Isokinetics and Exercise Science - Volume 29, 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: Squats are considered one of the main exercises for the lower limbs and are used in resistance training under different contexts, including rehabilitation and sports performance. OBJECTIVE: To compare the EMG activity of different muscles in back squat and lunge exercises in trained women. METHODS: Ten healthy women experienced in resistance training performed back squat and lunge exercises on a Smith machine (total work: 70% of 1RM, 1 set, 10 repetitions and 2-s/2-s of execution speed) with an interval of 20-min between exercises. Both exercises were standardized in relation to the trunk…inclination and were performed with an erect trunk parallel to the cursor of the guided bar. RESULTS: The EMG activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM) were analyzed. There were no significant differences in the EMG activity of the VM, VL, and BF muscles between the back squat and lunge exercises (P > 0.05); however, GM activation was greater during the lunge exercise (effect size = 1.15; P = 0.001). CONCLUSIONS: Lunges were more effective in recruiting the GM when compared to back squats. However, both exercises can be recommended when the goal is knee extensor and flexor muscle activity.
Abstract: BACKGROUND: Repetitive stretch-shortening cycle exercises generate high rates of mechanical work and consequently induce substantial muscular fatigue related to delayed neuromuscular functions. OBJECTIVE: To investigate the neuromuscular impairment after high-intensity exercise protocols involving different gravity loads in stretch-shortening cycle – running (RUN) and vertical jumps (VJ). METHODS: Twenty-two healthy men, divided into two groups, VJ and RUN participated in this study. The individuals performed a training session involving six bouts of 30 s of VJ or RUN. The isokinetic PM (PM) of the knee extensors and flexor muscles, rate of perceived exertion and…delayed onset muscle soreness (DOMS) were evaluated at pre, post, 24 h and 48 h post-training. RESULTS: The concentric and eccentric PM of the extensor in the RUN group was reduced until 24 h, while in the VJ a decrement was observed until 48 h. Following running, the PM of the flexors decreased until 48 h, while for VJ there was an eccentric PM decrement at 48 h. The DOMS increased at the anterior thigh and only after VJ training for 48 h. CONCLUSION: Acute and delayed neuromuscular impairment may be observed after both exercise regimens, but high-intensity training using vertical jumps seems to induce a more pronounced impairment than running.
Abstract: BACKGROUND: More practical and less fatiguing strategies have been developed to accurately predict the one-repetition maximum (1RM). OBJETIVE: To compare the accuracy of the estimation of the free-weight bench press 1RM between six velocity-based 1RM prediction methods. METHODS: Sixteen men performed an incremental loading test until 1RM on two separate occasions. The first session served to determine the minimal velocity threshold (MVT). The second session was used to determine the validity of the six 1RM prediction methods based on 2 repetition criteria (fastest or average velocity) and 3 MVTs (general MVT of 0.17…m⋅ s - 1 , individual MVT of the preliminary session, and individual MVT of the validity session). Five loads (≈ 2540557085% of 1RM) were used to assess the individualized load-velocity relationships. RESULTS: The absolute difference between the actual and predicted 1RM were low (range = 2.7–3.7%) and did not reveal a significant main effect for repetition criterion (P = 0.402), MVT (P = 0.173) or their two-way interaction (P = 0.354). Furthermore, all 1RM prediction methods accurately estimated bench press 1RM (P ⩾ 0.556; ES ⩽ 0.02; r ⩾ 0.99). CONCLUSIONS: The individualized load-velocity relationship provides an accurate prediction of the 1RM during the free-weight bench press exercise, while the repetition criteria and MVT do not appear to meaningfully affect the prediction accuracy.
Abstract: BACKGROUND: The difference between isokinetic eccentric to concentric strength ratios at high and low velocities (DEC) is a powerful tool for identifying submaximal effort in other muscle groups but its efficiency in terms of the wrist extensors (WE) and flexors (WF) isokinetic effort has hitherto not been studied. OBJECTIVE: The objective of the present study is to examine the usefulness of the DEC for identifying suboptimal wrist extensor and flexor isokinetic efforts. METHODS: Twenty healthy male volunteers aged 20–40 years (28.5 ± 3.2) were recruited. Participants were instructed to exert…maximal and feigned efforts, using a range of motion of 20 ∘ in concentric (C) and eccentric (E) WE and WF modes at two velocities: 10 and 40 ∘ /s. E/C ratios (E/CR) where then calculated and finally DEC by subtracting low velocity E/CR from high velocity ones. RESULTS: Feigned maximal effort DEC values were significantly higher than their maximal effort counterparts, both for WF and WE. For both actions, a DEC cutoff level to detect submaximal effort could be defined. The sensitivity of the DEC was 71.43% and 62.5% for WE ad WF respectively. The specificity was 100% in both cases. CONCLUSION: The DEC may be a valuable parameter for detecting feigned maximal WF and WE isokinetic effort in healthy adults.
Abstract: BACKGROUND: Different methods of treatment for preventing knee injuries, enhancing knee strength and minimising post-injury risks have been explored. Among these methods, Kinesio tape (KT) and knee braces (KB) are commonly used. OBJECTIVE : To investigate the acute effects of KT and KB on isokinetic knee strength parameters. METHODS: A total of 15 healthy sedentary male subjects voluntarily participated in the study. Concentric isokinetic knee extension (EX) and flexion (FLX) strength were measured at three sessions: 1. Baseline 2. with KT (’KT’) 3. with KB (’KB’). Tests were performed at 60, 180 and 240…∘ /s. Peak moment (PM), Hamstring/Quadriceps ratio (HQR), and joint angle at peak moment (JAPM) were measured. RESULTS: ‘KT’ and ‘KB’ were associated with increase in PM EX , PM FLX , HQR at 60 and 240 ∘ /s (p < 0.05) and increased JAPM EX . No significant difference was observed at 180 ∘ /s (p > 0.05). CONCLUSION: In healthy individuals, ‘I’ shape KT and KB positively affect EX and FLX strengths and HQR, especially at low angular velocity.
Keywords: Strength imbalance, acceleration time, isokinetic, H/Q ratio
Abstract: BACKGROUND: Knee osteoarthritis (KOA) is one of the most common chronic diseases impacting millions of elderly people. OBJECTIVES: The study compared the effects of two intensities of partial blood flow restriction (BFR) with low-intensity resistance training on quadriceps strength and cross-sectional area (CSA), and pain in people with knee osteoarthritis (PwKOA). METHODS: Thirty-five PwKOA, aged 50–65, participated. Quadriceps CSA was measured by ultrasonography, quadriceps strength – by isokinetic dynamometry and pain by VAS. These outcome variables were obtained at the beginning of the study and re-evaluated eight weeks after the intervention.…RESULTS: An interaction effect was present for quadriceps CSA (P = 0.042) and quadriceps strength (P = 0.006), showing that using 70% of total occlusion pressure with 30% 1RM had a more significant effect. Knee pain improved significantly through the main effect of BFR (P < 0.001), and low-intensity resistance training (P = 0.011). Pain improved more at 70% of total occlusion pressure, with 30% of 1RM (2.5 ± 1.06) than 50% total occlusion pressure with 10% of 1RM (5.77 ± 1.46). CONCLUSION: A combination of 70% of total occlusion pressure with 30% 1RM could be beneficial in PwKOA in improving pain, and increasing the quadriceps strength. The changes in the quadriceps strength could be a predictor for knee pain.
Abstract: BACKGROUND: The effects of contemporary cryo-compression devices on function are limited compared to traditional applications of cooling. Development of cooling protocols are warranted. OBJECTIVE: To investigate the effects of three different cryo-compressive modalities applied at the knee on the isokinetic strength of the quadriceps over a re-warming period. METHODS: Eleven healthy male participants took part (23 ± 14 years; 78.3 ± 14.5 Kg; 180 ± 9.5 cm) randomly assigned to receive all modalities (Game Ready ® (GR), Swellaway ®…(SA), Wetted Ice (WI)) applied for 15-min, separated by 1-week. Skin surface temperature (T s k ) via thermography and the concentric peak moment (PM) of the quadriceps at 60 and 180 ∘ /s were collected pre-, immediately-post and at 20-min post-intervention. RESULTS: Significant reductions occurred in T s k across all timepoints for all modalities (p = ⩽ 0.05). Significant reductions in PM for WI were noted across all timepoints and PM for GR and SA immediately-post (p = ⩽ 0.05) only. CONCLUSION: Precaution for immediately returning to sport following cryotherapy is required and influenced by type of cooling on muscle strength responses. Alternate targeted treatment modalities to minimise deferred deleterious effects on muscle strength may be considered. Research into length of application, periodisation and location is warranted for the development of such contemporary cryo-compressive modalities in applied practice.
Keywords: Cooling, knee, isokinetic dynamometry, performance, sport injury
Abstract: BACKGROUND: The effects of whole-body vibration training (WBVT) with same frequency and different amplitudes on bone mineral density (BMD) in the elderly is not reported. OBJECTIVE: To compare the effect of 45-Hz WBVT with different amplitudes on the BMD in elderly women. METHODS: Age-, height-, and weight-matched patients were assigned to a low-amplitude group (n = 19, amplitude of 2 mm), medium-amplitude group (n = 18, amplitude of 3 mm), high-amplitude group (n = 19, amplitude 4 mm),…and control group (n = 20). The WBVT was conducted for 24 weeks in the three amplitude groups. The BMD at lumbar vertebrae L 2 - 4 and the proximal femur was measured at 0 and 24 weeks. RESULTS: The BMD at lumbar vertebrae L 2 - 4 was higher in the high-amplitude group than in the low-amplitude and middle-amplitude groups, and the BMD of the greater trochanter was significantly higher than that in the low-amplitude group (p < 0.05). The BMD of the greater trochanter was significantly higher in the middle- than low-amplitude group (p < 0.05). CONCLUSION: A higher amplitude should be considered when WBVT is performed in elderly patients to increase bone density and prevent osteoporosis.
Keywords: Whole-body vibration training, amplitude, frequency, elderly women, bone mineral density
Abstract: BACKGROUND: Adolescent Idiopathic Scoliosis (AIS) requires complex medical care because of multiple consequences especially on daily activities. Muscular involvement is part of the problem and may be treatable. OBJECTIVE: To analyze trunk muscle strength using an isokinetic dynamometer in female adolescents with AIS one year after orthopedic treatment by brace and compare the findings to a matched group of an asymptomatic cohort. METHODS: The trunk flexors and extensors strength was measured using an isokinetic dynamometer at 60, 90 and 120 ∘ /s. Peak Moment (PM), Mean Power (MP) and…the flexor/extensor ratio in 100 patients aged 14 to 18 years old were compared to a control group (N = 32) of asymptomatic age-matched females. In the AIS group, correlation analyses were computed to search for contributing factors to isokinetic performances, including morphological characteristics of patients, as well as clinical and radiological characteristics of the scoliosis. RESULTS: The trunk flexors in the AIS group were significantly but moderately (15%) weaker across speeds compared to their control counterparts at all speeds. No parallel weakness was noted for the extensors. While the MP of AIS patients was significantly weaker than that of the controls, 33% for flexors and by 31% for extensors, no significant differences were observed for the F/E ratios. The correlational analyses has indicated that weight and BMI were contributing factors at all speeds. CONCLUSION: Adolescents with AIS had weaker trunk extensors and mostly flexors compared to healthy females. Within this AIS population, weight and BMI seem to have a negative impact on muscular performances, whereas clinical and radiological characteristics of the scoliosis do not seem to contribute.
Abstract: BACKGROUND: This study examined the differences in physical and anthropometric traits between specific playing positions (i.e., forwards: front row, second row, back row; backs: half backs, centers, wings/fullbacks) in amateur rugby players and analyzed the magnitude of correlations among jump, sprint, and strength measures in forwards and backs. METHOD: Sixty-four male rugby players were assessed in anthropometrics, a variety of vertical jumps, 10- and 30-m sprint, and strength tests (i.e., squat and bench press). RESULTS: Front row forwards (F FR ) demonstrated significantly higher body mass (BM) than second row…(F SR ) and back row (F BR ) (107.4 ± 12.8, 99.1 ± 9.9 and 91.6 ± 7.6 kg respectively; p < 0.001). F FR showed greater absolute strength in bench press and squat, although no differences were found in relative strength. Regarding the differences in jump performance, F BR and F SR showed significantly (p < 0.05) and significant to non-significant (p = 0.042–0.078, ES = 0.90–1.55) higher jumps in all tasks compared to F FR . Moreover, F BR demonstrated lower sprint times and greater maximum sprinting speed (MSS) than F FR (p < 0.01). For the backs, centers (B CEN ) were significantly heavier (p < 0.05) and exhibited a non-significantly moderate larger sprint momentum (p = 0.068, ES = 0.75) compared to half backs (B HB ). MSS values were small to moderately greater in favor of wings/fullbacks [B WFB ] (p = 0.188–0.059, ES = 0.50–0.71). Finally, statistically significant correlations were found between drop jump (flight time) and jump height across all jump tasks, sprint times and speed for both forwards (r = 0.541 to 0.996, p < 0.001) and backs (r = 0.422 to 0.995, p < 0.05). CONCLUSIONS: In conclusion, F FR demonstrated significant, small to very large differences, when compared to their specific peers, whereas the backs were more similar. Additionally, our results indicated moderate to strong associations between explosive tasks such as sprinting and jumping in both playing positions.
Keywords: Physical performance, rugby union, testing, training