Immediate Physiological Responses to Training

When an athlete engages in physical training, their body undergoes a range of immediate physiological responses as it adapts to the demands of exercise. These responses are essential for sustaining activity and ensuring the body is able to deliver oxygen and nutrients to the muscles while removing waste products. 

Key physiological factors such as heart rate, ventilation rate, stroke volume, cardiac output, and lactate levels are all affected during exercise. Understanding these responses is crucial in assessing an athlete's fitness level and the efficiency of their cardiovascular and muscular systems during physical exertion. This section will explore each of these factors and their role in supporting physical performance during training.

Ventilation Rate

Ventilation rate, also known as respiratory rate, measures how many breaths a person takes per minute. It increases in response to training, similar to heart rate, as the body works to remove carbon dioxide from the blood and take in more oxygen. 

The increase in ventilation rate is directly linked to exercise intensity; the higher the intensity, the greater the increase in ventilation. For example, an athlete training at 85% of their maximum heart rate (MHR) will have a higher ventilation rate than when training at 65% MHR, due to higher oxygen demand and carbon dioxide production. Just before exercise, ventilation rate increases slightly in anticipation of movement. 

Trained athletes have lower ventilation rates at a given intensity compared to untrained athletes, and they return to their normal resting ventilation rate more quickly after exercise, reflecting their improved respiratory efficiency.

Lactate Levels

NOTE: We’ve already spent considerable time exploring how and why lactate is formed. If you’re not yet confident with this concept, please review the Energy Systems lesson. This topic will focus more on how lactate levels respond once we begin exercising.

During moderate exercise, lactate levels remain relatively stable and low. As intensity increases past the aerobic threshold, lactate levels begin to rise steadily. Once the intensity reaches a point where oxygen demand exceeds supply (the anaerobic threshold), lactate levels increase rapidly, known as the onset of blood lactate accumulation (OBLA). This continues until maximum effort is reached, at which point the athlete may need to slow down or stop.

Trained athletes have a higher lactate threshold compared to untrained individuals, meaning they can exercise at higher intensities before lactate accumulates significantly. As a result, trained athletes can sustain high-intensity efforts longer and experience less fatigue, while untrained individuals accumulate lactate more quickly, leading to faster onset of fatigue.