Effects of different isokinetic knee extension warm-up protocols on muscle performance (original) (raw)
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Acute effect of three different warm-up protocols on maximal isokinetic strength in young men
Revista Andaluza de Medicina del Deporte, 2019
Objective: To investigate the acute effect of three different warm-up protocols on a maximal isokinetic strength test. Methods: Twenty-two male, recreational athletes involved in regular resistance training were evaluated. Subjects performed a maximal isokinetic strength test of the knee extensors in an isokinetic dynamometer after completing a control session or one of the following warm-up protocols using a randomized design: a general warm-up, stretching warm-up, or specific warm-up. The comparison between treatments was completed through Repeated-Measures Analysis of Variance, followed by a Bonferroni “post hoc” test (p < 0.05). Results: The only difference found was the concentric peak moment following the application of the specific warm-up protocol, which was lower than the control session (12.94%; p < 0.05). No other differences were noted in eccentric peak movement or total work (concentric + eccentric) parameter after application of any the warm-up protocols within c...
The purpose of this study, which was conducted at the Institute of sport on Faculty of sport and physical education University of Sarajevo, within the project “Gold badge”, was to investigate the acute effects of 2 types of warm-up protocols on peak torque of dominant leg extensor muscles. Concentric knee extension power was measured isokinetically at 60 degrees in 50 male pro and semipro level athletes (ages 15-27) which came from five different sports (Soccer, Track and Field, Tae Kwon Do, Boxing and Karate). The first protocol included 10 minutes of stationary cycling at 50W, after which 7 static stretching exercises were performed. The second protocol combined 3 self-myofascial release (SMR) exercises via foam roller (applied to gastrocnemius, hamstring and quadriceps muscles), after which another 2 proprioceptive neuromuscular facilitation (PNF) exercises were performed (applied to hamstring and quadriceps muscles). Resting period between two tests was 48 hours. The results of ...
PloS one, 2018
The current study aimed to examine the reliability of the conventional and functional ratios derived from peak torques (PTs) and those obtained from the combination of knee flexors torque at the angle of knee extensors PT. Twenty-six male athletes (mean of 24.0±0.7 years) from different sports completed a test-to-test variation in isokinetic strength (Biodex, System 3) within a period of one week. Anthropometry and body composition assessed by Dual Energy X-ray Absorptiometry were also measured. The proposed isokinetic strength ratio measurements appeared to be highly reliable: conventional ratio at PT angle (intra-class correlation, ICC = 0.98; 95% confidence interval; 95%CI: 0.95 to 0.99); functional extension ratio at PT angle (ICC = 0.98; 95%CI: 0.96 to 0.99); and, functional flexion ratio at PT angle (ICC = 0.95; 95%CI: 0.89 to 0.98). Technical error of measurement (TEM) and associated percentage of the coefficient of variation (%CV) were as follows: conventional ratio at PT an...
Isokinetics and Exercise Science
Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue. Isokinetics and Exercise Science , 10:167-175 ***Note: Figures may be missing from this format of the document Abstract.: This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t = pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC's and three maximal isotonic contractions, respectively. Following each exercise, strength and power were assessed immediately after (t =: 00) and at 2.5 (t =: 02.5), 5 (t =: 05), 10 (t =: 10), and 15 (t =: 15) minutes. All strength and power measures were normalized to the respective t = pre value. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective tire value. Following isometric exercise, both strength and power at t =: 00 (68.7% ± 8.7% & 88.0% ± 8.7%) and t =: 02.5 (82.2% ± 17.8% & 95.2% ± 5.0%) significantly decreased from t=pre (100% ± 0.0%) (p < 0.05) with greater decreases in strength at each time point (p < 0.05). EMG analysis revealed a significant EMG amplitude decrease (p < 0.05) at t =: 00 and t =: 02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t =: 00 (68.0% ± 13.2% & 38.8% ± 10.7%) and t =: 02.5 (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t=pre (100% ± 0.0%) with a greater power decrease at t =: 00 (p < 0.05). The EMG amplitude of males was significantly less at t =: 00 than the respective EMG amplitude for females (p < 0.05) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed. Article: INTRODUCTION: During the past years of research addressing muscle performance during and following fatiguing exercise, the isometric contraction has been considered the gold standard of muscle force producing capability in the laboratory setting. The muscle force production values acquired from isometric contractions are often referred to as "strength" [11]. However in sporting activities the majority of muscle contractions are dynamic in nature. Power, a variable that takes into account contraction force and velocity, is important in sports that demand explosive movements. Throughout the remainder of this paper strength will refer to isometric torque production and power will refer to dynamic, maximal efforts of the muscle/joint complex.
Journal of Electromyography and Kinesiology, 2008
Despite the common use of standardised methods analysing neuromuscular function during knee extension, there is a lack of testretest reliability studies. Furthermore, for most of the investigated variables it is unknown which changes of values indicate an enhancement of performance. The aim of the present study was to investigate performance-dependent variations of muscle functions during isometric contraction of knee extensors and to examine test-retest reliability of their measurement methods. For test-retest reliability sports students completed three test sessions. Highly skilled athletes, sports students and untrained subjects were investigated to determine the performance-dependent variations. The following variables were analysed: maximal voluntary contraction (MVC), voluntary activation (VA), absolute muscle reaction time (AR), muscle endurance (ME), and EMG frequency analysis (MF) of m. vastus lateralis (VL), m. vastus medialis (VM) and m. rectus femoris (RF). Results test-retest-reliability: A high reliability between session 1 vs. 2 and session 2 vs. 3 was shown for MVC (ICC = 0.92 and .97), VA (0.92/0.95) and ME (0.87/0.95). ICC in AR (0.23) was low between the first and second session and moderate between the second and third session (0.74). MF of VL, VM and RF showed low ICC between sessions. Performance dependent variations: Significant differences in nearly all variables (except VA) were found between trained (athletes and sports students) and untrained subjects.
An Adequate Interset Rest Period for Strength Recovery During a Common Isokinetic Test
Journal of Strength and Conditioning Research, 2013
Isokinetic testing is used in rehabilitation settings on a regular basis; yet, there is a lack of consistency in rest period usage among protocols. Furthermore, the allotment of rest periods has been arbitrary (e.g., 30, 60, 90 seconds or more). This investigation examines the work:rest ratio as an effective method of standardizing rest periods in isokinetic testing. The purpose of this study was to establish an adequate rest period that would allow reproducibility of strength during a common isokinetic strength test. Twenty-seven healthy college-aged men (age, 23 6 3.8 years; body weight, 79.54 6 11.09 kg) were tested on 5 separate occasions: 2 familiarization sessions and 3 experimental sessions. Each subject performed a knee extension/flexion isokinetic strength protocol (Cybex NORM; Lumex, Inc., Ronkonkoma, NY, USA) to determine peak torque by performing 5 maximal reciprocal repetitions at each ascending velocity of 60, 180, and 3008$s 21. Work:rest ratios of 1:3, 1:8, and 1:12 were counterbalanced between sets. A 3 3 3 repeated measures analysis of variance was used to analyze the data. A significance level of a # 0.05 was used for all tests. There was no significant difference in either knee extension or knee flexion peak torque when comparing work:rest ratios. These findings suggest that a 1:3 work:rest ratio is sufficient during a common isokinetic strength test.
Effects of antagonist pre-load on knee extensor isokinetic muscle performance
Journal of Sports Sciences, 2011
The aim of this study was to evaluate and compare acute effects of a reciprocal action protocol and a super-set protocol on knee extensor performance during concentric isokinetic exercise. Fourteen men aged 29.4 + 6.1 years were tested on three different protocols, with 1 min of rest between sets: control (3 sets of 10 isokinetic knee extension repetitions), reciprocal action protocol (3 sets of 10 repetitions of reciprocal isokinetic concentric knee flexion and knee extension repetitions), and super-set protocol (3 sets of a combination of 10 repetitions of knee flexion immediately followed by 10 repetitions of knee extension repetitions). Tests were performed at 608 Á s 71 and 1808 Á s 71 , randomized across 3 days and separated by at least 72 h. There were no significant differences between protocols for peak torque at 608 Á s 71 or 1808 Á s 71 . Total work was significantly higher during the reciprocal action protocol compared with the super-set protocol at 608 Á s 71 . There was a significant decline in peak torque (from 240.6 to 212.9 N Á m) and total work (from 2294 to 1899 J) for the control condition at 608 Á s 71 . Also, total work declined significantly across sets for the super-set protocol at 608 Á s 71 (from 2157 to 1707 J). Results indicate that a reciprocal action protocol provides torque maintenance during multiple sets of isokinetic training, both at slow and high velocities.
Test-retest reliability of reciprocal isokinetic knee extension and flexion peak torque measurements
Journal of athletic training, 1992
Our purpose in conducting this study was to estimate the reliability of reciprocal concentric knee extension and flexion peak torque obtained in uninjured male athletes using the Biodex isokinetic dynamometer. Twenty-six male intercollegiate athletes (age=19.5+/-4.1 yr; ht=70.3+/-14.9 in; wt=212.9+/-48.5 lb) participated in this study. We used the Biodex to measure peak torque occurring during right knee extension and flexion over 3 consecutive days. Means and standard deviations were calculated for both extension and flexion on each of the 3 days. We observed a significant main effect for days for both extension and flexion. Mean peak torque for the first day was significantly higher (Turkey, p<.05) than the means for the other 2 days, which were not significantly different from each other (Turkey, p>0.05). Intraclass correlation coefficients (ICCs) were estimated for each of the six trials on each of the 3 days. Intraclass correlation coefficients (ICCs) ranged from .88 on t...
Journal of Human Kinetics, 2011
The aim of this study was to investigate the effects of two training protocols on the isokinetic performance of athletes. The study was conducted in 38 athletes, (age 23.3 ± 3.6 years) participating in national level leagues of different sports, whose initial concentric hamstrings-to-quadriceps (conH/Q) torque ratio was lower than 0.5. During seasonal testing, an isokinetic measurement of knee extensors and flexors was performed at 60º/s. The athletes were divided into two groups. Nineteen athletes performed the isokinetic training protocol (IT) while the second group of 19 athletes followed the isotonic training protocol (RT). Both protocols lasted 4 weeks. After completing the training protocols, both groups underwent a final isokinetic testing. The isokinetic data revealed significant increases after training in measures of peak torque in both extensor and flexor muscle groups, in both the IT and RT study groups (p < 0.05). There were significant increases (p< 0.05) in conH/Q ratio in both groups after the implemented protocols, but greater in IT group. Consequently, applied IT protocol induced changes in working muscles, thereby restoring detected asymmetry to an acceptable balance more efficiently compared to RT protocol.
The effect of warm-ups with stretching on the isokinetic moments of collegiate men
Performing warm-ups increases muscle temperature and blood flow, which contributes to improved exercise performance and reduced risk of injuries to muscles and tendons. Stretching increases the range of motion of the joints and is effective for the maintenance and enhancement of exercise performance and flexibility, as well as for injury prevention. However, stretching as a warm-up activity may temporarily decrease muscle strength, muscle power, and exercise performance. This study aimed to clarify the effect of stretching during warm-ups on muscle strength, muscle power, and muscle endurance in a nonathletic population. The subjects of this study consisted of 13 physically active male collegiate students with no medical conditions. A self-assessment questionnaire regarding how well the subjects felt about their physical abilities was administered to measure psychological readiness before and after the warm-up. Subjects performed a non-warm-up, warm-up, or warm-up regimen with stretching prior to the assessment of the isokinetic moments of knee joints. After the measurements, the respective variables were analyzed using nonparametric tests. First, no statistically significant intergroup differences were found in the flexor and extensor peak torques of the knee joints at 60˚/sec, which were assessed to measure muscle strength. Second, no statistically significant intergroup differences were found in the flexor and extensor peak torques of the knee joints at 180˚/sec, which were assessed to measure muscle power. Third, the total work of the knee joints at 240°/sec, intended to measure muscle endurance, was highest in the aerobic-stretch-warm-ups (ASW) group, but no statistically significant differences were found among the groups. Finally, the psychological readiness for physical activity according to the type of warm-up was significantly higher in ASW. Simple stretching during warm-ups appears to have no effect on variables of exercise physiology in nonathletes who participate in routine recreational sport activities. However, they seem to have a meaningful effect on exercise performance by affording psychological stability, preparation, and confidence in exercise performance .