Isokinetics and Exercise Science - Volume 26, issue 4
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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: 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: The diagnostic accuracy of manual muscle testing (MMT) has been examined- but not for grip strength. OBJECTIVE: Determine the diagnostic accuracy of MMT relative to grip dynamometry for identifying patients with weak grip strength. METHODS: This study involved the secondary analysis of grip strength data obtained from 61 patients managed in a home care setting. The concordance between weakness identified using MMT and grip dynamometry was examined. RESULTS: The agreement between MMT and dynamometry was about 70%. Kappa suggested fair agreement beyond chance. Sensitivity and specificity ranged from 66.7 to…73.4 percent. CONCLUSIONS: Grip strength measured using MMT lacks sufficient diagnostic accuracy to advocate its use – at least with patients seen in a home setting.
Abstract: BACKGROUND: Isokinetic dynamometers measure moment and calculate work and power values, which are generally used to interpret muscle performance. OBJECTIVE: This study aimed to determine the differences of peak moment (PM), work, and power between FRoM and calculated valid isokinetic sector (VIS) data to define the possibility of the misinterpretation of isokinetic dynamometer data. METHODS: Fourteen professional male soccer players who had ACL reconstruction were recruited to the muscle strengthening program which was conducted four days a week for six weeks with increasing training intensity each week. Isokinetic muscle peak moment, work, and…power of knee extensors and flexors were measured at angular velocities of 60, 120, 180 and 240 ∘ /s. RESULTS: The results of the standard full-RoM (FRoM) report were compared with the calculated VIS data. Analyses of the FRoM data showed that PM, work, and power values for both extensor and flexor muscle groups improved significantly. However, a comparison of FRoM and VIS data showed significant differences for the work and power values at 120, 180 and 240 ∘ /s. CONCLUSION: The evaluation of FRoM isokinetic data may cause improper interpretations in muscle performance, particularly for contractions with higher angular velocities.
Abstract: BACKGROUND: Muscle stretch reflexes are widely considered to beneficially influence joint stability and power generation in the lower limbs. While in the upper limbs and especially in the muscles surrounding the shoulder joint such evidence is lacking. OBJECTIVE: To quantify the electromyographical response in the muscles crossing the shoulder of specifically trained overhead athletes to an anterior perturbation force. METHODS: Twenty healthy male participants performed six sets of different external shoulder rotation stretches on an isokinetic dynamometer over a range of amplitudes and muscle pre-activation moment levels. All stretches were applied with a…dynamometer acceleration of 10,000 ∘ /s 2 and a velocity of 150 ∘ /s. Electromyographical response was measured via sEMG. RESULTS: Consistent reflexes were not observed in all experimental conditions. The reflex latencies revealed a significant muscle main effect (F (2,228) = 99.31, p < 0.001; η 2 = 0.466; f = 0.934) and a pre-activation main effect (F (1,228) = 142.21, p < 0.001; η 2 = 0.384; f = 1.418). The stretch reflex amplitude yielded a significant pre-activation main effect (F (1,222) = 470.373, p < 0.001; η 2 = 0.679; f = 1.454). CONCLUSION: Short latency muscle reflexes showed a tendency to an anterior to posterior muscle recruitment whereby the main internal rotator muscles of the shoulder revealed the most consistent results.
Abstract: BACKGROUND: During the first two decades of life, athletes pass through intense changes in body size, which can directly influence physical fitness, especially anaerobic tasks. OBJECTIVE: We examined which body size variables can discriminate the level of anaerobic performance in young soccer players. METHODS: The sample was composed of 102 regional players (14.5 ± 1.6 years) belonging to youth soccer clubs at a regional level. Anthropometric measures of weight and height were carried out. A left hand-wrist radiograph was taken to identify bone age of the players. To assess anaerobic…fitness, the 7-sprints test protocol was applied. To analyze the relationship between body size variables and anaerobic capacity, the Pearson correlation coefficient was used. Through the non-hierarchical k-means cluster method, players were grouped into three anaerobic levels: high (n = 22), average (n = 44), and low (n = 36). Subsequently, discriminant analysis (stepwise method) was used to verify which growth variable discriminates the level of anaerobic fitness (p < 0.05). RESULTS: Results indicated that 7 sprints performance is related to chronological age (r = - 0.41; p < 0.01), bone age (r = - 0.43; p < 0.01), height (r = - 0.33; p < 0.01), and body mass (r = - 0.23; p < 0.01) in U-14 soccer players. Height was able to discriminate the level of anaerobic fitness across U-14 players (λ = 0.46, Λ = 0.68, X 2 (6) = 19.89). No significant predictors were identified for U-17 anaerobic performance. DISCUSSION: Body size is related to 7 sprints performance in U-14 youth players, while biological maturation seems to influence physical fitness.
Keywords: Bone age, repeated sprint, youth, athletes
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
Abstract: BACKGROUND: Strength assessments are used to monitor physical progression and evaluate the impact of training interventions, which is extremely valuable for both athletic performance and clinical populations. For results to be useful, measurements must be relevant, reliable and show sensitivity to change. OBJECTIVES: The aim was to establish the practicality of isometric force assessment at two different knee-joint angles; 90 ∘ (ISO 90 ) and 120 ∘ (ISO 120 ). More specifically, to address the familiarisation effects, reproducibility and sensitivity of measurements…associated with each method of assessment, and the discrepancy in force output when altering the angle at the knee joint. METHODS: Thirty-five strength trained males attended three sessions; familiarisation (T 1 ), test (T 2 ) and retest (T 3 ), separated by 7 days. During each session, ISO 90 and ISO 120 was assessed using an incline leg press device. RESULTS: Force output was similar during T 1 , T 2 and T 3 for ISO 90 and ISO 120 , separately (p > 0.05). Measurements taken from both assessment methods demonstrated good reproducibility (ICC = 0.96, CV < 5%) and showed sufficient sensitivity to detect changes in performance. Force output was greater during ISO 120 (5153 ± 1446 N) versus ISO 90 (2660 ± 597 N, p < 0.001) but the magnitude of the difference in force output showed great intra-subject variability. CONCLUSION: Isometric assessment performed on a leg press device requires minimal habituation to demonstrate a good degree of reproducibility and sensitivity to detect small changes in performance. It is a simple and practical method to evaluate strength at different joint angles, which may prove useful in strength diagnosis in performance and clinical contexts.
Keywords: Reliability, maximum force, testing, monitoring, diagnosis
Abstract: BACKGROUND: Estimations of deep muscles electromyography (EMG) 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: 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: 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.