Neural contribution to postactivation potentiation

Abstract

The current study was designed to investigate the contribution of neural factors to postactivation potentiation (PAP). Neuromuscular function (i.e. twitches, H-reflexes, motor evoked potentials, and voluntary isometric ballistic contractions) of 8 power-trained (POW) and 8 endurance-trained (END) athletes was recorded before and after a 8-second maximal isometric conditioning contraction (CC) to induce PAP, to elucidate discriminating neural factors in exploiting PAP that might arise from the former training background compared to the latter. After CC, twitch peak force and rate of force development were significantly increased, with higher potentiation in POW (29 ± 11% and 64 ± 24%) than END (8 ± 12% and 34 ± 20%). Among evoked potentials, only motor evoked potentials were short-term facilitated (127 ± 111% and 93 ± 89%, for END and POW respectively), similarly between groups. No differences were reported in ballistic performance (P ≥ 0.069), whose neural drive was significantly depressed in POW at 1 and 2 minutes post-CC, respectively compared to END and to baseline (19 ± 11%). PAP was characterized from enhanced muscle contractile characteristics as well as short-term facilitation of corticospinal excitability, whose individual contribution to performance enhancement could not be quantified. However, when POW were compared to END, the former group benefited from PAP in triceps surae muscles only in terms of higher potentiation of muscular contractile characteristics, as neural pathways were affected likewise from CC. In addition, neural drive of ballistic performance, if affected, might be depressed in POW rather than enhanced, presumably due to neural fatigue from CC. Differences between groups in exploiting PAP in ballistic actions might be therefore primarily related to muscular potentiating mechanisms, although only non-significant potentiation (p-value close to the significance threshold) was found in ballistic performance in our experiments.