Influence of Dynamic Strength Index on Countermovement Jump Force-, Power-, Velocity-, and Displacement-Time Curves

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.

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Comparison of Methods of Calculating Dynamic Strength Index

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2017-0255 ◽

2018 ◽

Vol 13 (3) ◽

pp. 320-325 ◽

Cited By ~ 6

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.

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The Influence of Countermovement Jump Protocol on Reactive Strength Index Modified and Flight Time: Contraction Time in Collegiate Basketball Players

Sports ◽

10.3390/sports7020037 ◽

2019 ◽

Vol 7 (2) ◽

pp. 37 ◽

Cited By ~ 3

Author(s):

Aaron Heishman ◽

Brady Brown ◽

Bryce Daub ◽

Ryan Miller ◽

Eduardo Freitas ◽

...

Keyword(s):

Force Plate ◽

Flight Time ◽

Contraction Time ◽

Strength Index ◽

Countermovement Jump ◽

Basketball Players ◽

Arm Swing ◽

Collegiate Basketball ◽

Positive Correlations ◽

The Relationship

The purpose of the present investigation was to evaluate differences in Reactive Strength Index Modified (RSIMod) and Flight Time to Contraction Time Ratio (FT:CT) during the countermovement jump (CMJ) performed without the arm swing (CMJNAS) compared to the CMJ with the arm swing (CMJAS), while exploring the relationship within each variable between jump protocols. A secondary purpose sought to explore the relationship between RSIMod and FT:CT during both jump protocols. Twenty-two collegiate basketball players performed both three CMJNAS and three CMJAS on a force plate, during two separate testing sessions. RSIMod was calculated by the flight-time (RSIModFT) and impulse-momentum methods (RSIModIMP). CMJ variables were significantly greater during the CMJAS compared to CMJNAS (p < 0.001). There were large to very large correlations within each variable between the CMJAS and CMJNAS. There were significant positive correlations among RSIModFT, RSIModIMP, and FT:CT during both the CMJAS (r ≥ 0.864, p < 0.001) and CMJNAS (r ≥ 0.960, p < 0.001). These findings identify an increase in RSIMod or FT:CT during the CMJAS, that may provide independent information from the CMJNAS. In addition, either RSIMod or FT:CT may be utilized to monitor changes in performance, but simultaneous inclusion may be unnecessary.

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Impulse-Based Dynamic Strength Index

The Journal of Strength and Conditioning Research ◽

10.1519/jsc.0000000000004032 ◽

2021 ◽

Vol Publish Ahead of Print ◽

Author(s):

Michael H. Haischer ◽

John Krzyszkowski ◽

Stuart Roche ◽

Kristof Kipp

Keyword(s):

Dynamic Strength ◽

Strength Index

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

Isokinetics and Exercise Science ◽

10.3233/ies-210210 ◽

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.

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Reliability of the Dynamic Strength Index in College Athletes

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2014-0255 ◽

2015 ◽

Vol 10 (5) ◽

pp. 542-545 ◽

Cited By ~ 12

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.

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The Effects of Combined Balance and Complex Training Versus Complex Training Only on Measures of Physical Fitness in Young Female Handball Players

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2020-0765 ◽

2020 ◽

pp. 1-8

Author(s):

Helmi Chaabene ◽

Yassine Negra ◽

Senda Sammoud ◽

Jason Moran ◽

Rodrigo Ramirez-Campillo ◽

...

Keyword(s):

Physical Fitness ◽

Young Female ◽

Strength Index ◽

Countermovement Jump ◽

Balance Test ◽

Standing Long Jump ◽

Balance Exercises ◽

Long Jump ◽

Complex Training ◽

Versus Complex

Purpose: To examine the effects of balance exercises conducted prior to complex training (bCT) versus complex training (CT) only on measures of physical fitness in young female elite handball players. Methods: Participants aged 17 years were randomly assigned to bCT (n = 11) or CT (n = 12). The 2 training interventions lasted 8 weeks with 2 sessions per week in replacement of some technical/tactical handball exercises and were matched for total training volume. Before and after training, tests were performed for the evaluation of proxies of muscle power (countermovement jump height, standing long-jump distance, and reactive strength index), muscle strength (back half-squat 1-repetition maximum), dynamic balance (Y-balance test), linear sprint speed (20-m sprint test), and change-of-direction speed (T test). Results: Two-factor repeated-measures analysis of variance revealed significant group × time interactions for the reactive strength index (d = 0.99, P = .03) and Y-balance test score (d = 1.32, P < .01). Post hoc analysis indicated significant pre–post reactive strength index improvements in CT (d = 0.69, P = .04) only. For the Y-balance test, significant pre–post increases were found in bCT (d = 0.71, P = .04) with no significant changes in CT (d = 0.61, P = .07). In addition, significant main effects of time were observed for half-squat 1-repetition maximum, countermovement jump, standing long jump, and T test performance (d = 1.50 to 3.10, P < .05). Conclusions: Both bCT and CT interventions were effective in improving specific measures of physical fitness in young elite female handball players. If the training goal is to improve balance in addition, balance exercises can be conducted within a CT training session and prior to CT exercises.

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The Main and Interactive Effects of Biological Maturity and Relative Age on Physical Performance in Elite Youth Soccer Players

Journal of Sports Medicine ◽

10.1155/2020/1957636 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

James Parr ◽

Keith Winwood ◽

Emma Hodson-Tole ◽

Frederik J. A. Deconinck ◽

James P. Hill ◽

...

Keyword(s):

Physical Performance ◽

Interactive Effect ◽

Soccer Players ◽

Adolescent Male ◽

Performance Tests ◽

Strength Index ◽

Countermovement Jump ◽

Relative Age ◽

Professional Soccer ◽

Biological Maturity

The main and interactive effect of biological maturity and relative age upon physical performance in adolescent male soccer players was considered. Consistent with previous research, it was hypothesised that participants of greater maturity or born earlier in the selection year would perform better in terms of physical performance tests. This cross-sectional study consisted of 84 male participants aged between 11.3 and 16.2 years from a professional soccer academy in the English Premier League. Date of birth, height, weight, and parental height were collected. Sprint, change of direction, countermovement jump, and reactive strength index were considered for physical performance. Relative age was based on the birth quarter for the selection year. Maturity status was based upon the percentage of predicted adult height attained. Linear regression models highlighted that maturation was associated with performance on all but one of the physical performance tests, the reactive strength index. In contrast, relative age only served as a significant predictor of performance on the countermovement jump. This study indicated that physical performance (in the tests studied) seems to be related to the biological maturity status of a player but not their relative age. This finding is important because it suggests that early-maturing players perform better in the majority of physical performance tests, and the commonly held belief that relative age effect influences performance may be overstated.

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