This randomized cross-over study compares two identical cardiorespiratory exercise bouts, differing only in the inclusion or exclusion of a dynamic period of increasing exercise intensity prior to the exercise bout. Planned comparisons include physiological responses and perceived effort during exercise, leukocyte mobilization, and mood between the two exercise sessions.

Physically active adult men and women are asked to complete three study visits to the laboratory. On Visit 1, participants provide informed consent and are screened for study inclusion criteria: being between 18 and 40 years of age, a non-smoker, not pregnant, free of disease impacting exercise performance or immunity, and performing at least one hour per week of vigorous exercise training (any modality) for at least the prior six months. Participants also complete an incremental submaximal exercise test on a stationary bicycle. The results of this test are used to calculate the resistance corresponding to 80% of estimated maximal heart rate. Participants return within 2-14 days for Visits 2 and 3. These visits consist of 30 min of bicycling at this resistance. One visit included a 10 min dynamic warm-up prior to the exercise bout. Participants were stratified by sex and randomized such that half of the men and women completed the exercise trial with warm-up during Visit 2.

Heart rate, perceived exertion, and wattage are recorded during each minute of the exercise bouts. Participants donate blood before, immediately after, and 1h after each exercise. Blood is analyzed by flow cytometry to characterize leukocyte subsets. After each exercise session, participants complete surveys assessing mood and affect.

Physiological, immunological, and psychological parameters recorded will be compared within participants between the two experimental exercise sessions using appropriate statistical tests. p<0.05 will be accepted as significant.

Inclusion Criteria:

• identifies as exercising 1-3 hours per week or more than 6 hours per week, on average (last 6 months)
• meets American College of Sports Medicine criteria for participation in exercise

Exclusion Criteria:

• underlying medical problems that contraindicate supervised high intensity exercise
• past or present history of autoimmune disease, HIV, hepatitis, stroke, or cardiovascular disease
• chronic/debilitating arthritis
• central or peripheral nervous disorders
• asthma, emphysema, or bronchitis
• bedridden in the past three months
• history of blood clotting disorders
• administration of any medication that might affect physiological response to exercise
• functional or cognitive impairment that would limit exercise performance or prohibit informed consent
• having any common-cold or influenza like symptoms (scratchy throat, runny nose, inflamed sinuses, frequent sneezing or coughing) in the last 2 weeks
• pregnancy
• tobacco use

All individual participant data that underlie results in a publication will be made available upon request

Will be available upon publication

Requests should be sent to and will be reviewed by the principle investigator