Dissertation planning- potentiation

Dissertation planning- potentiation

1. What physical characterstic am i trying to learn more about/ potentiate

   • Power/ RFD- WHat is RFD- The ability to produce force within a certain time frame ( fast 90 ms) slow >90ms
     • What adaptations Underpin RFD
       • Fast
         • Increase MU dishcarge- decreasing MU threshold/ High firing rate
           • TII Fibres Isoform
             • Minimosing Calcium fatigue / proximity
           • Movement Speed/ INtent
             • Rapid activation of musculature
               • Specificity is key at slower movement velocities
       • SLow
         • Tendinous stiffness
           • FCSA of TII Fibres
             • MU recruitment
           • Mechanical tension
       • What adaptations/ stimulus am i targetting
         • Increased firing rate - trying to enhance movement soeeds
         • MU activation- high levels of MU recruitment to allow the utilisation of the high threshold fast twitch fibres
         • Reductions in antagonist coactivation ?- Blavevich plyometrics paper

2. What is potentiation

   • PAP- Post activation potentation
     • Enhanced mudcle contraction response following an intense voluntary contraction - measured as enhanced twitch force evoked by suprmaximal stimulation ( MacIntosh et al 2012)
       • 3 forms of adtivity dependent potentiation - Staircase(low magnitude contractionsat high frequency which sequentially increase in amplitude), Post tetanic( following a brief high frequency train of electrical stimulation) potentiation and PAP(Voluntary activation)
         • Burke et al 1976- highlighted PAP speficially as an augmentation of twitch tension following any type of repetitive activation
           • 80' papers highlight importance of otther charactersitics effecting PAP( duration, intensity , muscle length) decreases dramatically to one half life of 28s
             • 1973- found that muscle contained a phosphorylatable light chainResearches found that PAP was maintained while MLC was phosphorylated - Calcium dependent MLCP rendered increased calcium sensitvity- greater crossbridge formation rates
     • Mechanisms
       • Myosin light chain phosphorylation- immediately a an increase in peak force and RFD ( caralysed by myosin light chain kinase)
         • Small polypeptide sub unit of myosin- determined by the twich force and magniytide of phosphorylation of mrlc - force for a given submax calcium concentration
           • Improves mobility of the myosin head to move closer to actin binding site increasing rate of cross bridges -- effect is greater in TII fibres which have lower basal calcium sensitivity and greater mlck
             • Phosphorylation does not affect the detatchment rayes therefore should not effect the maximal unloaded shortening speed --------------------Despite this potentiation is measured more in maximal concentric shortening- shortening ( maximal) is found to be associated with less time in cross bridge non force generating state - allows amplified effect of increased attachment
   • PAPE- Post activation performance enhancement
     • a high-intensity voluntary conditioning contraction(s) leads to enhancement in voluntary muscular performance in a subsequent test without confirmatory evidence of classical PAP (i.e., twitch force assessment). (Cuenca-Fernandez et al., 2017)
       • Because the different time course of effect (e.g., Figure 2) as well as possible differences in the mechanisms underpinning force enhancement, Cuenca-Fernandez et al. (2017) recently proposed that the term “post-activation performance enhancement” (PAPE) should be used when high-intensity voluntary conditioning contraction(s) are performed with the intent of enhancing subsequent voluntary, rather than electrically evoked (twitch), force production.
     • Mechanisms
   • Activity-dependent potentiation - the change in contractile response for a given stimulation that is dependent on contraction history