Can I blame the dark for running less in winter?

Up here in Sweden the days are short at the moment, sunrise at 8:30 and sunset at 2.30 pm. So it´s dark and it´s also getting quite cold, at least to the point where outdoor exercise is a more difficult logistical exercise. Many people reduce the amount of exercise they do in the winter months, and although I try not to, it feels like getting motivated in the winter is generally a bit harder. But is it just psychological, or are there actually physiological explanations for this?

DIURNAL RHYTHM

Melatonin is a hormone secreted during darkness and inhibited by outdoor light which helps regulate mood, and also sleep. The diurnal rhythm is "phase-advanced" in winter compared with summer because of the darkness, and this change can have consequences for people´s mental states. The long hours of darkness in winter can lead to a type of depression known as seasonal affective disorder (SAD) [an appropriate acronym right?]. SAD is associated with feelings of chronic fatigue, which obviously counters any motivation towards physical activity. Interestingly, bright light has been used as therapy to counter this, and there are actually light bars in Stockholm where you can go and get "treatment". 

Vitamin D, a hormone normally produced in the skin using energy from sunlight, also has a role in this. A lack of vitamin D contributes to fatigue by its interaction with melatonin, because melatonin levels are inversely related to levels of vitamin D. In the summer, increased vitamin D means lower levels of melatonin and the reverse is also true, less vitamin D equals increased melatonin and increased fatigue. Vitamin D deficiency is also linked to myopathy, which is a muscular disease in which the muscle fibres do not function properly, resulting in muscular weakness. I should say this is in the case of extreme Vitamin D deficiency and won´t be an issue for most people, but interesting nonetheless.

SPORT PARTICIPATION AND PERFORMANCE

There is evidence to show that both participation and performance vary by season. A study from Norway reported that sport participation of subjects mirrored the seasonal changes in daylight hours, with higher participation during the summer.  Furthermore, superior aerobic performances have been recorded in Norway in summer compared with winter, as well as in Denmark, with one cohort of soldiers showing higher average VO2max in summer compared to a matched cohort performing the same physical examinations in winter. The exact explanation for why this was the case was unclear, but may have been linked to motivation or energy levels.

For recreation exercisers however, their seasonal variations in fitness levels tend to reflect the fact that they are more easily deterred from engaging in exercise during the winter months. Many studies point towards a psychological component for reductions in winter exercising, so it seems that it can not all be blamed on changes in diurnal rhythm and melatonin levels. Therefore we probably need a combination of physical and psychological interventions to keep us exercising through the dark months of winter.

HOW TO EXERCISE IN WINTER

I think there are a few ways to combat the usual winter reduction in exercise, many of which are based around psychology. Here are my top five tips:

1. Exercise with others. If your friend is waiting for you in the cold and dark then you are much more likely to turn up than if you only have yourself to answer to. If you are looking for some exercise friends in Stockholm check out our community here.

2. Find winter appropriate activities. You don´t have to stick to the same form of exercise year round, so why not substitute some of your runs for cross country skiing when the snow arrives.

3. Set a goal for spring. I often sign myself up for a spring half or full marathon. You literally have no choice but to prepare through the coldest months or you won´t be ready to run once the sun comes out and the spring race arrives. A goal provides you with a focus other than the weather.

4. Get the right clothes. There is nothing worse than exercising and being cold. Buy the things you need to keep you warm and keep comfortable while running in the winter.

5. Book a winter escape and go exercising somewhere warmer!

If you want to know more about anything discussed in this article you can check out the full articles below.

REFERENCES

1. Reilly, Thomas, and Benny Peiser. Seasonal variations in health-related human physical activity. Sports Medicine 36.6 (2006): 473+. Expanded Academic ASAP. Web. 9 Dec. 2015.

2. Wehdahl A. Covariance of daylight, sport participation and sleep patterns. Prog Clin Biol Res 1990; 341B: 306-11

3. Erikssen J, Rodahl K. Seasonal variation in work performance and heart rate responses to exercise: a study of 1835 middle-aged men. Eur J Appl Physiol 1979; 42: 133-40

4. Ingleman-Hansen T, Halkjaer-Kristensen J. Seasonal variation of maximal oxygen consumption rate in humans. Eur J Appl Physiol 1982; 49: 151-7