Does training intensity differ with upper vs. lower body exercise?

Arnt_ErikWe are now in the first autumn month, and the winter is fast approaching. For some, this is a sad part of the year, but for others (like me) winter is something to look forward to. We have the woods with all its beautiful colors, the excitement of the first approaching snow and a chance to try out our new cross country skis.

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On the dark side of the year..

As an Australian moving to Trondheim, there were many things that I had to learn about and get used to. For example:

  • That white stuff falling from the sky is snow.
  • “Det finnes ikke dårlig vær – bare dårlige klær.”
  • Drive on the right side of the road. Change gears with right hand, and use of left and right indicator lights is optional.
  • Coffee coffee coffee coffee. Coffee. Wow, you Norwegians drink a lot of coffee.
  • Bacon and alcohol are only affordable if you drive to Sweden.
  • Apart from this, everything about Norway is better than Sweden.

With a little bit of effort, these facts of my new life are all quite easy to adapt to and even enjoy. The long days of summer weren’t a problem either after investing in some dark curtains. However, part of the way through my second Trondheim winter, it is still difficult to avoid or get used to the very long nights and dimly lit days.

Just wait, Nathan - it's getting better!

Just wait, Nathan – it’s getting better!

This comes as no surprise, as humans and most other mammals follow what is known as circadian rhythm; a roughly 24 hour cycle that influences body temperature, heart rate, behaviours such as activity and sleep, and many other biological processes. This rhythm will persist even if the environment changes (for example if you fly to Australia and experience jetlag), but is also constantly altered or “entrained” by external factors – the most important of these factors being daylight. Disruptions to the circadian rhythm cause poor sleep patterns and fatigue and can increase the likelihood of developing metabolic syndrome (symptoms such as obesity and insulin resistance), leading to cardiovascular disease and diabetes. In extreme cases, such as in shift workers who must be active at night and sleep during the day, circadian disruption is very dangerous in the long run and has even been listed as a probable carcinogen by the WHO International Agency for Research on Cancer.

But since we can’t control the rising and setting of the sun, and we can’t always be in brightly lit rooms while we are awake, what else can be done to cope with the lack of daylight to reinforce circadian rhythms during winter? Given that you are reading the CERG blog, it probably won’t surprise you to learn that exercise is one very good approach.

A generally active lifestyle is one way to strengthen circadian rhythms. In aged mice that were subjected to an 8 hour shift in their light-dark cycle (similar to jetlag), those mice able to exercise with free access to a running wheel were able to adapt to their new light dark cycle faster than mice without a wheel. In addition, the suprachiasmatic nuclei of the brain (the centre that regulates circadian rhythms) was found to be more active in the exercising mice. In human subjects, a dip in blood pressure at night is considered to be a healthy circadian event and is associated with a lower cardiovascular risk. This dip is most common in people who expend more energy per day and spend less time performing sedentary activities.

And could we use the timing of exercise to specifically alter our circadian rhythm? It does seem that exercise alone is powerful enough alone to cause a shift in circadian rhythm. In mice with a set light-dark cycle, scheduled exercise alone is able to shift behavioural patterns and change the timing of circadian gene expression. However, it isn’t yet clear how exactly how exercise should be timed or performed to get specific results.

So, if you struggle to wake up in the mornings or feel lethargic at this time of the year, perhaps you could try exercise to help keep your circadian clock on time while there is little sunlight. However, it is not a perfect replacement for regular sun – and you can exercise all you want, but it still won’t get you a sun-kissed Australian tan!

Nathan Scrimgeour, post doc at CERG.