Distinguishing Chronic Fatigue Syndrome
Tomorrow is International Awareness Day for Chronic Immunological and Neurological Diseases, such as Chronic Fatigue Syndrome (CFS) and Myalgic Encephalomyelitis (ME).
In New Zealand, an estimated 20,000-25,000 people suffer from CFS. Although it is a debilitating illness, medical practitioners often find diagnosis and management of the disease challenging and, despite compelling evidence, some are still skeptical of the disease.
Dr Lynette Hodges from Massey University's School of Sport and Exercise recently conducted a study comparing the physiological responses of CFS/ME, Multiple Sclerosis (MS) and healthy controls following a repeated maximal exercise test.
CFS/ME and MS sufferers reported feeling fatigued and Dr Hodges hopes this study may be able to distinguish the two conditions from each other. "We want to figure out how and why the fatigue process is different in those with MS compared with those with CFS/ME."
Participants were asked to cycle on an exercise bike. During the cycling, it got progressively harder, until they could not sustain the exercise and had to stop. "During the exercise, we measured heart rate, and the amount of oxygen and carbon dioxide they were breathing in and out. Based on this, we can calculate anaerobic threshold – the point at which lactic acid starts to build up in the body faster that it can be cleared away. Study participants then came back the next day and repeated the exercise test."
Dr Hodges found that on the first test, there was no difference between healthy controls and CFS/ME. The first exercise test also showed that those with MS were significantly less fit than those who were healthy and compared to those with CFS/ME.
"On the second exercise test, those with MS and those who were healthy were able to repeat the same results on the exercise as on day one. However, those with CFS/ME were unable to achieve this and reached their anaerobic threshold faster and at a lower workload compared to day one," Dr Hodges says.
"This suggests that even though they were as fit as the healthy controls, post-exertional malaise [the feeling of fatigue] after exercise, shows up by them not being able to achieve the same workload at anaerobic threshold or at their peak."
Dr Hodges says there are still a number of factors which need to be examined. "Our study also showed that some individuals with CFS/ME took up to four weeks to recover following the two exercise tests, which was not apparent in the healthy individuals who were back to normal the following day." The outcomes of the study will soon be published in the Journal of Clinical Physiology and Functional Imaging.
To find out more, Dr Hodges is completing another trial examining the physiological differences in repeated maximal exercise at 48 hours and 72 hours. "We will be taking blood samples to examine markers of inflammation, blood pressure and heart rate, asking questions about fatigue, and participants will be asked to do simple computer tasks to examine cognition, as well as ultrasound to measure arterial stiffness, and the cycle test to examine anaerobic threshold. All tests will then be repeated at either 48 hours or 72 hours later."
Provided by Massey University
