Question

The physical fitness of athletes is measured by \({ }^{4} V_{\mathrm{O}_{2}}\) max," which is the maximum volume of oxygen consumed by an individual during incremental exercise (for example, on a treadmill). An average male has a \(V_{\mathrm{O}_{2}}\) max of \(45 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{kg}\) body mass \(/ \mathrm{min}\), but a world-class male athlete can have a \(V_{\mathrm{O}_{2}}\) max reading of \(88.0 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{kg}\) body mass/min. (a) Calculate the volume of oxygen, in mL, consumed in \(1 \mathrm{hr}\) by an average man who weighs \(85 \mathrm{~kg}\) and has a \(V_{\mathrm{O}_{2}}\) max reading of \(47.5 \mathrm{~mL}\) \(\mathrm{O}_{2} / \mathrm{kg}\) body mass \(/ \mathrm{min} .(\mathbf{b})\) If this man lost \(10 \mathrm{~kg},\) exercised, and increased his \(V_{\mathrm{O}_{2}}\) max to \(65.0 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{kg}\) body mass \(/ \mathrm{min}\), how many mL of oxygen would he consume in \(1 \mathrm{hr} ?\)

Short answer

In the first case, the man consumes \(242,250 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{hr}\), and in the second case, he consumes \(292,500 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{hr}\).

Step-by-step solution

1. Calculate the oxygen consumption rate:

Multiply the man's weight (85 kg) with his \(V_{\mathrm{O}_{2}}\) max reading (47.5 mL O₂/kg/min): Oxygen consumption rate = \(85 \mathrm{~kg} * 47.5 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{kg} / \mathrm{min} = 4037.5 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{min}\).

2. Convert the rate from minutes to hours:

Multiply the oxygen consumption rate (4037.5 mL O₂/min) by the number of minutes in an hour (60 min): Total oxygen consumption in 1 hr = \(4037.5 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{min} * 60 \mathrm{~min} / \mathrm{hr} = 242250 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{hr}\). # b) Calculate the oxygen consumed in 1 hr after weight loss and \(V_{\mathrm{O}_{2}}\) max increase#:

1. Update the weight and \(V_{\mathrm{O}_{2}}\) max readings:

Subtract 10 kg from the initial weight (85 kg): New weight = \(85 \mathrm{~kg} - 10 \mathrm{~kg} = 75 \mathrm{~kg}\). Update the \(V_{\mathrm{O}_{2}}\) max reading to 65.0 mL O₂/kg/min.

2. Calculate the new oxygen consumption rate:

Multiply the new weight (75 kg) with the new \(V_{\mathrm{O}_{2}}\) max reading (65.0 mL O₂/kg/min): New oxygen consumption rate = \(75 \mathrm{~kg} * 65.0 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{kg} / \mathrm{min} = 4875 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{min}\).

3. Convert the new rate from minutes to hours:

Multiply the new oxygen consumption rate (4875 mL O₂/min) by the number of minutes in an hour (60 min): New total oxygen consumption in 1 hr = \(4875 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{min} * 60 \mathrm{~min} / \mathrm{hr} = 292500 \mathrm{~mL} \mathrm{O}_{2} / \mathrm{hr}\). So, in the first case, the man consumes 242250 mL O₂/hr, and in the second case, he consumes 292500 mL O₂/hr.

Key concepts

Oxygen Consumption

Oxygen consumption is an essential metric, especially in exercise physiology, to understand how well the body utilizes oxygen during physical activity. When you exercise, your muscles need more energy, and oxygen plays a crucial role in energy production. This process is measured by a value known as \( \dot{V}_{\mathrm{O}_2} \) max, which represents the maximum rate at which an individual can consume oxygen during intense exercise. This value is determined by the combination of your lungs, heart, and muscles working efficiently.

• Oxygen is inhaled into the lungs and diffuses into the bloodstream.
• It is then transported to the muscles, where it participates in the production of energy.
• The more efficiently your body manages this process, the higher your \( \dot{V}_{\mathrm{O}_2} \) max.

For example, if a person weighs 85 kg and has a \( \dot{V}_{\mathrm{O}_2} \) max of 47.5 mL/kg/min, they would consume a significant amount of oxygen as calculated by multiplying their body weight and \( \dot{V}_{\mathrm{O}_2} \). This number helps identify cardiovascular fitness and performance potential.

Physical Fitness

Physical fitness is a broad term that describes the body's capability to function efficiently and effectively in work and leisure activities, to be healthy, resist hypokinetic diseases, and meet emergency situations. It involves several components such as cardiovascular endurance, muscular strength, flexibility, body composition, and more.
An essential part of physical fitness is cardiovascular endurance, often measured by tests of \( \dot{V}_{\mathrm{O}_2} \) max. This test assesses aerobic endurance, which is crucial because it reflects how well your heart and lungs supply oxygen to your body during sustained physical activity.
Improving physical fitness, especially cardiovascular endurance, can be achieved through regular aerobic exercises like:

• Running
• Cycling
• Swimming

As individuals train and improve their fitness, they may experience increases in their \( \dot{V}_{\mathrm{O}_2} \) max, indicating enhanced physical performance and overall health.

Exercise Physiology

Exercise physiology is the scientific study of how the body responds and adapts to physical activity. It focuses on understanding the acute responses of the body systems to exercise, as well as chronic adaptations to sustained training.
During exercise, various body systems, including the cardiovascular, respiratory, and muscular systems, work together to meet the demands placed on the body. Some key aspects of exercise physiology include:

• How effectively muscles use oxygen.
• The impact of training on muscle endurance and strength.
• Adaptations in oxygen delivery and increased \( \dot{V}_{\mathrm{O}_2} \) max after regular training.

Exercise physiology helps in understanding how changes in body weight, fitness levels, and exercise intensity can influence \( \dot{V}_{\mathrm{O}_2} \) max. For example, if someone improves their fitness and loses weight, they often experience a boost in their \( \dot{V}_{\mathrm{O}_2} \) max, exhibiting better efficiency in energy consumption during physical activities.