Reactive-strength index modified as an explosive ...

D1.S3.4(2)

Reactive-strength index modified as an explosive measurement in male sprint and endurance athletes. Thomas Comyns, Colin McNamara, Oliver White University of Limerick, Ireland

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Introduction • Monitoring of various performance characteristics of athletes is a crucial component of the overall training process (Suchomel et al., 2015) • Stretch-shortening cycle function testing using a force platform is an example of such monitoring. • Analysis of force-time curves has been widely used to assess skeletal muscle function (Haff et al., 1997). 29-30 November East Midlands Conference Centre

Introduction • Reactive-strength index modified (RSImod) is a monitoring measure that provides data on an athlete’s reactive strength (Suchomel et al., 2015). • RSImod is a modification of the measure ‘reactive strength index’ (Height/ Contact Time) derived from a drop jump. Height Jumped (m)

RSImod: Time to Take-off (s)

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Introduction

Adapted from Suchomel et al., 2015 29-30 November East Midlands Conference Centre

Introduction • RSImod has been derived from unloaded and loaded counter-movement jump (CMJ) testing (Suchomel et al., 2015). • Suchomel et al. (2015) reported that RSImod is a reliable performance measurement in male testing (ICC = 0.96). • Authors also noted that statistically significant correlations exist between RSImod and force-time variables, such as rate of force development. • Can RSImod distinguish between sports and different athlete population groups? 29-30 November East Midlands Conference Centre

Aim of Study Two key aims of this study:

1 2

• Assess the RSImod profile of sprint and endurance athletes • Examine if RSImod differences exist between these two athlete population groups

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Methods • 7 male sprinters and 7 male endurance runners Table 1: Participant information (mean ± s) Variable Athlete

Height (m)

Mass (kg)

Age (years)

Sprint (n = 7)

1.83 ± 0.04

75.88 ± 0.05

21.57 ± 1.50

Endurance (n = 7)

1.78 ± 0.04

73.54 ± 4.37

24.29 ± 5.20

• Two testing sessions; familiarisation and data collection session • Research project had institutional ethics approval and all participants volunteered and consented. 29-30 November East Midlands Conference Centre

Methods: Test Procedure 1 2 3

• Standardised warm-up, including 3 x CMJ at increasing intensity (50, 75 & 100%) • 1 minute rest • 2 x CMJ with 30 seconds rest between trials

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Methods • All CMJ were performed on a force platform (AMTI OR6-5) sampled at 1,000 Hz. • Force-time data was used to calculate time to takeoff, height jumped and subsequently RSImod. • Statistical analysis involved: • Independent sample t-test to assess any group differences • Calculation of the effect size of these differences, Cohen’s d. 29-30 November East Midlands Conference Centre

Results • Results related to height jumped (m) and the time to take-off (TTT) in seconds for the sprint and endurance groups Table 2: Jump height and TTT scores (mean ± s) Variable

Sprint Group

Endurance Group

J ump Height (m)*

0.42 ± 0.05

0.26 ± 0.10

TTT (s)*

0.75 ± 0.13

0.96 ± 0.09

* Significant difference between groups, p ≤ 0.01

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Results

*p ˂0.001 29-30 November East Midlands Conference Centre

Results • Effect size, Cohen’s d, results with classifications: Table 3: Cohen’s d results with classifications Variable

Cohen’s d

Classification*

Jump height (m)

2.14

Very Large

TTT (s)

1.96

Very Large

RSImod

3.04

Very Large * Cohen (1988)

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Discussion • Reported RSImod scores are similar to values reported by Suchomel et al. (2015), i.e. 0.41 ± 0.09. • Sprint male athletes have significantly higher jump height, lower time to take-off and higher RSImod scores than endurance athletes. • RSImod can distinguish between sprint and endurance population groups.

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Conclusions • RSImod can be used as a measure of explosiveness for sprint and endurance athletes.

• RSImod can distinguish between different athlete population groups. • Previous RSImod published values can help the interpretation of an athlete’s RSImod level. • More research is needed, particularly on correlation between RSImod and performance indicators. 29-30 November East Midlands Conference Centre

References • Cohen, J., 1988. Statistical analysis for the behavioral sciences. Hillsdale: Lawrance Erlbaum. • Haff GG, Stone M, OʼBryant HS, Harman E, Dinan C, Johnson R, and Han K-H, 1997. Force-time dependent characteristics of dynamic and isometric muscle actions. Journal of Strength & Conditioning Research, 11:269-272. • Suchomel, T.J., Bailey, C.A., Sole, C.J., Grazer, J.L. and Beckham, G.K., 2015. Using reactive strength index-modified as an explosive performance measurement tool in Division I athletes. The Journal of Strength & Conditioning Research, 29(4):899-904.

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