Post activation potentiation – modulating factors and mechanisms for muscle performance

Tisdagen den 2 februari 2016 kl 12:30 disputerar Paulo Gago i idrottsvetenskap. Avhandlingens titel är "Post activation potentiation – modulating factors and mechanisms for muscle performance".

Paulo Jorge Russo Gago har skrivit en idrottsvetenskaplig avhandling inom rörelselära. Han tillhör GIH:s enhet för prestation och träning.

Disputationen äger rum tisdag 2 februari 2016 kl. 12:30 i GIH:s aula.

Opponent är Nicola Maffiuletti, Associate Professor och Lab Director vid Schulthess Clinic, Zurich

Huvudhandledare: docent Maria Ekblom (GIH). Bihandledare är professor Toni Arndt (GIH).

Betygsnämnden består av:

Läs mer om Paulo Gago.

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Abstract

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Om avhandlingen

Avhandlingen handlar om hur explosiviteten i idrottares muskler kan förhöjas efter en 6 sekunders maximal muskelaktivering, ett fenomen som benämns PostAktiveringsPotentiering.

Omslag Paulo Gagos avhandling

Resultaten påvisar att en kraftigt förhöjd explosivitet i vadmusklerna kan åstadkommas under några minuter utan att samtidigt påverkahälsenans styvhet. Framför allt snabbt koncentriskt muskelarbete potentieras, men också musklernas längd är en faktor som modulerar hur stor förbättringen blir.

I avhandlingen diskuterar Paulo Gago även hur fynd från avhandlingen tillsammans med närliggande forskning kan vägleda idrottare till att utpröva bättre uppvärmningsprotokoll inför tävling och träning.

Abstract

Introduction: Acute enhancements of muscle contractile properties and performance subsequent to a maximal or near maximal conditioning contraction are often termed post activation potentiation (PAP). Although still controversial, PAP is commonly linked to enhancements in the myosin regulatory light chain phosphorylation, leading to improvements in the excitation–contraction coupling. The PAP seen after a conditioning task often coexists with fatigue and is known to depend on strength level, muscle fiber type and age. Less is known about how factors such as static and dynamic changes in muscle length affect PAP, and on the relative contribution of contractile and tensile components to PAP.

Aim: To enhance our understanding of how, and under what conditions, a single maximal isometric contraction affects plantar flexor muscle contractile performance, and other muscle tendon properties, in power athletes.

Methods: Supramaximal twitches were evoked via electrical stimulation of the tibial nerve of athletes before and on several occasions after a 6-second maximal voluntary isometric contraction (6-s MVIC) in both static muscle, and during passive muscle lengthening and shorting at different angular velocities. Several contractile variables were measured from the twitches. The effects of a 6-s MVIC on Achilles tendon stiffness was calculated from torque and ultrasonography based measurements of tendon length at two submaximal contraction intensities. Overall stiffness index was calculated by analyzing the passive lengthening torque/angle curve.

Results: A single MVIC enhanced muscle contractile properties and electromechanical delay for up to 5 minutes. Plantar flexor twitch variables such as peak twitch, rate of torque development and rate of torque relaxation were enhanced during shortening compared to lengthening muscle actions, and in an extended as compared to a flexed knee position. Achilles tendon stiffness and overall stiffness index were not significantly modulated by a single 6-s MVIC.

Conclusion: The results of this thesis imply that functional enhancements from a 6-s conditioning MVIC would mainly come from improvements in contractile rather than tensile components. Stiffness changes should be monitored in future PAP-related studies since they may still occur after more extensive conditioning protocols than the current one. Improvements in contractile components subserving muscle strength after a conditioning MVIC suggests that enhancements in muscle power after a conditioning task should be greatest in fast concentric muscle actions, though still present in muscle lengthening. Conditioning should be performed in a position where full activation is easy to achieve and tailored to mach an athlete or group of athletes' current status and characteristics, maximizing performance in a specific sport event.

Adress till denna sida: www.gih.se/disputationPG