Procedures (methods): In a randomized, placebo-controlled intervention, subjects will complete 3 different testing sessions (pre-screening, 1 baseline, 1 post-testing session) as well as a 6-week intervention period. Prescreening will include written informed consent, a health history questionnaire, baseline anthropometric measures, assessment of resting heart rate, and exercise protocol familiarization. Baseline testing will involve body composition, a fasted blood draw, mood surveys, and an exercise treadmill test. Subjects will be randomized to a treatment group (multi-strain probiotic or placebo) for 6 weeks of supplementation that includes 2 electronic contacts, followed by post-testing that will occur in the same fashion as baseline testing.