Isokinetics and Exercise Science - Volume 27, 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 AND OBJECTIVE: Stark inter-gender differences in vertical jump performance exist. Performance-based correlates to the vertical jump are not well understood in women. METHODS: Women (n = 129) did countermovement vertical jumps as their data were collected concurrently by a Vertec and force plate; the latter provided performance-based correlates to their jumps. Multivariate regression examined the ability of the performance-based variable to serve as correlates of vertical jump height and power variances. RESULTS: Performance-based variables predicted moderate (r 2 = 0.28) and…large (r 2 = 0.74) amounts of vertical jump height and power variance respectively. Per criterion measure, peak force did not have the highest univariate correlation. CONCLUSIONS: Peak force, typically the strongest correlate to vertical jump performance in men, was not as strong a predictor of the variance in women. Instead women rely on a variety of kinetic and temporal variables to maximize their vertical jump height and power values.
Abstract: BACKGROUND: Vertical jumping capacity is important in modern soccer to gain advantage over opponent during the defensive and offensive activities. Predictors of jumping capacity in soccer players are not well studied. OBJECTIVE: The main aim of our study was to evaluate how isokinetic strength of the thigh muscles is related to jump performance. METHODS: Twenty-five (N = 25) elite soccer players volunteered to participate in the study. Thigh muscle strength (concentric for hamstrings and quadriceps, and eccentric for hamstrings only) was evaluated at 60 ∘…/sec using an isokinetic dynamometer, while jump capacity was evaluated using a bilateral force plate to measure the jump height of squat (SJ) and countermovement (CMJ) jump. Linear regression model was used to evaluate how well can isokinetic strength parameters (independent predictors) predict jumping capacity in soccer players (dependent variable). RESULTS: In a linear regression model concentric quadriceps strength has significantly explained the vertical jump height, while other parameters (hamstring concentric or eccentric strength) did not reach the significance level (p > 0.05). When left and right concentric quadriceps strength was used the model was statistically significant (F = 4.76, p = 0.02; R square 0.31), but only right concentric quadriceps strength was significant predictor (t = 2.62, p = 0.016). Strength asymmetry did not significantly influence the jump height, but was associated with lower ratio of CMJ/SJ height indicating that players without asymmetry have better jumping capacity in the terms of utilizing the stretch shortening cycle. CONCLUSIONS: Coaches should consider quadriceps strength as an important predictor of jumping capacity in top-level soccer players which is again related to sprint performance in soccer. Future studies are needed to evaluate the contributing impact of hamstring strength in this regard.
Keywords: Isokinetics, strength, asymmetry, leg power, vertical jump performance
Abstract: BACKGROUND: Small-sided games (SSG) are widely used in soccer due its potential to improve technical, tactical and physical performance. Different approaches are used to modify physical demands during SSG. Despite this, little is known about the impact of rule modifications on the internal load imposed to young soccer players. OBJECTIVE: This study aimed to compare the magnitude of the internal load imposed on young soccer players between small-sided soccer games with different amounts of goals. METHODS: Sixteen male athletes (15.7 ± 0.43 years, 64 ± 7 kg,…1.71 ± 0.05 m, 21.8 ± 1.7 kg/m 2 ) performed a SSG with one goal (SSG1 goal ) and three goals (SSG3 goal ) in a randomized order separated by 48 hours. The markers of internal load were: i) percentage of maximum heart rate (%HR) max , ii) Edward’s Training Impulse (TRIMP), and iii) performance on the repeated sprint ability (RSA) test immediately post-SSG. Paired t-test and repeated measures ANOVA were used to compare the direct (i.e. Edward’s TRIMP and HR max ) and indirect (i.e. RSA) markers of internal load between the different SSG formats. A p-value < 0.05 was set as statistically significant. RESULTS: HR max was higher in the SSG1 goal compared to the SSG3 goal (91 ± 2% vs. 89 ± 3%; p < 0.05). No difference was found in the Edward’s TRIMP (SSG1 goal : 86.4 ± 15.7 arbitrary units; SSG3 goals : 78.2 ± 12.8 arbitrary units; p = 0.15). Performance on the RSA test was worse post-SSG1 goal compared to the post-SSG3 goals (p < 0.01). SSG1 goal elicits a higher internal load than SSG3 goals . CONCLUSIONS: Therefore, the amount of goals in SSG may impact the internal load imposed on young soccer players.
Keywords: Sports, physiological monitoring, heart rate, young player, sport performance
Abstract: BACKGROUND: While interval training is considered an effective modality for improving performance, its effectiveness among athletes may be influenced by previous training experience. OBJECTIVE: To investigate whether differences in training background are reflected in the development of exercise capacity and level of muscle damage following a single bout of repeated maximal sprints after an 8-week intervention of high-intensity interval training (HIIT), sprint interval training (SIT), and endurance training (ET). METHODS: Three groups of male cyclists were studied: E1 (n = 10) included cyclists with a background in high-volume…moderate-intensity training, E2 (n = 7) comprised cyclists with low-volume high-intensity training experience, and C (n = 7) served as a control group with an identical training background as E1. During 8-week intervention HIIT, SIT, and ET were performed by cyclists in group E1 and E2, group C performed only ET. At pre- and post-intervention, cyclists performed two exercise tests: 1) incremental testing protocol (ITP) to assess maximal oxygen uptake (VO 2 max) and maximal power (Pmax); and 2) sprint interval testing protocol (SITP) to determine oxygen uptake (VO) 2 , work, and change in creatine kinase (Δ CK) and myoglobin (Δ Mb) levels. RESULTS: After intervention, VO 2 max increased in E1 and E2 group although Pmax increased only in E1. During post-intervention sprint interval testing protocol, VO 2 and work increased only in E1, whereas Δ CK and Δ Mb decreased in E1 but increased in E2. CONCLUSIONS: A history of high-volume moderate-intensity training can induce beneficial performance adaptations by reducing muscle damage and allowing greater work output. It is suggested that interval training be preceded by a longer period of high-volume training in athletes.
Abstract: BACKGROUND: Information regarding the relationship between methods for assessment of voluntary and involuntary muscle contractile properties is of importance in sport science and medicine. OBJECTIVE: To appraise the concurrent and predictive validity of isokinetic dynamometry and tensiomyography (TMG) in differently trained men and women. METHODS: Fifty men and 45 women were divided into three groups: physically inactive, physically active and athletes. Isokinetic testing was performed on knee muscles in concentric mode at 60 and 180 ∘ s while tensiomyographic measurements were obtained from the rectus and the biceps femoris muscles.…RESULTS: A small, statistically significant correlation was detected between the peak moment and tensiomyography parameters relating to contraction time and maximal displacement (Adj. R= 2 0.086, p = 0.028). CONCLUSION: In general, isokinetic dynamometry and tensiomyography are not related and represent different technologies that measure different contractile properties of muscles. A hierarchical structure of predictive validity at the level of individual variables was detected as a function of gender and training level.
Abstract: BACKGROUND: Fatigability measured and derived parameters are commonly used in research and clinical contexts to characterize performance during isokinetic fatigue protocols. The fatigability measured parameters are the best repetition, the total and the partial sums while the fatigability derived parameters are ratios and formula-based parameters. OBJECTIVES: To comprehensively evaluate the reproducibility of fatigability measured and derived parameter and to determine which of these is/are sufficiently interpretable for assessment of knee muscles. METHODS: Eighteen sedentary men underwent three isokinetic knee fatigability testing sessions with 7–10 days of rest between each session. Peak moment (PM)…and maximal work (MW) were computed for each repetition and analyzed to calculate 54 measured and derived parameters. Relative (Intra-class Correlation Coefficients – ICC) and absolute (Coefficient of Variation of Method Error – CV ME %, standard error of measurement – SEM and minimum detectable change – MDC) parameters of reproducibility were determined to assess the inter-session agreement. RESULTS: All fatigability measured parameters (save one) were associated with a high relative and absolute reproducibility for knee extensors (ICC ⩾ 0.80; almost all SEM ⩽ SD 2 ; MDCs largely ranging 10–30%) and a high relative but weak absolute reproducibility for flexors (ICC ⩾ 0.70; SEM > SD 2 ; MDCs ranging 35–95%). On the other hand, all knee extensor and flexor fatigability derived parameters were characterized by low relative and absolute reproducibility (ICC extensors < 0.70 and ICC flexors < 0.50; all SEM > SD 2 ; MDCs largely ranging 30–100%). CONCLUSIONS: All fatigability measured parameters may be used for assessing knee extensors fatigue with either PM or MW; for assessing knee flexors, no measured parameters can be utilized. Above all, knee fatigability derived parameters, either PT- or MW-based, should not be used, for both the extensors and the flexors of the knee, due to clinically unacceptable reproducibility.
Abstract: BACKGROUND: Stages device is an affordable power meter used by several professional and competitive cyclists. However, few studies have investigated its validity and reliability. OBJECTIVE: The aim of this study was to analyze the validity and the reliability of the Stages mountain biking power meter. METHODS: Twenty-six cyclists (age: 35 ± 7 years, VO 2 max: 58 ± 7 ml⋅ kg - 1 ⋅ min - 1 ) completed six testing sessions…within a 4-week period. Cyclists performed an incremental exercise test, a 5-min time trial (TT), and a 20-min TT in different days using the Velotron cycle ergometer attached with the power meter. RESULTS: The power output of the Stages was significantly lower during each step of the incremental exercise test (11.8 to 16.4%) and performance testing (∼ 18%) compared with the cycle ergometer. Bland Altman plots presented high bias and limits of agreements when comparing the power output of the Stages and Velotron. In general, high coefficient of variation was found for the power and cadence of the Velotron and Stages, except for the Velotron’s power during the 20-min TT. CONCLUSIONS: The interchangeable use of the power from the Velotron and Stages is not recommended due to the observed high within-subject variation.
Keywords: Cyclists, power output, Stages, mountain biking, time trial
Abstract: BACKGROUND: The accurate assessment of step variability remains problematic. OBJECTIVE: To determine the minimum time required for assessing spatiotemporal variability during continuous running. METHODS: Seventeen endurance runners performed a running protocol on a treadmill, with a 3-min recording period at 12 km/h. Spatiotemporal parameters (contact and flight times, step length and step frequency) were measured using the OptoGait system and step variability was considered for each parameter, in terms of within-participants standard deviation (SD) and coefficient of variation (CV%). Step variability was calculated over 6 different durations: 0–10 s, 0–20 s, 0–30 s, 0–60 s, 0–120 s and 0–180 s.…RESULTS: The repeated measures ANOVA revealed no significant differences between measurements in mean spatiotemporal gait parameters (p ⩾ 0.396, ICC ⩾ 0.90 in all parameters). The post-hoc analysis confirmed no significant differences in step variability (of each spatiotemporal parameter) between measurements. The Bland-Altman limits of agreement method showed that longer recording intervals yield smaller systematic bias, random errors, and narrower limits of agreement. CONCLUSIONS: The duration of the recording interval plays an important role in the accuracy of the measurement (i.e. variability in spatiotemporal gait parameters), with longer intervals (180 s) showing smaller systematic bias and narrower limits of agreement than shorter intervals (10 s, 20 s, 30 s, 60 s or 120 s).
Keywords: Biomechanics, endurance runners, gait variability, movement variability
Abstract: BACKGROUND: The volume in resistance training (RT) perhaps improve the autonomic modulation cardiac in untrained adults. OBJECTIVE: The aim was to analyze the effect of RT volume on heart rate variability (HRV) in young adults. METHODS: The intervention order was randomized and counterbalanced. Participants (n = 27) performed 1, 3 or 5 sets of the same exercises with equalized intensity (loading zones) and rested for eight weeks following eight weeks of washout between each experimental condition (1 vs. 3 vs. 5 sets). The researchers assessed HRV by cardiac…monitoring seventy-two hours, both before (pre) and after (post) each experimental RT condition (1 vs. 3 vs. 5 sets). Factorial repeated measures ANOVA 2 × 3 were used to analyze the interaction between time (pre vs. post) and intervention (1 set vs. 3 sets vs. 5 sets) for the HRV index (RMSSD, SDNN, and pNN50). RESULTS: An interaction was identified between time and condition for RMSSD (F ( 5 , 22 ) = 37.02, p < 0.01), SDNN (F ( 5 , 22 ) = 32.80, p < 0.01), and pNN50 (F ( 5 , 22 ) = 29.92, p < 0.02). Five set conditions (p = 0.01) showed improvement in HRV indicators when compared to one set and three set conditions. CONCLUSION: The study concluded that 5 set conditions improved HRV in young untrained adults.
Keywords: Heart rate, health, exercise, strength training