Dose–response relationship between light exposure and cycling performance

Light has a stimulating effect on physical performance if scheduled according to the chronotype, but dose‐dependent effects on performance have not yet been examined. Three groups of healthy men (25.1 ± 3.1 years) were exposed to light for different durations in a parallel group design before a 40‐min time‐trial. In each group, subjects were exposed to either bright light ( BL , 4420 lx) or moderate light ( ML , 230 lx) in a randomized order in a crossover design. The durations of light exposure were 120 min prior to and during exercise ( 2HEX ; n  = 16), 60 min prior to and during exercise ( 1HEX ; n  = 10), or only for 60 min prior to exercise ( 1H ; n  = 15). Total work performed during the time‐trial in kJ in the 2HEX group was significantly higher in the BL setting (527  kJ ) than in ML (512  kJ ) ( P  = 0.002), but not in 1HEX ( BL : 485  kJ ; ML : 498  kJ ) or 1H ( BL : 519  kJ ; ML : 514  kJ ) ( P  = 0.770; P  = 0.485). There was a significant ( P  = 0.006) positive dose–response relationship between the duration of light exposure and the work performed over the three doses of light exposure. A long duration light exposure is an effective tool to increase total work in a medium length time‐trial in subjects normalized for their individual chronotype.