Tuesday, 27 November 2012

Cognitive fatigue and exercise

#MSBlog: "Cognitive and physical exercise, or loading, exacerbates cognitive fatigue."

Claros-Salinas et al. Induction of cognitive fatigue in MS patients through cognitive and physical load. Neuropsychol Rehabil. 2012 Nov.

Objective: To investigate whether cognitive fatigue in MSers is a spontaneous phenomenon or whether it can be provoked or exacerbated through cognitive effort and motor exercise. 

Methods: 32 MSers with cognitive fatigue according to the Fatigue Scale for Motor and Cognitive Functions (FSMC ≥ 22) performed attention tests (alertness, selective, and divided attention subtests from the TAP test battery for attention performance) twice during rest (baseline), and before and after treadmill training and cognitive load (a standardised battery of neuropsychological tests lasting 2.5 hours). Subjective exhaustion was assessed with a 10-point rating scale. 

Results: Tonic alertness turned out to be the most sensitive test and showed significantly increased reaction times after treadmill training and after cognitive load. MSers' subjective assessment of exhaustion (10-point rating scale) and the objective test results were discrepant. In contrast, healthy control subjects (N = 20) did not show any decline of performance in the subtest alertness after cognitive or physical load. 

Conclusion: Data favour the concept that fatigue is induced by physical and mental load. Discrepancies between subjective and objective assessment offer therapeutic options. The common notion of a purely "subjective" lack of physical and/or mental energy should be reconsidered.

"This is a poor study because it is very small and did not include inflammatory controls without central nervous system involvement. In other words could the findings be non-specific due to the effects of inflammation rather than MS? People with active rheumatoid arthritis and other inflammatory syndromes also suffer from significant fatigue.How can we help MSers with fatigue?"

"Step 1: make sure you have good sleep hygiene and are not taking medication that is sedating. Sleep hygiene could be improved by avoiding stimulants or alcohol and not sleeping in the day; treating pain, spasms, restless legs, bladder dysfunction, anxiety and depression. All of these can affect sleep."

"Step 2: treating your energy levels as being a finite resource that need to rationed; i.e. plan your day and your activities so that you don't do too many tiring things in one day."
"Step 3: if you are deconditioned or unfit start a graded aerobic exercise programme; it is counter intuitive but exercise improves energy levels. I usually advise you do this through a physiotherapist."

"Step 4: enrol yourself on a behavioural therapy programme. This typically teaches your ways of changing your life to cope and deal with your fatigue."

"Step 5: speak to your neurologist. He/she may be able to prescribe medications that can help for fatigue. Don't hold your breath there are no licensed therapies for MS-related fatigue. We use drugs off-license with moderate effect and results. The most commonly prescribed drugs are amantadine and modafanil!"

"Please don't forget  that fatigue is a normal physiological phenomenon. So it is normal to get tired!  Ask me I feel tired most of the time; generation-F! F for fatigue!"


  1. "fatigue is a normal physiological phenomenon"

    MS fatigue is not. It is different to fatigue that "healthy controls" feel.

    "could the findings be non-specific due to the effects of inflammation rather than MS?"

    Ok, provided that we agree that inflammation is not part of MS(!). Still, why is there a trend for cognitive fatigue worsening after exercise? Poor oxygenation of the brain maybe?

    1. Interesting that many of the MS patients I have spoken to who were on Tysabri said the major thing they noticed was that their fatigue completely disappeared, which suggests that inflammation is indeed part of MS.

  2. Ok, provided that we agree that inflammation is not part of MS(!)

    In your freams I am afraid

  3. Replies
    1. It was not me who made the distinction. Inflammation is certainly part of MS, just not the causative one.

    2. Inflammation is not the cause, because it is always triggered, but what is the stimulus?

  4. VV: MS fatigue may be different to that of healthy controls but it sounds the same as in people with Lupus, Rheumatoid Arthritis, maybe other diseases too.

    Some quotes:
    "The fatigue of lupus can’t be ignored. It’s much more than just feeling tired. It can make getting out of bed every morning seem like climbing a mountain. Ordinary tasks, like cooking dinner or doing the laundry, can seem impossible."
    "The fatigue of Rheumatoid Arthritis is a weariness that rest cannot cure. It is tiredness without the benefit of the pleasure of activity. Over 90% of RA patients report fatigue as a clinical symptom."

    1. Many of the chemicals secreted by immune cells during inflammation have the potential to cause or exacerbate fatigue. It's nature's way of trying to get you to lie down and rest while you are fighting an infection. Unfortunately this also happens in autoimmune diseases too, causing chronic rather than acute fatigue.

    2. Sure, but how can exercise exacerbate this chronic fatigue? I believe prof GG is willing to dismiss the results because they don't fit right with the established view that exercise is generally beneficial to patients.

    3. We don't really know if exercise is always good for you. It may speed up neurodegeneration if it results in overactivity of vulnerable or damaged pathways. Acute exercise also raises body temperature that may exacerbate fatigue.

  5. It can't be true that "healthy control subjects (N = 20) did not show any decline of performance in the subtest alertness after cognitive or physical load."

    I have seen it in myself and others- people are less alert when they are mentally/physically drained.

  6. This blog will be so boring without VV's contribution. Like him or not, the kid keeps us on our toes and gets us thinking. Ataboy.

  7. To support VV's comments about oxygenation

    "On the basis of these findings, it is unlikely that changes in cerebral oxygenation limit incremental exercise performance in normoxia, yet it is possible that such changes play a more pivotal role in hypoxia."

    If MS was a condition of diminished cerebral oxygenation (due to CCSVI), it would be expected that exercise would worsen this condition.


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