First of All, Close Your Eyes: The Contribution of Vision to Countermovement Jump Performance
(Artur Struzik, Joanna Broda, Bogdan Pietraszewski)

Depending on the motor task or the situation, visual stimuli may facilitate or hinder task performance. The purpose of this study was therefore to investigate the role of vision in CMJ performance. The study was conducted on a group of 30 physically active men (age: 21.5 ± 1.1 years, body height: 1.83 ± 0.07 m, body mass: 78.6 ± 10.7 kg) with no visual impairment and high jumping abilities. All participants performed a total of 12 CMJs: 6 under a full-vision condition (FV) and 6 under a no-vision condition (NV), in randomized order. Measurements were conducted using two Kistler 9286A force plates with Noraxon MR3 software. No significant differences were found in jump height (JH), mean power (MP) in the propulsion phase, propulsive time (PT), countermovement depth (CD) or countermovement time (CT) between the FV and NV conditions. Under the FV condition, peak power (PP) in the propulsion phase was by 87 ± 222 W higher than under the NV condition (p < 0.05 with small effect size). Furthermore, the relationships among the variables describing the CMJs (JH, PP, MP, PT, CD, and CT) under the FV and NV conditions were large, very large or nearly perfect (p < 0.001). The results show that eliminating visual stimuli may not have a negative impact on CMJ performance. On the contrary, eliminating visual stimuli can reduce interference that negatively affects maximum performance (e.g., maximum jump height). This surprising observed phenomenon may be possible due to the important role played by the proprioceptive system and kinesthetic feedback.