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Can Submaximal Exercise Variables Predict Peak Exercise Performance in Women with Chronic Fatigue Syndrome?

https://doi.org/10.1016/j.arcmed.2006.10.009Get rights and content

This study aimed at examining whether physiological exercise variables at the submaximal level, defined as 75% of the age-predicted target heart rate, are able to predict peak exercise performance in women with chronic fatigue syndrome (CFS) (n = 222). Subjects performed a bicycle ergometric test against a graded increase in workload until exhaustion with continuous monitoring of electrocardiographic and ventilatory variables. Oxygen uptake at the submaximal level (VO2SUBMAX) correlated strongly with peak oxygen uptake (VO2PEAK) (r = 0.70). For the prediction of VO2PEAK, linear regression analysis determined the line of best fit as:VO2PEAK=0.95×VO2SUBMAX+372.3.Using this equation, the mean error in the prediction was 14.6 ± 11.2% (range 0.1–63.7%). It is concluded that the prediction of VO2PEAK based on VO2SUBMAX might be useful for analyzing group differences or treatment effects but not for individual (clinical) purposes.

Introduction

Chronic fatigue syndrome (CFS) is a debilitating disorder characterized by debilitating fatigue, widespread musculoskeletal pain, sleep impairments, headache, and symptoms of poor concentration and memory (1). Maximal or peak exercise performance testing is widely used for the assessment of people with CFS, and it appears to be both reproducible and valid (2). Peak exercise capacity variables correlate with activity limitations and participation restrictions (3), supporting the clinical importance of peak exercise testing in individuals with CFS. However, the role of maximal exercise tests is limited in people whose performance may be limited because of pain or fatigue rather than exertion (4). In CFS, symptoms are typically made worse after a peak exercise stress test 5, 6, and a delayed recovery from exercise appears characteristic of the disorder (7). Therefore, a submaximal exercise test appropriate for CFS patients would have a number of advantages over a test performed until exhaustion: submaximal testing is likely to diminish symptom exacerbations following peak exercise testing (8) and consequently, decrease recovery time; it may encourage more severely disabled people with CFS to participate in research studies using exercise testing (8); and it has greater (clinical) applicability (for instance, to physical therapists) (4). The Aerobic Power Index Test has been used as a submaximal test in people with CFS: the test-retest reliability has been established (9), and it was the first submaximal test able to replicate previous findings of decreased exercise performance in CFS cases compared to healthy controls (8). However, there are currently no published data indicating that a submaximal exercise test is able to predict peak exercise performance in CFS patients. Prediction of peak aerobic capacity is one of the primary goals of submaximal exercise testing (4). Therefore, the present study aimed at examining whether physiological exercise data corresponding to a submaximal level, defined as 75% of the age-predicted target heart rate (8), are able to predict peak exercise performance in women with CFS.

Section snippets

Patient Recruitment and Research Design

The exercise capacity testing data of all women with CFS attending our university-based Chronic Fatigue Clinic between November 2003 and December 2005 were reanalyzed. The study focused on women to preclude bias originating from pooling of gender data (10). All participants fulfilled the Centers for Disease Control and Prevention criteria for CFS (1). Therefore, all patients underwent an extensive medical evaluation prior to exercise testing (for more details regarding the diagnostic strategies

Results

Of the 222 study participants, only 156 (71%) achieved the submaximal level (defined as 75% of the age-predicted target heart rate) and were used for further data analysis. The descriptive statistics of the exercise testing variables are presented in Table 1. In addition to the peak (p = 0.045) and submaximal work capacity attained (p = 0.025), all variables were normally distributed. The outcome of the correlation analysis is presented in Table 2. Oxygen uptake at the submaximal level (VO

Discussion

There is a need for standardized submaximal ergometer tests not only for patients with CFS but for people with various disorders that require close monitoring during exercise (4). Therefore, the present study aimed at examining whether a standardized submaximal ergometer test was able to predict peak exercise performance (including peak aerobic work capacity) in people with CFS. We utilized an exercise protocol (starting at 10 W with an increase of 10 W/min) that has previously been used for

Acknowledgments

The authors are grateful to Kenny De Meirleir for diagnosing the study participants.

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