Walter N. Tapp

Metabolic and cardiovascular effects of a progressive exercise test in patients with chronic fatigue syndrome

PURPOSE To evaluate the aerobic power (as maximum volume of oxygen consumed [VO2 max]) of women with chronic fatigue syndrome (CFS). PATIENTS AND METHODS Twenty-one women with CFS and 22 sedentary healthy controls (CON) were studied at the CFS Cooperative Research Center Exercise Laboratory at the VA Medical Center, East Orange, New Jersey. Performance was measured on an incremental treadmill protocol walking to exhaustion. Expired gases were analyzed by a metabolic system, heart rate was recorded continuously, and ratings of perceived exertion (RPE) were taken at each workload. The groups were divided into those who achieved VO2 max (CFS-MAX and CON-MAX) and those who stopped at a submaximal level (CFS-NOMAX and CON-NOMAX) by using standard criteria. RESULTS Seventeen CON and 10 CFS subjects achieved VO2 max. The VO2 max (mL/kg/min) of the CFS-MAX (28.1 +/- 5.1) was lower than that of the CON-MAX (32.1 +/- 4.3, P = 0.05). The CFS-MAX achieved 98 +/- 11% of predicted VO2 max. The CFS group had a higher RPE at the same absolute workloads as controls (P < 0.01) but not the same relative workloads. CONCLUSION Compared with normal controls, women with CFS have an aerobic power indicating a low normal fitness level with no indication of cardiopulmonary abnormality. Our CFS group could withstand a maximal treadmill exercise test without a major exacerbation in either fatigue or other symptoms of their illness.

Vagal tone is reduced during paced breathing in patients with the chronic fatigue syndrome

Patients with chronic fatigue syndrome (CFS) often complain of an inability to maintain activity levels and a variety of autonomic-like symptoms that make everyday activiry intolerable at times. The purpose of the study was to determine if there were differences in vagal activiry at fixed breathing rates in women with CFS. Twelve women with the diagnosis of CFS between the ages of 32 and 59 years volunteered for the study. Healthy women, who were between the ages of 30 and 49, served as controls. Full signal electrocardiograph and respiratory signals were collected during a paced breathing protocol of three fixed breathing rates (8, 12 and 18 breaths/min) performed in the sitting and standing postures. Vagal activity was analyzed by means of heart rate spectral analysis to determine the subjects response to specific breathing rates and postures. Heart rate variability was used as a non-invasive method of measuring the parasympathetic component of the autonomic nervous system. Using this method, although there was significantly less vagal power in the sitting versus the standing postures for both groups, the overall vagal power was significantly lower (p < 0.034) in the CFS group versus healthy controls. Vagal power was also significantly lower (p < 0.01 to p < 0.05) at all breathing rates in both postures except while standing and breathing at 18 breaths/min. Knowledge of the differences in vagal activity for CFS patients may allow stratification for the analysis of other research variables.

Decreased vagal power during treadmill walking in patients with chronic fatigue syndrome

The purpose of this study was to determine if patients with the chronic fatigue syndrome have less vagal power during walking and rest periods following walking, in comparison to a group of healthy controls. Eleven patients (ten women and one man) who fulfilled the case definition for chronic fatigue syndrome modified to reduce heterogeneity and eleven healthy, but sedentary, age- and sex-matched controls walked on a treadmill at 2.5 mph four times each for 4 min duration. Between each period of walking, subjects were given a 4-min seated rest period. Vagal power, a Fourier-based measure of cardiac, parasympathetic activity in the frequency range of 0.15 to 1.0 Hz, was computed. In each period of walking and in one period of rest, patients had significantly less vagal power than the control subjects despite there being no significant group-wise differences in mean heart rate, tidal volume, minute volume, respiratory rate, oxygen consumption or total spectrum power. Further, patients had a significant decline in resting vagal power after periods of walking. These results suggest a subtle abnormality in vagal activity to the heart in patients with the chronic fatigue syndrome and may explain, in part, their post-exertional symptom exacerbation.

Gait abnormalities in chronic fatigue syndrome

To evaluate our clinical impression that patients with the chronic fatigue syndrome (CFS) did not walk normally, we assessed gait kinematics at slow walking speeds (i.e., 0.45, 0.89 and 1.34 m/sec) and 30 m run time speeds on CFS patients and on a comparison group of sedentary controls. Run time was significantly slower for CFS than control subjects (p < 0.001). There was a significant interaction (p < 0.01) between group and speed for maximum hip angle during stance and swing phase with hip angle being significantly larger at 1.34 m/sec for CFS than controls subjects for both cases (p < 0.05). Knee flexion during stance and swing phases was significantly larger for controls than CFS subjects at 0.45 m/sec (p < 0.01). Ratio of stride length divided by leg length was significantly larger for the control subjects than for the CFS subjects with differences occurring at 0.45 and 0.89 m/sec (p < 0.01) but not 1.34 m/sec. The data indicate that CFS patients have gait abnormalities when compared to sedentary controls. These could be due to balance problems, muscle weakness, or central nervous system dysfunction; deciding which will require further research. Evaluation of gait may be a useful tool to measure outcome following therapeutic interventions.

Feeding cycles in smokers, exsmokers and nonsmokers

Smokers, exsmokers and nonsmokers showed 50 to 150 minute cycles of consummatory behavior (eating and drinking) that appear to reflect a biological rhythm of oral drive. Smokers and exsmokers had significantly shorter cycles, i.e., more frequent consummatory peaks, than nonsmokers. If a greater frequency of consummatory peaks contributes to heightened oral drive in smokers, it may constitute a physiological factor underlying the initiation or maintenance of compulsive smoking and the degree of difficulty in quitting smoking and remaining abstinent.

Comparison of normal and amputee gait with added weight

The area of prosthetic design has long focused on the lightest and presumably most energy efficient designs of prosthetics. Tests to measure energy efficiency are often time consuming or require expensive metabolic equipment. Therefore, it has been assumed that lighter designs are better than heavier ones. However, simple measures such as maximum ambulation time have been shown to be useful for determining functional status in clinical populations. In the study described, a 1-lb weight was attached to the ankle to simulate prosthetic design changes: specifically, to manipulate weight asymmetry between legs. Normal controls and amputees were analyzed with and without added weight during a maximum ambulation time test and during walking on a treadmill. In addition to metabolic data, kinematic data were analyzed to obtain biomechanical gait parameters.<<ETX>>

Telemetry recovery antenna (primate body temperature)

A telemetry system used to remotely record a primates body temperature is presented. A transmitter implanted in the retroperitoneal space of each monkey transmits a pulse at a frequency that is linearly proportional to the body temperature of the monkey. This signal is transmitted on a carrier frequency in the AM band of 27 MHz. The signal is demodulated using a Sony ICF-2020 receiver. Once it is filtered, the signal is sent to a Digital PDP11 data collection system. A solution to the problem of antenna placement is described. Results show an immense improvement in the signal strength and reduction of noise.<<ETX>>

Primate behavioral instrumentation

A Rhesus monkey model has been developed that makes it possible to investigate physiological rhythms and circadian effects on performance in an integrated framework. Body temperature and animal activity are of great importance in the study of circadian rhythms. To monitor a free-ranging monkeys temperature, a telemetry system is used. Monkey activity is measured using strain-gage transducers mounted under the animals home cage. Nonhuman primates are not always the most cooperative experimental subjects; therefore, some unique solutions are necessary to overcome these constraints.<<ETX>>

Modeling and analysis of non-periodic stimulus on the dynamics of circadian rhythms

Nonperiodic stimuli applied to circadian rhythms to produce phase shifts were modeled, and their transient behavior was studied by dynamic spectrum analysis and frequency demodulation. This type of stimulus produces phase advances and delays that are accompanied by transients. The transients exhibit complicated, nonmonotonic patterns such as those described by previously published data for human biological rhythms following a phase-shift. However, the results suggest that the transient behavior of an oscillator is sufficiently complex to account for the data and that no competing processes need to be involved.<<ETX>>