scholarly journals Interlimb Asymmetries and Ipsilateral Associations of Plantar Flexors and Knee Extensors Rate-of-Force Development Scaling Factor

Symmetry ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1522
Author(s):  
Darjan Smajla ◽  
Olivera M. Knezevic ◽  
Dragan M. Mirkov ◽  
Nejc Šarabon
Keyword(s):  
Regression Line ◽  
Force Production ◽  
Scaling Factor ◽  
Lower Limbs ◽  
Knee Extensors ◽  
Future Research ◽  
Isometric Contractions ◽  
Plantar Flexors ◽  
Muscle Groups ◽  
Torque Development

Rate of force/torque development scaling factor (RFD-SF/RTD-SF) was recently introduced as a tool to quantify the neuromuscular quickness, and it could have potential for interlimb asymmetry identification. Moreover, positive relationships in RFD-SF ability among different muscle groups were shown, but not in the lower extremity. The first aim of our study was to use RTD-SF for interlimb asymmetry identification. The second aim was to determine associations between plantar flexors (PF) and knee extensors (KE). Forty young healthy athletes (14.8 ± 1.2 years) performed explosive isometric contractions to a span of torque levels for PF and KE. From rapid isometric contractions, the RTD-SF and linearity (r2) of the regression line were calculated. Using RTD-SF we identified 10% (PF) and 15% (KE) of subjects with contralateral asymmetries (>15% criterion). The results revealed significant positive moderate correlation in RTD-SF between PF and KE (r = 0.401, p < 0.05). We supported that RTD-SF can be a useful tool for interlimb asymmetry identification. Future research about observed asymmetry in rapid submaximal contractions deserves more attention, as most of the functional sport specific activities put high demands on rapid force production. Our study as first confirmed positive associations in RTD-SF ability between muscle groups in lower limbs.

scholarly journals Exercise tolerance during muscle contractions below and above the critical torque in different muscle groups

2018 ◽  
Vol 43 (2) ◽  
pp. 174-179 ◽  
Author(s):  
Leonardo Henrique Perinotto Abdalla ◽  
Benedito Sérgio Denadai ◽  
Natália Menezes Bassan ◽  
Camila Coelho Greco
Keyword(s):  
Exercise Intensity ◽  
Maximal Voluntary Contraction ◽  
Exercise Tolerance ◽  
Voluntary Contraction ◽  
Knee Extensors ◽  
Isometric Contractions ◽  
Plantar Flexors ◽  
Significant Difference ◽  
Muscle Groups

The objective of this study was to test the hypotheses that end-test torque (ET) (expressed as % maximal voluntary contraction; MVC) is higher for plantar flexors (PF) than knee extensors (KE) muscles, whereas impulse above ET (IET) is higher for KE than PF. Thus, we expected that exercise tolerance would be longer for KE than PF only during the exercise performed above ET. After the determination of MVC, 40 men performed two 5-min all-out tests to determine ET and IET. Eleven participants performed a further 4 intermittent isometric tests, to exhaustion, at ET + 5% and ET – 5%, and 1 test for KE at the exercise intensity (%MVC) corresponding to ET + 5% of PF. The IET (7243.2 ± 1942.9 vs. 3357.4 ± 1132.3 N·m·s) and ET (84.4 ± 24.8 vs. 73.9 ± 19.5 N·m) were significantly lower in PF compared with KE. The exercise tolerance was significantly longer for PF (300.7 ± 156.7 s) than KE (156.7 ± 104.3 s) at similar %MVC (∼60%), and significantly shorter for PF (300.7 ± 156.7 s) than KE (697.0 ± 243.7 s) at ET + 5% condition. However, no significant difference was observed for ET – 5% condition (KE = 1030.2 ± 495.4 s vs. PF = 1028.3 ± 514.4 s). Thus, the limit of tolerance during submaximal isometric contractions is influenced by absolute MVC only during exercise performed above ET, which seems to be explained by differences on both ET (expressed as %MVC) and IET values.

scholarly journals Elbow Extensors and Volar Flexors Strength Capacity and Its Relation to Shooting Performance in Basketball Players—A Pilot Study

2020 ◽  
Vol 10 (22) ◽  
pp. 8206
Author(s):  
Darjan Smajla ◽  
Žiga Kozinc ◽  
Nejc Šarabon
Keyword(s):  
Scaling Factor ◽  
Long Distance ◽  
Basketball Players ◽  
Rate Of Torque Development ◽  
Strength Capacity ◽  
Isometric Torque ◽  
Muscle Groups ◽  
Sufficient Strength ◽  
Torque Development ◽  
Basketball Shooting

Rate of force/torque development scaling factor (RFD-SF/RTD-SF) has been used as a tool for assessing neuromuscular quickness. The aim was to investigate strength capacities of two major shooting muscle groups and their relationship to basketball shooting performance, and to compare the RFD-SF as well as shooting performance between junior and senior basketball players, and finally to examine the differences in RTD-SF between elbow extensors and volar flexors. In 23 male basketball players (13 juniors and 10 seniors) we assessed maximal isometric torque (TMVC), maximal rate of torque development and RTD-SF slope (kRTD-SF) for elbow extensors and volar flexors. The subjects performed 10 throws at 2.3 m (short) and 8.9 m (long) from the basket. Our results showed similar kRTD-SF and TMVC in both groups. Better shooting performance from short distance was observed in senior players. Significant associations between kRTD-SF, TMVC and shooting performance were found only in juniors. Elbow extensors TMVC was found to have a significant positive large association with shooting performance from long distance. It seems that muscle capacity has an important role in shooting performance in junior compared to players. Sufficient strength capacity of major shooting muscles is important for juniors’ shooting performance from a long distance.

Comparison of neuromuscular adjustments associated with sustained isometric contractions of four different muscle groups

2013 ◽  
Vol 114 (10) ◽  
pp. 1426-1434 ◽  
Author(s):  
Daria Neyroud ◽  
Jennifer Rüttimann ◽  
Anne F. Mannion ◽  
Guillaume Y. Millet ◽  
Nicola A. Maffiuletti ◽  
...  
Keyword(s):  
Muscle Fatigue ◽  
Upper Limb ◽  
Voluntary Contraction ◽  
Voluntary Activation ◽  
Knee Extensors ◽  
Elbow Flexors ◽  
Plantar Flexors ◽  
Task Failure ◽  
Before And After ◽  
Muscle Groups

The extent and characteristics of muscle fatigue of different muscle groups when subjected to a similar fatiguing task may differ. Thirteen healthy young men performed sustained contractions at 50% maximal voluntary contraction (MVC) force until task failure, with four different muscle groups, over two sessions. Per session, one upper limb and one lower limb muscle group were tested (knee extensors and thumb adductor, or plantar and elbow flexors). Changes in voluntary activation level and contractile properties were derived from doublet responses evoked during and after MVCs before and after exercise. Time to task failure differed ( P < 0.05) between muscle groups (220 ± 64 s for plantar flexors, 114 ± 27 s for thumb adductor, 77 ± 25 s for knee extensors, and 72 ± 14 s for elbow flexors). MVC force loss immediately after voluntary task failure was similar (−30 ± 11% for plantar flexors, −37 ± 13% for thumb adductor, −34 ± 15% for knee extensors, and −40 ± 12% for elbow flexors, P > 0.05). Voluntary activation was decreased for plantar flexors only (from 95 ± 5% to 82 ± 9%, P < 0.05). Potentiated evoked doublet amplitude was more depressed for upper limb muscles (−59.3 ± 14.7% for elbow flexors and −60.1 ± 24.1% for thumb adductor, P < 0.05) than for knee extensors (−28 ± 15%, P < 0.05); no reduction was found in plantar flexors (−7 ± 12%, P > 0.05). In conclusion, despite different times to task failure when sustaining an isometric contraction at 50% MVC force for as long as possible, diverse muscle groups present similar loss of MVC force after task failure. Thus the extent of muscle fatigue is not affected by time to task failure, whereas this latter determines the etiology of fatigue.

scholarly journals Interactions Between Perceptions of Fatigue, Effort and Affect Decrease Knee Extensor Endurance Performance Following Upper Body Motor Activity, Independent of Changes to Neuromuscular Function.

2019 ◽  
Author(s):  
Aaron Greenhouse-Tucknott ◽  
James Graeme Wrightson ◽  
Mitchell Raynsford ◽  
Neil Harrison ◽  
Jeanne Dekerle
Keyword(s):  
Knee Extensor ◽  
Endurance Performance ◽  
Neuromuscular Function ◽  
Affective Responses ◽  
Lower Limbs ◽  
Upper Body ◽  
Knee Extensors ◽  
Handgrip Exercise ◽  
Affective Valence ◽  
Muscle Groups

Prior exercise has previously been shown to impair subsequent endurance performance in non-activated muscles. Declines in neuromuscular function and altered perceptual/affective responses offer possible mechanisms through which endurance performance may be limited in these remote muscle groups. We thus conducted two experiments to better understand these performance limiting mechanisms. In the first experiment, we examined the effect of prior handgrip exercise on the behavioural, perceptual and affective responses to a sustained, sub-maximal contraction of the knee extensors. In the second experiment, transcranial magnetic stimulation (TMS) was used to assess neuromuscular function of the knee extensors before and after handgrip exercise. The results of the first experiment demonstrated prior handgrip exercise increased perceptions of effort and reduced affective valence during the subsequent knee extensor endurance exercise. Both effort and affect were associated with endurance performance. Subjective ratings of fatigue were also increased by the preceding handgrip exercise but were not directly related to knee extensor endurance performance. However, perceptions of fatigue were correlated with heightened effort perception and reduced affect during the knee extensor contraction. In the second experiment, prior handgrip exercise did not significantly alter neuromuscular function of the knee extensors. The findings of the present study indicate that motor performance in the lower limbs following demanding exercise in the upper body appears to be regulated by complex, cognitive-emotional interactions, which may emerge independent of altered neuromuscular function. Subjective fatigue states are implicated in the control of perceptual and affective processes responsible for the regulation of endurance performance.

scholarly journals Postactivation Potentiation Biases Maximal Isometric Strength Assessment

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Leonardo Coelho Rabello Lima ◽  
Felipe Bruno Dias Oliveira ◽  
Thiago Pires Oliveira ◽  
Claudio de Oliveira Assumpção ◽  
Camila Coelho Greco ◽  
...  
Keyword(s):  
Force Production ◽  
Peak Torque ◽  
Isometric Strength ◽  
Isometric Contractions ◽  
Postactivation Potentiation ◽  
Healthy Male ◽  
Strength Assessment ◽  
Rate Of Torque Development ◽  
Electromyographic Signal ◽  
Torque Development

Postactivation potentiation (PAP) is known to enhance force production. Maximal isometric strength assessment protocols usually consist of two or more maximal voluntary isometric contractions (MVCs). The objective of this study was to determine if PAP would influence isometric strength assessment. Healthy male volunteers (n=23) performed two five-second MVCs separated by a 180-seconds interval. Changes in isometric peak torque (IPT), time to achieve it (tPTI), contractile impulse (CI), root mean square of the electromyographic signal during PTI (RMS), and rate of torque development (RTD), in different intervals, were measured. Significant increases in IPT (240.6 ± 55.7 N·mversus248.9 ± 55.1 N·m), RTD (746 ± 152 N·m·s−1versus727 ± 158 N·m·s−1), and RMS (59.1 ± 12.2%RMSMAX  versus54.8 ± 9.4%RMSMAX) were found on the second MVC. tPTI decreased significantly on the second MVC (2373 ± 1200 msversus2784 ± 1226 ms). We conclude that a first MVC leads to PAP that elicits significant enhancements in strength-related variables of a second MVC performed 180 seconds later. If disconsidered, this phenomenon might bias maximal isometric strength assessment, overestimating some of these variables.

scholarly journals The Influence of Stretching the Hip Flexor Muscles on Performance Parameters. A Systematic Review with Meta-Analysis

2021 ◽  
Vol 18 (4) ◽  
pp. 1936
Author(s):  
Andreas Konrad ◽  
Richard Močnik ◽  
Sylvia Titze ◽  
Masatoshi Nakamura ◽  
Markus Tilp
Keyword(s):  
Systematic Review ◽  
Lumbar Spine ◽  
Positive Impact ◽  
Meta Analysis ◽  
Force Production ◽  
Performance Parameters ◽  
Plantar Flexors ◽  
Performance Change ◽  
Flexor Muscles ◽  
Hip Flexor

The hip flexor muscles are major contributors to lumbar spine stability. Tight hip flexors can lead to pain in the lumbar spine, and hence to an impairment in performance. Moreover, sedentary behavior is a common problem and a major contributor to restricted hip extension flexibility. Stretching can be a tool to reduce muscle tightness and to overcome the aforementioned problems. Therefore, the purpose of this systematic review with meta-analysis was to determine the effects of a single hip flexor stretching exercise on performance parameters. The online search was performed in the following three databases: PubMed, Scopus, and Web of Science. Eight studies were included in this review with a total of 165 subjects (male: 111; female 54). In contrast to other muscle groups (e.g., plantar flexors), where 120 s of stretching likely decreases force production, it seems that isolated hip flexor stretching of up to 120 s has no effect or even a positive impact on performance-related parameters. A comparison of the effects on performance between the three defined stretch durations (30–90 s; 120 s; 270–480 s) revealed a significantly different change in performance (p = 0.02) between the studies with the lowest hip flexor stretch duration (30–90 s; weighted mean performance change: −0.12%; CI (95%): −0.49 to 0.41) and the studies with the highest hip flexor stretch duration (270–480 s; performance change: −3.59%; CI (95%): −5.92 to −2.04). Meta-analysis revealed a significant (but trivial) impairment in the highest hip flexor stretch duration of 270–480 s (SMD effect size = −0.19; CI (95%) −0.379 to 0.000; Z = −1.959; p = 0.05; I2 = 0.62%), but not in the lowest stretch duration (30–90 s). This indicates a dose-response relationship in the hip flexor muscles. Although the evidence is based on a small number of studies, this information will be of great importance for both athletes and coaches.

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

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] &lt;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] &lt;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 &lt; 0,05 Abstract Figure. dynamics of stimulated muscles

scholarly journals Isokinetic Profile of Elite Serbian Female Judoists

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.

scholarly journals Biomechanical analysis of an unpowered hip flexion orthosis on individuals with and without multiple sclerosis

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Ross M. Neuman ◽  
Staci M. Shearin ◽  
Karen J. McCain ◽  
Nicholas P. Fey
Keyword(s):  
Multiple Sclerosis ◽  
Muscle Activity ◽  
Healthy Subjects ◽  
Muscle Activation ◽  
Assistive Technologies ◽  
Lower Limbs ◽  
Biomechanical Analysis ◽  
Foot Drop ◽  
Plantar Flexors ◽  
Hip Flexion

Abstract Background Gait impairment is a common complication of multiple sclerosis (MS). Gait limitations such as limited hip flexion, foot drop, and knee hyperextension often require external devices like crutches, canes, and orthoses. The effects of mobility-assistive technologies (MATs) prescribed to people with MS are not well understood, and current devices do not cater to the specific needs of these individuals. To address this, a passive unilateral hip flexion-assisting orthosis (HFO) was developed that uses resistance bands spanning the hip joint to redirect energy in the gait cycle. The purpose of this study was to investigate the short-term effects of the HFO on gait mechanics and muscle activation for people with and without MS. We hypothesized that (1) hip flexion would increase in the limb wearing the device, and (2) that muscle activity would increase in hip extensors, and decrease in hip flexors and plantar flexors. Methods Five healthy subjects and five subjects with MS walked for minute-long sessions with the device using three different levels of band stiffness. We analyzed peak hip flexion and extension angles, lower limb joint work, and muscle activity in eight muscles on the lower limbs and trunk. Single-subjects analysis was used due to inter-subject variability. Results For subjects with MS, the HFO caused an increase in peak hip flexion angle and a decrease in peak hip extension angle, confirming our first hypothesis. Healthy subjects showed less pronounced kinematic changes when using the device. Power generated at the hip was increased in most subjects while using the HFO. The second hypothesis was not confirmed, as muscle activity showed inconsistent results, however several subjects demonstrated increased hip extensor and trunk muscle activity with the HFO. Conclusions This exploratory study showed that the HFO was well-tolerated by healthy subjects and subjects with MS, and that it promoted more normative kinematics at the hip for those with MS. Future studies with longer exposure to the HFO and personalized assistance parameters are needed to understand the efficacy of the HFO for mobility assistance and rehabilitation for people with MS.

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