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

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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.