6th Grade · Science · Activity · shared by Luke Morgan
This 6th Grade Science activity explores how an athlete's body adapts to high altitude, analyzing data on red blood cell and oxygen changes.
Training in the Mile High City
Denver, Colorado, is known as the "Mile High City" because its elevation is exactly 5,280 feet above sea level. Athletes from all over the world travel to Denver to train. When an athlete first arrives from a coastal city (at sea level), they often feel tired and out of breath quickly. However, after staying in Denver for several weeks, their performance improves. This process is called acclimatization .
Scientists have tracked a professional runner named Marcus who moved from Miami (sea level) to Denver to prepare for a race. Use the data and facts below to investigate how Marcus's body changed to handle the high-altitude environment.
High mountain areas have thin air. This means every breath gives the body less oxygen. To deal with this change, the body starts a slow adaptation . Parts of the body sense the low oxygen and tell the bone marrow to make more red blood cells . These cells carry oxygen from the chest to the rest of the body. Inside these cells, a part called hemoglobin grabs the oxygen to move it. As the number of these cells grows, the blood gets better at moving the small amount of oxygen found in the air. This change helps a sports player keep up their energy during a hard workout. At first, the heart beats fast to move blood quickly. Later, the new blood cells help the heart and body stay steady. This natural change helps people live and work well in high places.
Marcus's Training Data
The table below shows measurements taken from Marcus during his first day in Denver and after twenty-one days of training.
Measurement Type
Day 1 (Arrival)
Day 21 (After Training)
Red Blood Cell Count (millions per microliter)
4.8 million
5.6 million
Hemoglobin Levels (grams per deciliter)
14.2 g/dL
16.5 g/dL
Resting Heart Rate (beats per minute)
78 bpm