Circadian phenotype influence on neuromuscular performance in male volleyball players.

Circadian phenotype (i.e. chronotype) may affect athletic performance across different times of day, but its role in team sports is underexplored. The aim of this study was to assess the impact of chronotype on neuromuscular performance in male volleyball players. Forty-six male volleyball players (age: 26.8 ± 7.9 years) completed the Morningness-Eveningness Questionnaire and were classified as morning-type (n = 12), intermediate-type (n = 15) or evening-type (n = 19). Then, in a randomized and cross-over design, participants completed a neuromuscular test battery comprising vertical jumps (squat jump, countermovement jump, spike jump), spike tests (standing and jump spike), agility (modified T-test), isometric handgrip strength, and dynamic balance; performed in the morning (8:00-10:00 AM) and the evening (18:00-20:00). No significant circadian phenotype by time-of-day interaction was found (p = 0.133-0.743, ηp2 = 0.09-0.14). However, time-of-day effect was found in squat jump, countermovement jump, spike jump, standing spike test, and non-dominant handgrip strength (p = 0.001-0.046, ηp2 = 0.09-0.41), observing an evening improvement in performance ranging from 1.8% to 3.0% (p = 0.001-0.035, d = 0.47-1.16). circadian phenotype had limited impact on neuromuscular performance while diurnal variation enhanced evening performance with a significant role in vertical jump ability and spike velocity among male volleyball players.