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 Dynamic Strength Index: Relationships with Common Performance Variables and Contextualization of Training Recommendations

2020 ◽  
Vol 74 (1) ◽  
pp. 59-70
Author(s):  
Timothy J. Suchomel ◽  
Christopher J. Sole ◽  
Christopher R. Bellon ◽  
Michael H. Stone
Keyword(s):  
Peak Power ◽  
Female Athletes ◽  
Training Stimulus ◽  
Monitoring Program ◽  
Collegiate Athletes ◽  
Dynamic Strength ◽  
Peak Force ◽  
Power Performance ◽  
Strength Index

Abstract The purposes of this study were to examine the relationships between dynamic strength index (DSI) and other strength-power performance characteristics and to contextualize DSI scores using case study comparisons. 88 male and 67 female NCAA division I collegiate athletes performed countermovement jumps (CMJ) and isometric mid-thigh pulls (IMTP) during a pre-season testing session as part of a long-term athlete monitoring program. Spearman’s correlations were used to assess the relationships between DSI and CMJ peak force, height, modified reactive strength index, peak power and IMTP peak force and rate of force development (RFD). Very large relationships existed between DSI and IMTP peak force (r = -0.848 and -0.746), while small-moderate relationships existed between DSI and CMJ peak force (r = 0.297 and 0.313), height (r = 0.108 and 0.167), modified reactive strength index (r = 0.174 and 0.274), and IMTP RFD (r = -0.341 and -0.338) for men and women, respectively. Finally, relationships between DSI and CMJ peak power were trivial-small for male (r = 0.008) and female athletes (r = 0.191). Case study analyses revealed that despite similar DSI scores, each athlete’s percentile rankings for each variable and CMJ force-time characteristics were unique, which may suggest different training emphases are needed. Based on the explained variance, an athlete’s IMTP performance may have a larger influence on their DSI score compared to the CMJ. DSI scores should be contextualized using additional performance data to ensure each individual athlete receives the appropriate training stimulus during different training phases throughout the year.

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 PREDICTING MAXIMAL COUNTERMOVEMENT JUMP HEIGHT FROM UPRIGHT AND SQUAT POSITIONS HEAD TITLE: UPRIGHT AND SQUAT MAXIMUM JUMP HEIGHT PREDICTORS

2021 ◽  
Vol 2 (2021) ◽  
pp. 3-16
Author(s):  
David N. Suprak ◽  
◽  
Tal Amasay ◽  
Keyword(s):  
Peak Power ◽  
Collegiate Athletes ◽  
Arm Movement ◽  
Peak Force ◽  
Rate Of Force Development ◽  
Jump Height ◽  
Countermovement Jump ◽  
Jump Performance ◽  
Force Development ◽  
Height Prediction

Introduction. Countermovement jump is common in sport and testing and performed from various starting positions. Little is known about effective contributors to maximal countermovement jump height from various starting positions. Purpose and Objectives. Determine effective jump height predictors and effect of starting position on countermovement jump height. Applied Methodology. Forty-nine collegiate athletes performed maximal height countermovement jumps from upright and squatting positions with arm movement. Several variables were calculated from kinetic data. Correlation and regression determined variables related to and predictive of jump height in both conditions. Paired t-tests evaluated differences in jump height. Achieved Major Results. Upright condition jump height positively correlated with peak force and power, eccentric and concentric impulses, and countermovement depth. Jump height prediction included peak force and power, and eccentric and concentric impulses. Squat condition jump height positively correlated with peak force and power, mean rate of force development, force generated at the beginning of propulsion, and concentric impulse. Jump height prediction equation included mean rate of force development, force at the beginning of propulsion, and peak power. Jump height was higher in the upright condition. Conclusions. Higher jumps are achieved from the upright position. Peak force, peak power, and concentric and eccentric impulses best contribute to upright jump height. Mean rate of force development, force at the beginning of propulsion, and peak power best predicted squat jump height. Limitations. We did not restrict arm movement, to encourage natural motion. Depth was not controlled, rather advising a comfortable depth. Subjects were recruited from various collegiate sports. Practical implications. Maximal jump height from various positions may be achieved through efforts to maximize jump peak power and increase musculotendinous loading in sport-specific starting positions. Originality/Value. This is the first study to explore the predictors of upright and squat countermovement jumps. These results can guide jump performance training.

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.

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

Sports ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 37 ◽  
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.

Effects of complex strength training with elastic band program on repeated change of direction in young female handball players: Randomized control trial

2021 ◽  
pp. 174795412110621
Author(s):  
Mehrez Hammami ◽  
Nawel Gaamouri ◽  
Yosser Cherni ◽  
Sabri Gaied ◽  
Mohamed Souhaiel Chelly ◽  
...  
Keyword(s):  
Strength Training ◽  
Young Female ◽  
Control Group ◽  
Countermovement Jump ◽  
Elastic Band ◽  
Squat Jump ◽  
Change Of Direction ◽  
Jump Test ◽  
Back Extensor ◽  
Experimental Group

This study examined the effect of 10-week complex strength training with elastic band program on fitness components in young female handball players. Thirty-eight handball players aged 15.8 ± 0.2 years were randomly assigned to an experimental group or control group. The experimental group performed complex strength training with elastic band twice a week over 10 weeks, which included 8 workshops of progressing set length (number of sets) and band resistance for each specific exercise. Sessions were lasted approximately 35 min. The control group maintained regular in-season training. Tests included handgrip; back extensor; medicine ball throw; 30 m sprint times; Modified Illinois change-of-direction (Illinois-MT); four jump tests (squat jump, countermovement jump, countermovement jump with arms and five jump test; static (stork test) and dynamic (Y balance test) balance; and repeated sprint T-test. The experimental group enhanced all strength performance (handgrip right ( p < 0.001), handgrip left ( p < 0.001), back extensor strength ( p < 0.001) and medicine ball throw ( p < 0.001) compared to the controls); sprint performance (5 m ( p<0.001), 10 m ( p < 0.001), 20 m ( p < 0.001), and 30 m ( p < 0.001)); the change of direction (Illinois-MT ( p < 0.001)); jump performance (squat jump ( p < 0.001), countermovement jump ( p < 0.001), countermovement jump with arms ( p < 0.001), and five jump test ( p < 0.01)); and the repeated sprint T-test scores ( p<0.001in all scores). In contrast, no significant difference in both static and dynamic balance performance between experimental group and control group. Ten weeks of complex strength training with elastic band improve fitness components measures in young female handball players then habitual training.

Impulse-Based Dynamic Strength Index

2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Michael H. Haischer ◽  
John Krzyszkowski ◽  
Stuart Roche ◽  
Kristof Kipp
Keyword(s):  
Dynamic Strength ◽  
Strength Index

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.

Effects of contrast strength training with elastic band program on sprint, jump, strength, balance and repeated change of direction in young female handball players

2021 ◽  
pp. 174795412110507
Author(s):  
Mehrez Hammami ◽  
Nawel Gaamouri ◽  
Yosser Cherni ◽  
Mohamed Souhaiel Chelly ◽  
Lee Hill ◽  
...  
Keyword(s):  
Strength Training ◽  
Physical Performance ◽  
Young Female ◽  
T Test ◽  
Countermovement Jump ◽  
Elastic Band ◽  
Change Of Direction ◽  
Repeated Sprint ◽  
Back Extensor ◽  
Medicine Ball

Maximal strength, power and his derivates (sprint, change of direction repeatedly and jump) are considered as major determinants of success in elite handball players. Contrast strength training with elastic band (CSTEB) program is form of resistance training, and may play an important method of training to improve this quality. This study examined the effects of 10-week contrast strength training with elastic band (CSTEB) program on physical performance in young female handball players. Thirty participants (age: 15.7  ±  0.3 years; body mass: 63.7  ±  3.7 kg; body height: 166.8  ±  3.8 cm; body fat: 26.9  ±  3.4; and Maturity-offset: 2.9  ±  0.3 years) were randomly assigned between experimental group (EG; n = 15) and control group (CG; n = 15). Two-way analyses of variance (group × time) were assessed for handgrip; back extensor; medicine ball throw; 30-m sprint times; Modified Illinois change-of-direction (Illinois-MT); four jump tests [(squat jump (SJ), countermovement jump (CMJ), countermovement jump with arms (CMJA) and five jump test (5JT)]; static (stork) and dynamic (Y balance) balance tests; and repeated sprint T-test (RSTT). The EG enhanced all strength performance [handgrip right, handgrip left, back extensor strength and medicine ball throw (p < 0.001)] compared to CG. The EG enhanced all sprint performance. The EG also improved performance in the Illinois-MT. All jump performance improved significantly [SJ (p = 0.007), CMJ (p = 0.001) and CMJA (p = 0.001)] except 5JT in the EG. Of the same, 3 of 4 repeated sprint T-test scores [RSTT-Best-Time, RSTT-Mean-Time and RSTT-Total-Time] increased significantly in the EG relative to the CG. Conversely, there were no significant changes in balance performance between groups. It is concluded that 10-weeks of CSTEB improved physical performance (strength, sprint, change of direction, jump, and repeated change of direction) measures in young female handball players.

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