Human Performance and Colder Environments: Not all Racing Days are Equal
In a previous article written ‘Time Trials, Power Meters and Wind Direction: When the Race of Truth is Compromised’ we outlined a case for an external variable, in wind direction, effecting velocity of an individual’s structure, in the rider moving through air, at a given power output when time trialing. The premise being that in cross winds a cyclists is open to a greater resistance than either a head or tail wind as measured by their entire resistance or CdA. The present article will outline research showing another external variable that has been shown to hamper performance on the individual’s physiology as opposed to an individuals’ structure.
The individuals’ physiology (measured as how much oxygen they can consume and their associated power output) is an ‘internal concept’, as opposed to the individuals structure (a cyclist on a bike) which can be described as an ‘external concept’. An external concept can be affected by external variables, such as wind direction and speed, however an internal measure such as power production will not necessarily be affected as wind direction and speed may not affect one’s physiology rather only their moving-speed.
This is the beauty of power as a unit of measure of human performance. It is an objective performance measure: either you’re putting out 4watts/kilogram when you are travelling along nicely or you’re putting out 3.5watts/kilogram when you are not. Thus fitness can be quantified. Considering ones physiology cannot be impacted on by external elements wattage is reflective of one’s fitness, right? Maybe not…
Recently, where I reside, we have experienced many cold mornings of around 5c ambient temperature. Ambient temperature when competing is an example of an external variable that should not really affect an athlete. If an athlete can produce 4w/kg at threshold then they should be able to do this regardless of ambient temperature, however some scientific research has shown that this is not the case, with temperature being associated with a decrease in performance.
Research (Muller, Kim, Bellar, Ryan, Seo, Muller, & Glickman, 2011) has highlighted an increase in the amount of oxygen required to produce certain sub-maximal wattage at 5 degrees Celsius compared to 25c. What this means is that at exercise intensities below ones maximal oxygen uptake (VO2max) the body requires a greater amount of oxygen to do the same amount of work (power
output), this research outlined an increase of around 15-20% in oxygen for a given power output while cycling at lower temperatures in athletes that had not adapted to lower temperatures compared to athletes who had adapted to lower temperature exercise. This decrease in efficiency and performance has been attributed to an increase in metabolic rate as the body works harder to maintain its core temperature in colder climates (Sandsund, Sue-Che, Helgerud, Reinertsen, Bjermer, 1998). This metabolic effect is owing to hormonal, respiratory and mechanical mechanisms (Muller, et.al, 2011) and deters the body from producing power as it also works to maintain an appropriate body temperature.
These findings highlight how the body’s ability to produce power may be hampered by the external environment, meaning that power production and measure may not be as ‘objective’ as previously thought. Here it is seen that the external environment can affect an individuals’ ability to produce power due to a ‘weakening’ of the physiological structure.
Finally, and worthy of brief comment, is the point that external structures are also impacted by cooling air temperatures. Specifically, air density is inversely related to air temperature; air density varies with temperature as follows: at 0C, density is 1.292 kg/m^3, at 10C it is 1.247kg/m^3, at 20C it is 1.204kg/m^3, and at 30C it is 1.165 kg/m^3, meaning as the temperature decreases air density increases thereby slowing a moving object down for a given power output. This is an example of an external variable (temperature) impacting on an external concept (cyclist as a moving object) by way of slowing an object at a given output.
In concluding when racing in colder conditions athletes should be wary of any comparison to previous exercise performances completed in warmer conditions as an individuals’ physiology is hampered by an increased metabolic demand, whilst your moving structure also requires a higher output in maintaining a given speed.
Much research goes into advancing the mechanics of structural cycling: aerodynamic wheels, bicycles, helmets, etc, at a great financial cost to the cyclist. However there is also benefit in understanding the complexities of environment on performance and how best to adapt to these variables. For example, in making use of the ambient temperature recorded through your head unit when recording power may give you some insight into the suitability of comparing data across different trial periods. These findings highlight the need for vigilance when interpreting data across sessions and highlight the increased complexity in assuming homogeneity across experimental instances: not all racing days are equal.
Muller, M., Kim, C., Bellar, D.M., Ryan, E.J., Seo, Y., Muller, S.M., Glickman, E.L. (2011). Effect of cold acclimatization on exercise economy in the cold. European Journal of Applied Physiology.
Sansund, M, Sue-Chu, M., Helgerud, J., Reinertsen, R. E., Bjermer, L. (1998). Effect of cold exposure (-15c) and salbutamol treatment on physical performance in elite nonasthmatic cross-country skiers. European Journal of Applied Physiology and Occupational Physiology
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