The Applied Exercise Science Lab is seeking 18-35 year old volunteers: 1) UCI ranked cyclists training for >8hrs/wk, and 2) non-cyclists training ≥3 sessions/wk of >30 min of aerobic exercise totaling 2.5–5hrs/wk. Additional activity screening questions will be asked upon inquiry. The study will require ~8hrs: 4 visits, ~2hrs/visit. You will be compensated $50 for your participation. Assessment of VO2max, lactate threshold, and efficiency/economy as well as training zone breakdowns by heart rate and power will be provided.