Diurnal Variation in Stretch Shortening Cycle and Non-Stretch Shortening Cycle Jumping Performance

This study assessed the diurnal variations, as well as the subjects’ perceptions of how time of day affects their jumping performance. Eighteen subjects participated in testing sessions at 7 a.m., noon, and 5 p.m., on the same day. Subjects performed squat jumps (SJ) and countermovement jumps (CMJ) on a force platform with peak ground reaction force (GRF), jump height, and reactive strength index-modified (RSImod) obtained for each jump. Diurnal differences for the CMJ were found for GRF (P = 0.048). Diurnal differences for the SJ were found in RSImod (P= 0.04). Subjective assessment of jumping explosiveness was significantly different across time of day (P = 0. 047). Lower body power training such as plyometrics, may be more effective at mid day than early morning or late afternoon.