Isokinetics and Exercise Science - Volume 13, 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: This study compared the strength and endurance of shoulder internal rotators (IR) and external rotators (ER) among baseball pitchers of four age levels. Eighty baseball pitchers aged 10–23 years participated this study. Strength was assessed by the average peak torque of the middle 3 out of 5 repetitions. Endurance was assessed by thirty concentric internal and external contractions. Percentage of strength loss, initial and final torque ratio were used to assess endurance ability. The results showed…that IR strength was greater than the ERs for all groups. The ER/IR ratio ranged 0.71–0.77. In endurance assessment, the players were found to have 70% strength loss in the IRs. Adolescent and pre-pubescent players had larger p<0.05) strength loss in the ERs. Compared with adult pitchers, adolescent and pre-pubescent baseball pitchers had relatively weaker shoulder ERs especially after high repetition muscle contraction. In order to prevent shoulder injury in adolescent and pre-adolescent baseball throwers, muscle endurance in ER should be emphasized.
Abstract: Strength is an important factor in athletic performance. Although maximal strength is readily measurable using isokinetic dynamometry other parameters are needed to assess the specific explosive component of muscular strength. To identify these parameters, 41 high-level long-distance runners (17 female and 24 male) and 65 high-level sprinters (22 female and 43 male) performed maximal isokinetic knee flexion/extension exertions at 60°/s and 300°/s using the dominant limb. Multiple strength parameters of hamstrings and…quadriceps were studied including peak torque (PT) at both velocities, %PT at 0.2 s of contraction initiation at 60°/s, average explosive work at 300°/s, average power at 300°/s, average power at 300°/s divided by the PT at 60°/s (Relative Power Index – RPI), and average power at 300°/s divided by the PT at 300°/s. The only parameter which did not significantly correlate with (PT60) was the RPI in both flexion and extension. Irrespective of gender, this parameter was also significantly higher in sprinters compared with long-distance runners, and higher in the hamstrings than in the quadriceps. Therefore the use of this parameter is recommended for measuring explosive strength related to sprinting performance in the athlete. Reference data for the RPI in high-level sprinters are provided.
Abstract: Our objective was to examine age and sex associated development of isokinetic tibial rotation strength in 94 athletes aged 11 to 17 y. A calibrated Biodex system 3 was used to measure internal rotation (IR) and external rotation (ER) peak torque and time to peak torque (TPT) at 120°/s and 180°/s, and knee extension and flexion peak torque at 180°/s. All data were normalized for body weight and ANOVA identified significant (p…<0.05) effects of lower limb dominance, age and gender. Males aged 14 to 17 y had significantly greater mean IR, ER, flexion, and extension peak torques than males aged 11 to 13 y. No such age-related effect existed in females. There was no difference between genders aged 11 to 13~y in isokinetic strength. Males aged 14 to 17 y had on average 17% greater IR strength, 28% faster time to reach IR peak torque, 17% greater extension strength, and 20% greater knee flexion strength than age-matched females. To conclude, no sex differences were found in peak torque or TPT in knee IR, ER, extension or flexion in athletes 11 to 13 y. Age related changes were found in these factors in males, but not in females.
Abstract: The purpose of this study was to investigate the differences in recovery between adult and prepubertal males after a maximal isokinetic fatigue protocol. Ten adults and 14 prebupertal boys exerted 25 subsequent maximal isokinetic knee extensions at 60°/s. The electromyogram (EMG) of the vastus lateralis (VL), vastus medialis (VM) and biceps femoris (BF) was recorded. The obtained results showed that the Peak Torque (PT) decreased at a higher rate in adults compared to children. The…recovery of PT, and the agonist muscle activity was faster in children in comparison to the men. No differences were observed in the recovery of the antagonist muscle between age groups. The findings indicated that the PT recovery is faster in children and this could be partially attributed to neural factors since in children the recovery of their agonist muscle activation was faster than adults.
Abstract: Both isokinetic testing and functional tests are commonly used to evaluate patients following reconstruction of the anterior cruciate ligament (ACLR). To determine the relationship of scores on an isokinetic test to scores on a variety of lower extremity functional tests ten healthy subjects and eleven ACLR patients at least six months after surgery performed knee isokinetic test at 60 and 180 deg/sec and three functional tests: leg vertical jump, single hop, and triple cross-over hop for…distance. Correlation coefficients of isokinetic peak torque to body weight and functional testing were not significant at the P<0.05 level in patients or control subjects, whi1e ratio of involved to uninvolved knee quadriceps isokinetics peak torque and Limb Symmetry Index (LSI) of functional test were significant at the P<0.05 level (r=0.54 to 0.97). These results indicate a significant relationship between the LSI of various functional tests and side-to-side ratio of isokinetic testing just in ACLR patients.
Keywords: ACL-reconstruction, isokinetic strength, hop test, limb symmetry index
Abstract: Background: Resistive training has been introduced in exercise programs to improve the results of traditional rehabilitation. Changes in blood pressure (BP) and heart rate (HR) during resistive have mainly been measured out of the rehabilitation context, using discontinuous monitoring of BP, while exercising small muscular mass during isometric exercise or low intensity contraction. Method: The BP and HR responses to low, moderate and high intensity resistive training were continuously assessed in 21 healthy subjects.…The total amount of work was the same for the three modalities, hence the number of repetition was inversely related to exercise intensity. Results: Blood pressure and HR increased from set 1 to set 3 for all 3 training modalities and were highest, intermediate and lowest during low, moderate and high intensity training respectively (all p<0.001). Conclusions: BP and HR changes during resistive training are related principally to exercise duration. Short sets using heavy weights is preferable to limit BP and HR rises.
Keywords: Hemodynamics, blood pressure, resistive exercise, strength training
Abstract: In this study we tested the reproducibility for torque measurements of the shoulder musculature in subjects with spinal cord injury (SCI) on an isokinetic dynamometer. Ten subjects with motor and sensory complete SCI (ASIA A) were studied. The subjects were asked to produce maximal torque for flexion/extension in the elbow, adduction/abduction and internal/external rotation in the shoulder. They were recruited four times – twice by two investigators separately – on which occasions three contraction modes…(concentric, eccentric and isometric) were tested. The intra class correlations of the shoulder isometric strength were the highest (range: 0.71–0.88). The smallest real differences were lower for the shoulder (range: 5.5– 21.4 Nm) in comparison to the elbow measurements (range: 17.3–38.4 Nm) as were the coefficients of variation, 4.4–19.4% and 9.0–21.7%, respetively. This implies that measurements in the elbow were less reproducible than those in the shoulder. The coefficients of variation were higher for the inter- than the intra-tester measurements. This study demonstrates that among the muscles tested the most reproducible strength was obtained during isometric effort of shoulder rotators when these were performed by the same experimenter.
Abstract: Warm-up and stretching exercises constitute an essential part of physical preparation before any athletic event. The aim of this study was to examine the acute effect of static and dynamic stretching exercises on maximal isokinetic torque of knee extensor and flexor muscles. Thirty-two (n=32) physical education students aged 19–22 years were asked to perform three different protocols consisting of A) warm-up, B) warm-up and static stretching and C) warm-up and dynamic stretching exercises, on three…non-consecutive days. Each treatment was followed by measurements of knee extensor and flexor muscles maximal concentric torque on an isokinetic dynamometer at 60 and 180°/s. ANOVA for repeated-measures revealed significant differences in maximal torque following the different protocols. Tukey's post hoc tests showed a reduced torque for knee extensor p<0.01) and knee flexor muscles (p<0.01) at both velocities when static stretching exercises preceded the test. These findings indicate the negative influence of the static stretching exercises on maximal isokinetic torque production, while dynamic stretching approach does not seem to have any inhibitory effect.