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SOUTHWESTM I N N E S O T A S T A T E U N I V E R S I T Y

The Effects of Post-Activation Potentiation Using Maximum Isometric Contractions on College Football Players , Alex Oliver, Blake Pennock & Jeffrey W. Bell

Southwest Minnesota State University 1501 State Street Marshall, MN 56258

Results/Discussion Conclusion

References

Introduction

Abstract Methods

Acknowledgement

1. Sale, D.G. (2002). Postactivation Potentiation: Role in Human Performance. Exercise in sport science reviews, Vol. 30, Issue (3): 138-143.

2. Babajic, F., Bradic, A., Klino, A., Kovanecevic, E. Effects of Maximum Isometric Contraction on Explosive Power of Lower Limbs (Jump Performance). Sport SPA, Vol. 7, Issue (1): 69-75.

Post-Activation Potentiation allows for the potentiation of the neuromuscular system which may improve power and performance of the athlete.

A common theory for this improvement of power and performance is the concept of myosin light chain phosphorylation. Myosin light chain phosphorylation causes the actin-myosin interaction to be more sensitive when releasing the calcium ion from the sarcoplasmic reticulum, thus allowing for faster muscle twitch and contractions (Sale, 2002).

PAP research has used dynamic contractions, but few studies have investigated the effects of static isometric contractions to potentiate muscular power (Babajic, 2010).

The primary goal of our research was to determine whether maximal voluntary isometric contractions improve performance and power.

Post-Activation Potentiation (PAP) has been reported to increase force production through activating neuromuscular systems. PAP is typically performed by contracting skeletal muscle near maximum force development. The objective of this investigation is to determine if PAP using maximum voluntary isometric contractions (MVC) influences instantaneous peak-power output and performance in vertical jump and back squat. In two separate sessions, twelve collegiate football players performed either a dynamic warm-up or a dynamic warm-up followed by a six second MVC before each test. Vertical jump was similar with and without PAP (72.0±6.9 vs 72.8±7.2 vs cm, p=0.76). Back squat peak-power was greater, but not significantly different, with PAP compared to without (1864±315 vs. 1725±281 Watts, p=0.26) as was instantaneous peak-power during vertical jump (2528±390 vs. 2241±330 Watts, p=0.11. Additional subject recruitment and testing is needed to determine whether isometric PAP influences instantaneous peak power but does not appear to improve vertical jump height.

ParticipantsEthical approval received from SMSU’s IRB and participants were provided written informed consent.12 collegiate football players participated. Subject characteristics: age (20.8±1.37 years), weight (93.3±9.68 kg), and height (185.7±3.98 cm).

Study DesignThis study was performed in two sessions with each session being a week apart.Session 1 included a dynamic warm-up followed by testing.Session 2 included a dynamic warm-up and PAP followed by testing. PAP was performed 30. seconds before vertical jump tests and back squat tests.Testing included a vertical jump and back squat.

ProceduresVertical Jump- While standing on a vertical jump mat (Just Jump) and connected to a power analyzer (Tendo), subjects completed three trials of a maximal jump for height.Back Squat- The power analyzer (Tendo) was connected to the barbell and configured to the weight being lifted. Subjects performed three trials of 1 repetition at 50% of 1 Repetition Maximum as rapidly as they could lift the weight.Activation was performed by using the barbell to push against the power rack in the back squat position. The power rack was adjusted for about 90 degrees of knee flexion for the isometric contraction position. The subjects were then instructed and encouraged as they pushed up against the power rack for six-seconds (Figure 1B).

Thank you to those who volunteered as subjects for our research, Dr. Jeffrey W. Bell for assisting us throughout our study, and Caleb Heim for providing us with support and data documentation that was used for the subjects’ one-repetition maximums.

Vertical jump height was similar in both conditions.

The mean vertical jump peak power was 12.8% better when the testing was conducted following isometric contraction activation, but did not reach significance.

The mean back squat peak power was 8% higher when the testing was conducted following isometric contraction activation, but did not reach significance.

Table 2A: The mean results obtained for the combined subjects for each testing activity with and without activation.

Figure 1C: Comparison of mean peak power in the vertical jump test among all subjects with activation (2527.97 ± 389.6) and without activation (2240.65 ±

330.25).

Figure 1B: A photograph of the activation method used to potentiate the individual’s neuromuscular system

prior to testing.

Maximum voluntary isometric contractions may not effectively potentiate the neuromuscular system and improve peak power and performance.

Results of this study suggest only small, non-significant improvements in peak power.

The study may have been underpowered and additional recruitment and testing is needed.

The power analyzer did not capture data for vertical jump of three subjects and contributed to the lack of study power.

Future studies should perform PAP prior to each and every trial as previous trials may moderate performance.

Recovery time increments may need to be varied to determine the effect on potentiation to ensure fatigue was not inhibiting performance.

The joint angle of the maximum voluntary isometric contractions may also be altered in further research to determine the most effective angle to properly potentiate the neuromuscular system for each performance task.

Overall, this study allowed us to gain insight on the possibility of maximum voluntary isometric contractions ability to potentiate the neuromuscular system and will allow for improvements during follow-up studies.

Warm-Up Exercise Distance

Warm-Up Jog 200 yards

Walking Knee up & Grab 15 yards

Walking Single Leg Toe Touch 15 yards

Walking Ankle Grab 15 yards

High Knee Run 20 yards

Butt-Kick Run 20 yards

Carioca (high knee over) 20 yards each way

High Knee Skip 20 yards

Figure 1A: The dynamic warm-up exercises and distances that were performed prior to each session.

Test Without Activation With Activation

Vertical Jump Height (cm) 72.83 (± 7.16) 71.96 (± 6.82)

Vertical Jump Peak Power (Watts)

2240.64 (± 330.25) 2527.97 (± 389.6)

Back Squat Peak Power (Watts)

1725.4 (± 282) 1864 (± 314.6)

Figure 1D: Comparison of mean peak power in the Back Squat test among all subjects with activation(1864 ± 314.6) and without activation(1725.4 ± 282).