The Applied Exercise Science Lab is seeking 18-35 year-old men who participate in ≥three sessions of aerobic exercise per week of >30min totally 2.5–5.0 hrs/wk. This may not include cycling (commuting is ok), but may include running, hiking, swimming, basketball, soccer, tennis, etc. More screening questions will be asked upon inquiry. The study will require 8 hrs: 4 visits, 2 hrs/visit. You will be compensated $50 for your participation. Assessment of VO2max, lactate threshold, efficiency/economy and training zones is included.