Author(s): KOTIKANGAS, J.1,2, WALKER, S.1,2, HÄKKINEN, K.1,2, PELTONEN, H.3,1,2, Institution: UNIVERSITY OF JYVÄSKYLÄ, Country: FINLAND, Abstract-ID: 2064

INTRODUCTION:
Various power resistance training loadings are used to improve rapid force production during high-velocity dynamic movements [1,2]. In addition to the loading protocol, previous training background seems to affect acute responses and recovery to resistance loadings [3]. Thus, we compared the effect of two power loadings with different load levels on neuromuscular and hormonal responses and recovery in power-trained athletes (PA) and nonathletes (NA).
METHODS:
PA (n=6) and NA (n=8) performed two power loadings consisting of 7 sets of 6 repetitions with 3 minutes between-set rest in Smith-machine back squat. The intensity, i.e. barbell load, was either 50% (PL50) or 75% (PL75) of the participant’s one repetition maximum (1-RM). Maximal bilateral isometric force (MIVC) and rate of force development with 5-millisecond sampling window (RFD) during isometric leg press, dynamic average velocity (VEL) during back squat, and rest twitch force (RT) during isometric knee extension were measured before (PRE), during (MID) and after loadings (POST), and after recovery of 1 (POST1), 2 (POST2), and 24 hours (POST24). Serum concentrations of growth hormone, cortisol, creatine kinase (CK), and blood lactate (BL) were measured at PRE, MID, POST and POST1.
RESULTS:
Total work was significantly higher during PL75, and PA performed significantly more work than NA during both loadings (p=0.001). There were significant differences between groups in BL during PL50 (F=9.862, p=0.009, ηp2=0.473) and PL75 (F=12.535, p=0.005, ηp2=0.533) with greater increases in BL at MID (p=0.016 and p=0.003, respectively) and POST (p=0.009 and p=0.005, respectively) in PA. A trend for larger increases in CK at POST24 from PL75 was found in PA (p=0.060). Total work correlated positively with both BL and CK (r>0.830, p<0.001). A trend for between-subject effect was found for VEL during PL50 (F=4.592, p=0.057, ηp2=0.292) indicating that PA had a greater decrease in VEL at POST (p=0.045). Significant loading × time interactions were found for all measured variables (F>3.671, p<0.05, ηp2>0.220), indicating that significantly greater decreases in neuromuscular variables and increases in blood variables were observed during PL75 versus PL50 (p<0.05). All neuromuscular variables were recovered at POST24, except RFD after PL50 and RT after both loadings, which already recovered at POST2.
CONCLUSION:
Training background seemed to affect mainly blood variables, whereas higher load level led to greater neuromuscular and hormonal responses. These findings may be explained by differences in absolute total work performed between groups and loadings. Load level should be selected based on the individual’s training goals, as acute responses may be linked to long-term training adaptations. Moreover, recovery rates of maximal force and rapid force production should be considered in periodization, especially when selecting same-day exercise sessions.

1. Brandon et al. (2015), 2. Howatson et al. (2016), 3. Ahtiainen et al. (2009)