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Isokinetics and Exercise Science (IES) is an international journal devoted to the study of theoretical and applied aspects of human muscle performance. Since isokinetic dynamometry constitutes the major tool in this area, the journal takes a particular interest in exploring the considerable potential of this technology.
Isokinetics and Exercise Science publishes studies associated with the methodology of muscle performance especially with respect to the issues of reproducibility and validity of testing, description of normal and pathological mechanical parameters which are derivable from muscle testing, applications in basic research topics such as motor learning paradigms and electromyography. The journal also publishes studies on applications in clinical settings and technical aspects of the various measurement systems employed in human muscle performance research.
Isokinetics and Exercise Science welcomes submissions in the form of research papers, reviews, case studies and technical reports from professionals in the fields of sports medicine, orthopaedic and neurological rehabilitation and exercise physiology.
Abstract: BACKGROUND: Fatigability measured and derived parameters are commonly used in research and clinical contexts to characterize performance during isokinetic fatigue protocols. The fatigability measured parameters are the best repetition, the total and the partial sums while the fatigability derived parameters are ratios and formula-based parameters. OBJECTIVES: To comprehensively evaluate the reproducibility of fatigability measured and derived parameter and to determine which of these is/are sufficiently interpretable for assessment of knee muscles. METHODS: Eighteen sedentary men underwent three isokinetic knee fatigability testing sessions with 7–10 days of rest between each session. Peak moment (PM)…and maximal work (MW) were computed for each repetition and analyzed to calculate 54 measured and derived parameters. Relative (Intra-class Correlation Coefficients – ICC) and absolute (Coefficient of Variation of Method Error – CV ME %, standard error of measurement – SEM and minimum detectable change – MDC) parameters of reproducibility were determined to assess the inter-session agreement. RESULTS: All fatigability measured parameters (save one) were associated with a high relative and absolute reproducibility for knee extensors (ICC ⩾ 0.80; almost all SEM ⩽ SD 2 ; MDCs largely ranging 10–30%) and a high relative but weak absolute reproducibility for flexors (ICC ⩾ 0.70; SEM > SD 2 ; MDCs ranging 35–95%). On the other hand, all knee extensor and flexor fatigability derived parameters were characterized by low relative and absolute reproducibility (ICC extensors < 0.70 and ICC flexors < 0.50; all SEM > SD 2 ; MDCs largely ranging 30–100%). CONCLUSIONS: All fatigability measured parameters may be used for assessing knee extensors fatigue with either PM or MW; for assessing knee flexors, no measured parameters can be utilized. Above all, knee fatigability derived parameters, either PT- or MW-based, should not be used, for both the extensors and the flexors of the knee, due to clinically unacceptable reproducibility.
Abstract: BACKGROUND: Small-sided games (SSG) are widely used in soccer due its potential to improve technical, tactical and physical performance. Different approaches are used to modify physical demands during SSG. Despite this, little is known about the impact of rule modifications on the internal load imposed to young soccer players. OBJECTIVE: This study aimed to compare the magnitude of the internal load imposed on young soccer players between small-sided soccer games with different amounts of goals. METHODS: Sixteen male athletes (15.7 ± 0.43 years, 64 ± 7 kg,…1.71 ± 0.05 m, 21.8 ± 1.7 kg/m 2 ) performed a SSG with one goal (SSG1 goal ) and three goals (SSG3 goal ) in a randomized order separated by 48 hours. The markers of internal load were: i) percentage of maximum heart rate (%HR) max , ii) Edward’s Training Impulse (TRIMP), and iii) performance on the repeated sprint ability (RSA) test immediately post-SSG. Paired t-test and repeated measures ANOVA were used to compare the direct (i.e. Edward’s TRIMP and HR max ) and indirect (i.e. RSA) markers of internal load between the different SSG formats. A p-value < 0.05 was set as statistically significant. RESULTS: HR max was higher in the SSG1 goal compared to the SSG3 goal (91 ± 2% vs. 89 ± 3%; p < 0.05). No difference was found in the Edward’s TRIMP (SSG1 goal : 86.4 ± 15.7 arbitrary units; SSG3 goals : 78.2 ± 12.8 arbitrary units; p = 0.15). Performance on the RSA test was worse post-SSG1 goal compared to the post-SSG3 goals (p < 0.01). SSG1 goal elicits a higher internal load than SSG3 goals . CONCLUSIONS: Therefore, the amount of goals in SSG may impact the internal load imposed on young soccer players.
Keywords: Sports, physiological monitoring, heart rate, young player, sport performance
Abstract: BACKGROUND: Information regarding the relationship between methods for assessment of voluntary and involuntary muscle contractile properties is of importance in sport science and medicine. OBJECTIVE: To appraise the concurrent and predictive validity of isokinetic dynamometry and tensiomyography (TMG) in differently trained men and women. METHODS: Fifty men and 45 women were divided into three groups: physically inactive, physically active and athletes. Isokinetic testing was performed on knee muscles in concentric mode at 60 and 180 ∘ s while tensiomyographic measurements were obtained from the rectus and the biceps femoris…muscles. RESULTS: A small, statistically significant negative, correlation was detected between the peak moment and tensiomyography parameters relating to contraction time and maximal displacement (Adj. R= 2 0.086, p = 0.028). CONCLUSION: In general, isokinetic dynamometry and tensiomyography are not related and represent different technologies that measure different contractile properties of muscles. A hierarchical structure of predictive validity at the level of individual variables was detected as a function of gender and training level.
Abstract: BACKGROUND: Research suggests that the effect of short bouts of stretching on muscle strength and ROM gains depends on the total stretching volume. OBJECTIVE: We assessed the effects of short bouts of static passive (SSS) and contract-relax (SCR) stretching on range of motion (ROM) and muscular strength. METHODS: Twenty volunteers performed two stretch protocols in a randomized order on two separate days, using the SSS and SCR techniques. Maximal ROM was tested prior to (pre-S), immediately after (post-I) and 10 minutes after (post-10) the stretch protocol. Maximal isometric voluntary contraction (MVC), isokinetic concentric…peak moment (F-PM) and angle of peak moment (F-PMa) in the knee flexors, and concentric flexion/extension PM ratio (F/E) were measured and evaluated before (pre) and after (post) the stretch protocol. RESULTS: Both stretching techniques showed significant time-effects (pre vs post-I and post-10) but no interaction effects (time × techniques). There were small but significant effects between intervention-paired comparisons for F-PM, F-PMa and F/E ratios after SSS, and for F-MVC and F-PMa measures after SCR stretch techniques. CONCLUSIONS: Short-stretch techniques have trivial and small effects on loss of strength, increase the ROM for at least 10 min and slightly decrease the concentric F/E ratio. Using SSS could create some risk of hamstring injuries.
Abstract: BACKGROUND: Vertical jumping capacity is important in modern soccer to gain advantage over opponent during the defensive and offensive activities. Predictors of jumping capacity in soccer players are not well studied. OBJECTIVE: The main aim of our study was to evaluate how isokinetic strength of the thigh muscles is related to jump performance. METHODS: Twenty-five (N = 25) elite soccer players volunteered to participate in the study. Thigh muscle strength (concentric for hamstrings and quadriceps, and eccentric for hamstrings only) was evaluated at 60 ∘…/sec using an isokinetic dynamometer, while jump capacity was evaluated using a bilateral force plate to measure the jump height of squat (SJ) and countermovement (CMJ) jump. Linear regression model was used to evaluate how well can isokinetic strength parameters (independent predictors) predict jumping capacity in soccer players (dependent variable). RESULTS: In a linear regression model concentric quadriceps strength has significantly explained the vertical jump height, while other parameters (hamstring concentric or eccentric strength) did not reach the significance level (p > 0.05). When left and right concentric quadriceps strength was used the model was statistically significant (F = 4.76, p = 0.02; R square 0.31), but only right concentric quadriceps strength was significant predictor (t = 2.62, p = 0.016). Strength asymmetry did not significantly influence the jump height, but was associated with lower ratio of CMJ/SJ height indicating that players without asymmetry have better jumping capacity in the terms of utilizing the stretch shortening cycle. CONCLUSIONS: Coaches should consider quadriceps strength as an important predictor of jumping capacity in top-level soccer players which is again related to sprint performance in soccer. Future studies are needed to evaluate the contributing impact of hamstring strength in this regard.
Abstract: BACKGROUND: While interval training is considered an effective modality for improving performance, its effectiveness among athletes may be influenced by previous training experience. OBJECTIVE: To investigate whether differences in training background are reflected in the development of exercise capacity and level of muscle damage following a single bout of repeated maximal sprints after an 8-week intervention of high-intensity interval training (HIIT), sprint interval training (SIT), and endurance training (ET). METHODS: Three groups of male cyclists were studied: E1 (n = 10) included cyclists with a background in high-volume…moderate-intensity training, E2 (n = 7) comprised cyclists with low-volume high-intensity training experience, and C (n = 7) served as a control group with an identical training background as E1. During 8-week intervention HIIT, SIT, and ET were performed by cyclists in group E1 and E2, group C performed only ET. At pre- and post-intervention, cyclists performed two exercise tests: 1) incremental testing protocol (ITP) to assess maximal oxygen uptake (VO 2 max) and maximal power (Pmax); and 2) sprint interval testing protocol (SITP) to determine oxygen uptake (VO) 2 , work, and change in creatine kinase (Δ CK) and myoglobin (Δ Mb) levels. RESULTS: After intervention, VO 2 max increased in all groups although Pmax increased only in E1 and C. During post-intervention sprint interval testing protocol, VO 2 and work increased only in E1, whereas Δ CK and Δ Mb decreased in E1 but increased in E2. CONCLUSIONS: A history of high-volume moderate-intensity training can induce beneficial performance adaptations by reducing muscle damage and allowing greater work output. It is suggested that interval training be preceded by a longer period of high-volume training in athletes.
Abstract: BACKGROUND: The legitimacy of manual muscle testing (MMT) is dependent in part on the reliability of assessments obtained using the procedure. OBJECTIVE: The purpose of this review, therefore, was to consolidate findings regarding the test-retest and inter-rater reliability of MMT from studies meeting inclusion and exclusion criteria. METHODS: An electronic search of PubMed, Scopus, and CINAHL databases and a hand search were conducted to identify articles addressing the test-retest or inter-rater reliability of MMT. Data on participants, testing specifics, and findings regarding reliability were extracted. RESULTS: Of 189 unique articles…identified, 9 were found to meet inclusion/exclusion criteria. The studies were highly variable in regard to the population tested, MMT procedure and scoring, and findings. Nevertheless, based on pairwise comparisons, substantial or almost perfect test-retest and inter-rater agreement was demonstrated for most muscle actions tested. CONCLUSIONS: Reliable assessments of strength may be obtained by MMT but not assumed. Further research is required to address the reliability of MMT across pathologies, muscle groups, and test procedures.
Abstract: BACKGROUND: Traditional warm-up exercises generally consist of submaximal aerobic running. Thereafter static or dynamic stretching exercises appropriate to the field are advised to keep the strength, which is the main component of physical fitness, stabilized. OBJECTIVE: To examine and compare the acute effects of static stretching (SS) and dynamic stretching (DS) on the knee and ankle flexor and extensor concentric (CON) isokinetic strength in well-trained male taekwondo athletes. METHODS: A total of 14 male taekwondo athletes who train at least 4 days a week, 90 min. a day, were tested for knee and ankle flexor and…extensor isokinetic peak moment (PM) at 60 and 180 ∘ /s before and 4 min. after three different stretching exercise sessions, namely, non-stretching (NS), SS, and DS, with 48-h rest intervals in a randomized crossover study design. RESULTS: None of the exercises: NS, SS and/or DS had any effect on the concentric strength of the knee and ankle flexor and extensor muscles. CONCLUSIONS: These findings suggest that in well-trained taekwondo athletes who are accustomed to static or dynamic movement actions may be less suscePMible to stretching-induced strength deficit. Whether this conclusion may be extended to other sporting events requires further research.
Abstract: BACKGROUND: Estimations of deep muscles electromyography (EMG) of deep muscles with surface electrodes can be usually performed only indirectly. OBJECTIVE: To investigate the impact of using different approaches for estimating vastus intermedius EMG on the moment sharing patterns among quadriceps femoris components (QF), obtained with an EMG-Driven model, as well as on the joint total moment estimation accuracy, by comparing the calculated knee moment with isometric dynamometer measurements. METHODS: Extensor knee moment and surface isometric EMGs from the four QF components were collected synchronously with knee moment from an isokinetic dynamometer, with the…knee flexed at 80 ∘ and moment level at 40% of the maximum. Neuromuscular excitations u ( t ) for each QF were derived from the EMGs. Three different estimates of vastus intermedius excitation u VI ( t ) were tested: (1) surface electrodes on the exposed portion of vastus intermedius; (2) average between vastus lateralis and vastus medialis; and (3) a regression equation to estimate VI EMG from the other QF components. RESULTS: No statistical differences were found among the relative moments, excitation signals, and estimation accuracy by using the three methods. CONCLUSIONS: The average between vastus lateralis and vastus medialis is the recommended choice for being the simplest one.
Keywords: EMG-Driven muscle models, vastus intermedius, knee muscles, joint moment
Abstract: OBJECTIVE: The purpose of this investigation was to examine the effects of two back squat exercise protocols on recovery responses of maximal unloaded velocity (Vmax) and angular acceleration (ACC240, ACC500) of the knee extensors. METHODS: Fourteen resistance-trained men (mean ± SD: age = 22.07 ± 2.6 years) and sixteen women (age = 21.75 ± 1.0 years) performed maximum voluntary contractions at 240 ∘ ⋅ s - 1 and 500 ∘…⋅ s - 1 before (Pre) and after (Post0-Post30) a squat exercise using either a power-endurance (PE) (5 × 16 at 40% one-repetition maximum), or controlled hypertrophic (CH) (5 × 8 at 80% one-repetition maximum) protocol. RESULTS: There was a significant main effect for time (p ⩽ 0.001) in which ACC240 was greater at Pre compared to Post0, Post15 and Post30 (p = 0.001–0.023), no differences were observed at Post7 (p = 0.186). For ACC500, all post-recovery time phases (Post0-Post30) were lower than Pre (p ⩽ 0.001). A sex × intensity × time (p = 0.040) interaction was observed for Vmax where only the CH protocol was significantly decreased (p = 0.019) for the males at Post0. All other post-recovery time phases for Vmax were lower compared to Pre for both protocols (p = 0.002–0.025). CONCLUSIONS: Similar fatigue and recovery-related responses were observed between genders in regards to ACC and Vmax following volume-matched PE and CH squat protocols. Knowing that a variety of populations implement compound movements into their resistance training routines, the present findings suggest that ACC and Vmax may be negatively affected following moderate to heavy exercise for up to 30 minutes. Thus, assessing ACC and Vmax post-exercise may be a valuable measure in identifying the residual consequences of fatigue over a short-term recovery period.
Keywords: Acceleration, back squat, fatigue, males and females, resistance trained, voluntary activation