Time of Day, Fatigue and Walking Ability

I don't know about you, but when I am feeling fatigued, things are hard. In fact, the more fatigued I feel, the harder everything is – and I mean everything. I find it harder to think, to talk and certainly to do anything physical.
Therefore, I found it interesting that a European study found no correlation between fatigue levels and how people with MS scored on a walking test.
It is pretty well reported by people with MS that fatigue levels worsen as the time of day progresses. It is assumed by many that fatigue levels affect physical functioning, such as mobility. Therefore, it could be deduced that a person with MS-related mobility problems would do worse on a walking test in the late afternoon or evening than they would in the morning.
In this multicenter test among 8 European MS centers in 5 countries, 102 people participated. The group was split into those with "mild" ambulatory dysfunction (EDSS 1.5-4.0) and "moderate" ambulatory dysfunction (EDSS 4.5-6.5). They were asked about fatigue levels at 3 different points in the day (morning, noon and late afternoon). They also were given two walking tests at the same 3 times of day – the 6-Minute Walk Test and the 10-meter walk test, performed at their usual and their fastest speed.
Here's what happened:
  • Although the people in the mild and moderate ambulatory dysfunction group clearly had different degrees of mobility problems, fatigue levels in both groups were the same.
  •  In both groups, reported fatigue was worse later in the day than it was in the morning.
  •  However, time of day did not affect performance on the walking tests in either group.
This is pretty important stuff to understand. For one thing, if researchers are conducting a clinical trial to see if a certain drug or intervention helps with either fatigue or walking ability, it is important to know whether time of day when these things are being measured or reported matters. Looks like it is not that crucial to measure walking ability at the same time of day. However, to measure fatigue, one would want to make sure to ask about many parts of the day and overall ability to function.
On a personal level, this data makes me wonder, then, if things just seem harder when I am fatigued. I am sure that I am much less likely to want to do anything as the day wears on – maybe, in my case, this is a cycle of being tired, thinking things are hard, avoiding doing them and feeling more tired from not accomplishing things. Perhaps I'll try to fight the fatigue when I can and see what I can really do, rather than assuming it's too hard. It may be worth a try.
However, it should be noted that a research situation is much different than real life. Although participants' walking speed seemed unaffected by their fatigue in the study setting, this does not necessarily translate to meaning that fatigue is not a factor in endurance or simple physical ability to get things done. What I am going to try is pushing through the fatigue on a couple of small things and seeing how that works out.  
What do you think? Do you feel worse as the day wears on? Do you have more problems walking later in the day? What about other things? Let us hear from you in the comments section.
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Julie Stachowiak, PhD

Julie is the author of the Multiple Sclerosis Manifesto, the winner of the 2009 ForeWord Book of the Year Award in the Health Category. She is an epidemiologist who is also a person living with MS, Julie has an in-depth understanding about current research and scientific developments around MS. She also has first-hand knowledge of the frustrations and anxiety surrounding the disease, as she had MS for at least 15 years before receiving a diagnosis in 2003 and has had several relapses since her diagnosis.