Due to SARS-CoV-2 pandemic research restrictions placed by university, we were unable to complete enrollment of all participants in a timely manner. Data analyses and publications will occur with the participants who did complete the study.

The purpose of this study is to determine the effect of age and fitness level on the physiological response to an acute bout of resistance or aerobic exercise.

Young and middle-aged to older adults who are physically active or not physically active will participate in two moderate to vigorous intensity exercise bouts: aerobic exercise and resistance training exercise. Blood will be collected to assess immune function and metabolism.

Inclusion Criteria:

• "Young" Adults: ages 18-30
• "Older" Adults: ages 55-75 and if a female postmenopausal
• Participants classified as "trained" must participate in at least 30 minutes of moderate to vigorous intensity cardiovascular activity at least 3 days per week and engage in resistance training for all of the major muscle groups approximately 2 days / week. They must have upheld this activity for the past 3 months
• Participants classified as "untrained" must be participating in less than 30 minutes of moderate to vigorous intensity cardiovascular activity and less than 2 days of resistance training per week for at least the last 3 months.

Exclusion Criteria:

• Have any contraindications to moderate to vigorous exercise
• Range of motion restrictions that would prevent them from participating in aerobic or resistance training with proper form (they must be ambulatory)
• aking medications (prescription or over the counter) known to influence immune function, including daily NSAID's, beta blockers, statins, bisphosphonates, or steroids.
• Have known cardiovascular, respiratory, metabolic, or renal disease, with the exception of controlled hypertension (as defined by resting BP below 140/90) and/or controlled asthma (self-reported).
• Be pregnant
• Be unable to complete all visits (i.e. must not be planning to leave the Houston area long-term before concluding their participation in the study which will span several weeks)
• Fall outside of a BMI range of (18.5 - 30)
• Consume alcohol or recreational drugs for 24h prior to visits
• Older women cannot be pre-menopausal (must have not had a menses for at least 12 months)
• Unable to speak or read English
• Participants must not have scheduling conflicts that would prevent them from reporting to the laboratory of integrated physiology 4 times over the course of the study

We are considering making available IDP to others upon request, but would have to get an IRB change because that is not in our protocol