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

^{*}

## Abstract

**:**

^{−1}) but a larger braking net impulse in the CMJ, leading to greater braking velocity and larger countermovement displacement. This strategy resulted in a similar CMJ propulsion peak force (25.9 ± 2.2 vs. 25.4 ± 3.1 N·kg

^{−1}) to the high DSI group. These results, taken together with those of previous studies, support the notion of ballistic versus maximal strength training likely being better suited to low versus high DSI scorers, respectively.

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Subjects

#### 2.2. Procedures

#### 2.3. Data Collection

#### 2.4. Data Analysis

^{−1}and finished at take-off [11,16,17]. Take-off was identified when vertical force fell below five times the standard deviation of the flight phase force [11,16,17,28].

_{mod}) was calculated as jump height divided by TTT (i.e., the time between the onset of movement and take-off) [29].

#### 2.5. Statistical Analysis

## 3. Results

^{−1}and 31.1 ± 6.6 N kg

^{−1}(p < 0.001, d = 1.35), respectively. IMTP peak force also demonstrated high reliability (ICC = 0.952) and acceptable variability (%CV = 4.7).

## 4. Discussion

^{−1}and CMJ propulsion peak force by ~3.0 N kg

^{−1}).

^{−1}) and weaker (relative back squat 1RM of 1.32 kg·kg

^{−1}) subjects where compared following the completion of a ballistic training program (10 weeks), it was revealed that both groups significantly increased CMJ propulsion peak force, but the stronger group showed marginally larger improvements [7]. This increase in peak propulsion force was accompanied by a reduction in TTT for both groups and similar and slight reduction in countermovement displacement (based on visual inspection of figures by the present authors) for the weaker and stronger groups, respectively [7]. Interestingly though, back squat 1RM reduced for the strong group (ES = 0.93) but increased slightly for the weaker group (ES not reported) [7]. Therefore, DSI would have likely increased for the stronger group but may have remained similar for the weaker group. The above-mentioned results somewhat support the efficacy of prescribing ballistic training to athletes with low DSI scores and strength training to athletes with high DSI scores, but the consideration of maximal strength level is also warranted and a combined maximal strength and ballistic training approach may be more effective for improving overall athleticism. Ballistic training also helps to improve the coupling of braking-propulsion phase kinetics [18] which may help those with a low DSI who, in line with the present results (Table 2), may put a lot more into the braking phase but gain little advantage in the proceeding propulsion phase [39]. Future research avenues should include exploration of the impact of maximal strength, ballistic, and concurrent (maximal strength and ballistic) training on DSI and CMJ phase characteristics. The present study could also be replicated with elite athletes to confirm whether high and low DSI scorers among this population demonstrate similar CMJ phase characteristics to the subjects tested here.

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

- Harris, N.K.; Cronin, J.; Taylor, K.-L.; Boris, J.; Sheppard, J. Understanding position transducer technology for strength and conditioning practitioners. Strength Cond. J.
**2010**, 32, 66–79. [Google Scholar] [CrossRef] - Sheppard, J.; Chapman, D.; Taylor, K. An evaluation of a strength qulities assessment method for the lower body. J. Aust. Strength Cond.
**2011**, 19, 4–10. [Google Scholar] - Secomb, J.L.; Lundgren, L.E.; Farley, O.R.; Tran, T.T.; Nimphius, S.; Sheppard, J.M. Relationships between lower-body muscle structure and lower-body strength, power, and muscle-tendon complex stiffness. J. Strength Cond. Res.
**2015**, 29, 2221–2228. [Google Scholar] [CrossRef] [PubMed] - Secomb, J.L.; Nimphius, S.; Farley, O.R.; Lundgren, L.; Tran, T.T.; Sheppard, J.M. Lower-body muscle structure and jump performance of stronger and weaker surfing athletes. Int. J. Sports Physiol. Perform.
**2016**, 11, 652–657. [Google Scholar] [CrossRef] [PubMed] - Comfort, P.; Thomas, C.; Dos’Santos, T.; Jones, P.A.; Suchomel, T.J.; McMahon, J.J. Comparison of methods of calculating dynamic strength index. Int. J. Sports Physiol. Perform.
**2017**. [Google Scholar] [CrossRef] [PubMed] - Thomas, C.; Jones, P.A.; Comfort, P. Reliability of the dynamic strength index in collegiate athletes. Int. J. Sports Physiol. Perform.
**2015**, 10, 542–545. [Google Scholar] [CrossRef] [PubMed] - Cormie, P.; McGuigan, M.R.; Newton, R.U. Influence of strength on magnitude and mechanisms of adaptation to power training. Med. Sci. Sports Exerc.
**2010**, 42, 1566–1581. [Google Scholar] [CrossRef] [PubMed] - Dowling, J.J.; Vamos, L. Identification of kinetic and temporal factors related to vertical jump performance. J. Appl. Biomech.
**1993**, 9, 95–110. [Google Scholar] [CrossRef] - Kirby, T.J.; McBride, J.M.; Haines, T.L.; Dayne, A.M. Relative net vertical impulse determines jumping performance. J. Appl. Biomech.
**2011**, 27, 207–214. [Google Scholar] [CrossRef] [PubMed] - McMahon, J.J.; Ripley, N.J.; Rej, S.J. Effect of modulating eccentric leg stiffness on concentric force-velocity characteristics demonstrated in the countermovement jump. J. Sports Sci.
**2016**, 34, S19. [Google Scholar] - McMahon, J.J.; Jones, P.A.; Suchomel, T.J.; Lake, J.; Comfort, P. Influence of reactive strength index modified on force- and power-time curves. Int. J. Sports Physiol. Perform.
**2017**. [Google Scholar] [CrossRef] [PubMed] - Gathercole, R.; Sporer, B.; Stellingwerff, T.; Sleivert, G. Alternative countermovement-jump analysis to quantify acute neuromuscular fatigue. Int. J. Sports Physiol. Perform.
**2015**, 10, 84–92. [Google Scholar] [CrossRef] [PubMed] - Sheppard, J.M.; Doyle, T.L.A. Increasing compliance to instructions in the squat jump. J. Strength Cond. Res.
**2008**, 22, 648–651. [Google Scholar] [CrossRef] [PubMed] - Secomb, J.L.; Nimphius, S.; Farley, O.R.L.; Lundgren, L.E.; Tran, T.T.; Sheppard, J.M. Relationships between lower-body muscle structure and, lower-body strength, explosiveness and eccentric leg stiffness in adolescent athletes. J. Sports Sci. Med.
**2015**, 14, 691. [Google Scholar] [PubMed] - Secomb, J.L.; Farley, O.R.L.; Lundgren, L.; Tran, T.T.; King, A.; Nimphius, S.; Sheppard, J.M. Associations between the performance of scoring manoeuvres and lower-body strength and power in elite surfers. Int. J. Sports Sci. Coach.
**2015**, 10, 911–918. [Google Scholar] [CrossRef] - McMahon, J.J.; Murphy, S.; Rej, S.J.; Comfort, P. Countermovement jump phase characteristics of senior and academy rugby league players. Int. J. Sports Physiol. Perform.
**2017**, 12, 803–811. [Google Scholar] [CrossRef] [PubMed] - McMahon, J.J.; Rej, S.J.; Comfort, P. Sex differences in countermovement jump phase characteristics. Sports
**2017**, 5, 8. [Google Scholar] [CrossRef] - Cormie, P.; McGuigan, M.R.; Newton, R.U. Adaptations in athletic performance after ballistic power versus strength training. Med. Sci. Sports Exerc.
**2010**, 42, 1582–1598. [Google Scholar] [CrossRef] [PubMed] - Cormie, P.; McBride, J.M.; McCaulley, G.O. Power-time, force-time, and velocity-time curve analysis of the countermovement jump: Impact of training. J. Strength Cond. Res.
**2009**, 23, 177–186. [Google Scholar] [CrossRef] [PubMed] - Cormie, P.; McBride, J.M.; McCaulley, G.O. Power-time, force-time, and velocity-time curve analysis during the jump squat: Impact of load. J. Appl. Biomech.
**2008**, 24, 112–120. [Google Scholar] [CrossRef] [PubMed] - Haff, G.G.; Carlock, J.M.; Hartman, M.J.; Kilgore, J.L.; Kawamori, N.; Jackson, J.R.; Morris, R.T.; Sands, W.A.; Stone, M.H. Force-time curve characteristics of dynamic and isometric muscle actions of elite women olympic weightlifters. J. Strength Cond. Res.
**2005**, 19, 741–748. [Google Scholar] [PubMed] - Haff, G.G.; Stone, M.; O’Bryant, H.S.; Harman, E.; Dinan, C.; Johnson, R.; Han, K.-H. Force-time dependent characteristics of dynamic and isometric muscle actions. J. Strength Cond. Res.
**1997**, 11, 269–272. [Google Scholar] - Dos’Santos, T.; Thomas, C.; Jones, P.A.; McMahon, J.J.; Comfort, P. The effect of hip joint angle on isometric mid-thigh pull kinetics. J. Strength Cond. Res.
**2017**. [Google Scholar] [CrossRef] [PubMed] - Dos'Santos, T.; Jones, P.A.; Comfort, P.; Thomas, C. Effect of different onset thresholds on isometric mid-thigh pull force-time variables. J. Strength Cond. Res.
**2016**. [Google Scholar] [CrossRef] [PubMed] - Beckham, G.; Mizuguchi, S.; Carter, C.; Sato, K.; Ramsey, M.; Lamont, H.; Hornsby, G.; Haff, G.; Stone, M. Relationships of isometric mid-thigh pull variables to weightlifting performance. J. Sports Med. Phys. Fitness
**2013**, 53, 573–581. [Google Scholar] [PubMed] - Beckham, G.K.; Sato, K.; Mizuguchi, S.; Haff, G.G.; Stone, M.H. Effect of body position on force production during the isometric mid-thigh pull. J. Strength Cond. Res.
**2017**. [Google Scholar] [CrossRef] [PubMed] - Owen, N.J.; Watkins, J.; Kilduff, L.P.; Bevan, H.R.; Bennett, M.A. Development of a criterion method to determine peak mechanical power output in a countermovement jump. J. Strength Cond. Res.
**2014**, 28, 1552–1558. [Google Scholar] [CrossRef] [PubMed] - Moir, G.L. Three different methods of calculating vertical jump height from force platform data in men and women. Meas. Phys. Educ. Exerc. Sci.
**2008**, 12, 207–218. [Google Scholar] [CrossRef] - Ebben, W.P.; Petushek, E.J. Using the reactive strength index modified to evaluate plyometric performance. J. Strength Cond. Res.
**2010**, 24, 1983–1987. [Google Scholar] [CrossRef] [PubMed] - Cortina, J.M. What is coefficient alpha? An examination of theory and applications. J. Appl. Psychol.
**1993**, 78, 98–104. [Google Scholar] [CrossRef] - Cormack, S.J.; Newton, R.U.; McGuigan, M.R.; Doyle, T.L.A. Reliability of measures obtained during single and repeated countermovement jumps. Int. J. Sports Physiol. Perform.
**2008**, 3, 131–144. [Google Scholar] [CrossRef] [PubMed] - Hopkins, W.G. A Scale of Magnitudes of Effect Statistics. Available online: http://sportsci.org/resource/stats/index.html (accessed on 8 May 2017).
- Suchomel, T.J.; Sole, C.J. Force-time curve comparison between weightlifting derivatives. Int. J. Sports Physiol. Perform.
**2017**, 12, 431–439. [Google Scholar] [CrossRef] [PubMed] - Kibele, A. Possibilities and limitations in the biomechanical analysis of countermovement jumps: A methodological study. J. Appl. Biomech.
**1998**, 14, 105–117. [Google Scholar] [CrossRef] - Mizuguchi, S.; Sands, W.A.; Wassinger, C.A.; Lamont, H.S.; Stone, M.H. A new approach to determining net impulse and identification of its characteristics in countermovement jumping: Reliability and validity. Sports Biomech.
**2015**, 14, 258–272. [Google Scholar] [CrossRef] [PubMed] - Beattie, K.; Carson, B.P.; Lyons, M.; Kenny, I.C. The relationship between maximal-strength and reactive-strength. Int. J. Sports Physiol. Perform.
**2017**, 12, 548–553. [Google Scholar] [CrossRef] [PubMed] - Thomas, C.; Jones, P.A.; Rothwell, J.; Chiang, C.Y.; Comfort, P. An investigation into the relationship between maximum isometric strength and vertical jump performance. J. Strength Cond. Res.
**2015**, 29, 2176–2185. [Google Scholar] [CrossRef] [PubMed] - Nuzzo, J.L.; McBride, J.M.; Cormie, P.; McCaulley, G.O. Relationship between countermovement jump performance and multijoint isometric and dynamic tests of strength. J. Strength Cond. Res.
**2008**, 22, 699–707. [Google Scholar] [CrossRef] [PubMed] - Haff, G.G.; Nimphius, S. Training principles for power. Strength Cond. J.
**2012**, 34, 2–12. [Google Scholar] [CrossRef]

**Figure 1.**A comparison of countermovement jump force-time (

**top**) and power-time (

**bottom**) curves between the low (green solid line) and high (black dotted line) DSI groups, along with shaded 95% confidence intervals.

**Figure 2.**A comparison of countermovement jump velocity-time (

**top**) and displacement-time (

**bottom**) curves between the low (green solid line) and high (black dotted line) DSI groups, along with shaded 95% confidence intervals.

All Subjects (n = 53) | Low DSI Group (n = 20) | High DSI Group (n = 20) | |||||||
---|---|---|---|---|---|---|---|---|---|

Age (years) | 23.1 | ± | 4.1 | 24.4 | ± | 4.3 | 20.4 | ± | 1.1 |

Height (m) | 181.5 | ± | 6.1 | 181.5 | ± | 6.1 | 181.6 | ± | 6.8 |

Body Mass (kg) | 78.3 | ± | 9.6 | 80.0 | ± | 10.8 | 76.6 | ± | 8.0 |

RT Experience (years) | 3.4 | ± | 2.9 | 4.5 | ± | 3.7 | 2.4 | ± | 1.4 |

Jump Variables | Low DSI | High DSI | p | d | ICC | %CV | ||
---|---|---|---|---|---|---|---|---|

Mean | SD | Mean | SD | |||||

Jump Height (cm) | 35.9 | 6.2 | 32.4 | 5.0 | 0.062 | 0.62 | 0.937 | 3.7 |

Time to Take-off (s) | 0.737 | 0.102 | 0.679 | 0.081 | 0.055 | 0.63 | 0.862 | 4.4 |

RSI_{mod} (ratio) | 0.49 | 0.08 | 0.46 | 0.08 | 0.275 | 0.35 | 0.819 | 6.5 |

Braking Phase Time (s) | 0.151 | 0.021 | 0.138 | 0.027 | 0.110 | 0.52 | 0.860 | 6.0 |

Propulsion Phase Time (s) | 0.240 | 0.034 | 0.213 | 0.030 | 0.011 | 0.85 | 0.927 | 3.7 |

Braking COM Displacement (cm) | 31.0 | 5.8 | 25.3 | 5.3 | 0.002 | 1.02 | 0.919 | 5.5 |

Propulsion COM Displacement (cm) | 41.0 | 6.8 | 35.3 | 5.3 | 0.005 | 0.93 | 0.943 | 3.7 |

Braking Peak Force (N·kg^{−1}) | 25.5 | 2.5 | 25.4 | 3.1 | 0.926 | 0.03 | 0.815 | 4.2 |

Propulsion Peak Force (N·kg^{−1}) | 25.9 | 2.2 | 27.0 | 3.3 | 0.202 | 0.41 | 0.890 | 3.2 |

Braking Peak Power (W·kg^{−1}) | 20.9 | 4.8 | 17.4 | 3.7 | 0.014 | 0.81 | 0.845 | 8.5 |

Propulsion Peak Power (W·kg^{−1}) | 54.4 | 5.8 | 53.0 | 5.7 | 0.430 | 0.25 | 0.928 | 3.7 |

Braking Peak Velocity (m·s^{−1}) | 1.37 | 0.20 | 1.18 | 0.16 | 0.002 | 1.08 | 0.880 | 4.9 |

Propulsion Peak Velocity (m·s^{−1}) | 2.78 | 0.21 | 2.65 | 0.18 | 0.044 | 0.66 | 0.944 | 1.5 |

Braking Impulse (N·kg^{−1}·s) | 1.38 | 0.21 | 1.18 | 0.16 | 0.001 | 1.10 | 0.883 | 5.0 |

Propulsion Impulse (N·kg^{−1}·s) | 2.60 | 0.24 | 2.43 | 0.20 | 0.027 | 0.70 | 0.936 | 2.0 |

_{mod}= Reactive Strength Index Modified; COM = Center of Mass.

© 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

McMahon, J.J.; Jones, P.A.; Dos’Santos, T.; Comfort, P. Influence of Dynamic Strength Index on Countermovement Jump Force-, Power-, Velocity-, and Displacement-Time Curves. *Sports* **2017**, *5*, 72.
https://doi.org/10.3390/sports5040072

**AMA Style**

McMahon JJ, Jones PA, Dos’Santos T, Comfort P. Influence of Dynamic Strength Index on Countermovement Jump Force-, Power-, Velocity-, and Displacement-Time Curves. *Sports*. 2017; 5(4):72.
https://doi.org/10.3390/sports5040072

**Chicago/Turabian Style**

McMahon, John J., Paul A. Jones, Thomas Dos’Santos, and Paul Comfort. 2017. "Influence of Dynamic Strength Index on Countermovement Jump Force-, Power-, Velocity-, and Displacement-Time Curves" *Sports* 5, no. 4: 72.
https://doi.org/10.3390/sports5040072