Author(s): SPUDIC, D., PRIMOŽ, P., VOJKO, S., NEJC, Š., IGOR, Š., Institution: UNIVERSITY OF LJUBLJANA, Country: SLOVENIA, Abstract-ID: 1677

INTRODUCTION:
Quantification of load magnitude is a limitation in flywheel (FW) resistance training protocols. Adaptation mechanisms for muscle strength and jumping performance improvement are velocity-specific [1]. However, it is unknown whether this specificity extends to the FW modality. Force-velocity-power (FvP) profiling has been proposed to assess neuromuscular characteristics of lower extremities in FW squats [2,3]. This method could also be utilized to individually allocate the magnitude of FW load [4]. This study aimed to evaluate the differences in adaptations of leg strength and jumping performance after FW squat resistance training performed under low and high loading conditions.
METHODS:
Physical education students were randomly assigned to two training groups and a control group. The training groups engaged in eight weeks of FW squat resistance training, 2-3 times per week, with low and high inertial loads. Individual load determination was based on FvP profile characteristics obtained during FW squats. The low-load group (n = 16) performed squats with the FW load that maximized power output, and the high-load group (n = 18) used a load corresponding to 70% of maximal theoretical power. The control group (n = 13) received no intervention. Various tests were conducted, including isometric knee extension strength and rate of force development (RFD), squat jump (SJ), countermovement jump (CMJ), FvP profiling in FW squats and CMJs. Mechanical and electromyography (EMG) variables were measured, along with an ultrasound assessment of vastus lateralis (vl) muscle thickness, pennation angle, and fascicle length. A mixed model analysis of variance with factors time (pre, post) and group (C, low-load, high-load) was performed to reveal differences in adaptations between groups over time.
RESULTS:
FW squat training induced improvements (all p < 0.05) in: knee extension strength; SJ RFD, force and power; CMJ height, force and power in concentric and eccentric phases; FW FvP profile outcomes in the concentric phase and the maximal theoretical force in the eccentric phase; CMJ FvP profile maximal theoretical velocity and power; vl muscle thickness and pennation angle. No significant differences were found in the adaptations between the two training groups (p > 0.05).
CONCLUSION:
FW squat resistance training emerged as an effective modality for enhancing the strength, power, and jumping abilities of athlete students. Interestingly, the magnitude of the FW load did not show a statistically significant influence on the observed adaptations. There was a trend toward higher changes in mechanical variables and muscle architecture in the high-load group. The improvements in mechanical variables were more strongly associated with the adjustment in vl muscle thickness than with neural activation enhancement, irrespective of the motor test performed.
REFERENCES:
1) Behm & Sale, Sport. Med. 1993
2) Spudić et al., J. Biomech. 2020
3) Spudić et al., PLoS One 2020
4) Spudić et al., Kinesiol. Slov. 2023