Isokinetics and Exercise Science - Volume 23, issue 2
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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: Peak torque (PT) is considered the most representative parameter of muscle performance in isokinetic dynamometry while other computable parameters such as mean peak torque (MPT), maximal work (maxW) and mean work (meanW) are generally neglected. OBJECTIVES: This cross-sectional study reassessed whether PT is the only necessary parameter in isokinetic testing and weighed the contribution of each variable to muscle performance. METHODS: Thirty apparently healthy volunteers underwent isokinetic assessment of the ankle dorsiflexors of both legs at 45 and 90°/s. Bivariate relationships and multivariate associations between PT, MPT, maxW and meanW were examined employing…Pearson's analysis and principal component analysis (PCA), respectively. RESULTS: At both velocities, Pearson's coefficients were very high between PT and MPT as well as between maxW and meanW (r > 0.9; p< 0.0001) and fair-to-good (r= 0.65-0.73; p < 0.0001) between torque and work measures. At 90°/s the PT and MPT mostly contributed to muscle performance while at 45°/s, MPT and meanW exhibited the highest component loadings, whereas PT performed poorly. CONCLUSIONS: Isokinetic variables contributed with different loadings to muscle performance of ankle dorsiflexors, depending on the angular velocity employed. In particular, work measures may usefully complement the conventional PT-only analysis, especially in rehabilitative settings where low speeds are recommended.
Abstract: BACKGROUND: Studies in adults have shown benefits in endurance performance by combining aerobic and resistance training. However, whether concurrent strength and aerobic training is beneficial in children remains to be identified. OBJECTIVE: The purpose of this study was to examine the effect of a 10 week aerobic training programme compared to a concurrent aerobic and resistance training programme on leg strength, fat free mass (%FFM), forced vital capacity (FVC) and 3 km-running performance in youth athletes. METHODS: Twelve trained youth competitive runners were pair matched into either an aerobic (AT) or concurrent…(CT) training group based on maturational status and initial 3 km-running performance. The aerobic training consisted of continuous and interval training twice weekly for all participants. The CT group additionally performed resistance training twice weekly. RESULTS: There were no statistically significant differences between groups for any parameters pre-training. Significant correlations were found between 3 km-running performance and leg strength, FVC and %FFM. No significant interaction or main effects for any of the key outcome variables were found. There was however, a 38 s group difference in 3 km-running time post intervention indicating some interference of the resistance training on ERP. CONCLUSIONS: These findings suggest that concurrent endurance and resistance training should be avoided in trained youth athletes.
Keywords: Training, 3-km running, body composition, lung function, isokinetic strength
Abstract: BACKGROUND: Fatigue due to running or local muscle exhaustion is a causative factor for running injuries. Standardized local muscle fatigue can be produced and assessed with isokinetic devices. OBJECTIVE: To examine the absolute and relative reproducibility of local muscle fatigue of the ankle dorsiflexors (DF) and plantar flexors (PF). METHODS: Using a test-retest design, 29 male runners (height: 181.4 ± 4.7 cm, mass: 79.4 ± 9.3 kg, age: 26.6 ± 4.3 years) were twice assessed, isometrically and isokinetically, at 60°/s. Reproducibility was determined by an intraclass correlation coefficient (ICC) and the…Bland-Altmann method. RESULTS: For the isometric test, the ICC values ranged from 0.90-0.99, whereas for the isokinetic fatigue protocol and index, they ranged from 0.87-0.97 and 0.76-0.96, respectively. Absolute reproducibility of the PM in the isometric test was 3.1% and 6.4%, for the DF and PF, respectively. The mean of the PM in the isokinetic fatigue protocol was 6.2% and 10.7% and in the fatigue index 12.3% and 21.8%, respectively. CONCLUSION: Using the protocol and instrument described in this paper, local muscle fatigue of the ankle DF and PF may be reproducibly measured.
Abstract: BACKGROUND: Little is known about the comparative relationships between knee muscles strength and anaerobic power in weightlifters, basketball and soccer players, popular sports that rely on lower extremity muscles strength. METHODS: Ten weightlifters, 12 basketball and 19 soccer players participated in the study. Concentric peak torque of hamstring (H) and quadriceps (Q) of the dominant (D) and non-dominant leg (ND) was evaluated at 60 and 240°/s. Subjects also performed Wingate Anaerobic Test (WAnT) 48 h after isokinetic measurements. RESULTS: Normalized peak moment of the hamstring (NPMh) of D in soccer players was significantly greater…than in basketball players and weightlifters at 60 and 240°/s. At 60°/s, weightlifters presented a greater NPMq when compared to soccer players in D. Significant correlations were observed between NPMq of both legs and peak and mean power at 60 and 240°/s in basketball. In soccer, significant correlations were found between the bilateral NPM of both muscles and the peak and mean power at 240°/s. CONCLUSIONS: Knee flexion strength plays a more decisive role in soccer due to the fast movement pattern while knee extension strength is more important in basketball and weightlifting due to vertical movement patterns.
Keywords: Concentric strength, dominant and non-dominant leg, Wingate test
Abstract: BACKGROUND: Hip belt squats are believed to have been introduced in 1970. By removing the load from the shoulders and upper trapezius, the hip belt squat places emphasis on the legs with less load on the spine. No peer-reviewed research exists on the muscle recruitment patterns of a hip belt squat, or how it compares in muscle activation to other squatting activities. OBJECTIVE: The purpose of the study was to determine lower extremity muscle activation in a hip belt squat (SquatMax = MD) in comparison with a barbell back squat. METHODS: Thirteen participants performed…four repetitions of an 8-RM squat using three different techniques: hip belt squat without a band, hip belt squat with a band, and barbell back squat. Electromyographic data were collected from six muscles: quadriceps, biceps femoris, hip adductors, hip abductors, gluteus maximus, and gastrocnemius. RESULTS: ANOVA revealed no significant difference in muscle activity between devices. The only muscle group statistically different between genders was the gastrocnemius (p = 0.04). Hip adductor activity was lowest and hip abductor activity was highest when performing a hip belt squat with the band for both genders. Likewise, the adductor to hamstring ratio was lowest with the hip belt squat. CONCLUSIONS: Given the lack of significant difference in the muscle activity between the squat techniques, one needs to look at other attributes to determine both the scientific and, consequently, the practical value. Given the placement of the belt around the pelvis, one positive attribute for the hip belt squat is the ability to unload the shoulders and spine. Another positive attribute for the hip belt squat is the higher hip abductor to adductor ratio. This could be very important for injury prevention and patella tracking. While the back squat has slightly higher hamstring recruitment, which is important in ACL injury prevention, the hip belt squat may address this by offsetting the free weight with the use of an additional band. If a free weight hip belt squat device is available, it may be a better alternative to the traditional barbell squat technique.
Keywords: Back squat, belt squat, muscle recruitment
Abstract: BACKGROUND: Studies have shown that reciprocal exercise using a pre-activation of antagonist muscles may increase the agonist neuromuscular performance. OBJECTIVE: To compare the efficiency of two modalities of resistance training (with and without antagonist muscle pre-activation) during a six week program on knee extension neuromuscular performance of healthy men. METHODS: Forty-nine men were randomly assigned into two groups: 1) reciprocal training: REC - one concentric knee flexion immediately followed by one concentric knee extension, and 2) control: CON - one concentric knee extension exercise, without pre-activation. Both training modes were characterized by three…sets of 10 repetitions at 60°/s, 2 days/week. Knee extensor peak moment (PM), load range (LR), electromyographic activity (EMG) of the vastus medialis (VM), rectus femoris (RF), and biceps femoris (BF) co-activation were assessed pre and post 6 weeks of training. A 2 × 2 mixed factor ANOVA was applied to evaluate differences between variables. RESULTS: Significant increases were found for PM between pre and post-evaluations for both groups. In relation to VM and RF activation, co-activation (BF/VM and BF/RF) and LR, no significant differences between groups and moments were found. CONCLUSION: In view of the results further research is indicated in order to examine the utility of longer programs in positively affecting antagonist muscle co-activation as well as in elucidating its clinical effects in individuals with musculoskeletal dysfunction.
Abstract: BACKGROUND: Inappropriate motor patterns such as incorrect roll out of the pelvis should be avoided during stabilization exercise in patients or also in healthy individuals. OBJECTIVE: To investigate the effects of visual feedback (VF) on internal oblique (IO), external oblique (EO), multifidus (MF), and erector spinae (ES) and the kinematics of the trunk and pelvis between healthy and chronic low back pain (CLBP) groups during arm and leg lift in quadruped (ALLQ) position. METHODS: Ten apparently healthy subjects and 10 patients with CLBP performed ALLQ position with and without VF while being monitored…using sEMG and a motion analysis system. RESULTS: In comparison to non-VF condition, a VF was associated with a significant increase in the EMG activity of both IOs, decrease in MF and decrease in right ES in the CLBP. Right ES activity significantly increased in the CLBP when VF was not present. Axial rotation of the pelvis decreased in the healthy group with VF. CONCLUSION: VF applied through wireless smart-phone mirroring system has a selective positive effect on trunk muscles and pelvic movement and may be beneficial for CLBP patients. Further research is necessary to explore this novel approach to muscle and segment action.
Keywords: EMG, movement dysfunction, stabilization
Abstract: BACKGROUND: The PowerCal device purports to effectively estimate power output (PO) using an algorithm computed from the HR response recorded during exercise. OBJECTIVE: To assess the reproducibility and validity of PO estimation using the PowerCal during sprints. METHODS: Ten well-trained male cyclists (maximal oxygen uptake -62.7 ± 5.9 ml ⋅ kg-1 ⋅ min-1 ) performed four separate experimental trials over a two-week period. Cyclists completed an incremental exercise test until volitional exhaustion followed by three maximal sprint sessions on separate days. Each sprint session consisted of 3 repeated maximal-effort sprints (15, 30, and…45 s) formatted with an effort/recovery duration ratio of 1:5. RESULTS: Peak power output (PPO) and mean power output (MPO) of the PowerCal showed high within-subject variation (6.7 to 21.5%) and low to high intra-class coefficient of correlation (ICC = 0.39 to 0.85). Furthermore, the PPO from PowerCal was underestimated by 6.6 to 13.9% and the MPO by 14.9 to 27.6% when compared to the Velotron. Furthermore, the data exhibited high bias (32 W to 129 W) and large confidence limits (-236 to 315 W) between the PO derived from the Powercal and the Velotron. CONCLUSION: We do not recommend competitive cyclists or sport scientists to use the PowerCal if reliable and valid PO information is required during maximal sprints.
Abstract: BACKGROUND: Practice based improvement (PBI) should be minimized in studies associated with evaluation and interpretation of tests intended for measuring cycling peak power (PP). OBJECTIVE: To assess the required number of 5-second Wingate All-out Test (5 s WAT) trials to obtain a stabilized PP in a single test session and to find out whether a single session is enough to avoid any PBI. METHODS: Twenty-four well-trained male athletes (PP: 14.2 ± 1.6 W ⋅ kg - 1 ) participated in two testing sessions separated by 5-8 days. In each session, participants performed nine 5…s WAT trials. The highest PP in the first ``n'' trials (1 ≤ n ≤ 9) was regarded as the representative PP. RESULTS: Only eight participants (≈ 33.3%) reached their real PP in the first five trials both in the first and second session. No statistically significant difference was found in the highest PP between sessions (p = 0.35, Hedge's d = -0.07, difference of 1.04%). Therefore, a single familiarization session including extensive number of short sprints seemed to be sufficient for avoiding the effect of PBI on PP. Based on comparison of mean values, sequential estimation procedure, and number of participants having performance improvement greater than the smallest worthwhile change score, ≥ 5 trials were required in both sessions to have a stabilized PP. CONCLUSIONS: Trainers and researchers should use ≥ 5 trials of 5-second sprints to assess accurate cycling PP of their athletes/participants whether they are familiarized with short cycling sprints or not.