scholarly journals Effect of Hip Flexion Angle on the Hamstring to Quadriceps Strength Ratio

Sports ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 43
Author(s):  
Eleftherios Kellis ◽  
Athanasios Ellinoudis ◽  
and Nikolaos Kofotolis
Keyword(s):  
Muscle Activation ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Quadriceps Strength ◽  
Flexion Angle ◽  
Electromyographic Activity ◽  
H:Q Ratio ◽  
Hip Flexion ◽  
Selection Of

The purpose of this study was to compare the hamstring to quadriceps ratio (H:Q) obtained from three different hip flexion angles. Seventy-three young athletes performed maximum isokinetic concentric and eccentric knee extension and flexion efforts at 60 °·s−1 and 240 °·s−1 from hip flexion angles of 90°, 60°, and 120°. The conventional (concentric to concentric), functional (eccentric to concentric) and mixed (eccentric at 30 °·s−1 to concentric torque at 240 °·s−1) H: Q torque ratios and the electromyographic activity from the rectus femoris and biceps femoris were analyzed. The conventional H:Q ratios and the functional H:Q ratios at 60 °·s−1 did not significantly differ between the three testing positions (p > 0.05). In contrast, testing from the 90° hip flexion angle showed a greater functional torque ratio at 240 °·s−1 and a mixed H:Q torque ratio compared with the other two positions (p < 0.05). The hip flexion angle did not influence the recorded muscle activation signals (p > 0.05). For the range of hip flexion angles tested, routine isokinetic assessment of conventional H:Q ratio and functional H:Q ratio at slow speed is not angle-dependent. Should assessment of the functional H:Q ratio at fast angular velocity or the mixed ratio is required, then selection of hip flexion angle is important.

scholarly journals Passive knee exoskeletons in functional tasks: Biomechanical effects of a SpringExo coil-spring on squats

2021 ◽  
Vol 2 ◽  
Author(s):  
Rand Hidayah ◽  
Dongbao Sui ◽  
Kennedi A. Wade ◽  
Biing-Chwen Chang ◽  
Sunil Agrawal
Keyword(s):  
Outcome Measures ◽  
Muscle Activation ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Lower Limbs ◽  
Flexion Angle ◽  
Coil Spring ◽  
Foot Pressure ◽  
Low Profile ◽  
Muscle Activations

Abstract Passive wearable exoskeletons are desirable as they can provide assistance during user movements while still maintaining a simple and low-profile design. These can be useful in industrial tasks where an ergonomic device could aid in load lifting without inconveniencing them and reducing fatigue and stress in the lower limbs. The SpringExo is a coil-spring design that aids in knee extension. In this paper, we describe the muscle activation of the knee flexors and extensors from seven healthy participants during repeated squats. The outcome measures are the timings of the key events during squat, flexion angle, muscle activation of rectus femoris and bicep femoris, and foot pressure characteristics of the participants. These outcome measures assess the possible effects of the device during lifting operations where reduced effort in the muscles is desired during ascent phase of the squat, without changing the knee and foot kinematics. The results show that the SpringExo significantly decreased rectus femoris activation during ascent (−2%) without significantly affecting either the bicep femoris or rectus femoris muscle activations in descent. This implies that the user could perform a descent without added effort and ascent with reduced effort. The exoskeleton showed other effects on the biomechanics of the user, increasing average squat time (+0.02 s) and maximum squat time (+0.1 s), and decreasing average knee flexion angle (−4°). The exoskeleton has no effect on foot loading or placement, that is, the user did not have to revise their stance while using the device.

scholarly journals Evaluation of the Lower Limb Muscles’ Electromyographic Activity during the Leg Press Exercise and Its Variants: A Systematic Review

2020 ◽  
Vol 17 (13) ◽  
pp. 4626
Author(s):  
Isabel Martín-Fuentes ◽  
José M. Oliva-Lozano ◽  
José M. Muyor
Keyword(s):  
Muscle Activation ◽  
Vastus Lateralis ◽  
Muscular Activity ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Quadriceps Muscle ◽  
Electromyographic Activity ◽  
Full Extension ◽  
Cross Sectional ◽  
Leg Press

The aim of this study was to analyze the literature on muscle activation measured by surface electromyography (sEMG) of the muscles recruited when performing the leg press exercise and its variants. The Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to report this review. The search was carried out using the PubMed, Scopus, and Web of Science electronic databases. The articles selected met the following inclusion criteria: (a) a cross-sectional or longitudinal study design; (b) neuromuscular activation assessed during the leg press exercise, or its variants; (c) muscle activation data collected using sEMG; and (d) study samples comprising healthy and trained participants. The main findings indicate that the leg press exercise elicited the greatest sEMG activity from the quadriceps muscle complex, which was shown to be greater as the knee flexion angle increased. In conclusion, (1) the vastus lateralis and vastus medialis elicited the greatest muscle activation during the leg press exercise, followed closely by the rectus femoris; (2) the biceps femoris and the gastrocnemius medialis showed greater muscular activity as the knee reached full extension, whereas the vastus lateralis and medialis, the rectus femoris, and the tibialis anterior showed a decreasing muscular activity pattern as the knee reached full extension; (3) evidence on the influence of kinematics modifications over sEMG during leg press variants is still not compelling as very few studies match their findings.

scholarly journals Healthy subjects with lax knees use less knee flexion rather than muscle control to limit anterior tibia translation during landing

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Michèle N. J. Keizer ◽  
Juha M. Hijmans ◽  
Alli Gokeler ◽  
Anne Benjaminse ◽  
Egbert Otten
Keyword(s):  
Knee Flexion ◽  
Muscle Activation ◽  
Reaction Force ◽  
Rectus Femoris ◽  
Knee Laxity ◽  
Biceps Femoris ◽  
Level Of Evidence ◽  
Jump Landing ◽  
Muscle Activation Patterns ◽  
Healthy Participants

Abstract Purpose It has been reported that there is no correlation between anterior tibia translation (ATT) in passive and dynamic situations. Passive ATT (ATTp) may be different to dynamic ATT (ATTd) due to muscle activation patterns. This study aimed to investigate whether muscle activation during jumping can control ATT in healthy participants. Methods ATTp of twenty-one healthy participants was measured using a KT-1000 arthrometer. All participants performed single leg hops for distance during which ATTd, knee flexion angles and knee flexion moments were measured using a 3D motion capture system. During both tests, sEMG signals were recorded. Results A negative correlation was found between ATTp and the maximal ATTd (r = − 0.47, p = 0.028). An N-Way ANOVA showed that larger semitendinosus activity was seen when ATTd was larger, while less biceps femoris activity and rectus femoris activity were seen. Moreover, larger knee extension moment, knee flexion angle and ground reaction force in the anterior-posterior direction were seen when ATTd was larger. Conclusion Participants with more ATTp showed smaller ATTd during jump landing. Muscle activation did not contribute to reduce ATTd during impact of a jump-landing at the observed knee angles. However, subjects with large ATTp landed with less knee flexion and consequently showed less ATTd. The results of this study give information on how healthy people control knee laxity during jump-landing. Level of evidence III

scholarly journals Midterm outcome and strength assessment after proximal rectus femoris refixation in athletes

2021 ◽  
Author(s):  
Maximilian Hinz ◽  
Stephanie Geyer ◽  
Felix Winden ◽  
Alexander Braunsperger ◽  
Florian Kreuzpointner ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Rectus Femoris ◽  
Knee Extension ◽  
Harris Hip Score ◽  
Postoperative Results ◽  
Postoperative Result ◽  
Strength Assessment ◽  
Competitive Athletes ◽  
Hip Flexion

Abstract Purpose Proximal rectus femoris avulsions (PRFA) are relatively rare injuries that occur predominantly among young soccer players. The aim of this study was to evaluate midterm postoperative results including strength potential via standardized strength measurements after proximal rectus femoris tendon refixation. It was hypothesized that the majority of competitive athletes return to competition (RTC) after refixation of the rectus femoris tendon without significant strength or functional deficits compared to the contralateral side. Methods Patients with an acute (< 6 weeks) PRFA who underwent surgical refixation between 2012 and 2019 with a minimum follow-up of 12 months were evaluated. The outcome measures compiled were the median Tegner Activity Scale (TAS) and mean RTC time frames, Harris Hip Score (HHS), Hip and Groin Outcome Score (HAGOS) subscales, International Hip Outcome Tool-33 (iHOT-33), and Visual Analog Scale (VAS) for pain. In addition, a standardized isometric strength assessment of knee flexion, knee extension, and hip flexion was performed to evaluate the functional result of the injured limb in comparison to the uninjured side. Results Out of 20 patients, 16 (80%) patients were available for final assessment at a mean follow-up of 44.8 ± SD 28.9 months. All patients were male with 87.5% sustaining injuries while playing soccer. The average time interval between trauma and surgery was 18.4 ± 8.5 days. RTC was possible for 14 out of 15 previously competitive athletes (93.3%) at a mean 10.5 ± 3.4 months after trauma. Patients achieved a high level of activity postoperatively with a median (interquartile range) TAS of 9 (7–9) and reported good to excellent outcome scores (HHS: 100 (96–100); HAGOS: symptoms 94.6 (89.3–100), pain 97.5 (92.5–100), function in daily living 100 (95–100), function in sport and recreation 98.4 (87.5–100), participation in physical activities 100 (87.5–100), quality of life 83.1 ± 15.6; iHot-33: 95.1 (81.6–99.8)). No postoperative complications were reported. Range of motion, isometric knee flexion and extension, as well as hip flexion strength levels were not statistically different between the affected and contralateral legs. The majority of patients were “very satisfied” (56.3%) or “satisfied” (37.5%) with the postoperative result and reported little pain (VAS 0 (0–0.5)). Conclusion Surgical treatment of acute PRFA yields excellent postoperative results in a young and highly active cohort. Hip flexion and knee extension strength was restored fully without major surgical complications. Level of evidence Retrospective cohort study; III.

Muscle Activation in the Main Muscle Groups of the Lower Limbs in High-Level Dancesport Athletes

2018 ◽  
Vol 33 (4) ◽  
pp. 231-237
Author(s):  
Encarnación Liébana ◽  
Cristina Monleón ◽  
Raquel Morales ◽  
Carlos Pablos ◽  
Consuelo Moratal ◽  
...  
Keyword(s):  
Tibialis Anterior ◽  
Muscle Activation ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Lower Limbs ◽  
Gastrocnemius Medialis ◽  
Leg Muscles ◽  
Relative Activation ◽  
Muscle Groups ◽  
High Level

Dancers are subjected to high-intensity workouts when they practice dancesport, and according to the literature, they are prone to injury, primarily of the lower limbs. The purpose of this study was to determine whether differences exist in relative activation amplitudes for dancers involved in dancesport due to muscle, gender, and type of dance. Measurements were carried out using surface electromyography equipment during the choreography of a performance in the following leg muscles: rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius medialis. Eight couples of active dancesport athletes (aged 20.50±2.75 yrs) were analyzed. Significant gender differences were found in rumba in the tibialis anterior (p≤0.05) and gastrocnemius medialis (p≤0.05). Based on the different activations, it is possible to establish possible mechanisms of injury, as well as tools for preventing injuries and improving sports performance.

scholarly journals Modeling of Muscle Activation from Electromyography Recordings in Patients with Cerebral Palsy

2018 ◽  
Vol 8 (12) ◽  
pp. 2345
Author(s):  
Susmita Roy ◽  
Ana Alves-Pinto ◽  
Renée Lampe
Keyword(s):  
Cerebral Palsy ◽  
Reference Values ◽  
Muscle Activation ◽  
Muscle Force ◽  
Rectus Femoris ◽  
Biceps Femoris ◽  
Force Modeling ◽  
Lower Extremity Muscle ◽  
Musculus Gastrocnemius ◽  
Parameter Dependent

The present study estimated muscle activation from electromyographic (EMG) recordings in patients with cerebral palsy (CP) during cycling on an ergometer. This could be used as an input to the modeling of muscle force following the neuromusculoskeletal modeling technique which can help to understand the alterations in neuromotor processes underlying disabilities in CP. EMG signals of lower extremity muscle activity from 14 adult patients with CP and 10 adult healthy participants were used here to derive muscle activation. With a self developed EMG system, signals from the following muscles were recorded: Musculus tibialis anterior, Musculus gastrocnemius, Musculus rectus femoris, and Musculus biceps femoris. Collected EMG signals were mathematically transformed into muscle activation following a parameter dependent and a nonlinear transformation. Muscle activation values from patients with CP were compared to equivalent reference values obtained from healthy controls. Muscle activation calculated at specific foot positions deviated clearly from reference values. The deviation was larger for patients with higher degree of spasticity. Observations underline the need of muscle force modeling during cycling for individualized cycling training for rehabilitation strategy.

Impact of a stance phase microprocessor-controlled knee prosthesis on level walking in lower functioning individuals with a transfemoral amputation

2013 ◽  
Vol 38 (6) ◽  
pp. 447-455 ◽  
Author(s):  
Valerie J Eberly ◽  
Sara J Mulroy ◽  
JoAnne K Gronley ◽  
Jacquelin Perry ◽  
William J Yule ◽  
...  
Keyword(s):  
Knee Prosthesis ◽  
Knee Extension ◽  
Electromyographic Activity ◽  
Transfemoral Amputation ◽  
Prosthetic Limb ◽  
Level Walking ◽  
Single Limb Support ◽  
Hip Flexion ◽  
The Impact ◽  
Improve Stability

Background: For individuals with transfemoral amputation, walking with a prosthesis presents challenges to stability and increases the demand on the hip of the prosthetic limb. Increasing age or comorbidities magnify these challenges. Computerized prosthetic knee joints improve stability and efficiency of gait, but are seldom prescribed for less physically capable walkers who may benefit from them. Objective: To compare level walking function while wearing a microprocessor-controlled knee (C-Leg Compact) prosthesis to a traditionally prescribed non-microprocessor-controlled knee prosthesis for Medicare Functional Classification Level K-2 walkers. Study design: Crossover. Methods: Stride characteristics, kinematics, kinetics, and electromyographic activity were recorded in 10 participants while walking with non-microprocessor-controlled knee and Compact prostheses. Results: Walking with the Compact produced significant increase in velocity, cadence, stride length, single-limb support, and heel-rise timing compared to walking with the non-microprocessor-controlled knee prosthesis. Hip and thigh extension during late stance improved bilaterally. Ankle dorsiflexion, knee extension, and hip flexion moments of the prosthetic limb were significantly improved. Conclusions: Improvements in walking function and stability on the prosthetic limb were demonstrated by the K-2 level walkers when using the C-Leg Compact prosthesis. Clinical relevance Understanding the impact of new prosthetic designs on gait mechanics is essential to improve prescription guidelines for deconditioned or older persons with transfemoral amputation. Prosthetic designs that improve stability for safety and walking function have the potential to improve community participation and quality of life.

scholarly journals Muscle Coactivation Before and After the Impact Phase of Running Following Isokinetic Fatigue

2011 ◽  
Vol 46 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Eleftherios Kellis ◽  
Andreas Zafeiridis ◽  
Ioannis G. Amiridis
Keyword(s):  
Muscle Activation ◽  
Biceps Femoris ◽  
Knee Extension ◽  
Knee Extensors ◽  
Training Experience ◽  
Cross Sectional ◽  
Muscle Activation Patterns ◽  
Strength Capacity ◽  
Before And After ◽  
The Impact

Abstract Context: The effects of fatigue on impact loading during running are unclear, with some authors reporting increased impact forces and others reporting decreased forces. Objective: To examine the effects of isokinetic fatigue on muscle cocontraction ratios about the knee and ankle during running. Design: Cross-sectional study. Setting: Neuromechanics laboratory. Patients or Other Participants: Female middle-distance runners (age  =  21.3 ± 1.93 years) with at least 5 years of training experience. Intervention(s): Participants ran on the treadmill at 3.61 m/s before and immediately after the fatigue protocol, which consisted of consecutive, concentric knee extension-flexion at 120°/s until they could no longer produce 30% of the maximum knee-extension moment achieved in the familiarization session for 3 consecutive repetitions. Main Outcome Measure(s): Electromyographic (EMG) amplitude of the vastus medialis (VM), biceps femoris (BF), gastrocnemius (GAS), and tibialis anterior (TA) was recorded using surface electrodes. Agonist∶antagonist EMG ratios for the knee (VM∶BF) and ankle (GAS∶TA) were calculated for the preactivation (PR), initial loading response (LR1), and late loading response (LR2) phases of running. Hip-, knee-, and ankle-joint angular displacements at initial foot contact were obtained from 3-dimensional kinematic tracings. Results: Fatigue did not alter the VM∶BF EMG ratio during the PR phase (P &gt; .05), but it increased the ratio during the LR1 phase (P &lt; .05). The GAS∶TA EMG ratio increased during the LR1 phase after fatigue (P &lt; .05) but remained unchanged during the PR and LR2 phrases (P &gt; .05). Conclusions: The increased agonist EMG activation, coupled with reduced antagonist EMG activation after impact, indicates that the acute decrease in muscle strength capacity of the knee extensors and flexors results in altered muscle-activation patterns about the knee and ankle before and after foot impact.

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