via normalising partial functions of mitochondria.

Competition through ritualized aggressive interactions between sympatric colonies in solitary foraging neotropical ants.

Understanding the structure of food competition between conspecifics in their natural settings is paramount to addressing more complex questions in ecology, evolution, and conservation. While much research on ants focuses on aggressive food competition between large and foraging trail-using societies, we lack a thorough understanding of inter-colony competition in socially less derived, solitarily foraging species. To fill this gap, we explored the activity of ten neighbouring colonies of the giant ant Dinoponera quadriceps, monitoring 2513 foraging trips of hundreds of workers and all its inter-individual interactions. We found that, on encountering, workers from different colonies rarely engaged in aggressive fights but instead avoided each other or performed ritualised agonistic bouts. We discovered that during foraging trips, a few workers within each colony repeatedly rubbed their gaster on the substrate, a behaviour not observed in the field before. We propose that workers use this behaviour to mark the foraging area and mark more frequently in its periphery. Only 25% of the individuals specialised in this behaviour, and we hypothesise that the specialisation results from the history of interactions and experience of individual foragers. Our study suggests that workers of contiguous D. quadriceps colonies engage in low-risk conflict, mainly displaying ritualised behaviours. As these small societies mainly rely on tiny, unpredictably scattered, albeit abundant in the environment, arthropod prey, and not on persistent food sources, they do not aggressively defend exclusive foraging territories. On the other hand, colonies rely on large overlapping foraging areas to sustain their survival and growth, most often tolerating foragers from nearby colonies. We discuss whether this type of competitive interaction is expected in all solitary foraging species.

Reliability and reference values for diaphragmatic excursion, thickness, and thickening fraction and quadriceps femoris muscle thickness in full-term newborns evaluated by ultrasound.

To determine the diaphragm thickness, thickening fraction, and excursion and thickness of the quadriceps femoris muscle in full-term newborns and to evaluate the intra- and interrater reliability of these measurements. This was a prospective, observational clinical study including full-term newborns born within the first 48 h after birth. Serial measurements of the thickness, thickening fraction, and mobility of the diaphragm muscles and the thickness of the quadriceps muscle were obtained using ultrasound images. A total of 69 newborns with a mean gestational age of 39 weeks were included. The following measurements were obtained and are expressed as the mean (standard deviation): inspiratory diaphragm thickness, 0.19 cm (0.04); expiratory diaphragm thickness, 0.16 cm (0.04); diaphragm thickness fraction, 16.70 cm (10.27); diaphragmatic excursion, 0.68 cm (0.22); and quadriceps thickness, 0.99 cm (0.14). Intrarater reliability was assessed using intraclass correlation coefficients (ICCs). Excellent intrarater agreement was observed for the two groups of operators (ICC > 0.86, p < 0.001) for all measurements except for the diaphragm thickening fraction, which showed good agreement for both operator groups (ICC = 0.70, p < 0.001). Regarding interrater reliability, moderate agreement between the raters was observed in the means of all measures (ICC > 0.49, p < 0.001), except for the diaphragm thickening fraction, which showed poor agreement.    Conclusion: Good intrarater and moderate interrater reliability were achieved in ultrasound evaluations of the thickness and mobility of the diaphragm and quadriceps femoris muscles in full-term newborns, demonstrating the feasibility of this technique for clinical use. This pioneering study offers reference values for these muscles in a single study, allowing comparisons between different clinical conditions. What is Known: • Ultrasound is a highly reliable tool for muscle assessment that can be used to assess muscular atrophy in critically ill patients. • Muscle atrophy worsens the patient's condition and has been associated with worse outcomes. What is New: • To our knowledge, this is the first study to jointly evaluate the diaphragm and quadriceps muscle thickness and evaluate the reliability of all measurements. • Our study presents reference values for both muscles, enabling comparisons between different clinical conditions.

Analysis of Quadriceps Strength and Knee Pain.

OBJECTIVE: To investigate the association of quadriceps strength with the presence of knee pain. DESIGN: This cross-sectional study was based on data from the 1999-2000 to 2001-2002 National Health and Nutrition Examination Survey. SETTING: This was a community-based study. PARTICIPANTS: This study included 2619 adults with complete data for knee pain, quadriceps strength, and covariates. INTERVENTION: Not applicable. MAIN OUTCOME MEASURES: Self-reported knee pain. RESULTS: This study included 2619 individuals, 1287 (52.66%) of whom were women and 1543 (81.66%) identified as Non-Hispanic White. The mean ±standard deviation age was 62.48±9.71 years. After adjusting for covariates, the odds of knee pain decreased with every 20 N/m increase in quadriceps strength (odds ratio, 0.87; 95% confidence interval, 0.81-0.94). Individuals in the upper quartile of quadriceps strength had lower odds of knee pain than those in the lower quartile (Q4 vs Q1 [reference]: odds ratio, 0.28, 95% confidence interval, 0.15-0.52; Ptrend=.006). Nonlinear analyses indicated L-shaped associations for knee pain. The subgroup analyses showed no significant interactions, except for sex (Pinteraction=.046). The significance of the sex interaction indicated a correlation exclusively in women. CONCLUSIONS: The results demonstrated an inverse association between quadriceps strength and the presence of knee pain. The subgroup analysis by sex showed that this inverse relationship was statistically significant in the women but not in the men subgroup.

Epidemiology of quadriceps muscle strain injuries in elite male Australian football players.

OBJECTIVE: To describe the epidemiology of quadriceps muscle strain injury (QMSI) in elite Australian Football League (AFL) players, explore recovery milestones and determine whether recovery is impacted by factors such as injury type (index vs. re-injury), the primary muscle injured and the mechanism of injury. MEASURES: All QMSI data reported to the Soft Tissue Injury Registry of the AFL from the 2014 to 2020 seasons were evaluated. Player demographic data, circumstances of injury, MRI reports and recovery outcomes following injury were extracted. Descriptive statistics and frequency distributions are presented. Recovery outcomes for injury type, primary muscle injured and the mechanism of injury were compared using univariate analyses. RESULTS: There were 164 QMSIs from 122 players reported (134 index; 30 re-injuries). Almost all (91.3%) QMSIs involved the rectus femoris. Half (48.4%) of the QMSIs occurred during kicking and most commonly affected the dominant kicking leg (72%). The majority occurred at training (64.6%). All re-injuries involved the rectus femoris, most occurred from kicking (63.0%) and within 6 months of the preceding injury (70%). The mean return to play (RTP) time was 25.4 days (95%CI = 22.6-28.2) and rectus femoris injuries took around 14 days longer to RTP than vastii injuries (p = 0.001). QMSIs with a kicking mechanism took the longest to RTP of all injury mechanisms. CONCLUSION: In AFL players, QMSIs occur mostly in the dominant leg from a kicking mechanism. Rectus femoris injuries are more prevalent and result in longer RTP time frames. Re-injuries exclusively involved the rectus femoris, primarily from kicking.

Change in body weight is positively related to the change in muscle mass of the quadriceps in older inpatients with severely low BMI according to the GLIM criteria.

BACKGROUND & AIMS: Body weight is one of the essential indicators of nutritional status, and body weight management is vital in nutritional care. In addition, low body mass index (BMI) was included as a phenotypic criterion in the Global Leadership Initiative on Malnutrition (GLIM) criteria. Furthermore, low BMI has been used in grading the severity of malnutrition (moderate or severe malnutrition) in the GLIM criteria. A recent cross-sectional study reported that muscle mass of the quadriceps in older inpatients with severely low BMI is less than those of older inpatients with moderately low BMI and non-low BMI. However, the longitudinal relationship between body weight and muscle mass of the quadriceps in older inpatients in each BMI category according to the GLIM criteria remains unclear. This study aimed to examine the longitudinal relationship between body weight and muscle mass of the quadriceps in older inpatients in each BMI category according to the GLIM criteria. METHODS: This retrospective cohort study included 179 older inpatients (aged ≥ 70 years) (median [IQR] age: 84.0 [79.0-89.0]). The period of this study was between January 2017 and March 2020. In accordance with the cut-off value of a low BMI for patients aged ≥ 70 years in the Asian population according to the GLIM criteria, the participants were divided into the following three groups: the severely low BMI group (< 17.8 kg/m2) (n = 47), moderately low BMI group (≥ 17.8 to < 20.0 kg/m2) (n = 38), and non-low BMI group (≥ 20.0 kg/m2) (n = 94). The medians (IQR) of the length of hospital stay of the severely low BMI, moderately low BMI, and non-low BMI groups were 71.0 (49.0-98.0) days, 71.0 (50.0-98.0) days, and 50.5 (36.5-103.0) days, respectively. The primary outcome was a change in muscle mass of the quadriceps. The muscle mass of the quadriceps was examined using ultrasound images (i.e., quadriceps thickness). The changes in quadriceps thickness and body weight were calculated by subtracting the quadriceps thickness and body weight at admission from those values at discharge. Multiple linear regression analysis adjusting for confounding factors was used to determine whether the change in body weight was independently and significantly related to the change in quadriceps thickness in the severely low BMI, moderately low BMI, and non-low BMI groups. RESULTS: The means (SD) of the change in quadriceps thickness of the severely low BMI group, moderately low BMI group, and non-low BMI group were 0.0 ± 0.3 cm, 0.1 ± 0.3 cm, and 0.1 ± 0.5 cm, respectively. The means of the change in body weight in those groups were 0.4 ± 2.8 kg, - 1.1 ± 2.7 kg, and - 1.3 ± 4.3 kg, respectively. In the severely low BMI group, the change in body weight (ß = 0.34, p = 0.006) and quadriceps thickness at admission (ß = -0.62, p < 0.001) were significantly and independently related to the change in quadriceps thickness (R2 = 0.645, f2 = 1.817, statistical power = 1.000). In the moderately low BMI and non-low BMI groups, there were no factors that were significantly and independently related to the change in quadriceps thickness. CONCLUSIONS: The results of this study suggest that change in body weight is positively related to the change in muscle mass of the quadriceps in older inpatients with severely low BMI according to the GLIM criteria. These results imply the importance of body weight management for older inpatients with severely low BMI perspective from the muscle mass of the quadriceps.

Increased intramuscular adipose tissue of the quadriceps at admission is more strongly related to activities of daily living recovery at discharge compared to muscle mass loss in older patients with aspiration pneumonia.

BACKGROUND: Recent studies reported that an increase in intramuscular adipose tissue of the quadriceps in older patients negatively affects the recovery of activities of daily living (ADL) more than the loss of muscle mass. However, whether intramuscular adipose tissue of the quadriceps in older patients with aspiration pneumonia is related to ADL recovery remains unclear. This study aimed to determine the relationship between intramuscular adipose tissue of the quadriceps and ADL recovery in older patients with aspiration pneumonia. METHODS: Thirty-nine older inpatients who were diagnosed with aspiration pneumonia participated in this prospective study. The main outcome of this study was ADL at discharge. ADL were assessed using the Barthel Index (BI). The intramuscular adipose tissue and muscle mass of the quadriceps were evaluated at admission using echo intensity and muscle thickness observed on ultrasound images. A multiple linear regression analysis was performed to confirm whether the quadriceps echo intensity was related to the BI score at discharge, even after adjusting for confounding factors. RESULTS: The medians [interquartile range] of the BI score at admission and discharge were 15.0 [0.0-35.0] and 20.0 [5.0-55.0], respectively. The BI score at discharge was significantly higher than that at admission (p = 0.002). The quadriceps echo intensity (ß = - 0.374; p = 0.036) and BI score at admission (ß = 0.601; p < 0.001) were independently and significantly related to the BI score at discharge (R2 = 0.718; f2 = 2.546; statistical power = 1.000). In contrast, the quadriceps thickness (ß = - 0.216; p = 0.318) was not independently and significantly related to the BI score at discharge. CONCLUSIONS: Increased intramuscular adipose tissue of the quadriceps at admission is more strongly and negatively related to ADL recovery at discharge than the loss of muscle mass among older patients with aspiration pneumonia. Interventions targeting the intramuscular adipose tissue of the quadriceps may improve ADL among these patients.

Age-related effects of neuromuscular fatigue and acute recovery responses on maximal and rapid torque measures of the leg extensors and flexors.

PURPOSE: To examine the effects of neuromuscular fatigue and recovery on maximal and rapid torque characteristics in young and old men for the leg extensors and flexors. METHODS: Twenty-one young (age = 24.8 years) and 19 old (72.1 years) men performed maximal voluntary contractions (MVCs) before and at 0, 7, 15, and 30 min following an intermittent submaximal fatigue task. Outcome measures included endurance time, maximal (peak torque; PT) and rapid (absolute and normalized rate of torque development; RTD and nRTD) torque characteristics. RESULTS: The old men had greater endurance times than the young men. Differential recovery patterns were observed for PT, and early and late RTD phases between the leg extensor and flexor muscle groups such that the early rapid torque variables and the flexors demonstrated slower recovery compared to later rapid torque variables and the extensors. The normalized RTD variables were reduced less after the fatigue task and differential muscle and age effects were observed where the flexors were reduced more at the early phase (nRTD1/6) compared to the extensors, however, for the later phase (nRTD2/3) the young men exhibited a greater reduction compared to the old men. CONCLUSIONS: Dissimilar fatigue recovery patterns across different phases of RTD, lower limb muscles, and age groups may have important fatigue-related performance and injury risk implications across the adult lifespan.

Exploring the biomechanics and fatigue patterns of eccentric quasi-isometric muscle actions in the knee extensors and flexors.

PURPOSE: Eccentric quasi-isometric (EQI) resistance training is emerging as a promising option in sports medicine and rehabilitation. Despite prior research on EQI contractions in quadriceps and biceps brachii, their use in hamstring injury contexts is underexplored. Therefore, our study examines and contrasts the biomechanics and fatigue effects of EQI training on knee extensors and flexors. METHODS: Following familiarization, 16 healthy, active participants (9 men, 7 women; 23.5 ± 2.6 years, 72.1 ± 12.8 kg, 173.4 ± 10.7 cm) performed, in random order, four EQI contractions for knee extensions and flexions, respectively. EQI contractions were isotonically loaded to 70% of concentric (60°·s-1) maximal voluntary contraction. Rest between repetitions was set at three minutes, while four minutes separated each muscle group. Peak torque, mean torque, and optimal angle were evaluated pre- and post-bouts. Inter-repetition contraction time and angular velocity were also assessed. RESULTS: Average torque was 160.9 ± 44.2 and 71.5 ± 23.2 Nm for the extensors and flexors. Peak and mean torque significantly decreased for both extensors (p < 0.001, d = 0.70-0.71) and flexors (p ≤ 0.022, d = 0.36) after EQI contractions, respectively. However, the optimal angle increased for extensors (p < 0.001, d = 1.00) but not flexors (p = 0.811, d = 0.06). During EQI contractions, knee flexors exhibited greater intra-repetition velocity than extensors (p = 0.002; η2 = 0.50). Decreases in inter-repetition time and range of motion were more consistent for the extensors. CONCLUSIONS: Distinct responses exist when comparing EQI contractions of the knee extensors and flexors, particularly their effect on peak torque angles. These findings suggest knee flexors may require lower relative intensities to align more closely with extensor EQI contractions.

Effects of 12 weeks of neuromuscular electrical stimulation of the quadriceps muscles on the function and physio-biochemical traits in functionally fit female nursing-home residents aged 75 + years: a pilot study.

PURPOSE: Muscular changes induced by neuromuscular electrical stimulation (NMES) are well recognized, but knowledge of how NMES influences the physio-biochemical traits of the oldest old is still limited. This study investigated the effect of NMES applied for 12 weeks to the quadriceps muscles of female nursing-home residents aged 75 + on their functional capability and inflammatory, bone metabolism, and cardiovascular traits. METHODS: Nineteen women regularly taking part in two body conditioning sessions per week were randomized into an electrical stimulation group (ES; n = 10; 30 min sessions, 3 times per week) or a control group (CON; n = 9). At baseline and study week 12, all women performed the 30 s chair stand test (30sCST), the 6-minute walk test (6MWT), and the instrumented timed up and go test (iTUG). Resting heart rates, blood pressure, and the blood concentrations of inflammatory and bone metabolism markers were also measured twice. RESULTS: NMES increased the strength of participants' quadriceps muscles and their performance on the 30sCST and 6MWT while lowering resting arterial blood pressure and inflammatory marker levels; osteoclast activity showed a tendency to decrease. Changes in the iTUG results were not observed. A multiple regression analysis found that the results of functional tests in the ES group were best correlated with pulse pressure (the 30sCST and iTUG tests) and diastolic blood pressure (the 6MWT test). CONCLUSION: Twelve weeks of NMES treatment improved participants' functional capacity and inflammatory, bone metabolism, and cardiovascular traits. The ES group participants' performance on functional tests was best predicted by hemodynamic parameters.

Downhill running increases markers of muscle damage and impairs the maximal voluntary force production as well as the late phase of the rate of voluntary force development.

PURPOSE: To examined the time-course of the early and late phase of the rate of voluntary force development (RVFD) and muscle damage markers after downhill running. METHODS: Ten recreational runners performed a 30-min downhill run at 10 km h-1 and -20% (-11.3°) on a motorized treadmill. At baseline and each day up to 4 days RVFD, knee extensors maximum voluntary isometric force (MVIC), serum creatine kinase (CK) concentration, quadriceps swelling, and soreness were assessed. The early (0-50 ms) and late (100-200 ms) phase of the RVFD, as well as the force developed at 50 and 200 ms, were also determined. RESULTS: MVIC showed moderate decrements (p < 0.05) and recovered after 4 days (p > 0.05). Force at 50 ms and the early phase were not impaired (p > 0.05). Conversely, force at 200 ms and the late phase showed moderate decrements (p < 0.05) and recovered after 3 and 4 days, respectively (p > 0.05). CK concentration, quadriceps swelling, and soreness increased (p < 0.05) were overall fully resolved after 4 days (p > 0.05). CONCLUSION: Downhill running affected the knee extensors RVFD late but not early phase. The RVFD late phase may be used as an additional marker of muscle damage in trail running.

Associations amongst dynamic knee stiffness during gait, quadriceps stiffness, and the incidence of knee osteoarthritis over 24 months: a cohort study with a mediation analysis.

BACKGROUND: Decreased strength and increased stiffness of the quadriceps have been associated with a higher risk of developing knee osteoarthritis (OA) in elders. Dynamic joint stiffness (DJS) represents collective resistance from active and passive knee structures for dynamic knee motions. Elevated sagittal knee DJS has been associated with worsening of cartilage loss in knee OA patients. Altered quadriceps properties may affect DJS, which could be a mediator for associations between quadriceps properties and knee OA. Hence, this study aimed to examine whether DJS and quadriceps properties would be associated with the development of clinical knee OA over 24 months, and to explore the mediation role of DJS in associations between quadriceps properties and knee OA. METHODS: This was a prospective cohort study with 162 healthy community-dwelling elders. Gait analysis was conducted to compute DJS during the loading response phase. Quadriceps strength and stiffness were evaluated using a Cybex dynamometer and shear-wave ultrasound elastography, respectively. Knee OA was defined based on clinical criteria 24 months later. Logistic regression with generalized estimating equations was used to examine the association between quadriceps properties and DJS and incident knee OA. Mediation analysis was performed to explore the mediation role of DJS in associations between quadriceps properties and the incidence of knee OA. RESULTS: A total of 125 participants (65.6 ± 4.0 years, 58.4% females) completed the 24-month follow-up, with 36 out of 250 knees identified as clinical knee OA. Higher DJS (OR = 1.86, 95%CI: 1.33-2.62), lower quadriceps strength (1.85, 1.05-3.23), and greater quadriceps stiffness (1.56, 1.10-2.21) were significantly associated with a higher risk of clinical knee OA. Mediation analysis showed that the DJS was not a significant mediator for the associations between quadriceps properties and knee OA. CONCLUSIONS: Higher sagittal knee dynamic joint stiffness, lower quadriceps strength, and greater quadriceps stiffness are potential risk factors for developing clinical knee OA in asymptomatic elders. Associations between quadriceps properties and knee OA may not be mediated by dynamic joint stiffness. Interventions for reducing increased passive properties of the quadriceps and knee joint stiffness may be beneficial for maintaining healthy knees in the aging population.

Effectiveness and mechanism of action of rTMS combined with quadriceps strength training in individuals with knee osteoarthritis: study protocol for a randomized controlled trial.

BACKGROUND: Quadriceps training is necessary in function and activity of daily living for patients with knee osteoarthritis (KOA). However, it did not reduce the rate of surgical treatment for end-stage KOA in the long term. This may be related to brain structure changes and maladaptive plasticity in KOA patients. Transcranial Magnetic Stimulation (TMS) could enhance the functional connectivity of brain regions and improves maladaptive plasticity. However, the synergistic effect of the combination of the two for treat KOA is still unclear. Therefore, the purpose of this study is to investigate whether the High-Frequency rTMS combined with quadriceps strength training can improve the pain and function in KOA more effectively than quadriceps training alone and explore the mechanism of action. METHODS: This study is an assessor-blind, sham-controlled, randomized controlled trial involving 12 weeks of intervention and 6 months follow-up. 148 participants with KOA will receive usual care management and be randomized into four subgroups equally, including quadriceps strength training, high-frequency rTMS training, sham rTMS and quadriceps strength training, high-frequency rTMS and quadriceps strength training. The rehabilitation interventions will be carried out 5 days per week for a total of 12 weeks. All outcomes will be measured at baseline, 4 weeks, 8 weeks, and 12 weeks during the intervention and 1 month, 3 months and 6 months during the follow-up period. The effectiveness outcomes will be included visual analog scale, isokinetic knee muscle strength, Knee Injury and Osteoarthritis Outcome score and 36-Item Short-Form Health Survey score; The act mechanism outcomes will be included motor evoked potential, grey matter density, white matter, subcortical nuclei volumes, cortical thickness and functional connectivity by MRI. Two-way of variance with repeated measures will be used to test the group and time effect for outcome measures. DISCUSSION: The study will be the first protocol to examine whether there are synergistic effects following high-frequency rTMS combined with quadriceps strength training for treat KOA and clarify the mechanism of action. High-frequency rTMS can be added into the training program for KOA patients if it is proven effective. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2300067617. Registered on Jan.13,2023.

Thigh muscle and fat volumes are associated with knee cartilage abnormalities and bone marrow edema-like lesions: data from the osteoarthritis initiative.

OBJECTIVE: To investigate the associations of thigh muscle and fat volumes with structural abnormalities on MRI related to knee osteoarthritis. MATERIALS AND METHODS: MRI studies of the thighs and knees from 100 individuals were randomly selected from the Osteoarthritis Initiative Cohort. Whole Organ MR Scoring (WORMS) and effusion-synovitis scoring were performed in all knee MRI. Thigh muscles, intermuscular fat, and subcutaneous fat were manually segmented in 15 consecutive MR thigh images. Radiographic Kellgren-Lawrence grades (KLG) were also obtained in all knee radiographs. Independent t-tests were used to investigate the associations between thigh muscle and fat volumes, and sex. Mixed-effects analyses were obtained to investigate the associations between thigh muscle and fat volumes, KLG, WOMAC pain score, cartilage and bone marrow WORMS, as well as effusion-synovitis scores. RESULTS: Women had higher subcutaneous fat volume than men (616.82 vs. 229.13 cm3, p < 0.01) and men had higher muscle volumes than women (p < 0.01). Quadriceps (coef = -2.15, p = 0.01) and vastus medialis (coef = -1.84, p = 0.03) volumes were negatively associated with the WORMS cartilage scores. Intermuscular fat volume (coef = 0.48, p = 0.01) was positively associated with WORMS bone marrow edema-like lesion (BMEL) scores. The quadriceps (coef = -0.99, p < 0.01) and hamstring (coef = -0.59, p = 0.01) volumes were negatively associated with WORMS BMEL scores. No evidence of an association was found between thigh muscle and fat volumes with KLG and effusion-synovitis grading (p > 0.05). CONCLUSION: Increased quadriceps and hamstring volumes were negatively associated with cartilage lesion and BMEL scores while no evidence of an association was found between thigh muscle and fat volumes, and radiographic knee osteoarthritis or effusion-synovitis grading.

2D shear wave elastography for the assessment of quadriceps entheses-a methodological study.

OBJECTIVE: To establish the scanning protocol for 2-dimensional shear wave elastography (SWE) on normal entheses by investigating the possible confounding factors that may increase the variability of measured elasticity. MATERIAL AND METHODS: 30 normal quadriceps entheses were scanned using SWE to compare the stiffness and coefficient variation by changing the ultrasonic coupling gel thickness, knee position, region of interest size, and scanning plane. RESULTS: No significant difference in median shear wave velocity (SWV) was observed in different coupling gel thicknesses. The median SWV was higher in the knee flexion position than in the extended position (p < 0.001). Increased knee flexion led to stiffer quadriceps enthesis and higher SWV (ρ = 0.8, p < 0.001). The median SWV was higher when the diameter region of interest was 4.0 mm than 2.0 mm (p = 0.001). The median SWV was higher in the transverse plane than in the longitudinal plane (p < 0.001). Strong correlation was found between SWV and the degree of the shear wave to muscle fiber direction (ρ = 0.8, p < 0.001). The coefficient variation was lower in a gel thickness of 2.5 cm, with an extended knee, a region of interest of 2.0 mm, and a longitudinal plane (p > 0.05). For interobserver reliability for the proposed protocol, the intraclass correlation coefficients was 0.763. CONCLUSION: In this study, we determined supine position with the knee extended; using 2.0 mm diameter region of interest and image acquisition at the longitudinal plane with thicker layer coupling gel seems most appropriate to reliably image healthy quadriceps entheses with SWE.

No Clinical Advantage of Harvesting a Patellar Bone Block Compared to All Soft Tissue Graft in Primary Quadriceps Tendon Anterior Cruciate Ligament Reconstruction.

PURPOSE: To compare patient-reported outcomes measurements (PROMs) and subsequent surgical interventions in patients treated with anterior cruciate ligament reconstruction (ACLR) using either quadriceps tendon autograft with a patellar bone block (bQT) or soft tissue only (sQT). METHODS: All ACLRs performed between 01.2010 and 03.2022 were prospectively followed for 24 months and retrospectively evaluated. All primary ACLRs with full 24 months of follow-up data, without any previous surgery or any additional ligamentous interventions, were matched for major ACL risk factors, including gender, age, Tegner activity level (TAL), pivoting sports, and concomitant injuries. PROMs (Lysholm score, Visual Analog Scale (VAS) for pain, and TAL) and subsequent surgical interventions were registered after 6, 12, and 24 months postoperative. Binary logistic regression was used to assess the influence of graft type, age, preinjury TAL, gender, pivoting sports and concomitant interventions on the need to undergo subsequent surgery. RESULTS: After matching, 246 patients were included in the final analysis. Both groups did not differ regarding any preoperative patient demographics or intraoperative details. At final follow-up, no significant difference in mean Lysholm score (sQT: 90.8±10.6, bQT: 91.8±10.6, p= .46), median TAL (sQT: 6 [1-10], bQT: 6 [1-10], p= .53) and VAS for pain (sQT: 0.7±1.1, bQT: 0.7±1.2, p= .70) was reported between both groups. 70.3% (sQT-A: 70.7%, bQT: 69.9%, p= .89) of patients returned to or exceeded their preinjury activity level. In terms of revision ACLR, there was no statistically significant difference between bQT (3.3%) and sQT (4.1%). Similarly, no difference was observed in contralateral ACLR (bQT: 7.3% sQT: 11.4%). Regression analysis indicated that none of the studied factors, including the use of a patellar bone block, influenced subsequent surgery, revision ACLR, or contralateral ACLR. CONCLUSION: Harvesting an additional patellar bone block in quadriceps tendon ACL reconstruction does not seem to impact postoperative patient-reported outcomes, ACL revision- or contralateral ACL reconstruction rates. LEVEL OF EVIDENCE: Level 3 - Cohort Study.