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Introduction: Patellofemoral pain (PFP) patients often show an altered lower limb alignment during the single-leg squat (SLS). There is evidence that proximal and distal-to-the-knee muscle alterations can modify the lower limb alignment in PFP patients. However, we observed a lack of studies investigating the possible association between the thickness and strength of proximal and distal-to-the-knee muscles and lower limb alignment during SLS in women with PFP. Therefore, this study aimed to investigate the association between the thickness and strength of lower limb muscles and dynamic knee valgus (DKV) during SLS in women with PFP., Methods: Cross-sectional study, where fifty-five women with PFP were submitted to the following evaluations: (1) muscle thickness (MT) of Gluteus Medius (GMed), Gluteus Maximus (GMax), Vastus Lateralis (VL), and Tibialis Anterior (TA); (2) isometric peak torque of hip abductors, hip external rotators, knee extensors, and foot inversors; and (3) DKV during SLS., Results: There was a significant negative association between GMax's MT and DKV (r = -0.32; p = 0.01), and between TA's MT and DKV (r = -0.28; p = 0.03). No significant correlations were observed between isometric torques and DKV. Regression analysis found that GMax's MT explained 10% of the DKV's variance during SLS., Discussion: Poor lower limb alignment during SLS is weakly associated with proximal and distal-to-the-knee muscle thicknesses, with no association with isometric torque in PFP women., Conclusion: Our results suggest that other factors besides strength and muscle thicknesses may explain and improve lower limb alignment in women with PFP., Competing Interests: Declaration of competing interest None, (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The objective of this study was to evaluate the intra- and inter-rater reliability and agreement between conditions with and without a special device (SD) in the evaluation of the patellar tendon (PT) cross-sectional area (CSA). Forty trained adult volunteers participated in the study. With the knee positioned at 90°, the ultrasound probe was placed in the transverse plane at 25, 50, and 75% of the PT length. Two raters and one analyzer obtained the images. We use a two-way ANOVA with a significance level of α = 0.05. No significant differences were found between raters or conditions. Intra-rater reliability ranged from moderate to good. Inter-rater reliability without the SD ranged from low to good, improving from moderate to good when the SD was used. Evaluation of the PT ends showed a lower coefficient of variation with the SD. We observed a moderate correlation at the ends and a strong correlation in the middle between conditions. The mean difference in the three positions is small (~ 0.013 cm 2 / ~ 1.7%) with an upper limit of 43.2% and a lower limit of 32.5%. Therefore, we conclude that the use of the SD can be employed for evaluating the PT ends, while for the central region, it becomes optional., (© 2023. Società Italiana di Ultrasonologia in Medicina e Biologia (SIUMB).)

Context: Pulsed current and kilohertz frequency alternating current are 2 types of neuromuscular electrical stimulation (NMES) currents often used by clinicians during rehabilitation. However, the low methodological quality and the different NMES parameters and protocols used in several studies might explain their inconclusive results in terms of their effects in the evoked torque and the discomfort level. In addition, the neuromuscular efficiency (ie, the NMES current type that evokes the highest torque with the lowest current intensity) has not been established yet. Therefore, our objective was to compare the evoked torque, current intensity, neuromuscular efficiency (evoked torque/current intensity ratio), and discomfort between pulsed current and kilohertz frequency alternating current in healthy people., Design: A double-blind, randomized crossover trial., Methods: Thirty healthy men (23.2 [4.5] y) participated in the study. Each participant was randomized to 4 current settings: 2 kilohertz frequency alternating currents with 2.5 kHz of carrier frequency and similar pulse duration (0.4 ms) and burst frequency (100 Hz) but with different burst duty cycles (20% and 50%) and burst durations (2 and 5 ms); and 2 pulsed currents with similar pulse frequency (100 Hz) and different pulse duration (2 and 0.4 ms). The evoked torque, current intensity at the maximal tolerated intensity, neuromuscular efficiency, and discomfort level were evaluated., Results: Both pulsed currents generated higher evoked torque than the kilohertz frequency alternating currents, despite the similar between-currents discomfort levels. The 2 ms pulsed current showed lower current intensity and higher neuromuscular efficiency compared with both alternated currents and with the 0.4 ms pulsed current., Conclusions: The higher evoked torque, higher neuromuscular efficiency, and similar discomfort of the 2 ms pulsed current compared with 2.5-kHz frequency alternating current suggests this current as the best choice for clinicians to use in NMES-based protocols.

Développé à la seconde is a classic ballet movement that requires the maintenance of a high hip joint range of motion (ROM) and muscle strength. However, the contribution of these hip joint biomechanical parameters to this movement's esthetic performance is unclear. Therefore, this study evaluated hip joint biomechanical characteristics of 21 experienced ballet dancers (15-29 y old) and verified the relationship between these variables with the développé à la seconde static and dynamic performance. Correlations between age, ballet practice time, gluteus maximus and gluteus medius thicknesses, ROM, and muscle strength with absolute and relative static and dynamic performances were verified. Flexors, extensors, and internal rotators peak strength and external rotation ROM were highly correlated with absolute and relative static performances (0.5-0.7). Flexors and extensors strength and external and internal rotation ROM showed the highest correlations with the développé dynamic performance (0.49-0.67). Flexor strength and flexor and internal rotation ROM predicted 26% to 41% of this movement's static and dynamic performances. Thus, from a biomechanical perspective, clinical assessment of hip strength and ROM may be used to predict the quality of the ballet dancers' performance of the développé à la seconde and guide classical ballet training.

Objective: To verify the effects of replacing exercises targeted on core/hip muscles by exercises targeted on leg/foot muscles in a rehabilitation program for patellofemoral pain (PFP)., Design: Randomized Controlled Trial., Participants: Fifty women with PFP., Methods: PFP participants were randomized into the standard rehabilitation group (SRG, n = 25) or distal exercise group (DEG, n = 25). Knee pain, patient-reported function, dynamic knee valgus and muscle strength were measured at baseline and after six and twelve weeks of the program start., Results: SRG and DEG presented similar responses to rehabilitation (except for muscle strengthening). Knee pain reduced after 6 weeks (SRG: -37.7%, ES = 1.23; DEG: -30%, ES = 0.93) and 12 weeks (SRG: -47.4%, ES = 1.53; DEG: -43.3%, ES = 1.46). Patient-reported function improved after 6 weeks (SRG: +7.3%, ES = 0.45; DEG: +3.8%, ES = 0.22) and 12 weeks (SRG: +14.1%, ES = 0.80; DEG: +8.8%, ES = 0.50). Dynamic knee valgus reduced after 12 weeks (SRG: -29.7%, ES = 0.38; DEG: -34.5%, ES = 0.32). Both groups experienced increases in knee extension strength (SRG: +9%, ES = 0.28; DEG: +6%, ES = -0.29), but only SRG had strength gains for hip abduction (+10%, ES = 0.36) and extension (+11%, ES = 0.44)., Conclusion: Exercises targeted on core/hip muscles can be replaced by exercises targeted on leg/foot muscles in a lower limb exercise-based rehabilitation program for women with PFP., Clinical Trial Registration: NCT03663595., Competing Interests: Declaration of competing interest None declared., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Purpose: This study aimed to determine whether triceps surae's muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners. Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h -1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young's modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young's modulus, and FL and PA of triceps surae muscles) and C (J kg -1 m -1 ) at 12 and 16 km h -1 . Results: SO PA and Achilles tendon CSA were negatively associated with C ( r 2 = 0.69; p < 0.001) at 12 km h -1 , whereas SO PA was negatively and Achilles tendon stress was positively associated with C ( r 2 = 0.63; p = 0.001) at 16 km h -1 , respectively. Our results presented a small power, and the multiple linear regression's cause-effect relation was limited due to the low sample size. Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h -1 ). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young's modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Machado, Lanferdini, da Silva, Geremia, Sonda, Fletcher, Vaz and Peyré-Tartaruga.)

Introduction: The aim of this study was to evaluate the intra and inter-rater and inter-analyzer reliability of neuromuscular variables and functional tests., Methods: Cross-sectional crossover design. Two independent raters and analyzers evaluated twenty-two healthy subjects. Knee-extensor strength was assessed from three maximal voluntary isometric contractions. Muscle activation was obtained from the vastus lateralis (VL), rectus femoris (RF), and vastus medialis (VM) muscles. VL and RF muscles' architecture [fascicle length (FL), pennation angle (PA), muscle thickness (MT)] was obtained at rest by ultrasound. The time from five sit-to-stand (STS) trials, and the distance from the 6-min walk test (6MWT) were obtained. Intraclass correlation coefficient was determined and classified as strong (r = 0.75-1.00), moderate (r = 0.40-0.74), and weak (r < 0.40)., Results: Strong intra-rater reliability values were observed for strength (r = 0.97), muscle activation [VL (r = 0.91); RF (r = 0.92); VM (r = 0.80)], VL [FL (r = 0.90); PA (r = 0.94); MT (r = 0.99)] and RF [MT (r = 0.85)] muscle architecture, STS (r = 0.95), and 6MWT (r = 0.98). Inter-rater reliability also presented strong values for strength (r = 0.97), muscle activation [VL (r = 0.94); RF (r = 0.79); VM (r = 0.78)], muscle architecture VL [PA (r = 0.81) and MT (r = 0.88)] and RF [MT (r = 0.80)], STS (r = 0.93), and 6MWT (r = 0.98). A moderate correlation VL muscle architecture [FL (r = 0.69)]. Inter-analyzer muscle architecture reliability presented strong VL [FL (r = 0.77); PA (r = 0.76); MT (r = 0.91)] and RF [MT (r = 0.99)]., Conclusion: The high intra and inter-rater and inter-analyzer reliability values for most variables is evidence that they can be used for clinical evaluation. Muscle architecture might need a longer training period by different raters and analyzers to increase reliability., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Objective: To verify the effect of 10-min static stretching on the triceps surae mechanical properties., Design: Quasi-experimental one-group pre test-post test study compared the time points of before, after, and minute by minute of one session of triceps surae passive static stretching., Methods: 15 participants performed a 10-min plantar flexor passive static stretching on the isokinetic dynamometer. We evaluated passive torque and myotendinous junction (MTJ) displacement before, minute by minute, and after the intervention. In contrast, we evaluated the range of motion (ROM), passive torque, MTJ displacement, and hysteresis before and after the intervention. Paired t-test compared pre and post-intervention time points. Passive torque and MTJ displacement in the minute-by-minute evaluations were compared by repeated measures one-way ANOVA with a Bonferroni post-hoc test., Results: ROM increased (effect size d = 0.56) and passive torque and muscle-tendon unit stiffness decreased (effect size d = 0.65 and d = 0.73, respectively) post-stretching. There was a reduction only in passive torque in the minute-by-minute evaluation, mainly at minutes five and seven., Conclusions: passive torque decreased over a 10-min static stretching session of the ankle plantar flexors, followed by a ROM increase and muscle-tendon unit, a stiffness decrease., Competing Interests: Declaration of competing interest The authors no have conflicts of interest and did not receive financial assistance to perform this review., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The objective of this study was to evaluate effects of photobiomodulation therapy (PBMT) on the 3000 m running performance (primary outcome), running economy (RE), metabolic cost and ratings of perceived exertion during running (secondary outcomes). Twenty male endurance athletes performed 4-min treadmill rectangular test at 12 km.h-1 monitored by a gas analyser. After that, PBMT or placebo in each lower limb was applied, followed performed a maximum test of 3000 m. Immediately after 3000 m test, the athletes repeated the treadmill test. Another application of PBMT/placebo was done after the treadmill test, and athletes went back to the laboratory 24 h later to repeat the treadmill test. After a 72 h interval, athletes repeated all procedures with another treatment intervention (PBMT/placebo). Athletes performed the 3000 m running test ~7s faster when treated with PBMT with similar effort score compared placebo condition. The RE remains unchanged immediately post 3000 m running test, nonetheless RE measured post-24 h improved by 5% with PBMT application without changes in metabolic cost. The PBMT pre- and post-conditioning enhanced the 3000 m running performance and improved RE 24 h following the 3000 m test. However, no changes on ratings of perceived exertion and metabolic cost with the application of PBMT.

Objective: The aim of this study was to compare proximal and distal muscle thickness between patellofemoral pain (PFP) and asymptomatic women (CG) and to verify the possible association between morphology and lower limb alignment during single leg-squat., Methods: Thirty women (PFP, n = 15 and CG, n = 15) performed the following evaluations: (i) muscle thickness of external oblique (EO), gluteus medius (GMed), tensor fascia latae (TFL), peroneus (PER) and tibialis anterior (TA); (ii) knee frontal plane projection angle (FPPA) during single-leg squat., Results: Compared with the CG, PFP showed: (1) smaller GMed (-10.02%; p = 0.04; effect size = 0.82), greater TFL (+18.44%; p = 0.02; effect size = 0.92) and PER (+14.23%; p = 0.02; effect size = 0.87) muscle thickness and greater knee FPPA during single-leg squat (+31.8%; p = 0.04; effect size = 1.12). No differences were observed in EO (+7.17%; p = 0.37; effect size = 0.34) and TA (-1.35%; p = 0.81; effect size = 0.12) muscle thickness. Additionally, we failed to observe significant associations between muscle morphology and knee FPPA in both groups., Conclusion: PFP patients showed alterations in proximal and distal muscle thickness, despite the lack of association with poor lower limb alignment. Prospective studies are necessary to determine if differences in muscle morphology are the cause or the consequence of PFP and to confirm the absence of relationship with lower limb alignment., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Muscle fatigue is a potential risk factor for hamstring strain injuries in soccer players. The aim of this study was to verify the effect of photobiomodulation therapy (PBMT) on the hamstrings' muscle fatigue of soccer players during a simulated match. Twelve male amateur soccer players (~ 25 years) participated in this randomized, crossover, double-blinded, placebo-controlled trial. The volunteers were evaluated in two sessions, with a minimum 7-day interval. At each session, volunteers received either PBMT (300 J per thigh) or placebo treatment on the hamstrings prior to the simulated soccer match. Muscle strength and functional capacity were evaluated through isokinetic dynamometry and countermovement jump (CMJ) tests, respectively, before and immediately after the simulated soccer match. Players had lower reductions on hamstring eccentric peak torque [4.85% (ES = 0.31) vs. 8.72% (ES = 0.50)], hamstring-to-quadriceps torque ratio [3.60% (ES = 0.24) vs. 7.75% (ES = 0.50)], and CMJ height [1.77% (ES = 0.09) vs. 5.47% (ES = 0.32)] when treated with PBMT compared to placebo. Magnitude-based inference supports that PBMT promoted 75%, 69%, and 53% chances for beneficial effects on hamstring eccentric peak torque, hamstring-to-quadriceps torque ratio, and CMJ height, respectively, compared to placebo treatment. In conclusion, PBMT applied before a simulated soccer match proved to be effective in attenuating the hamstrings' muscle fatigue. These findings support PBMT as a promising tool to prevent hamstring strain injury in soccer players.

Objectives: To document the magnitude and the time course of neuromechanical and morphological adaptations in response to a triceps surae eccentric training program., Methods: Twenty healthy male subjects completed a control period followed by a 12-week isokinetic eccentric training program. Triceps surae neuromechanical and morphological evaluations were performed every 4 weeks., Results: The training program led to increases in: eccentric (32%), isometric (13%) and concentric (20%) torques; eccentric (32%) and isometric (24%) electromyographic activity; and, muscle thickness (14%). Torque and muscle thickness increased until the 8th training week. Eccentric and isometric activation increased until the 4th training week. No change was found in concentric activation. The angles of peak torque in eccentric and concentric tests shifted towards longer muscle lengths. While eccentric and isometric strength gains are explained by increased neural activation and muscle mass, changes in concentric torque are not related to neural effects., Conclusions: Eccentric training led to increases in maximum eccentric and isometric force production due to adaptations in muscle activation and muscle mass. Among the advantages of the shift in the optimal length for force production towards longer lengths, are the increased total joint range of motion and a lower predisposition for muscle strain injuries., (Copyright © 2018 Elsevier Ltd. All rights reserved.)