Search Results (503)

Background: Persistent neuromuscular deficits following anterior cruciate ligament reconstruction (ACLR) are frequently attributed to arthrogenic muscle inhibition (AMI). The type of autologous graft used may influence the trajectory of neuromuscular recovery. Objective: To investigate the influence of graft type—bone–patellar tendon–bone (BPTB), hamstring tendon (HT), and quadriceps tendon (QT)—on the contractile properties of periarticular knee muscles over a 9-month post-operative period. Hypothesis: Each graft type would result in distinct recovery patterns of muscle contractility, as measured by tensiomyography (TMG). Methods: Thirty-one patients undergoing ACLR with BPTB (n = 8), HT (n = 12), or QT (n = 11) autografts were evaluated at 3, 6, and 9 months post-operatively. TMG was used to measure contraction time (Tc) and maximal displacement (Dm) in the rectus femoris, vastus medialis, vastus lateralis, and biceps femoris. Results: Significant within-group improvements in Tc and Dm were observed across all graft types from 3 to 9 months (Tc: p < 0.001 to p = 0.02; Dm: p < 0.001 to p = 0.01). The QT group showed the most pronounced Tc reduction in RF (from 30.16 ± 2.4 ms to 15.44 ± 1.6 ms, p < 0.001) and VM (from 31.05 ± 2.6 ms to 18.65 ± 1.8 ms, p = 0.004). In contrast, HT grafts demonstrated limited Tc recovery in BF between 6 and 9 months compared to BPTB and QT (p < 0.001), indicating a stagnation phase. BPTB exhibited persistent bilateral deficits in both quadriceps and BF at 9 months. Conclusions: Autograft type significantly influences neuromuscular recovery patterns after ACLR. TMG enables objective, muscle-specific monitoring of contractile dynamics and may support future individualized rehabilitation strategies. Full article

Quadricep weakness is frequently observed in patients following anterior cruciate ligament (ACL) injury or in those with knee osteoarthritis, often contributing to functional impairments and persistent symptoms. While high-intensity resistance training has been shown to effectively improve muscle strength, its application may be limited in certain populations due to pain or the risk of surgical complications. In recent years, blood flow restriction (BFR) training has emerged as a promising alternative. Growing evidence indicates that low-load BFR exercise can significantly improve muscle strength, induce hypertrophy, and enhance knee function, with outcomes comparable to those of high-intensity resistance training. When implemented using appropriate protocols, BFR training appears to be a safe and efficacious rehabilitation strategy for individuals with knee pathology. Full article

Eccentric muscle actions are integral to human movement, rehabilitation, and performance training due to their characteristic high force output (overload) and low energy cost and perceived exertion. Despite the growing use of eccentric devices, a gap in the research exists exploring multi-muscle activation profiles during multi-joint eccentric-only, isokinetic exercise. This study aimed to quantify and compare surface electromyographic (EMG) activity of four leg muscles—vastus lateralis (VL), tibialis anterior (TA), biceps femoris (BF), and medial gastrocnemius (GM)—during a standardized (isokinetic) submaximal eccentric multi-joint exercise using the Eccentron dynamometer. Eighteen healthy adults performed eccentric exercise at 40% of their maximal eccentric strength. Surface EMG data were analyzed using root mean square (RMS) and integrated EMG (iEMG) variables. Repeated-measures ANOVAs and effect sizes (ES) were used to evaluate within-subject differences across muscles. Results showed significantly greater activation in the VL compared to all other muscles (p < 0.05; and ES of 1.28–3.17 versus all other muscles), with the TA also demonstrating higher activation than the BF (p < 0.05). The BF exhibited the lowest activation, suggesting limited hamstring engagement. These findings highlight the effectiveness of the multi-joint isokinetic eccentric leg press movement (via an Eccentron machine) in targeting the quadriceps and dorsiflexors, while indicating the possible need for supplementary hamstring and plantar flexor exercises when aiming for a comprehensive lower body training routine. This study provides important insights for optimizing eccentric training protocols and rehabilitation strategies. Full article

Background: Soccer performance is largely dependent on high-intensity, unilateral actions such as sprints, jumps, and changes of direction. These demands can lead to strength and power differences between limbs, highlighting the importance of individualised assessment in professional players. Rotational inertial devices offer a valuable method to evaluate and train these mechanical variables separately for each leg. The aim of this study was twofold: (a) to characterise the mechanical variables derived from several lower-body strength exercises performed on rotational inertial devices, all targeting the same muscle group; and (b) to compare the mechanical variables between the dominant and non-dominant leg for each exercise. Methods: Twenty-six male professional soccer players (age = 26.3 ± 5.1 years; height = 182.3 ± 0.6 cm; weight = 75.9 ± 5.9 kg; body mass index = 22.8 ± 1.1 kg/m²; fat mass percentage = 9.1 ± 0.6%; fat-free mass = 68.8 ± 5.3 kg), all belonging to the same professional Belgian team, voluntarily participated in this study. The players completed a single assessment session consisting of six unilateral exercises (i.e., quadriceps hip, hamstring knee, adductor, quadriceps knee, hamstring hip, and abductor). For each exercise, they performed two sets of eight repetitions with each leg (i.e., dominant and non-dominant) in a randomised order. Results: The quadriceps hip exercise resulted in higher mechanical values compared to the quadriceps knee exercise in both limbs (p < 0.004). Similarly, the hamstring hip exercise produced greater values across all variables and limbs (p < 0.004), except for peak force, where the hamstring knee exercise exhibited higher values (p < 0.004). The adductor exercise showed higher peak force values for the dominant limb (p < 0.004). The between-limb comparison revealed differences only in the abductor exercise (p < 0.004). Conclusions: These findings suggest the necessity of prioritising movement selection based on targeted outcomes, although it should be considered that the differences between limb differences are very limited. Full article

Despite the benefits of resistance training in mitigating sarcopenia, adherence among frail older adults is often limited by osteoarticular pain, comorbidities, and logistical barriers. Pulsed electromagnetic field (PEMF) therapy has emerged as a potential alternative. However, evidence regarding its effects on functional and psychological parameters remains scarce. Objectives: To assess the effects of 12 PEMF therapy sessions on knee extensor strength and functional performance (Timed Up and Go test—TUG) in older adults with sarcopenia. Secondary outcomes included changes in calf circumference (CC), SARC-F + CC scores, and depressive symptoms. Methods: A controlled, non-randomized experimental design was employed, with a pre-intervention control group serving as a baseline reference (PEMF group: n = 25; control group: n = 16). Participants received 12 PEMF therapy sessions (three times per week) targeting the quadriceps and gastrocnemius muscles. Outcomes were measured using knee-extension dynamometry, TUG, CC, SARC-F + CC, and the Yesavage Geriatric Depression Scale. Statistical analyses included ANCOVA, with baseline values as covariates. Results: Significant improvements were observed in knee-extension strength, which increased from 13.05 ± 4.8 kgf to 18.56 ± 8 kgf (p < 0.001); TUG test time improved from 23.1 ± 14.4 to 18.7 ± 10 s (p = 0.048); SARC-F + CC scores decreased from 11.6 ± 8.2 to 6.5 ± 7.6 (p < 0.001), though the interaction effect with time was not significant (p = 0.252). No statistically significant changes were observed in CC, which increased from 34.0 ± 4.0 cm to 36.0 ± 3.9 cm following the intervention (p = 0.548). Yesavage Geriatric Depression Scale scores improved significantly (7.9 ± 2.4 to 5.4 ± 1.7, p = 0.0013). Conclusions: PEMF therapy significantly improved lower-limb muscle strength and functional mobility in elderly individuals with sarcopenia. Additionally, depressive symptoms were significantly reduced. However, no significant changes were observed in CC or SARC-F + CC. Full article

Studying normative values for muscle activation in the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF), as well as the hamstrings/quadriceps (H:Q) ratio during the Countermovement Jump (CMJ). Determine whether there were differences between the CMJ and the trial of 5 consecutive CMJs (5 CMJ) and between the take-off and landing phases. A cross-sectional descriptive study. Thirty-one participants (20 females and 11 males, 22.52 ± 3.295 years, BMI 24.32, weight 58.23 ± 4.32 Surface electromyography has been used to determine muscle activation during the CMJ and 5 CMJ. Muscle activation in the VL, VM, and BF, as well as the hamstrings/quadriceps ratio in take-off and landing phases of the CMJ and 5 CMJ. The results show normative values in the VL, VM, and BF during both the CMJ and 5 CMJ, with the exception of the BF during the landing phase of the 5 CMJ. In conclusion, the activation in the take-off phase of the VM and VL is greater than during the landing phase. The BF shows similar activation in both the take-off and landing phases. The 5 CMJ does not induce greater muscular fatigue than the CMJ. Full article

This study investigates how three technical factors—steering wheel tilt, torque, and cabin vibration frequency—affect driver posture. Heavy-truck drivers often suffer from musculoskeletal disorders (MSDs), mainly due to poor cabin ergonomics and prolonged postures during work. In countries like Ecuador, making major structural changes to cabin design is not feasible. These factors were identified through video analysis and surveys from drivers at two Ecuadorian trucking companies. An experimental system was developed using a simplified cabin to control these variables, while posture and muscle activity were recorded in 16 participants using motion capture, inertial sensors, and electromyography (EMG) on the upper trapezius, middle trapezius, triceps brachii, quadriceps muscle, and gastrocnemius muscle. The test protocol simulated key truck-driving tasks. Data were analyzed using ANOVA (${\displaystyle p<0.05}$), with technical factors and mass index as independent variables, and posture metrics as dependent variables. Results showed that head mass index significantly affected head abduction–adduction (${\displaystyle -}$8.12 to ${\displaystyle -}$2.18°), and spine mass index influenced spine flexion–extension (${\displaystyle -}$0.38 to 6.99°). Among technical factors, steering wheel tilt impacted trunk flexion–extension (${\displaystyle -}$13.56 to 16.99°) and arm rotation (${\displaystyle -}$31.1 to 19.7°). Steering wheel torque affected arm rotation (${\displaystyle -}$30.49 to ${\displaystyle -}$6.77°), while vibration frequency influenced forearm flexion–extension (3.76 to 16.51°). EMG signals showed little variation between muscles, likely due to the protocol’s short duration. These findings offer quantitative support for improving cabin ergonomics in low-resource settings through targeted, cost-effective design changes. Full article

Strength training has established itself as an essential component in physical conditioning programmes, not only to improve sports performance, but also for health purposes. To evaluate the effects of a strength training protocol with a predominance of the eccentric component on blood count, blood chemistry, and quadriceps muscle ultrasound in university students. 31 students (22.3 ± 4.14 years) of the professional programme in Sports of the Politécnico Colombiano Jaime Isaza Cadavid participated. A mesocycle was developed with three weekly sessions of eccentric training focused on the lower body and core zone. Pre and post-intervention measurements were taken anthropometry, haemogram, lipid profile, ultrasound of the right quadriceps, Bosco test, and Rockport test. The Wilcoxon signed-rank test was used, and the effect size was calculated using rank correlation. Statistically significant changes were observed in haematocrit, mean corpuscular volume, HDL, muscle thickness and echo-intensity, vertical jump power, and maximal oxygen consumption. A four-week eccentric strength training programme generates improvements in haematology, lipid profile, muscle quality assessed by ultrasound, and functional performance in university students. Full article

As life expectancy increases, muscle atrophy, characterized by a decline in muscle mass and strength that can impair mobility, has become a growing concern, highlighting the potential of protein supplementation as a promising intervention strategy. A horse meat hydrolysate, with a molecular weight of less than 3 kDa, derived from m. biceps femoris and produced using the food-grade enzyme Alcalase^® (A4 < 3kDa) was evaluated for its efficacy in mitigating dexamethasone-induced muscle atrophy, a widely accepted model for studying catabolic muscle loss. Administered orally to C57BL/6 mice at dosages of 200 mg/kg or 500 mg/kg body weight for 35 days, A4 < 3kDa effectively countered the weight loss induced by dexamethasone in the whole body, quadriceps, tibialis anterior, and gastrocnemius muscles. Moreover, it increased muscle fiber cross-sectional area and grip strength. These effects were attributed to increased protein synthesis via the protein kinase B (AKT)/forkhead box O3 (FoxO3a)/mammalian target of rapamycin (mTOR) signaling pathway. A4 < 3kDa augmented the phosphorylation of key components of the signaling pathways associated with muscle atrophy, resulting in reduced mRNA expression of Atrogin-1 and MuRF-1. These findings demonstrate the potential of A4 < 3kDa as a functional food ingredient for preventing muscle atrophy. Full article

Background and Objectives: This study aims to investigate the relationship between isokinetic knee strength and competition performance in elite male ski mountaineering sprint athletes and to identify strength parameters that predict performance and contribute to injury prevention. Materials and Methods: Thirteen male athletes participating in the Ski Mountaineering Turkey Cup final stage were included. Isokinetic knee flexion (FLX) and extension (EXT) strength of dominant (DM) and non-dominant (NDM) legs were measured at angular velocities of 60°/s and 180°/s using the DIERS-Myolin Isometric Muscle Strength Analysis System. Competition performance was evaluated using the ISMF scoring system. Data were analyzed using SPSS 26.0 with Pearson correlation and multiple regression analyses after normality, linearity, and homoscedasticity checks. Results: Strong positive correlations were found between hamstring strength at high angular velocities (180°/s) and performance (DM FLX: r = 0.809; NDM FLX: r = 0.880). Extension strength showed moderate correlations at low velocities (60°/s) (DM EXT: r = 0.677; NDM EXT: r = 0.699). Regression analysis revealed that DM FLX at 180°/s and DM EXT at 60°/s explained 49% of performance variance (Adj. R² = 0.498). For NDM legs, only 180°/s FLX was a significant predictor (β = 1.468). Conclusions: High-velocity hamstring strength plays a critical role in ski mountaineering sprint performance, particularly during sudden directional changes and dynamic balance. Quadriceps strength at low velocities contributes to prolonged climbing phases. Moreover, identifying and addressing bilateral strength asymmetries may support injury prevention strategies in elite ski mountaineering athletes. These findings provide scientific support for designing training programs targeting explosive hamstring strength, bilateral symmetry, and injury risk reduction, essential for optimizing performance in the 2026 Winter Olympics sprint discipline. Full article

Background: Patellar resection is recommended in cases of massive cortical bone disruption or malignancies. Modern literature lacks a consensus surgical reconstruction after total patellectomy. Our study reviews the surgical techniques described in the literature and summarizes the reported functional outcomes and complication rates. Materials: We systematically reviewed the existing literature, searching the PubMed, Embase, and Scopus databases for articles published between 1950 and 2024. We recorded age, diagnosis, tumor size, Lodwick classification, soft tissue involvement, and pre-operative fractures for each case or case series. We also recorded the reconstructive approaches. Complications, local recurrences, MSTS scores, and knee range of motion (ROM) were considered when reported. Results: Twenty-eight articles met our inclusion criteria. Among these, 4 were case series and 24 were case reports. A total of 47 cases treated with total patellectomy were reviewed. Reconstruction was performed with direct suture in 8 cases, while 17 had local augments, including allograft (10 cases), muscle flaps or transportations (4), autologous bone (1), or a composite (2). Reconstruction was not mentioned in 22 cases. ROM was reported for 17 cases, and the MSTS score was reported for 9 cases. Conclusions: In cases of relatively small tissue defects, a direct suture of the extensor apparatus can allow adequate functional recovery. In cases of larger gaps, surgeons should use muscle flaps, transfers, or soft tissue augments. Massive bone and tendon allografts should mainly be considered in cases where the neoplasm was not confined to the patella but extensively involved the patellar ligament or the quadriceps tendon. Full article

Background: The quadriceps femoris (QF) muscle is traditionally described as a four-headed structure (QF4), yet recent anatomical studies have identified significant morphological variations, including accessory heads and complex quadriceps femoris tendon (QFT) layering. These anatomical differences are especially relevant when harvesting the QFT for anterior cruciate ligament (ACL) reconstruction, where graft quality and structure are critical to surgical success. This study aimed to systematically review and quantitatively synthesize available data on QF variants, with a focus on accessory heads and tendon architecture. Methods: This systematic review and meta-analysis followed PRISMA 2020 and Evidence-Based Anatomy Workgroup guidelines. Cadaveric studies reporting QF variants were identified through searches of multiple databases and anatomical journals. Pooled prevalence estimates and mean QFT lengths were calculated using random-effects models. Heterogeneity and publication bias were also assessed. Results: Eighteen studies encompassing 1066 lower limbs met inclusion criteria. The five-headed QF (QF5) was the most common variant (54.11%), followed by the classical four-headed form (QF4) (40.74%). Rare morphologies with six to eight heads (QF6–QF8) were also documented. Among accessory heads, the vastus lateralis (VL) type was most prevalent (21.35%), while an independent tensor vastus intermedius (TVI) occurred in 13.54% of limbs. The QFT most frequently displayed a trilaminar structure (47.73%), with quadrilaminar architecture observed in 42.49%. The mean QFT length was 78.63 mm. Conclusions: This meta-analysis confirms that the QF often deviates from classical anatomical descriptions, frequently exhibiting supernumerary heads and multilayered tendon architecture. These findings highlight the importance of detailed preoperative imaging and personalized surgical planning to minimize complications and optimize graft selection in ACL reconstruction. Full article

Background: Motor irradiation is a concept in which the muscles of the talocrural joint can influence the torque of the quadriceps femoris muscle. The aims of this study are to compare the effects of three different talocrural joint positions on the torque of the quadriceps femoris muscle and to analyze the differences in torque measurements between two dynamometers. Methods: 33 students from the Faculty of Health Studies at the University of Rijeka participated in the study. The torque of the quadriceps femoris muscle was measured using the Cybex CSMi isokinetic dynamometer and the EasyForce^® hand-held fixed dynamometer. The measurements were performed three times continuously for each talocrural joint position. Results: When measured with the isokinetic dynamometer (p = 0.210) and the EasyForce^® dynamometer (p = 0.925), no significant difference was found in the torque of the quadriceps femoris muscle between the three talocrural joint positions. The dynamometers measured the torque consistently and showed a significant, from very good to excellent correlation of the data (p < 0.001), but did not provide identical results due to constant and proportional differences. Conclusions: There was no significant influence of the three talocrural joint positions on the torque of the quadriceps femoris muscle under isometric contraction conditions without a specific angular velocity. The use of the two dynamometers led to similar but inconsistent results in the measurement of muscle torque. This inconsistency is not only because of the differences between the devices themselves, but also due to fundamental methodological differences in participant stabilization and testing procedures. Full article

Obesity is associated with reduced cardiorespiratory fitness and altered metabolic responses. However, the acute effects of forward and backward locomotion training in individuals with a body mass index (BMI) ≥ 30 remain underexplored. This study investigated this population’s cardiorespiratory, metabolic–perceptual, and muscle electromyography (EMG) responses to forward and backward locomotion at different speeds. Twenty-eight male participants were divided into four seven-member groups, following a randomized crossover design with a Latin Square-like counterbalancing approach. Participants completed four 10 min walking conditions (3 km/h forward, 3 km/h backward, 4 km/h forward, and 4 km/h backward) on separate days, with cardiorespiratory parameters (e.g., VO₂, VCO₂, and heart rate), metabolic responses (e.g., lactate and energy expenditure), and lower-limb muscle EMG activity measured. Statistical analysis using two-way repeated measures (MANOVA) revealed significant direction effects (p < 0.05) on VO₂, VCO₂, heart rate, energy expenditure, Borg RPE, final lactate, and the EMG activity of quadriceps, hamstrings, and tibialis anterior, but not on pre-lactate or soleus activity (p > 0.05). These findings provide valuable insights for optimizing exercise programs in obese individuals, supporting tailored movement strategies to enhance physiological outcomes. Full article

Background/Objectives: As aging leads to a decline in muscle mass, strength, and functional capacity, identifying effective, low-risk interventions for older adults is essential. Blood flow restriction training (BFRT) has gained recognition as a potential substitute for traditional high-load resistance training, offering comparable benefits with reduced mechanical stress. This scoping review explores current BFRT protocols—specifically cuff pressure, training frequency, and duration—and their impact on muscular strength, hypertrophy, and functional capabilities among healthy elderly individuals. Methods: Following PRISMA-ScR and Arksey and O’Malley’s framework, six databases were searched (2010–2024), yielding 13 eligible studies. Data were charted for BFRT parameters, training regimens, and outcomes related to strength, muscle size, and functionality. Risk of bias was assessed using Cochrane guidelines. Results: Low-load BFRT (20–40% 1RM), applied 2–4 times weekly for 6–12 weeks, significantly improved muscle strength, hypertrophy (e.g., quadriceps CSA), and functional performance (e.g., TUG, 6MWT). Cuff pressures ranged from 50 to 80% arterial occlusion pressure (AOP) for the lower limbs and 30–50% above systolic pressure for the upper limbs. Wider cuffs enhanced safety and comfort. BFRT demonstrated comparable or superior outcomes to conventional training in most studies, with minimal adverse effects reported. Conclusions: The existing evidence suggests that BFRT may be a promising intervention for improving muscle health and functionality in older adults; however, future research should focus on standardizing protocols, long-term outcomes, and tailored guidelines to optimize safety and efficacy. Full article