Exercise capacity in chronic fatigue syndrome.

BACKGROUND: Patients with chronic fatigue syndrome (CFS) suffer from various symptoms, including debilitating fatigue, muscle pain, and muscle weakness. Patients with CFS can experience marked functional impairment. In this study, we evaluated the exercise capacity in a large cohort of female patients with CFS. METHODS: Patients with CFS and matched sedentary control subjects performed a maximal test with graded increase on a bicycle ergometer. Gas exchange ratio was continuously measured. In a second stage, we examined only those persons who achieved a maximal effort as defined by 2 end points: a respiratory quotient of at least 1.0 and an age-predicted target heart rate of at least 85%. Data were assessed using univariate and multivariate statistical methods. RESULTS: The resting heart rate of the patient group was higher, but the maximal heart rate at exhaustion was lower, relative to the control subjects. The maximal workload and maximal oxygen uptake attained by the patients with CFS were almost half those achieved by the control subjects. Analyzing only those persons who performed a maximal exercise test, similar findings were observed. CONCLUSIONS: When compared with healthy sedentary women, female patients with CFS show a significantly decreased exercise capacity. This could affect their physical abilities to a moderate or severe extent. Reaching the age-predicted target heart rate seemed to be a limiting factor of the patients with CFS in achieving maximal effort, which could be due to autonomic disturbances. Arch Intern Med. 2000;160:3270-3277.

Validity and reliability in a Flemish population of the WHO-MONICA Optional Study of Physical Activity Questionnaire.

PURPOSE: This study assessed the validity and reliability of a self-administered physical activity questionnaire used in the WHO-MONICA project. METHODS: Subjects (N = 167) were physical education and physical therapy alumni. The questionnaire (MOSPA-Q) covers a 1-yr period and measures the average weekly time and energy expenditure spent in one's occupation, transport-related activities, household chores, and leisure time activities. Test-retest reliability was reported as the intra-class correlation between calculated time or energy expenditure in different questionnaire items determined from two MOSPA-Q administrations. Validity was assessed using biometrical and physiological parameters as criterion measures. RESULTS: Test-retest reliability ranged from 0.45 to 0.92 with the highest correlation coefficients obtained for the leisure time physical activities. The correlation between calculated daily total energy expenditure (TEE, Kcal.d-1) and lean body mass was 0.53 (P < 0.001). The correlation between energy expenditure in leisure time activities (Kcal.wk-1) and VO2peak was 0.44. CONCLUSIONS: The MOSPA-Q provides a relatively valid and reliable estimate of physical activity.

Blood ammonia--heart rate relationship during graded exercise is not influenced by glycogen depletion.

The blood lactate (La) - heart rate (HR) relationship assessed during a graded maximal exercise test (GXT) is often used to provide training guidelines to athletes. Glycogen depletion is a condition that is known to influence the La response during a GXT and therefore can bias the interpretation of La curves. The purpose of our study was to determine an influence of glycogen depletion through long-term exercise (GDE) on blood La and ammonia (NH3) accumulation during a GXT. Eleven persons (5 males, 6 females; 26.3 +/- 4 yrs) performed a cycle ergometer GXT (3 min protocol) on two separate occasions with a 1-week interval. Using a randomized cross-over design, one of the two GXTs was preceded by a GDE. After GDE, blood NH3 increased more rapidly in the depleted versus control state whereas La increased less rapidly in the depleted state. The NH3 to HR relationship was not altered by glycogen depletion. We conclude, therefore, that determination of NH3 during a GXT may provide helpful additional information for training recommendations which is not available through La determination only.

The influence of cold and compression on lymph flow at the ankle.

OBJECTIVE: To investigate the effects of cold application with different temperatures on lymph flow in healthy persons and to examine the effects of the combination of cold and compression on lymph vessels. PARTICIPANTS: Thirty-nine healthy persons were included in the study, and each served as his or her own control. INTERVENTION: Water bags (1 degree, 15 degrees, and 32 degrees) with or without 25 mm Hg pressure were applied to the experimental legs for 30 minutes. Cold, pressure, or both were administered by an Aircast-Cryo-cuff (Aircast Europe GMBH, Rosenheim, Germany). MAIN OUTCOME MEASURES: Skin temperature was measured with a TESTO 901 (Testoterm GMBH, Leuven, Belgium) precision thermometer. Lymph flow was recorded continuously using lymphoscintigraphy. MANOVA with repeated measures was used for data analysis. RESULTS: As expected, skin temperature dropped relative to the temperature of the water. The migration of the tracer was comparable in both ankles during the first 30 minutes of the experiment (rest). When the water bag was applied, lymph flow increased significantly (p < 0.01). The application of water of 1 degree C without pressure influenced lymph evacuation significantly differently from the other temperatures. The application of pressure of 25 mm Hg influenced lymph evacuation significantly at 1 degree C and 32 degrees C. CONCLUSION: These results indicate that lymph evacuation at the ankle is influenced significantly when cold water is applied with or without pressure. When pressure is added to the application of water of 32 degrees C, lymph flow will also increase significantly, indicating the importance of pressure in lymph evacuation.

Endurance performance in humans: the effect of a dopamine precursor or a specific serotonin (5-HT2A/2C) antagonist.

In this study we examined the effect of a dopamine (DA) precursor (L-DOPA) or a serotonin (5-HT) antagonist (Ritanserin) on time to exhaustion. The study had a double-blind, randomised, placebo controlled and cross-over design. Seven moderately trained men performed three tests to exhaustion at 65% Wattmax. Each test was separated by two weeks to allow washout of the drugs (dose: 4 mg/kg Sinemet, and 0.3 mg/kg Ritanserin). Blood lactate, hematocrit, glucose, ammonia, free fatty acids (FFA), growth hormone (GH) and catecholamines were determined before and after exercise. Time to exhaustion did not differ between the three trials. Most of the parameters measured in this study responded as predicted during cycling to exhaustion in man. DA agonism significantly increased heart rate, lactate, and plasma DA values at rest, while other parameters such as FFA, lactate, plasma noradrenaline (NA) and adrenaline (A), and plasma GH showed the highest absolute levels at exhaustion. Ritanserin did not influence basal glucose and heart rate at rest, but this group showed a much lower increase in plasma catecholamine levels. We conclude that under the present conditions, neither a metabolic precursor of DA nor a specific centrally acting 5-HT2A/2C antagonist, when given in two single doses 24 h and immediately before the experiments, influences the time to exhaustion on a bicycle trial at 65% Wattmax.

An early effect of acute plasma volume expansion in humans on serum erythropoietin concentration.

The effect of acute plasma volume change in humans on serum erythropoietin [EPO]s, plasma active renin [REN] and plasma aldosterone [ALDO] concentrations was examined. Plasma volume (PV) expansion was induced by intravenous infusion of 150 ml (30g) of plasma albumin and 500 ml of physiological saline. The [EPO]s decreased by 14.3% (corrected values for PV expansion) and remained decreased for 5 h. The [REN] was decreased by more than 25% during the day of the experiment and [ALDO] by more than 60%. Only a weak positive correlation was found between [EPO]s and [REN] (r = 0.35; P < 0.05) but a lack of correlation between changes in PV and [EPO]s as well as between [EPO]s and [ALDO] was seen. We postulated that in healthy men an acute PV expansion by 10% to 17.5% would not appear to promote stimulation of EPO synthesis for at least 11 h. Since a weak positive correlation was observed between [EPO]s and [REN] and a lack of correlation between [EPO]s and [ALDO], it would seem that there is no direct link between [REN] and [ALDO] and erythropoietin synthesis in healthy subjects.