scholarly journals Does ischemic preconditioning really improve performance or it is just a placebo effect?

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0250572
Author(s):  
Hiago L. R. de Souza ◽  
Rhaí A. Arriel ◽  
Gustavo R. Mota ◽  
Rodrigo Hohl ◽  
Moacir Marocolo
Keyword(s):  
Ischemic Preconditioning ◽  
Placebo Effect ◽  
A Priori ◽  
Knee Extension ◽  
Fatigue Index ◽  
Maximal Voluntary Isometric Contraction ◽  
Leg Extension ◽  
Volume Load ◽  
Ergogenic Effects ◽  
Sham Intervention

This study examined the effects of a simultaneous ischemic preconditioning (IPC) and SHAM intervention to reduce the placebo effect due to a priori expectation on the performance of knee extension resistance exercise. Nine moderately trained men were tested in three different occasions. Following the baseline tests, subjects performed a first set of leg extension tests after the IPC (3 X 5 min 50 mmHg above systolic blood pressure) on right thigh and the SHAM (same as IPC, but 20 mmHg) on left thigh. After 48 hours, the subjects performed another set of tests with the opposite applications. Number of repetitions, maximal voluntary isometric contraction (MVIC) and perceptual indicators were analyzed. After IPC and SHAM intervention performed at the same time, similar results were observed for the number of repetitions, with no significant differences between conditions (baseline x IPC x SHAM) for either left (p = 0.274) or right thigh (p = 0.242). The fatigue index and volume load did not show significant effect size after IPC and SHAM maneuvers. In contrast, significant reduction on left tight MVIC was observed (p = 0.001) in SHAM and IPC compared to baseline, but not for right thigh (p = 0.106). Results from the current study may indicate that applying IPC prior to a set of leg extension does not result in ergogenic effects. The placebo effect seems to be related to this technique and its dissociation seems unlikely, therefore including a SHAM or placebo group in IPC studies is strongly recommended.

ELECTROMYOGRAPHIC ANALYSIS OF LEG EXTENSION EXERCISE DURING DIFFERENT ANKLE AND KNEE POSITIONS

2015 ◽  
Vol 15 (02) ◽  
pp. 1540037 ◽  
Author(s):  
GUIDO BELLI ◽  
LUCA VITALI ◽  
MATTEO BOTTEGHI ◽  
LEYDI NATALIA VITTORI ◽  
ELISABETTA PETRACCI ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Vastus Lateralis ◽  
Pain Syndrome ◽  
Knee Extension ◽  
Maximal Voluntary Isometric Contraction ◽  
Leg Extension ◽  
Isometric Knee Extension ◽  
Medial Rotation ◽  
Electromyographic Analysis ◽  
Main Factor

The imbalance between vastus medialis oblique (VMO) and vastus lateralis (VL) strength is one of the main factor for patellofemoral pain syndrome (PFPS) onset, related to improper alignment of the patella. The aim of this paper is to investigate the effects of knee flexion, knee rotation and ankle flexion attitudes on the activity of the VMO and VL muscles during unilateral maximal voluntary isometric contraction (MIVC) of the quadriceps femoris. Eighteen healthy subjects volunteered for the study. Five conditions for two different knee flexion angles (90°; 30°) were tested using leg extension machine: Neutral (N) condition, maximal knee medial rotation (MR), maximal knee lateral rotation (LR), maximal ankle plantarflexion (PF) and maximal ankle dorsiflexion (DF). Data were normalized in order to calculate the normalized VMO/VL ratio. The normalized VMO/VL ratio for all the conditions occurred at 90° of knee flexion was higher than the same conditions at 30° of knee flexion (p = 0.02). No statistical differences between conditions at the same knee angle and for angle x condition interaction were observed (p > 0.05). These findings suggest that knee flexion should be the first variable to be managed during isometric knee extension movement performed by leg extension machine, in order to increase VMO/VL ratio.

scholarly journals Reference Values for Isometric, Dynamic, and Asymmetry Leg Extension Strength in Patients with Multiple Sclerosis

2020 ◽  
Vol 17 (21) ◽  
pp. 8083
Author(s):  
Kora Portilla-Cueto ◽  
Carlos Medina-Pérez ◽  
Ena Monserrat Romero-Pérez ◽  
José Aldo Hernández-Murúa ◽  
Claudia Eliza Patrocinio de Oliveira ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Reference Values ◽  
Knee Extension ◽  
Knee Extensors ◽  
Neurological Disability ◽  
Maximal Voluntary Isometric Contraction ◽  
Leg Extension ◽  
Relapsing Remitting ◽  
Degree Of Disability ◽  
Strength Asymmetry

Having recognized the value of resistance training in patients with multiple sclerosis (PwMS), there are a lack of lower limb normative reference values for one repetition maximum (1RM) and maximal voluntary isometric contraction (MVIC) in this population. Hence, the purposes of this study were to provide reference values for 1RM and MVIC of knee extensors in PwMS across the disability spectrum and to examine knee extension strength asymmetry. Three hundred and ninety PwMS participated in the study, performing MVIC and 1RM tests of bilateral (both legs together at once) and unilateral (each leg singly) knee extensors. There was no difference in 1RM according to the disease course of MS, but there was according to the degree of neurological disability, being more preserved in those with a lower degree of disability. MVIC tends to be higher in patients with relapsing–remitting MS respect those with progressive MS, and in patients with lower levels of neurological disability. Asymmetry above the values considered normal in 1RM was present in 20–60% of patients and 56–79% in the MVIC test, depending on the type of MS and tended to be lower in those with less disability. Reference values are given by quartiles for 1RM, MVIC, and asymmetry.

scholarly journals What Is the Optimal Strength Training Load to Improve Swimming Performance? A Randomized Trial of Male Competitive Swimmers

2021 ◽  
Vol 18 (22) ◽  
pp. 11770
Author(s):  
Sofiene Amara ◽  
Emmet Crowley ◽  
Senda Sammoud ◽  
Yassine Negra ◽  
Raouf Hammami ◽  
...  
Keyword(s):  
Resistance Training ◽  
Strength Training ◽  
Bench Press ◽  
Swimming Performance ◽  
Training Volume ◽  
Front Crawl ◽  
Leg Extension ◽  
Low Resistance ◽  
Volume Load ◽  
Competitive Swimmers

This study aimed to compare the effectiveness of high, moderate, and low resistance training volume-load of maximum strength training on muscle strength and swimming performance in competitive swimmers. Thirty-three male swimmers were randomly allocated to high (age = 16.5 ± 0.30 years), moderate (age = 16.1 ± 0.32 years) and a low resistance training volume-load group (age = 15.9 ± 0.31). This study was carried out in mid-season (January to March). Pre and post strength (e.g., repetition maximum [1RM] leg extension and bench press tests), swimming (25, 50 m front-crawl), start (speed, time, distance) and turn (time of turn) performance tests were conducted. Our findings revealed a large main effect of time for 1RM bench press: d = 1.38; 1RM leg extension: d = 1.55, and for 25 (d = 1.12), and 50 m (d = 1.97) front-crawl, similarly for start and turn performance (d = 1.28–1.46). However, no significant Group × Time interactions were shown in all strength swimming performances, start and turn tests (p > 0.05). In conclusion, low training loads have been shown to elicit the same results as moderate, and high training loads protocol. Therefore, this study shows evidence that the addition of low training volume-loads as a regular part of a maximal strength training regime will elicit improvements in strength and swimming performance.

scholarly journals ROLE OF HAMSTRING MUSCLES IN KNEE JOINT STABILITY PROVIDING AND INJURY PREVENTION

2016 ◽  
Vol 3 ◽  
pp. 522
Author(s):  
Inese Pontaga
Keyword(s):  
Stance Phase ◽  
Knee Extension ◽  
Swing Phase ◽  
Joint Stability ◽  
Distance Runners ◽  
Leg Extension ◽  
Hamstring Muscles ◽  
Extreme Extension ◽  
Torque Values

The aim of our investigation was to determine the ratio of maximal torque values and the torques in the certain positions of range of movements (ROM) between hamstring (H) and quadriceps femoris (Q) muscles at medium and high velocity of movement in concentric (CC) and eccentric (ECC) action of hamstring muscles. The knee muscles of 15 amateur female short and middle distance runners were tested by the dynamometer system in the isokinetic movements with the angular velocity of 90º/s and 240º/s in CC and at the velocity of 90º/s in ECC H/ CC Q muscles contractions. The torque values produced by the muscles are detected at the different angular positions of the ROM with the step of 10º. The ratios of H/ Q muscles torques are calculated. The H/Q muscles maximal torques ratio is 0.51 ± 0.13 at the velocity of 90º/s in CC and 0.60 ± 0.09 in ECC H/ CC Q muscles contractions, and 0.59 ± 0.09 CC at the velocity of 240º/s. The H/Q maximal torques ratio and this ratio in the knee extreme extension and flexion at the ECC contraction of H is higher due to greater torques produced by the H in comparison with Q muscle. The H must be stronger to decelerate the thigh and lower leg extension in the late swing phase of running and to extend the hip in early stance phase to provide powerful sprint running and prevent the knee and H injury. The H/Q muscles torques ratio in extended knee positions are similar in medium (90º/s) and fast (240º/s) velocity of motions because CC action of H muscles cannot prevent extreme knee extension.

scholarly journals Effects of Combined Endurance and Resistance Training in Women With Multiple Sclerosis: A Randomized Controlled Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Luca Correale ◽  
Cosme Franklim Buzzachera ◽  
Giulia Liberali ◽  
Erwan Codrons ◽  
Giulia Mallucci ◽  
...  
Keyword(s):  
Quality Of Life ◽  
Muscle Strength ◽  
Well Being ◽  
Controlled Study ◽  
Intervention Period ◽  
Maximal Voluntary Isometric Contraction ◽  
Leg Extension ◽  
Before And After

Purpose: To test the hypothesis that combined resistance and endurance training would improve muscle strength, fatigue, depression, and quality of life in persons with MS.Methods: Twenty-seven women with MS were randomly assigned to either control (CON, n = 13) or the experimental (EXP, n = 14) group. The participants in the EXP group trained twice a week for 12 weeks, followed by 12 weeks of detraining. Both CON and EXP groups were tested before and after 12 weeks of the intervention period, as well as 12 weeks after training cessation (follow-up), where measures of muscle strength, fatigue, depression, and quality of life were evaluated.Results: There were significant changes in maximal voluntary isometric contraction (MVIC), 1RM leg extension, and 1RM chest press following the intervention period in the EXP group (P < 0.05), but not in the CON group (P > 0.05). These changes persisted after 12 weeks of detraining. Similar findings were found for fatigue, depression, and physical and mental composites of quality of life.Conclusion: These results suggest that combined exercise training, at a minimum, prevents the disease-related deterioration of muscular performance and quality of life and well-being in persons with MS.

scholarly journals The effect of self myofascial release and static stretching on the antagonist muscles before agonist performance

2020 ◽  
Vol 14 (4) ◽  
pp. 233-237
Author(s):  
Rogerson Pessanha Da Ressurreição ◽  
Eric Rosário Pereira ◽  
Luis Fernando Martinez ◽  
Igor Nasser ◽  
João Antônio Souza ◽  
...  
Keyword(s):  
Perceived Exertion ◽  
Random Order ◽  
Rating Of Perceived Exertion ◽  
Static Stretching ◽  
Leg Extension ◽  
Myofascial Release ◽  
The Third ◽  
Volume Load ◽  
Maximum Test ◽  
Antagonist Muscles

Objective: the aim of this study was to compare differences in volume load, total repetition performed and rating of perceived exertion between static stretching and self-myofascial release on antagonist muscles. Methods: Eighteen recreationally trained men (23.4 ± 3.3 years; 80.7 ± 11.1 kg; 1.76 ± 0.06 cm) performed 10 repetitions maximum test and retest in the leg extension exercise on the first two visits. Then, three experimental sessions were conducted in a random order, in which two consisted of self-myofascial release and static stretching on hamstrings, and the other was used as a control. Results: significant higher repetitions were performed in the third set of static stretching when compared to control protocol. Additionally, significant reductions in total repetitions performed were observed only in the control session. No significant differences were noticed in the volume load of leg extension and rating of perceived exertion between protocols. Conclusion: self-myofascial release and static stretching performed before a session in the antagonist muscles can maintain repetitions performance by optimizing recovery between sets and reducing fatigue of agonist muscle.

scholarly journals Post-Activation Potentiation and Fatigue in Quadriceps Femoral Muscle after a 5 s Maximal Voluntary Isometric Contraction

2018 ◽  
Vol 1 (68) ◽  
Author(s):  
Nerijus Masiulis ◽  
Albertas Skurvydas ◽  
Sigitas Kamandulis ◽  
Audrius Sniečkus ◽  
Marius Brazaitis ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Isometric Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Simultaneous Occurrence ◽  
Contraction Force ◽  
Maximal Voluntary Isometric Contraction ◽  
Low Frequency Fatigue

Following an acute physical exercise, both post-activation potentiation and fatigue of the neuromuscular apparatus may occur. The voluntary recruitment of motor units occurs with frequencies that elicit incompletely fused tetanic contractions and these frequencies are most susceptible for post-activation potentiation as well as low-frequency fatigue. Therefore, the goal of the present study was to investigate which of the processes post-activation potentiation or low-frequency fatigue will be prevalent after 5 s maximal voluntary contraction (MVC). Eight healthy untrained men (age 24—35 years, mass 81.2 ± 5.1 kg) performed maximal sustained isometric knee extension for 5 s at a knee angle of 90 degrees. The contractile properties of quadriceps muscle evoked by electrical stimulation at 1, 7, 10, 15, 20, 50 Hz and 100 Hz, were recorded before and immediately after the exercise and 3, 5, and 10 min following the exercise. The rest interval between muscle electrical stimulation was 3 s. A significant raise of force evoked by 1—15 Hz stimulation was observed immediately after the 5 s MVC exercise (p < 0.01). Later in recovery (at 10 min) the contraction force at 15 Hz and 20 Hz significantly decreased (p < 0.05). Tetanic force at 50 Hz and 100 Hz demonstrated a significant decrease immediately after the exercise and remained depressed up to 3 min (p < 0.01). The ratio of 20 / 50 Hz recorded immediately after the 5 s MVC increased significantly (p < 0.05), however 10 min after the exercise there was a significant decrease compared to its initial level (p < 0.05). The simultaneous occurrence of post-activation potentiation at low stimulation frequencies and suppressed forces at high stimulation frequencies suggests that potentiation and fatigue mechanisms were acting concurrently. Moreover, when post-activation potentiation is lost (in 10 min after the 5 s MVC exercise), the contraction force at low stimulation frequencies decreases resulting in significant low-frequency fatigue.Keywords: isometric exercise, electrical stimulation, low-frequency fatigue, recovery.

scholarly journals Muscle fiber typology substantially influences time to recover from high-intensity exercise

2020 ◽  
Vol 128 (3) ◽  
pp. 648-659 ◽  
Author(s):  
Eline Lievens ◽  
Malgorzata Klass ◽  
Tine Bex ◽  
Wim Derave
Keyword(s):  
Maximal Voluntary Contraction ◽  
A Priori ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
Resonance Spectroscopy ◽  
Mean Power ◽  
Test Protocol ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Human fast-twitch muscle fibers generate high power in a short amount of time but are easily fatigued, whereas slow-twitch fibers are more fatigue resistant. The transfer of this knowledge to coaching is hampered by the invasive nature of the current evaluation of muscle typology by biopsies. Therefore, a noninvasive method was developed to estimate muscle typology through proton magnetic resonance spectroscopy in the gastrocnemius. The aim of this study was to investigate whether male subjects with an a priori-determined fast typology (FT) are characterized by a more pronounced Wingate exercise-induced fatigue and delayed recovery compared with subjects with a slow typology (ST). Ten subjects with an estimated higher percentage of fast-twitch fibers and 10 subjects with an estimated higher percentage of slow-twitch fibers underwent the test protocol, consisting of three 30-s all-out Wingate tests. Recovery of knee extension torque was evaluated by maximal voluntary contraction combined with electrical stimulation up to 5 h after the Wingate tests. Although both groups delivered the same mean power across all Wingates, the power drop was higher in the FT group (−61%) compared with the ST group (−41%). The torque at maximal voluntary contraction had fully recovered in the ST group after 20 min, whereas the FT group had not yet recovered 5 h into recovery. This noninvasive estimation of muscle typology can predict the extent of fatigue and time to recover following repeated all-out exercise and may have applications as a tool to individualize training and recovery cycles. NEW & NOTEWORTHY A one-fits-all training regime is present in most sports, though the same training implies different stimuli in athletes with a distinct muscle typology. Individualization of training based on this muscle typology might be important to optimize performance and to lower the risk for accumulated fatigue and potentially injury. When conducting research, one should keep in mind that the muscle typology of participants influences the severity of fatigue and might therefore impact the results.

scholarly journals Determination of muscle fatigue index for strength training in patients with Duchenne dystrophy

2010 ◽  
Vol 23 (3) ◽  
pp. 351-360 ◽  
Author(s):  
Adriano Rodrigues Oliveira ◽  
Fernanda Ishida Corrêa ◽  
Márcia Moreira Valim ◽  
Cláudia Santos Oliveira ◽  
João Carlos Ferrari Corrêa
Keyword(s):  
Muscle Strength ◽  
Strength Training ◽  
Muscle Fatigue ◽  
Vastus Lateralis ◽  
Regression Line ◽  
Case Series ◽  
Median Frequency ◽  
Fatigue Index ◽  
Maximal Voluntary Isometric Contraction

INTRODUCTION: Muscle weakness is the most prominent impairment in Duchenne muscular dystrophy (DMD) and often involves the loss of functional ability as well as other limitations related to daily living. Thus, there is a need to maintain muscle strength in large muscle groups, such as the femoral quadriceps, which is responsible for diverse functional abilities. However, the load and duration of training for such rehabilitation has proven to be a great unknown, mainly due to the undesired appearance of muscle fatigue, which is a severe factor for the injury of muscle fibers. OBJECTIVES: The aim of the present study was to determine a fatigue index by means of surface electromyography (EMG) for the parameterization of muscle strengthening physiotherapy training. METHODS: A cross-sectional study (case series) was carried out involving four patients with DMD. Three pairs of surface electrodes were placed on the motor point of the Rectus femoris, Vastus lateralis and Vastus medialis of the dominant limb, maintaining the knee at 60º of flexion. The participants were instructed to perform the extension movement of this joint at four strength levels (100%, 80%, 60% and 40% of maximal voluntary isometric contraction). RESULTS: The slope of the linear regression line was used for the determination of the fatigue index, performed by Pearson's test on the median frequency of each strength level. CONCLUSION: Electromyographic measurements of the strength index for muscle training proved to be a simple accessible assessment method, as well as an extremely valuable tool, allowing the design of a muscle strength training program with an individualized load threshold.

scholarly journals Analysis of three different equations for predicting quadriceps femoris muscle strength in patients with COPD

2015 ◽  
Vol 41 (4) ◽  
pp. 305-312 ◽  
Author(s):  
Aline Gonçalves Nellessen ◽  
Leila Donária ◽  
Nidia Aparecida Hernandes ◽  
Fabio Pitta
Keyword(s):  
Muscle Weakness ◽  
Muscle Force ◽  
Knee Extension ◽  
Quadriceps Femoris ◽  
Fat Free Mass ◽  
Maximal Voluntary Isometric Contraction ◽  
Copd Patients ◽  
Predicted Values ◽  
Quadriceps Femoris Muscle Strength ◽  
Femoris Muscle

AbstractObjective: To compare equations for predicting peak quadriceps femoris (QF) muscle force; to determine the agreement among the equations in identifying QF muscle weakness in COPD patients; and to assess the differences in characteristics among the groups of patients classified as having or not having QF muscle weakness by each equation.Methods: Fifty-six COPD patients underwent assessment of peak QF muscle force by dynamometry (maximal voluntary isometric contraction of knee extension). Predicted values were calculated with three equations: an age-height-weight-gender equation (Eq-AHWG); an age-weight-gender equation (Eq-AWG); and an age-fat-free mass-gender equation (Eq-AFFMG).Results: Comparison of the percentage of predicted values obtained with the three equations showed that the Eq-AHWG gave higher values than did the Eq-AWG and Eq-AFFMG, with no difference between the last two. The Eq-AHWG showed moderate agreement with the Eq-AWG and Eq-AFFMG, whereas the last two also showed moderate, albeit lower, agreement with each other. In the sample as a whole, QF muscle weakness (< 80% of predicted) was identified by the Eq-AHWG, Eq-AWG, and Eq-AFFMG in 59%, 68%, and 70% of the patients, respectively (p > 0.05). Age, fat-free mass, and body mass index are characteristics that differentiate between patients with and without QF muscle weakness.Conclusions: The three equations were statistically equivalent in classifying COPD patients as having or not having QF muscle weakness. However, the Eq-AHWG gave higher peak force values than did the Eq-AWG and the Eq-AFFMG, as well as showing greater agreement with the other equations.

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