Isokinetics and Exercise Science - Volume 28, issue 1
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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: Many different squatting techniques have been recommended, but few studies tried to identify how different muscle groups contributed to this movement in each technique. OBJECTIVE: To compare the electromyographic activation (EMG) of the thigh, hip and trunk muscles during maximal voluntary isometric contractions in the back and front squat performed in different degrees of knee flexion, while also comparing the levels of force produced during different ranges of motion. METHODS: Ten healthy men (30.7 ± 7.9 years), regularly practicing strength training, performed maximal isometric actions during back and front squats,…at 60 ∘ , 90 ∘ and 120 ∘ degrees of knee flexion. The electromyographic activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, gluteus maximus, and erector spinae was recorded. RESULTS: At 60 ∘ a lower EMG activation in both squats was observed although this depth showed the highest levels of maximal voluntary isometric strength. Increasing knee flexion to 120 ∘ did not result in greater muscle activation. Only at 90 ∘ there was no significant difference in EMG activity between the front and back squat. CONCLUSIONS: A greater squat depth did promote a decrease in EMG activity When executed in isometric contraction, parallel squatting offers better ratio of force X recruitment of primary motor muscles. Therefore, this amplitude can be used in training or rehabilitation strategies, both in frontal and posterior variations (with higher level of strength), observed the most convenient option for the practitioner.
Abstract: BACKGROUND: Individuals may suffer from repeated sprints-induced muscle damage, which could lead to a prolonged recovery period, thereby influencing subsequent closely-scheduled training or competitions. OBJECTIVE: To examine whether an initial muscle-damaging sprint exercise could confer a protective effect against muscle damage induced by the subsequent identical exercise performed four days later. METHODS: Fourteen physically-active men completed two sprinting bouts (15 sets of 30-m maximal sprints) with 4 days apart. Before, 24, 48, and 72 hours after both bouts, muscle damage markers were measured. In addition, time trial, along with the peak heart rate (HR) and…rating of perceived exertion (RPE) during each sprint set were also recorded. RESULTS: Comparing to the initial bout, less muscle soreness and faster recoveries of the knee flexion eccentric peak torque and angle of peak torque were found following the second bout. In addition, the time trial and HR for each sprint set were not different between the two bouts, but the average RPE was less during the second bout (p = 0.013). CONCLUSIONS: The protective effect from the exposure to the initial sprint was evident. Thus, repeated exposures to the sport-specific sprints can positively influence the symptoms of muscle damage without influencing the sprinting performance.
Abstract: BACKGROUND: The abdominal draw-in maneuver (ADIM) has been suggested to increase trunk stabilizing muscle activity; however, no study has identified the effects of the ADIM on trunk muscles and trunk movements during lifting and lowering (L & L) tasks. OBJECTIVE: We examined the effects of the ADIM on transversus abdominis (TrA) thickness during standing, the activity of the TrA, internal oblique (IO) and multifidus (MF), and the kinematics of the lumbo-pelvic-hip complex during L & L tasks. METHODS: Fifteen male participants practiced expirations without and with the ADIM using ultrasound biofeedback. After…training for each condition, the participants performed expirations with and without the ADIM in the standing position and during L & L tasks. TrA thickness during the standing position and muscular activities (EMG) of the bilateral TrA/IO and MF, and the peak angle of the lumbo-pelvic-hip complex in the sagittal plane during L & L tasks were measured. RESULTS: TrA thickness during standing was increased with expiration with ADIM compared to that without the ADIM (p < 0.05). When performing expiration with the ADIM, increased activity of the TrA/IO and MF was observed by EMG, as well as peak pelvic anterior tilt and hip flexion with decreased peak lumbar flexion during L & L tasks (p < 0.05). CONCLUSIONS: The ADIM could be an effective strategy to improve trunk stability and reduce lumbar flexion during L & L tasks.
Keywords: Abdominal draw-in maneuver, electromyography, manual material handling, trunk stability
Abstract: BACKGROUND: Blood flow restriction (BFR) exercise benefits muscle performance. However, there is limited research on vascular dysfunction, particularly using involuntary muscle contraction modality plus BFR. OBJECTIVE: To investigate the acute and accumulative effects of whole body vibration (WBV) with BFR on vascular dysfunction, as evaluated by von Willebrand factor (vWF) levels. METHODS: Physically inactive men were randomly assigned to the WBV + BFR group (n = 8) and the WBV group (n = 8). Participants in the WBV group were…subjected to 10 sets of internment WBV exercise 20 min/day, 3 days/week for 8 weeks. Participants in the WBV + BFR group received the same WBV treatment, but the proximal portion of the thighs was compressed by inflatable cuffs. RESULTS: The increase in vWF levels in the acute WBV + BFR group was significantly higher (P < 0.05) by 17.2% than that in the WBV group. However, vWF levels exhibited equal decrements in the two groups after training (P > 0.05). CONCLUSIONS : WBV + BFR may acutely cause vascular dysfunction potential to a greater extent than WBV alone. However, regular WBV and WBV + BFR training may produce an equally beneficial effect on vascular function in a previously untrained population.
Abstract: BACKGROUND: Strengthening exercises help improve physical function and muscle strength in knee osteoarthritis (OA). However, optimal exercise programmes for treating knee OA remain unclear. OBJECTIVE : To compare efficacy of isometric exercises performed at different angles and isokinetic exercises in patients with knee OA. METHODS: Patients were randomly divided into two groups. For four weeks, Group I (n = 15) and II (n = 17) patients with grade 2–4 performed isokinetic and isometric exercises at several different angles, respectively. Flexor and extensor knee muscle…strengths were measured. Pain and physical function were assessed using VAS, WOMAC, the Lequesne Index and SF-36. All parameters were recorded at three time points: baseline (T0), after treatment (T1) and at 10-week follow-up (T2). RESULTS: VAS on movement, WOMAC, Leuqesne and SF-36 physical scores improved from T0 to T2 within each group, but Grade 3 and Grade 4 patients in the Group I showed better results compared with Group II at T2. Isokinetic exercise yielded higher extensor PM values than its isometric counterpart at T2 (P < 0.05) at 180 ∘ /s for Grade 2 and Grade 3 patients. CONCLUSIONS: Both isokinetic and isometric exercises were effective in the treatment of knee OA of all grades in terms of pain reduction and functional improvements. However, isokinetic exercise produced longer lasting effects than isometric exercise.
Abstract: BACKGROUND: Adolescence is characterized by a rapid and erratic growth period. Many factors completely change in growth period up to 20 years of age, with a very slight alteration during the later years of life. Bioelectric impedance analyzers (BIA) are used in estimating the total and segmental body composition compartments. OBJECTIVE: To determine the validity of different BIAs for young male athletes. METHODS: Sixty-one young male athletes (basketball, football, handball, swimming, and skiing) participated in the study. The validity of Tanita 401A (TANITA), Jawon Segmental Body Composition Analysers model AVIS 333 Plus (AVIS), and…Biodynamics Model 310e (BIODYNAMICS) was tested by Bland & Altman analysis and heteroscedasticity, providing the gold standard criterion method, hydrostatic weighing (HW) for body density (D b ), body fat percentage (%BF), and lean body mass (LBM). RESULTS: BIA models used for predicting body composition, except for %BF of TANITA, are valid and in accord with HW for young male athletes. TANITA had significantly lower %BF (5.75 ± 2.95%) and higher LBM (62.12 ± 7.53 kg), compared to HW (10.79 ± 4.17 %BF and 58.80 ± 7.38 kg LBM). Percent BF of BIODYNAMICS and AVIS results were significantly higher (2.04% and 3.3% respectively) than %BF of HW. CONCLUSION: Prediction of body composition compartments of young male athletes using BIA models is valid except for %BF by TANITA. LBM values of HW and BIA models can be used interchangeably. However, these BIA softwares do not have specific options concerning athletic status for the growing age and sex group to clarify population specificity in adolescent male athletes. Therefore, using the same BIA model is recommendable in following up training regimen and nutritional status, in order to avoid underestimating or overestimating the body composition compartments.
Keywords: Validity, bioelectric impedance analysis, body composition, hydrostatic weighing, young male athletes
Abstract: BACKGROUND: Rate of torque development (RTD) could serve as a useful index for the readiness and fatigue of soccer players. OBJECTIVE: The identification of RTDs time-course changes after a Loughborough Intermittent Shuttle Test (LIST), the effect of bovine colostrum (BC) supplementation on RTD changes, and to explore the relationships between RTD and selected muscle damage blood markers. METHODS: Twenty-two soccer players completed a pre-supplementation LIST (LIST1). Subsequently, subjects were randomly divided into whey protein (WP, N = 8) and bovine colostrum groups (BC, N =…10) receiving 3.2 g of WP or BC for 6 weeks. Participants repeated LIST (LIST2) after supplementation. Hematological markers, CK, CRP, IL-6 and RTD at 20–250 ms were determined pre- and 2–72 h post-LISTs. RESULTS: RTD declined after LIST1 (- 48.1 ± 22.1%–- 10.7 ± 8.2%). Late RTDs showed lower reductions compared to early RTDs’. Supplementation of WP or BC attenuated the decline of late RTDs until 72 hours post LIST (p < 0.05; η 2 : 0.236–0.287). BC group achieved lower reductions of RTDs after LIST2 compared to WP group. The percent changes of RTDs were correlated with changes of biochemical markers post-LIST. CONCLUSIONS: LIST induces a significant decline in RTD of soccer players. BC could be a promising supplement alleviating the impairment of RTD after a soccer game.
Keywords: Rate of torque development, rate of force development, soccer, bovine colostrum, recovery, muscle damage, inflammation
Abstract: BACKGROUND: The ergogenic effect of ischemic preconditioning (IPC) has been widely approved, but the mechanisms underlying the beneficial effects are still not fully clarified. OBJECTIVE: The aim of this study was to examine the effects of IPC on human isokinetic muscular function and hemodynamics during exercise. METHODS: In a counterbalanced, crossover study, 14 healthy non-athletic males (26.0 ± 3.5 years) performed isokinetic muscle strength and endurance tests of the dominant leg on an isokinetic dynamometer, preceded by either IPC on bilateral thighs (3 × 5-min compression/5-min reperfusion…cycles at 50 mmHg greater than the participant’s systolic blood pressure) or SHAM (10 mmHg) intervention. Participants underwent strength testing by performing three maximum isokinetic knee extensions and flexions at the angular velocities of 30⋅ ∘ s - 1 , 150⋅ ∘ s - 1 , and 270⋅ ∘ s - 1 . An endurance test was also conducted over 30 repetitions at 180 ∘ /s. Hemodynamics of the vastus lateralis muscle were monitored before and after the interventions and during exercise tests by near-infrared spectrometer (NIRS). RESULTS: Resting total hemoglobin significantly increased after IPC (p = 0.048, d = 0.15). During the endurance testing, the oxygen uptake was significantly improved after IPC as shown by the change of oxygenated hemoglobin, deoxygenated hemoglobin, and oxygen saturation, at small to moderate effect size. However, both muscular strength and endurance were found unchanged. CONCLUSION: IPC improves the local oxygenation status without altering maximal muscle strength and endurance in young non-athletic males.
Abstract: BACKGROUND: The introduction of high-intensity functional training (HIFT) in sport gave rise to the exploration of determinants of success in sport. OBJECTIVE: To analyze whether asymmetry inter-limb is related to reduction in physical performance in amateur HIFT athletes. METHODS: Twenty-four HIFT amateur athletes, 11 women and 13 men, participated in the study. All volunteers performed three different jump tests: the squat jump (SJ), the countermovement jump (CMJ), performed unilaterally and bilaterally, and the 20-m sprint test. RESULTS: An overall asymmetry inter-limb of 9.5% in women and 9.3% men was not…associated with any of the outcome measures. There were no significant differences in both genders between asymmetry, sprint, lower limbs’ muscle power (LLMP), SJ, CMJ and stretch-shortening cycle (SSC) (p > 0.05). CONCLUSIONS: Asymmetry inter-limb in CMJ does not seem to affect the performance of amateur athletes of HIFT. Thus, when the target is to maximise the performance, in the training programme, coaches should prioritise tasks that increase vertical jump capacity at the detriment of the unilateral jump.
Keywords: Inter-limb differences, jumping, performance reduction, sprint, muscle power
Abstract: BACKGROUND: No studies so far have investigated the effectiveness of the short-term intervention on the capacity of the ISP during throwing motion in baseball player with throwing disorder. OBJECTIVE: To investigate the effectiveness of short-term intervention on ISP during throwing motion and of physical examination in baseball player with throwing disorder. METHODS: Twenty-seven male baseball players with throwing disorder were hospitalized for 1 week and received physical therapy for 1 hour a day. In the pre- and post-hospitalized period, participants were evaluated using physical examinations (Hara test) and ISP and posterior deltoid muscle activity during…throwing motion. RESULTS: The ISP during the late-cocking phase and follow-through phase at the time of hospital discharge were significantly greater than that at the hospital admission (P < 0.05). The effect sizes revealed large effects for follow through phase (r = - 0.60). The positive rate of the Hara test decreased significantly in all examination items except scapula-spine distance, subacromial impingement test, and hyper-external rotation test. CONCLUSIONS: The ISP in throwing motion is important to the stability of the glenohumeral joint during follow-through phase. Our results indicated that the improvements in the physical examination reflected favorably on the ISP during the throwing motion.