scholarly journals Comparison of Methods of Calculating Dynamic Strength Index

2018 ◽  
Vol 13 (3) ◽  
pp. 320-325 ◽  
Author(s):  
Paul Comfort ◽  
Christopher Thomas ◽  
Thomas Dos’Santos ◽  
Paul A. Jones ◽  
Timothy J. Suchomel ◽  
...  
Keyword(s):  
Intraclass Correlation ◽  
Dynamic Strength ◽  
Rugby League ◽  
Strength Index ◽  
Countermovement Jump ◽  
Reliable Measure ◽  
Male Youth ◽  
Squat Jump ◽  
Youth Soccer ◽  
Very High

Purpose: To determine the reliability and variability of the Dynamic Strength Index (DSI) calculated from squat-jump (SJ) vs countermovement-jump (CMJ) peak force (PF) and to compare DSI values between methods. Methods: Male youth soccer and rugby league players (N = 27; age 17.2 ± 0.7 y, height 173.9 ± 5.7 cm, body mass 71.1 ± 7.2 kg) performed 3 trials of the SJ, CMJ, and isometric midthigh pull (IMTP) on 2 separate days. DSI was calculated by dividing the PF during each jump by the IMTP PF. Results: DSI-SJ exhibited moderate (intraclass correlation coefficient [ICC] = .419) within-session reliability and high variability (percentage coefficient of variation [%CV] = 15.91) during session 1; however, this improved noticeably during session 2 (ICC = .948, %CV = 4.03). In contrast, DSI-CMJ showed nearly perfect within-session reliability (ICC = .920–.952) and low variability (%CV = 3.80–4.57) for both sessions. Moreover, DSI-SJ values demonstrated a small yet significant increase between sessions (P = .01, d = 0.37), whereas only a trivial and nonsignificant increase was observed for DSI-CMJ between sessions (P = .796, d = 0.07). Between-sessions reliability was very high for the DSI-SJ (ICC = .741) and nearly perfect for the DSI-CMJ (ICC = .924). There was no significant or meaningful difference (P = .261, d = 0.12) between DSI-SJ (0.82 ± 0.18) and DSI-CMJ (0.84 ± 0.15). Conclusions: Practitioners should use DSI-CMJ, as it is a more reliable measure than DSI-SJ, although it produces similar ratios.

Interrelationship between specific high-intensity intermittent efforts ability with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes

2021 ◽  
pp. 1-10
Author(s):  
Alex Ojeda-Aravena ◽  
Tomás Herrera-Valenzuela ◽  
Pablo Valdés-Badilla ◽  
Eduardo Baez-San Martín ◽  
José Zapata-Bastías ◽  
...  
Keyword(s):  
Aerobic Capacity ◽  
High Intensity ◽  
Dynamic Strength ◽  
Multiple Regression Model ◽  
Strength Index ◽  
Male Athletes ◽  
Squat Jump ◽  
Stretch Shortening Cycle ◽  
The Relationship ◽  
Shuttle Run

BACKGROUND: Repeat high-intensity intermittent efforts is a taekwondo-specific ability but the influence of aerobic capacity and dynamic strength characteristics on this ability has received relatively little attention in the literature. OBJECTIVE: To examine the relationship between specific high-intensity intermittent efforts with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes. METHODS: Nineteen taekwondo male athletes were assessed by squat jump (SJ), countermovement jump (CMJ), 20-meter shuttle run (20MSR), and frequency speed of kick test multiple (FSKTMULT). From the FSKTMULT, total kicks and kick decrement index [KDI] were calculated. Additionally, from both jump tests, the slow stretch-shortening cycle utilization (Slow SSC Utilization) was determined from the eccentric utilization ratio [EUR], pre-stretch augmentation [PSA], and reactive strength index [RSI]. RESULTS: There were positive and significant correlations between total kicks with 20MSR (r= 0.85; p= 0.00) and SJ (r= 0.66; p< 0.05). The multiple regression model demonstrated that total kicks where significantly influenced by 20MSR (R2= 71%; p= 0.00). Additionally, only EUR and RSI explained total kicks performance to a greater proportion (R2= 76%). CONCLUSIONS: The FSKTMULT total kicks performance is positively correlated and influenced by aerobic capacity and slow SSC utilization.

Reliability of the Dynamic Strength Index in College Athletes

2015 ◽  
Vol 10 (5) ◽  
pp. 542-545 ◽  
Author(s):  
Christopher Thomas ◽  
Paul A. Jones ◽  
Paul Comfort
Keyword(s):  
College Athletes ◽  
Intraclass Correlation ◽  
Force Production ◽  
Dynamic Strength ◽  
Peak Force ◽  
Dynamic Force ◽  
Strength Index ◽  
Training Interventions ◽  
Change In The Mean ◽  
Change In Mean

Purpose:To determine the reliability of the Dynamic Strength Index (DSI) in college athletes.Method:Nineteen male college athletes performed the squat jump (SJ) and isometric midthigh pull (IMTP) to determine peak force, on 2 separate days. Reliability was assessed by intraclass correlation coefficient (ICC), typical error (TE), percentage change in the mean, smallest worthwhile change (SWC), and coefficient of variation (%CV).Results:Peak force for the SJ was 2137 ± 499 N and 2781 ± 435 N for the IMTP, resulting in a mean DSI of 0.78 ± 0.19. Peak forces in the SJ (ICC = .99, TE = 57.22 N, change in mean = 0.2%, SWC = 4.7%, CV = 2.6%) and IMTP (ICC = .95, TE = 104.22 N, change in mean = 0.5%, SWC = 3.1%, CV = 3.8%) were considered highly reliable between sessions. However, IMTP peak force was the only variable with an overall TE < SWC. The DSI was also highly reliable (ICC = .97, TE = 0.03, change in mean = −0.3%, SWC = 5.1%, CV = 4.6%) between sessions.Conclusion:This study demonstrates that peak force in the SJ and IMTP are reliable, resulting in a reliable assessment of dynamic-force-production capabilities via the DSI. The DSI may be used to guide individualized training interventions and monitor specific adaptations to training. Changes in SJ peak force, IMTP peak force, and DSI were >4.67%, 3.13%, and 5.13%, respectively, identifying meaningful changes in response to training or competition.

scholarly journals Differences in Squat Jump, Linear Sprint, and Change-of-Direction Performance among Youth Soccer Players According to Competitive Level

Sports ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 149
Author(s):  
Michael Keiner ◽  
Andreas Kapsecker ◽  
Tobias Stefer ◽  
Björn Kadlubowski ◽  
Klaus Wirth
Keyword(s):  
Age Groups ◽  
Cross Sectional Study ◽  
Soccer Players ◽  
Cross Sectional ◽  
Male Youth ◽  
Squat Jump ◽  
Youth Soccer ◽  
Change Of Direction ◽  
Talent Selection ◽  
Selection Test

The aim of this investigation was to analyze significant differences in performance depending on the level of play (elite vs. amateur) in youth soccer players (under 17 years. old (U17) and U19). A cross-sectional study was conducted, and 45 elite and amateur male youth soccer players (16.56 ± 0.9 years old) were evaluated in their performances in squat jump (SJ), 10 m linear sprint (LS), 20 m LS, 505 agility test (505) and Illinois agility test (IAT). Differences in performances were analyzed with a 2 × 2 MANOVA, post-hoc ANOVAs, and Hedges’ g (g) for pairwise comparisons of subgroups (level of play and age group). This investigation showed that the elite player performance was significantly (p < 0.05) better in all performance tests than amateur players in both age groups. Interestingly, this investigation showed that the more complex the target exercise, the larger the effect sizes for group differences (SJ: g = 0.64–1.18, LS: g = 0.05–2.23, change-of-direction (COD): g = 3.01–6.84). The SJ, LS, 505, and IAT may prove useful in talent selection test batteries to separate between competitive levels in youth soccer players.

scholarly journals Changes in Dynamic Strength Index in Response to Strength Training

Sports ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 176 ◽  
Author(s):  
Paul Comfort ◽  
Christopher Thomas ◽  
Thomas Dos’Santos ◽  
Timothy Suchomel ◽  
Paul Jones ◽  
...  
Keyword(s):  
Strength Training ◽  
Collegiate Athletes ◽  
Dynamic Strength ◽  
Minimal Change ◽  
Peak Force ◽  
Effect Sizes ◽  
Strength Index ◽  
Countermovement Jump ◽  
Strength Based ◽  
Moderate Difference

The primary aim of this investigation was to determine the effects of a four-week period of in-season strength training on the dynamic strength index (DSI). Pre and post a four-week period of strength-based training, twenty-four collegiate athletes (age = 19.9 ± 1.3 years; height = 1.70 ± 0.11 m; weight 68.1 ± 11.8 kg) performed three isometric mid-thigh pulls and countermovement jumps to permit the calculation of DSI. T-tests and Cohen’s effect sizes revealed a significant but small (p = 0.009, d = 0.50) decrease in DSI post-training (0.71 ± 0.13 N·N−1) compared to pre-training (0.65 ± 0.11 N·N−1); however, when divided into high and low DSI groups, differential responses were clear. The low DSI group exhibited no significant or meaningful (p = 1.000, d = 0.00) change in DSI pre to post-training (0.56 ± 0.05 N·N−1, 0.56 ± 0.09 N·N−1, respectively), whereas the high DSI group demonstrated a significant and large decrease (p = 0.034, d = 1.29) in DSI pre to post-training (0.85 ± 0.05 N·N−1, 0.74 ± 0.11 N·N−1, respectively), resulting in a significant and moderate difference (p = 0.034, d = 1.29) in the change in DSI between groups. These results demonstrate that DSI decreases in response to strength training, as expected, due to an increase in isometric mid-thigh pull peak force, with minimal change in dynamic (countermovement jump) peak force.

scholarly journals Effects of Two Contrast Training Programs on Jump Performance in Rugby Union Players During a Competition Phase

2012 ◽  
Vol 7 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Christos K. Argus ◽  
Nicholas D. Gill ◽  
Justin W.L. Keogh ◽  
Michael R. McGuigan ◽  
Will G. Hopkins
Keyword(s):  
Training Programs ◽  
Training Group ◽  
Rugby Union ◽  
Power Training ◽  
Strength Index ◽  
Countermovement Jump ◽  
Jump Performance ◽  
Squat Jump ◽  
Volume Load ◽  
High Level

Purpose:There is little literature comparing contrast training programs typically performed by team-sport athletes within a competitive phase. We compared the effects of two contrast training programs on a range of measures in high-level rugby union players during the competition season.Methods:The programs consisted of a higher volume-load (strength-power) or lower volume-load (speed-power) resistance training; each included a tapering of loading (higher force early in the week, higher velocity later in the week) and was performed twice a week for 4 wk. Eighteen players were assessed for peak power during a bodyweight countermovement jump (BWCMJ), bodyweight squat jump (BWSJ), 50 kg countermovement jump (50CMJ), 50 kg squat jump (50SJ), broad jump (BJ), and reactive strength index (RSI; jump height divided by contact time during a depth jump). Players were then randomized to either training group and were reassessed following the intervention. Inferences were based on uncertainty in outcomes relative to thresholds for standardized changes.Results:There were small between-group differences in favor of strength-power training for mean changes in the 50CMJ (8%; 90% confidence limits, ±8%), 50SJ (8%; ±10%), and BJ (2%; ±3%). Differences between groups for BWCMJ, BWSJ, and reactive strength index were unclear. For most measures there were smaller individual differences in changes with strength-power training.Conclusion:Our findings suggest that high-level rugby union athletes should be exposed to higher volume-load contrast training which includes one heavy lifting session each week for larger and more uniform adaptation to occur in explosive power throughout a competitive phase of the season.

Effects of Plyometric Training with Agility Ladder on Physical Fitness in Youth Soccer Players

2021 ◽  
Author(s):  
Alexis Padrón-Cabo ◽  
Miguel Lorenzo-Martínez ◽  
Alexandra Pérez-Ferreirós ◽  
Pablo B. Costa ◽  
Ezequiel Rey
Keyword(s):  
Physical Fitness ◽  
Linear Mixed Model ◽  
Group Analysis ◽  
Training Group ◽  
Soccer Players ◽  
Control Group ◽  
Plyometric Training ◽  
Countermovement Jump ◽  
Squat Jump ◽  
Youth Soccer

AbstractThe aim of this study was to assess the effects of plyometric training with an agility ladder on components of physical fitness in youth soccer players. A total of twenty male under-13 soccer players were randomly assigned to a plyometric training group with an agility ladder (n=10) or a control group (n=10). Before and after training intervention linear sprint test (5 m, 10 m, 20 m), vertical jump ability (squat jump, countermovement jump and countermovement jump with arms), agility test, and slalom dribble test were assessed. The plyometric training with agility ladder was applied two times per week over six weeks. Data were analyzed using linear mixed model. The plyometric training group showed significant improvements (p<0.001) from pre-test to post-test in countermovement jump, countermovement jump with arms, and slalom dribble test. In the control group, no significant enhancements were obtained in all performance tests (p>0.05). The between-group analysis showed significant differences in countermovement jump with arms (p=0.03), but no significant differences (p>0.05) were found in squat jump, countermovement jump, sprint, agility test, and slalom dribble test. In conclusion, the short-term plyometric training with agility ladder seems to be ineffective and not time-efficient to improve physical fitness in youth soccer players. However, the interpretation of these results must be understood within the sample size limitations.

scholarly journals Bilateral Deficit and Bilateral Performance: Relationship with Sprinting and Change of Direction in Elite Youth Soccer Players

Sports ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 82
Author(s):  
Giampiero Ascenzi ◽  
Bruno Ruscello ◽  
Cristoforo Filetti ◽  
Daniele Bonanno ◽  
Valter Di Salvo ◽  
...  
Keyword(s):  
Average Power ◽  
Motor Task ◽  
Soccer Players ◽  
Male Youth ◽  
Squat Jump ◽  
Bilateral Deficit ◽  
Youth Soccer ◽  
Change Of Direction ◽  
Contraction Type ◽  
Statistical Relationships

The purpose of the study was to examine the differences in bilateral deficit (BLD) at different loadings during the half-squat jump (SJ) and horizontal countermovement jump (HCMJ) to determine if there is a relationship with linear sprint or change of direction (COD). The second goal was to check if fast players were more powerful in SJ and HCMJ than slow players in bilateral performance (BP). Twenty-seven male youth soccer players participated in the study. Players were divided in two groups, faster and slower, according to their sprint performance (10 and 40 m). BLD average power with body weight (BW) and 25%BW were significantly higher than 50%BW (p < 0.01). BLD during HCMJ was significantly higher than BLD during SJ with BW, 25%BW and 50%BW (p < 0.01). There were no statistical relationships between BLD and sprint or COD performance (p > 0.05). Fast players showed significantly higher SJ power with all the different loads and HCMJ than slow players (p < 0.01), and fast players lost more time executing COD-90° than slow players (p < 0.01). There were no statistical differences between fast and slow players in BLD. BLD seems to be dependent on motor task, contraction type and load and could not be a proper measure to estimate sprint and COD performance. Faster players are confirmed to be more powerful players than slow players, and decrements in COD could be a key benchmark to identify deficit between linear and COD performance.

The Intraday Reliability of the Reactive Strength Index Calculated From a Drop Jump in Professional Men’s Basketball

2015 ◽  
Vol 10 (4) ◽  
pp. 482-488 ◽  
Author(s):  
William J. Markwick ◽  
Stephen P. Bird ◽  
James J. Tufano ◽  
Laurent B. Seitz ◽  
G. Gregory Haff
Keyword(s):  
Statistical Difference ◽  
Intraclass Correlation ◽  
Jump Height ◽  
Drop Jump ◽  
Strength Index ◽  
Countermovement Jump ◽  
Basketball Players ◽  
Professional Basketball ◽  
Men's Basketball ◽  
Large Groups

Purpose:To evaluate the reliability of the Reactive Strength Index (RSI) and jump-height (JH) performance from multiple drop heights in an elite population.Methods:Thirteen professional basketball players (mean ±SD age 25.8 ± 3.5 y, height 1.96 ± 0.07 m, mass 94.8 ± 8.2 kg) completed 3 maximal drop-jump attempts onto a jump mat at 4 randomly assigned box heights and 3 countermovement-jump trials.Results:No statistical difference was observed between 3 trials for both the RSI and JH variable at all the tested drop heights. The RSI for drop-jump heights from 20 cm resulted in a coefficient of variation (CV) = 3.1% and an intraclass correlation (ICC α) = .96, 40 cm resulted in a CV = 3.0% and an ICC α = .95, and 50 cm resulted in a CV = 2.1% and an ICC α = .99. The JH variable at the 40-cm drop-jump height resulted in the highest reliability CV = 2.8% and an ICC α = .98.Conclusion:When assessing the RSI the 20-, 40-, and 50-cm drop heights are recommended with this population. When assessing large groups it appears that only 1 trial is required when assessing the RSI variable from the 20, 40-, and 50-cm drop heights.

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