Effective Mechanical Advantage Allometry of Felid Elbow and Knee Extensors

Employing an arched back posture during the bench press exercise is increasingly popular. Vertical displacement of the barbell is commonly believed to be the key difference influencing strength performance between an arched and flat back bench press technique. However, comparisons between these back postures using a free weight barbell are lacking. Directly comparing performance between each posture is confounded by many variables such as proficiency and fatigue. This investigation aimed to investigate whether changing back posture alone can influence barbell kinematics, to indirectly assess potential performance differences. Twenty males performed one repetition of the bench press exercise using either an arched or flat back posture, at 25%, 50% and 75% of their one repetition maximum, in a repeated measures study design. Statistical significance was considered at p < 0.05. Changing back posture alone, reduced vertical displacement (approximately 11% average difference across all load conditions) and barbell to glenohumeral joint moment arm (approximately 20% difference) in the arched posture compared to the flat posture. These changes occurred without any specific cueing of the barbell motion and may increase the potential for lifting higher loads and decrease cumulative joint exposure. Additional cueing and training may be required to maximize the mechanical advantage available with each back posture. The arched posture appears to have an increased potential for further improvements in vertical displacement and moment arm through specific cueing. Future comparisons should consider if each back posture’s potential mechanical advantage has been maximized when assessing differences between techniques.

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Neuromuscular electrical stimulation in early rehabilitation of patients with postoperative complications after cardiovascular surgery

European Journal of Preventive Cardiology ◽

10.1093/eurjpc/zwab061.363 ◽

2021 ◽

Vol 28 (Supplement_1) ◽

Author(s):

P Oleinik ◽

AN Sumin ◽

AV Bezdenezhnykh

Keyword(s):

Postoperative Complications ◽

Cardiovascular Surgery ◽

Handgrip Strength ◽

Left Knee ◽

Baseline Data ◽

Knee Extensors ◽

Federal State ◽

Control Group ◽

Initial Strength ◽

Knee Flexors

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Federal State Budgetary Scientific Institution Research Institute for Complex Issues of Cardiovascular Diseases Introduction The purpose was to evaluate the effectiveness of NMES in patients with complications after cardiac surgery. Methods This study was 37 patients who had significant postoperative complications after cardiovascular surgery. Participants were randomly - NMES group, n = 18; control, n = 19. It was not possible to blind the investigator. Analyzed basic clinical data. The dynamometry of the muscles upper and lower extremities was carried out, as well as a 6-minute walk test (6MWT). Also, the thickness of the quadriceps was measured using ultrasound.The patients underwent NMES on the quadriceps femoris muscle, daily from the third postoperative day, until discharge. The duration session was 90 minutes. Outcomes No differences were found in the baseline characteristics of the groups, including the results of laboratory and instrumental studies. Groups were comparable in the surgery and perioperative parameteres. The initial strength indicators also had no significant differences in the groups. At discharge knee extensors strength (KES) was significantly higher in the NMES group. The knee flexor strength (KFS) and handgrip strength (HF) increased the same in both groups. The quadriceps crosssectional area (CSA) muscle increased more in the NEMS group than in the control to the time of discharge. Average KES increased to a greater extent in the NMES group. At the same time, average and maximum KFS increased equally in both groups. A 6MWT before discharge did not show a difference between groups (P=.166). The NMES course did not affect the duration of hospitalisation (P=.429). Discussion This pilot study show beneficial effects of NMES on muscle strength in patients with complications after cardiovascular surgery. Physical tests initially and in dynamics NEMS Group (n = 18) Control group (n = 19) Baseline Discharge Baseline Discharge P-level Right knee extensors strength (kg) 20,3 [17,9; 26,1] 28,05 [23,8; 36,2] * 20,1 [18,6; 25,4] 22,3 [20,1; 27,1] * 0,004 Left knee extensors strength (kg) 17,75 [15,5; 27,0] 27,45 [22,3; 33,1] * 20,8 [17,5; 24,2] 22,5 [20,1; 25,9] * 0,017 Right knee flexors strength (kg) 14,85 [11,7; 19,5] 17,5 [14,1; 23,4] * 16,9 [13,1; 23,8] 19,2 [12,5; 26,4] * 0,971 Left knee flexors strength (kg) 14,7 [12,6; 19,6] 19,75 [15,9; 24,2] * 16,2, [10,4; 25,1] 18,8 [13,1; 27,7] * 0,889 6-MWT (m) 148,5 [108,5; 174,0] 288,0 [242,0; 319,0] * 169,0 [115,0; 217,0] 315,0 [277,0; 400,0] * 0,166 Right handgrip strength (kg) 24,5 [15,0; 33,0] 25,5 [19,0; 36,0] * 27,0 [18,0; 32,0] 30,0 [20,0; 35,0] * 0,795 Left handgrip strength (kg) 17,0 [12,0; 27,0] 21,0 [15,0; 31,0] * 19,0 [14,0; 29,0] 23,0 [16,0; 30,0] * 0,541 * - p-level from baseline data < 0,05 ** - p-level from baseline data ≥ 0,05

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Prevalence of Balance Impairment and Factors Associated with Balance among Patients with Stroke. A Cross Sectional Retrospective Case Control Study

Healthcare ◽

10.3390/healthcare9030320 ◽

2021 ◽

Vol 9 (3) ◽

pp. 320

Author(s):

Fayaz Khan ◽

Mohamed Faisal Chevidikunnan

Keyword(s):

Case Control Study ◽

Binary Logistic Regression ◽

Berg Balance Scale ◽

Case Control ◽

Knee Extensors ◽

Retrospective Case ◽

Cross Sectional ◽

Balance Impairment ◽

Factors Associated ◽

Control Study

Stroke is a major cause of disability worldwide, and balance impairments are common disabling factors in patients with stroke, leading to falls. Thus, the study objectives were as follows: (i) To find the prevalence of balance impairment among patients with stroke. (ii) To find out the factors associated with balance impairment in patients with stroke. This cross-sectional retrospective case control study involved eighty-one post stroke patients with a mean age of 58.36 ± 14.06, recruited from six hospitals, who underwent an assessment of balance, walking speed, depression and isometric strength of the ankle and knee. These patients were later categorized into subjects with good balance (<45) in the Berg balance scale (BBS) and those with poor balance (≥45), as cases and controls, to assess the factors associated with balance impairment using binary logistic regression. The prevalence of balance impairment among patients with stroke was 48.1%. The reduction in power of knee flexors (OR = 0.858), knee extensors (OR = 0.880) and ankle dorsiflexors (OR = 0.820) was found to be significantly associated with balance impairment, along with speed (OR = 1.187 (95% CI = 1.100, 1.280)), depression (OR = 1.331 (95% CI = 1.055–1.679)) and activities of daily living (OR = 0.313 (95% CI = 0.150–0.650)). In summary, around half of the patients with stroke exhibited balance impairments, with females being more prone.

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Is the Occurrence of the Sticking Region in Maximum Smith Machine Squats the Result of Diminishing Potentiation and Co-Contraction of the Prime Movers among Recreationally Resistance Trained Males?

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18031366 ◽

2021 ◽

Vol 18 (3) ◽

pp. 1366

Author(s):

Roland van den Tillaar ◽

Eirik Lindset Kristiansen ◽

Stian Larsen

Keyword(s):

Muscle Activity ◽

Muscle Activation ◽

Gluteus Maximus ◽

Knee Extensors ◽

Force Output ◽

Activation Patterns ◽

Muscle Activation Patterns ◽

Prime Movers ◽

Almost All ◽

Height Data

This study compared the kinetics, barbell, and joint kinematics and muscle activation patterns between a one-repetition maximum (1-RM) Smith machine squat and isometric squats performed at 10 different heights from the lowest barbell height. The aim was to investigate if force output is lowest in the sticking region, indicating that this is a poor biomechanical region. Twelve resistance trained males (age: 22 ± 5 years, mass: 83.5 ± 39 kg, height: 1.81 ± 0.20 m) were tested. A repeated two-way analysis of variance showed that Force output decreased in the sticking region for the 1-RM trial, while for the isometric trials, force output was lowest between 0–15 cm from the lowest barbell height, data that support the sticking region is a poor biomechanical region. Almost all muscles showed higher activity at 1-RM compared with isometric attempts (p < 0.05). The quadriceps activity decreased, and the gluteus maximus and shank muscle activity increased with increasing height (p ≤ 0.024). Moreover, the vastus muscles decreased only for the 1-RM trial while remaining stable at the same positions in the isometric trials (p = 0.04), indicating that potentiation occurs. Our findings suggest that a co-contraction between the hip and knee extensors, together with potentiation from the vastus muscles during ascent, creates a poor biomechanical region for force output, and thereby the sticking region among recreationally resistance trained males during 1-RM Smith machine squats.

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Effects of the use neuromuscular electrical stimulation of the lower extremities in the prehabilitation of patients in a before cardiac surgery

European Journal of Preventive Cardiology ◽

10.1093/eurjpc/zwab061.365 ◽

2021 ◽

Vol 28 (Supplement_1) ◽

Author(s):

P Oleinik ◽

AN Sumin ◽

AV Bezdenezhnykh

Keyword(s):

Cardiac Surgery ◽

Handgrip Strength ◽

Lower Extremities ◽

Left Knee ◽

Knee Extensors ◽

Control Group ◽

Elective Cardiac Surgery ◽

Antagonist Muscles ◽

Muscle Groups ◽

Knee Flexors

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Research Institute for Complex Issues of Cardiovascular Diseases Aim To evaluate the effects of neuromuscular electrostimulation in the prehabilitation and prevention of muscle weakness in patients awaiting cardiac surgery. Materials and methods 122 patients waiting for elective cardiac surgery were included. Exclusion criteria: age less than 25 and more than 80 years; emergency and urgent surgical interventions; arthropathies; low pain threshold; rhabdomyolysis and other myopathies; cognitive dysfunction. Routine laboratory and instrumental examinations were performed in all patients upon admission to the hospital, as part of a standard examination. 62 patients were randomly selected for the preoperative NMES group, in addition to the standard preoperative preparation and treatment program. The standard program included 60 control patients. Patients of the NMES group underwent quadriceps stimulation for at least 5 sessions, lasting 90 minutes, daily before surgery. Results. The groups were comparable and did not have significant differences in gender and age characteristics, according to the main clinical and anamnestic data and types of operations. Initially, there were no differences in the state of the muscles of the lower extremities, the distance of the six-minute walking test (6MWT), and the strength of the hand grip. After NMES, there was an increase in muscle strength relative to the control group, both stimulated muscle groups and unstimulated antagonist muscles, as well as a greater 6MWT distance and hand compression force. All the differences were significant. Conclusions The course of pre-rehabilitation of NMES before surgery, allowed to maintain, and in some cases improve the condition of the muscle frame of the lower extremities. A positive effect was observed not only in stimulated muscle groups, but also in antagonist muscles Indicators of muscle status NMES (n = 62) Control group (n = 60) Baseline Discharge Baseline Discharge P-level Right knee extensors strength (kg) 24,4 [18,3; 31,4] 30,4 [23,8; 36,2]* 24,7 [20,1; 33,2] 22,25 [18,9; 30,4] <0,001 Left knee extensors strength (kg) 23,8 [19,3; 31,3] 29,2 [23,6; 35,4]* 25,75 [19,2; 31,3] 22,9 [18,9; 27,8] <0,001 Right knee flexors strength (kg) 18,9 [13,3; 24,0] 21,7 [16,6; 25,1] 19,55 [13,1; 26,0] 16,7 [12,1; 23,3] 0,006 Left knee flexors strength (kg) 19,3 [14,3; 24,5] 21,9 [17,3; 26,7] 19,5 [13,0; 24,3] 18,2 [13,4; 22,2] 0,005 6-MWT (m) 300,0 [261,0; 371,0] 331,0 [280,0; 375,0] 304,5 [253,0; 380,0] 285,5 [246,0; 342,0] 0,006 Right handgrip strength (kg) 28,5 [20,5; 34,0] 31,5 [22,0; 34,0] 29,0 [19,0; 34,0] 27,0 [19,0; 33,0] 0,054 Left handgrip strength (kg) 25,0 [18,0; 31,0] 25,0 [18,0; 32,0] 24,0 [15,0; 31,0] 22,0 [14,0; 28,0] 0,062 * - p-level from baseline data < 0,05 Abstract Figure. dynamics of stimulated muscles

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Muscle-tendon unit length changes in knee extensors and flexors during alpine skiing

Sports Biomechanics ◽

10.1080/14763141.2020.1862902 ◽

2021 ◽

pp. 1-12

Author(s):

Marine Alhammoud ◽

Sebastien Racinais ◽

Sylvain Dorel ◽

Gaël Guilhem ◽

Christophe André Hautier ◽

...

Keyword(s):

Unit Length ◽

Knee Extensors ◽

Alpine Skiing ◽

Length Changes

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Rostrocaudal Distribution of the C-Fos-Immunopositive Spinal Network Defined by Muscle Activity during Locomotion

Brain Sciences ◽

10.3390/brainsci11010069 ◽

2021 ◽

Vol 11 (1) ◽

pp. 69

Author(s):

Natalia Merkulyeva ◽

Vsevolod Lyakhovetskii ◽

Aleksandr Veshchitskii ◽

Oleg Gorskii ◽

Pavel Musienko

Keyword(s):

Spinal Cord ◽

Locomotor Activity ◽

Control Systems ◽

Muscle Activity ◽

Knee Extensors ◽

Emg Activity ◽

Lumbosacral Spinal Cord ◽

Adductor Muscles ◽

Spinal Network ◽

Hip Flexor

The optimization of multisystem neurorehabilitation protocols including electrical spinal cord stimulation and multi-directional tasks training require understanding of underlying circuits mechanisms and distribution of the neuronal network over the spinal cord. In this study we compared the locomotor activity during forward and backward stepping in eighteen adult decerebrated cats. Interneuronal spinal networks responsible for forward and backward stepping were visualized using the C-Fos technique. A bi-modal rostrocaudal distribution of C-Fos-immunopositive neurons over the lumbosacral spinal cord (peaks in the L4/L5 and L6/S1 segments) was revealed. These patterns were compared with motoneuronal pools using Vanderhorst and Holstege scheme; the location of the first peak was correspondent to the motoneurons of the hip flexors and knee extensors, an inter-peak drop was presumably attributed to the motoneurons controlling the adductor muscles. Both were better expressed in cats stepping forward and in parallel, electromyographic (EMG) activity of the hip flexor and knee extensors was higher, while EMG activity of the adductor was lower, during this locomotor mode. On the basis of the present data, which showed greater activity of the adductor muscles and the attributed interneuronal spinal network during backward stepping and according with data about greater demands on postural control systems during backward locomotion, we suppose that the locomotor networks for movements in opposite directions are at least partially different.

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Electrically-induced quadriceps fatigue in the contralateral leg impairs ipsilateral knee extensors performance

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00363.2020 ◽

2021 ◽

Author(s):

Fabio Giuseppe Laginestra ◽

Markus Amann ◽

Emine Kirmizi ◽

Gaia Giuriato ◽

Chiara Barbi ◽

...

Keyword(s):

Muscle Activation ◽

Central Fatigue ◽

Endurance Performance ◽

Voluntary Exercise ◽

Peripheral Fatigue ◽

Knee Extensors ◽

Motor Drive ◽

Time To Exhaustion ◽

Crossover Effect ◽

The Impact

Muscle fatigue induced by voluntary exercise, which requires central motor drive, causes central fatigue that impairs endurance performance of a different, non-fatigued muscle. This study investigated the impact of quadriceps fatigue induced by electrically-induced (no central motor drive) contractions on single-leg knee-extension (KE) performance of the subsequently exercising ipsilateral quadriceps. On two separate occasions, eight males completed constant-load (85% of maximal power-output) KE exercise to exhaustion. In a counterbalanced manner, subjects performed the KE exercise with no pre-existing quadriceps fatigue in the contralateral leg on one day (No-PreF), while on the other day, the same KE exercise was repeated following electrically-induced quadriceps fatigue in the contralateral leg (PreF). Quadriceps fatigue was assessed by evaluating pre- to post-exercise changes in potentiated twitch force (ΔQtw,pot; peripheral-fatigue), and voluntary muscle activation (ΔVA; central-fatigue). As reflected by the 57±11% reduction in electrically-evoked pulse force, the electrically-induced fatigue protocol caused significant knee-extensors fatigue. KE endurance time to exhaustion was shorter during PreF compared to No-PreF (4.6±1.2 vs 7.7±2.4 min; p<0.01). While ΔQtw,pot was significantly larger in No-PreF compared to PreF (-60% vs -52%, p<0.05), ΔVA was greater in PreF (-14% vs -10%, p<0.05). Taken together, electrically-induced quadriceps fatigue in the contralateral leg limits KE endurance performance and the development of peripheral fatigue in the ipsilateral leg. These findings support the hypothesis that the crossover-effect of central fatigue is mainly mediated by group III/IV muscle afferent feedback and suggest that impairments associated with central motor drive may only play a minor role in this phenomenon.

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Isokinetic Profile of Elite Serbian Female Judoists

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18136988 ◽

2021 ◽

Vol 18 (13) ◽

pp. 6988

Author(s):

Wieslaw Blach ◽

Miodrag Drapsin ◽

Nemanja Lakicevic ◽

Antonino Bianco ◽

Tamara Gavrilovic ◽

...

Keyword(s):

Knee Extensors ◽

Training Experience ◽

Lateral Asymmetry ◽

National Team ◽

Significant Difference ◽

Judo Athletes ◽

Muscle Groups ◽

Torque Values ◽

Training Modalities ◽

Knee Flexors

Elite judo athletes undergo vigorous training to achieve outstanding results. In pursuit of achieving competitive success, the occurrence of injuries amongst judo athletes is not rare. The study aimed to perform a knee flexors and extensors isokinetic torque analysis in elite female judo athletes. Fifty-eight elite female judo athletes of the Serbian national team (21.02 ± 3.11 years; 62.36 ± 11.91 kg, 165.04 ± 10.24 cm, training experience 12.72 ± 2.98 years) volunteered to participate in this study. The range of motion (ROM) was set at 90⁰. Testing was performed in a concentric–concentric mode for the testing speed of 60 ⁰/s. Five maximal voluntary contractions of knee extensors and knee flexors muscle groups were measured for both legs. The obtained data showed a statistically significant difference in absolute torque values among different categories as heavier athletes demonstrated higher values. Post hoc analysis showed a significant difference between weight categories, as heavier athletes demonstrated higher values, while no significant differences in normalized torque values for different weight categories were observed. The implementation of new elements and training modalities may improve performance and prevent lateral asymmetry, thus reducing the risk of injury.

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