Blanketed by darkness and zipping past streetlamps, night runners may feel as though their nocturnal hours award swifter speeds. But does logging midnight miles actually inspire greater speeds, or is the quickened pace merely a mind trick?

A Run on the Dark Side—Why It Matters

Donning sneakers at sunrise rarely seems more appealing than basking in bed—even for the most dedicated runners. And for some, nighttime running, if done safely, can be a more convenient cardio fix. Besides the less-crowded paths, cooler temperatures, and forgiving lighting of the moon (see ya, sweat stains and trouble spots!), late night escapades may prompt runners to feel as though they are running at a faster paceApparent speed increases at low luminance. Vaziri-Pashkam, M., Cavanagh, P. Vision Sciences Laboratory, Department of Psychology, Harvard University, Cambridge, MA. Journal of Vision, 2008 Dec 22;8(16):9.1-12.. Move over, Mr. Bolt. But, not so fast… Research suggests a runner’s perception of increased speed at night is just that: a perceptionPerceptual distortions of speed at low luminance: evidence inconsistent with a Bayesian account of speed encoding. Hammett, S.T., Champion, R.A., Thompson, P.G., et al. Department of Psychology, Royal Holloway University of London, UK. Vision Research, 2007 Feb;47(4):564-8. Epub 2006 Sep 29.. The brain perceives the body’s speed based on incoming visual cues from its surroundingsVisual flow influences gait transition speed and preferred walking speed. Mohler, B.J., Thompson, W.B., Creem-Regehr SH, et al. School of Computing, University of Utah, Lake City, UT. Experimental Brain Research, 2007 Aug;181(2):221-8. Epub 2007 Mar 20.Mechanisms of self-motion perception. Britten, K.H. Center for Neuroscience and Department of Neurobiology, Physiology, and Behavior, University of California, Davis, CA. Annual Review of Neuroscience, 2008;31:389-410.. One such speed cue is motion parallax (for example, when traveling in a car, nearby objects seem to fly by more quickly than objects further away)Visual depth from motion parallax and eye pursuit. Stroyan, K., Nawrot, M. Mathematics Department, University of Iowa, Iowa City, IA. Journal of Mathematical Biology, 2011 Jun 22.. The same experience applies to running, biking, scootering, crab-walking, and other forms of linear motion (and also explains why you feel zippier when running on ground than on a treadmill)Unmatched perception of speed when running overground and on a treadmill. Kong, P.W., Koh, T.M., Tan, W.C., et al. Physical Education & Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore. Gait Posture, 2012 Feb 20.Cycling rate is modulated by optic flow in a virtual bicycle environment. Gade, V., Maidan, I., Gallagher, R., et al. Rivers Lab, Dept of Rehabilitation and Movement Sciences UMDNJ, Newark, NJ. Virtual Rehabilitation, 2011 International Conference, 27-29 June 2011.. The reason why? To assess speed, the brain compares the relative speed of objects in both extremes of distance (think: the planted flowers along the path versus the distant horizon or skyline). But at night, the darkness limits our vision making the “slower-moving” objects in the distance invisibleDepth interval estimates from motion parallax and binocular disparity beyond interaction space. Gillam, B., Palmisano, S.A., Govan, D.G. School of Psychology, University of New South Wales, Sydney, Australia. Perception, 2011;40(1):39-49.. So our only gauge for speed is the road sign or the shadowed trees we just blew by (or wait, was that the boogeyman?!).

Night Sweats—The Answer/Debate

While the piqued pace may be a nighttime illusion, some research suggests evening workouts are indeed more energy-efficient, powerful, and allow for higher endurance compared to morning workoutsThe effects of circadian rhythmicity of salivary cortisol and testosterone on maximal isometric force, maximal dynamic force, and power output. Teo, W., McGuigan, M.R., Newton, M.J. Exercise and Sports Science Department, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, Australia. Journal of Strength and Conditioning Research, 2011 Jun;25(6):1538-45.Circadian variation in sports performance. Atkinson, G., Reilly, T. Centre for Sport and Exercise Sciences, School of Human Sciences, Liverpool John Moores University, City Name, England. Sports Medicine, 1996 Apr;21(4):292-312.. But how? Studies chalk this up to circadian rhythms and the fact that our body’s metabolism, mood, appetite, and other functions peak at different times of day. For example, the average person’s core body temperature peaks in the evening, which loosens up muscles and makes them more ready for movementWarm-up affects diurnal variation in power output. Taylor, K., Cronin, J.B., Gill, N., et al. Department of Physiology, Australian Institute of Sport, Canberra, Australia. International Journal of Sports Medicine, 2011 Mar;32(3):185-9.. Similar research suggests that lung function, alertness, and flexibility are also enhanced in the eveningDiurnal variation in temperature, mental and physical performance, and tasks specifically related to football (soccer). Reilly, T., Atikinson, G., Edwards, B., et al. Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK. Chronobiology International. 2007;24(3):507-19.Morning-to-evening differences in oxygen uptake kinetics in short-duration cycling exercise. Brisswalter, J., Bieuzen, F., Giacomoni, M., et al. Laboratoire Ergonomie Sportive et Performance, Université du Sud Toulon-Var, La Garde Cedex, France. Chronobiology International, 2007;24(3):495-506.. The result? The differences in a person’s AM to PM exercise capacity may be like night and day. So are circadian rhythms likely to help shave off seconds from a mile time? Maybe, but only if the run falls within circadian rhythm peak hours, and for most people that aligns with the early evening (between 4 and 6pm)Circadian rhythms in exercise performance: Implications for hormonal and muscular adaptation. Teo, W., Newton, M.J., McGuigan, M.R. School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, Western Australia. Journal of Sports Science and Medicine, 2011;10:600-606.. Even still, the change in performance is minimal. And a jog under the stars after the Nightly News likely won’t add that much speed either—except in our heads. But a confidence boost never hurts. And night owls can hit the snooze button feeling a little less guilty for skipping that morning run—the night awaits.

The Takeaway

There is no evidence that proves running at night and/or in the dark directly improves speed. Instead, a visual illusion is likely responsible for the deceiving (yet confidence-boosting) sensation.This article has been read and approved by Greatist Experts Vicki Vara andMichael George. Photo by Marissa Angell