Exercise-related Post-exertional Malaise

This supplement to the parent study, Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome
(ME/CFS): Activity patterns and autonomic function, is intended to enhance the larger
home-based study with a face-to-face laboratory arm. Specifically, the investigators propose
a pilot study to assess biobehavioral sex differences in ME/CFS during recovery after a brief
high exertion exercise task, i.e., a six-minute walk test repeated on two consecutive days.
The investigators expect adverse symptomatic, functional, and autonomic effects following
this repeat exercise test. This "post-exertional malaise (PEM)" and its impact on global
outcomes is a unique feature of ME/CFS that is being studied in the parent observational
study conducted by participants entirely in their homes. In the proposed supplement, PEM and
its impacts will be captured in real time under controlled conditions in the research team's
laboratory. Of particular interest, autonomic effects of PEM on heart function and blood
pressure using non-invasive research grade monitors. The specific aims are as follows:

Specific Aim 1: After two high-effort six minute walk tests conducted on consecutive days,
female subjects with ME/CFS as compared to male ME/CFS subjects will show slower recovery
with respect to cardiovascular autonomic functioning, physical functioning, and symptom
resolution. Specific Aim 2: Female subjects with ME/CFS as compared to males with ME/CFS will
show greater adverse impact on autonomic and physical functioning and symptom severity after
the day 2 exercise test.

To more accurately characterize exercise recovery abnormalities differentiated by sex, the
investigators propose to longitudinally monitor symptoms, activity levels, and autonomic
status during the week before (baseline) as compared to the week after (follow-up) the two
exercise tests. This pilot study will also provide potential cross-validation of the parent
project which hypothesizes specific relationships between autonomic function symptom severity
and activity limitations. A parallel analysis of sex differences will also be carried out on
the data collected in the parent project.

The pilot study will remain within the scope of the original aims of the parent study to
identify biobehavioral factors related to PEM, symptom-worsening activity patterns, and
non-improvement in ME/CFS. This supplement will expand the parent project's home-based data
collection to a controlled setting with direct observation and verification of exercise tests
carried out by participants in the principal investigator's laboratory.

Inclusion Criteria:

- patients aged 18-65 of both sexes who are considered physically capable of doing and
blood pressure monitors (10 min/day) and an actigraph (16 days; waking hours only).

- subjects must meet validated phone-screen eligibility for CFS which will also require
the symptom of post-exertional malaise. Also 3 out of 7 secondary symptoms of ME/CFS
are required i.e., headaches, tender lymph nodes, sore throat, myalgias, arthralgias,
sleep disturbance, and/or problems with memory or concentration.

Exclusion Criteria:

- Cases of fatigue clearly attributable to self-report medical conditions such as
untreated hypothyroidism, unstable diabetes mellitus, organ failure, chronic
infections, and chronic inflammatory diseases, or AIDS.

- psychiatric disorders include any psychosis, or alcohol/ substance abuse within two
years prior to illness onset and any time afterward, and current or past depression
with melancholic or psychotic features within 5 years prior to onset of ME/CFS or
anytime afterward.

- patients on heart medication or patients not dose-stabilized for at least 3 months on
antidepressant drugs

- patients at significant risk of suicide or in need of urgent psychiatric treatment.