Scientific research provides the rationale for the design and function of Veo.

Below we highlight three clinical studies representative of the evidence behind Veo's approach to the problem presented by sweat in the eyes and on glasses. The evidence demonstrates that:

  • The forehead is the best heat dissipating skin on the body.

  • Blood is preferentially directed to the forehead specifically for thermoregulatory cooling during exercise.

  • Covering the forehead defeats this purpose and also leads to significant local heat increase

  • The forehead increases sweat production more than any other area of the body during exertion, again for thermoregulatory purposes

  • Increased sweat production at the forehead makes it very difficult if not impossible to capture it by absorption

 

The Forehead produces more sweat per sq in than any other part of the body

Forehead thermal image.jpeg

Thermal Physiology PhD Caroline J. Smith and Medical Physiology PhD George Havenith of Loughborough University studied variations of sweat rates in varying regions of the body in elite and sub-elite athletes  (European Journal of Applied Physiology (2011) 111:1391–1404).  The authors had a particular interest in sportswear and skin coverage and its implications for heat transfer: “Sweat production in different body regions is relevant for the analysis of the body’s heat exchange since clothing cover varies over different body parts, in addition to regional heat transfer coefficient differences resulting from air and body movement.

The study recorded sweat rates in 41 regions of the body, including six on the head.  Study participants exercised at 55% and 75% of their maximum exercise intensity in a controlled environment at 78 degrees F.  The standard measure of exercise intensity, percentage of maximal oxygen uptake (VO2 max) was used.  This is a scientifically-accepted means of equating varying individuals’ exertion level.  The authors calculated sweat rates in the separate regions at each of the two intensity levels using absorbent pads and rigorous methods of collecting sweat from only the selected regions.  They compared both the absolute and relative changes in sweat rates in the various areas.

The forehead produced the largest absolute volume of sweat per unit of surface.  The athletes’ foreheads sweated 2.6 times the average overall sweat rate for all the measured areas, and 43% more than the next highest area.  Sweat production at 75% of VO2max averaged 12cc and ranged as high as over 18cc per hour.  Recalling that 75% of VO2 max is still below a long distance sustainable exercise rate, it is not possible absorb all sweat that can be produced at the forehead.  The problem is exacerbated when production from the scalp, draining via the forehead, is added and exercise intensity is increased beyond 75%.

Covering the forehead traps heat and rapidly increases athlete temperature

Though the purpose of the study was not to determine relative skin temperatures, the authors did collect data on the increase in skin temperature during the periods when the absorbent pads were applied (the final  5 minutes of a 30 minute session at the target exercise level).  Core temperature increased to 100.7 degrees F during exercise, and face and neck temperature changes due to skin occlusion with the sweat-collecting pads averaged an increase of 3 degrees F.  This was after only 5 minutes of skin coverage.

The study shows that the forehead is prime sweat producing territory, and that covering that territory can cause some big temperature increases.  

Temperature radiation.jpg

The forehead is particularly important to cooling and can dissipate heat at 4x the rate of the torso

Authors Taylor PhD et.al. at the University of Wollongong, Australia reported on their research into rates of heat dissipation potential from the hands and feet, published at the International Conference on Environmental Ergonomics.  Though their work did not focus on the forehead, they do state that “Indeed, when normalized to surface area, the potential evaporative heat loss from the two hands is 110% greater than at the torso, and 200% greater than at the two feet, but only half that at the forehead.” That is, the forehead can dissipate four times as much heat as the torso per unit of surface area.

Bloodflow to the forehead increases by 12x during exercise, specifically to aid cooling

Japanese researchers Kaho Sato PhD et. al. at the Toyo University and the Research Institute of Physical Fitness, Japan Women’s College of Physical Education, Tokyo, studied changes to blood flow to the  during cycling exercise (Journal of Physiology 589.11 (2011) pp 2847–2856).  They looked at blood flow to the head as exercise intensity increased, also measured by percentage of VO2 max.  They found that blood flow to the forehead grew by over twelve times as percent of VO2 max increased from 40% to 80%.

They conclude, in part, that the blood flow to the face is selectively increased for thermoregulatory (cooling) purposes, and that there is a positive relationship between forehead skin blood flow from moderate to heavy exercise, potentially reflecting a direction of blood flow to the skin to aid heat dissipation.  They point out that the skin blood flow increase at the forehead during exercise is significantly greater than skin blood flow at the chest, forearm, thigh and back, and suggest that this reflects the high priority the body places on cooling at the head.

These studies and others directly support diverting sweat rather than imagining it is possible to capture it all, and covering minimal skin to do it.  

References:

Smith, CJ and Havenith, G  (2011)  Body mapping of sweating patterns in male athletes in mild exercise-induced hyperthermia.  Eur J Appl Physiol 111: 1391–1404

Taylor, N. A.S.., Machado-Moreira, C., van den Heuvel, A., Caldwell, J., Taylor, E. A.. & Tipton, M. J.. De roles of hands and feet in temperature regulation in hot and cold environments. Thirteenth International Conference on Environmental Ergonomics; Boston, USA: University of Wollongong; 2009. 405-409.

Kohei Sato, Shigehiko Ogoh, Ai Hirasawa, Anna Oue and Tomoko Sadamoto (2011) The distribution of blood flow in the carotid and vertebral
arteries during dynamic exercise in humans; J Physiol 589.11 2847–2856