LYZ and Recurrent upper respiratory tract infections: ↓ Severity of GI and lower respiratory illness in males in probiotic vs. placebo; ↑ number and duration (↓ severity) of lower respiratory illness in females in probiotic vs. placebo; ↓ cytokine response to acute exercise in probiotic group; ↔ upper respiratory tract infection, mucosal immunity (lactoferrin, lysozyme, SIgA)