Background: Chronic fatigue syndrome (CFS) patients frequently describe difficulties with repeat exercise. Here we explore muscle bioenergetic function in response to 3 bouts of exercise.
Methods: 18 CFS (CDC 1994) patients and 12 sedentary controls underwent assessment of maximal voluntary contraction (MVC), repeat exercise with magnetic resonance spectroscopy and cardio-respiratory fitness test to determine anaerobic threshold.
[Note: Reaching the "anaerobic threshold" during exercise is when muscles switch from "aerobic" production of cellular fuel (ATP), using oxygen & glucose, to producing ATP "anaerobically" using stored phosphocreatine (PCr) without oxygen. That is, when there's a lack of sufficient oxygen supply in the working muscle cells and carbon dioxide production is increased, generating lactic acid. PCr stores are depleted fairly quickly, and normally PCr is regenerated/lactic acid is dispersed when aerobic exercise can resume/muscles are at rest.]
Results: CFS patients undertaking MVC fell into 2 distinct groups.
• 8 (45%) showed normal PCr depletion in response to exercise at 35% of MVC (PCr depletion > 33%; lower 95% CI for controls).
• 10 CFS patients (55%) had low PCr depletion (generating abnormally low MVC values).
The CFS whole group exhibited significantly reduced anaerobic threshold, heart rate, VO2, VO2 peak and peak work compared to controls. [VO2 peak is the maximum ability to take up oxygen for ATP creation.]
Resting muscle pH [measure of acidity/alkalinity] was similar in controls and both CFS patient groups.
However, the CFS group achieving normal PCr depletion values showed increased intra-muscular acidosis compared to controls after similar work after each of the 3 exercise periods with no apparent reduction in acidosis with repeat exercise of the type reported in normal subjects.
This CFS group also exhibited significant prolongation (almost 4-fold) of the time taken for pH to recover to baseline.
Conclusion: When exercising to comparable levels to normal controls, CFS patients exhibit profound abnormality in bioenergetic function and response to it.
Although exercise intervention is the logical treatment for patients showing acidosis, any trial must exclude subjects who do not initiate exercise, as they will not benefit.
This potentially explains previous mixed results in CFS exercise trials.
Source: European Journal of Clinical Investigation, online June 10, 2011. DOI:10.1111/j.1365-2362.2011.02567.x, by Jones DEJ, Hollingsworth Kg, Jokovljevic DG, Fattakhova G, Pairman J, Blamire AM, Trenell MI, Newton JL. Institute of Cellular Medicine; Newcastle Magnetic Resonance Centre; Institute for Ageing and Health; the UK NIHR Biomedical Research Centre in Ageing and Age Related Diseases; Newcastle Centre for Brain Ageing and Vitality, Newcastle University, Newcastle-upon-Tyne, UK.[Email: firstname.lastname@example.org]