Of larks and hearts - morningness/eveningness, heart rate variability and cardiovascular stress response at different times of day

► HRV at rest and in a stressful situation is lower in evening- than in morning-types. ► Cardiovascular activity at rest and under stress is higher in evening-types. ► Stress at 4-7 p.m. has stronger impacts on physiological measures than at 8-11 a.m. ► Physiological data support previous psychological and behavioral findings.