Question

A single individual can differ from time to time in his or her maximal rate of \(\mathrm{O}_{2}\) consumption. For example, athletic training in people can raise the maximal rate of \(\mathrm{O}_{2}\) consumption by \(10-30 \%\), whereas going to high altitudes can lower it (see Box 8.3). Explain how these sorts of changes in the maximal rate of \(\mathrm{O}_{2}\) consumption can make a single type of exercise (such as jogging at 6 miles per hour) shift from being submaximal to supramaximal, or vice versa. What are the physiological implications of such shifts?

Short answer

Changes in an individual's maximal \(\mathrm{O}_{2}\) consumption, such as through athletic training or moving to high altitudes, can shift an exercise from submaximal to supramaxial or vice versa. For instance, a submaximal exercise like running at 6 mph could become supramaximal to someone who moves to a high altitude and experiences reduced \(\mathrm{O}_{2}\) consumption. Physiological implications of such shifts include increased fatigue and longer required recovery time, as well as increased dependence on anaerobic systems resulting in an accumulation of lactate in muscles.

Step-by-step solution

Identify the Factors Affecting Maximal O2 Consumption

Understand that factors such as athletic training and high altitudes affect a person's highest possible rate of oxygen consumption, or \( \mathrm{O}_{2} \) consumption. Athletic training can increase \(\mathrm{O}_{2}\)consumption by \(10-30 \%\), enabling the person to take in more oxygen and use it more effectively. On the other hand, high altitudes, where oxygen levels are lower, can decrease \(\mathrm{O}_{2}\) consumption by forcing the body to adjust to less oxygen.

Determine the Effects on Exercise Intensity

Realize that these changes in maximal \(\mathrm{O}_{2}\) consumption can cause shifts in exercise intensity. A run at a certain pace, like six miles per hour, could be considered submaximal if a person's \(\mathrm{O}_{2}\) consumption is on the higher end of their personal scale (due to athletic training). However, if that same individual decreases their maximal \(\mathrm{O}_{2}\) consumption (by going to high altitudes for example), the same exercise could become supramaximal because their body is taking in and using less oxygen.

Consider the Physiological Implications

Understand that such changes would initialy result in higher levels of fatigue and may need a longer recovery period, especially in the case of the exercise becoming supramaximal. Submaximal exercises typically use the aerobic system, while supramaximal exercises place more reliance on the anaerobic systems, leading to an accumulation of lactate in the muscles which can result in a burning sensation and fatigue. With more acclimatization or training, the body can adjust to the new maximal \(\mathrm{O}_{2}\)consumption, and the intensity of exercise may return from supramaximal to submaximal.

Key concepts

athletic training effects

Engaging in regular athletic training can substantially affect a person's maximal oxygen consumption, often referred to as \( \text{VO}_2 \) max. This metric measures the highest rate at which oxygen can be taken in and used by the body during intense physical activity. Training enhances the efficiency of the cardiovascular and respiratory systems, facilitating increased oxygen uptake and utilization. As a result:

• Heart and lungs become more efficient in delivering oxygen to muscles.
• Muscle cells improve in their ability to extract and use oxygen.

Through consistent training, a person may experience a 10-30% increase in \( \text{VO}_2 \) max, leading to better endurance and performance. An increase in \( \text{VO}_2 \) max means that activities, which were once tough, might become more manageable, shifting the threshold of what is considered submaximal exercise.
This adaptation allows athletes to perform at a high intensity for longer periods, reducing fatigue and enhancing recovery.

high altitude physiology

Adapting to high altitudes poses significant challenges to the human body due to reduced oxygen availability in the air. The body's immediate response is to increase the breathing rate and heart rate to uptake more oxygen, yet these mechanisms can't fully compensate for lower oxygen levels. Over time, the body undergoes specific adaptations:

• Increased red blood cell production to carry more oxygen.
• Enhanced capillary density to increase oxygen delivery to tissues.

Despite these changes, maximal oxygen consumption often decreases at high altitudes, as the body can't use oxygen as efficiently as at sea level. This can cause familiar exercises to become more strenuous, shifting the activity from being submaximal to supramaximal. The implications of this are pivotal for athletes who train or compete at high altitudes, as they need to allow time for acclimatization to maintain performance.

exercise intensity shifts

The concept of exercise intensity is tied to how challenging an activity feels relative to an individual's maximal oxygen uptake capacity. When training increases \( \text{VO}_2 \) max, an exercise like jogging at 6 miles per hour might become a lighter effort, or submaximal, meaning it's sustainable over a longer duration using aerobic energy pathways.
Conversely, a decline in \( \text{VO}_2 \) max, such as with high-altitude exposure, can shift the same pace to supramaximal intensity. This intensity level requires reliance on anaerobic energy systems, which quicken fatigue and recovery time due to higher lactate accumulation in muscles.
Understanding these shifts in exercise intensity is crucial for planning workouts. It allows athletes to adjust their training programs based on their current state. With training or altitude acclimatization, these shifts gradually stabilize, helping an individual perform efficiently at various conditions.