Running in the Dark
by Doug Stewart
With the darker mornings and evenings in the Northern Hemisphere, I thought I’d share two recent studies exploring the impact of exercising in the dark on efficiency.
Research has previously shown that when soldiers walk on varying terrain at night, wearing night vision goggles, they have a higher oxygen uptake than during daylight (so, they are less efficient at night). Several factors may contribute to this, such as lifting their feet higher – to reduce the chance of tripping – to taking shorter strides.
However, a recent publication set out to explore the impact of walking on a treadmill (so a consistent surface) and the influence of reduced vision on mechanical efficiency.
15 volunteers walked at 3.3kph for 10 minutes on a flat treadmill in 4 scenarios:
Full vision carrying no weight
No vision carrying no weight
Full vision with a 25.5kg backpack
No vision carrying a 25.5kg backpack
Perhaps not surprisingly, the most efficient was the 1stcondition, whilst least was the 4th. The data does suggest that overall oxygen uptake was around 19% higher with lack of vision. The change in walking form saw step length reduce and an increased step width, as well as an increase in foot clearance, even when the subjects knew there were no obstacles ahead of them.
This therefore suggests that, even in obstacle free flat walking, biomechanics change with the degree of vision we have.
However, this was more extreme than what we encounter in winter: with 0 vision, whilst endurance athletes will be training and racing with a headtorch!
A second study that was released this month explored the impact difference between full vision, no vision and around 40% vision. They had 11 subjects walk on a treadmill at 2.3 degrees (c.4%) at 4kph. In addition to exploring the physical impact of the various conditions, measures of perceived exertion, discomfort and mental stress were also captured.
Similar to the first paper, the dark conditions were the least efficient, whilst full vision was the most efficient.
Additionally, the conditions with limited or no vision were perceived to be more physically demanding, uncomfortable and stressful than full vision. The complete darkness was deemed to be the most mentally stressful.
Whilst it is important to not take certain findings and assign them to other scenarios, this raises a couple of interesting questions for me around headtorch use during running:
Whilst a lot of endurance athletes look for the lightest kit - and this will help with running economy versus heavier kit - will a heavier headtorch which is brighter help offset the negative impact of its weight by enabling a more efficient running style?
With increased perception of effort, mental stress and discomfort, will the psychological benefits of a brighter headtorch offset the impact of its weight (and potential discomfort of having a heavier headtorch on your head)?
I am not sure research currently exists that explores these areas, but certainly it appears that a brighter headtorch may yield benefits over and above greater illumination.
References:
Eiken, O., Mekjavic, I.B., Babič, J., Danielsson, U., Hallberg, M. and Kounalakis, S.N., 2022. Effects of vision on energy expenditure and kinematics during level walking. European Journal of Applied Physiology, 122(5), pp.1231-1237.
Norrbrand, L., Grönkvist, M., Kounalakis, S., Halvorsen, K. and Eiken, O., 2022. Metabolic Demands and Kinematics During Level Walking in Darkness With No Vision or With Visual Aid. Military Medicine.