A single isometric maximal voluntary contraction (MVC) results in postactivation potentiation (PAP), but few studies have considered the impact of dynamic sport-specific contractions on subsequent twitch potentiation. The purpose of this study was to investigate PAP resulting from the skeletal muscle force modulating influences of isometric and sport-specific dynamic muscle activations. Competitive cyclists (male n = 4; female n = 5) had a 10-min warm-up (80% HRmax) and a 10-min rest, then were randomized to do either 5-s or 10-s MVC (crossover design), followed immediately by 10 min of resting contractile measurements. Similarly, they then did 5-s or 10-s all-out sprint on a cycle ergometer followed by 10 min of resting contractile measurements. After a similar warm-up, speed skaters (male n = 18; female n = 6) did 10-s all-out sprint or a 10-s submaximal (~80% all-out) sprint on a cycle ergometer, followed by contractile measurements. The 5-s and 10-s isometric MVC produced similar initial significant rise in active torque (5 s = 158.7% ± 7.6%; 10 s = 170.2% ± 8.3%) followed by a gradual decline over 5 min (5 s = 108.7% ± 1.5%; 10 s = 110.1% ± 2.7%) and at 10 min (5 s = 105.5% ± 1.5%; 10 s = 108.8% ± 3.5%). The active torque measured 1 min after 5-s and 10-s all-out sprints had a similar initial high value (5 s = 144.5% ± 6.4%; 10 s = 136.1% ± 7.4%) and subsequent fall after 5 min (5 s = 104.6% ± 4.0%; 10 s = 107.6% ± 2.8%) but interestingly displayed a rebound from 5 min to 10 min (5 s = 109.0% ± 5.2%; 10 s= 116.5% ± 4.1%). We recruited the speed skaters to further evaluate this delayed PAP. PAP in speed skaters was similar after submaximal sprint as the maximal sprint, but clearly not in the same league as the cyclists (Submax = 108.2% ± 2.8%; Max = 106.4% ± 3.4%). This was followed by a decline after 5 min of rest (Submax = 99.6% ± 1.9%; Max = 100.2% ± 1.7%) the delayed rebound (delayed PAP developed from 5 min to 10 min) (Submax = 106.6% ± 1.9%; Max = 110.7% ± 1.5%), then slowly dissipated over 30 min (Submax = 104.2% ± 1.7%; Max = 105.6% ± 1.5%), but still remained above resting active force. Skeletal muscle force is modulated differently following dynamic compared with isometric muscle contractions. High-intensity dynamic muscle activation permits a delayed enhancement of subsequent muscle contractile response. This has important practical implications.
© Copyright 2012 Applied Physiology, Nutrition, and Metabolism. Canadian Science Publishing. Alle Rechte vorbehalten.