Physiological responses at the lactate-minimum-intensity with and without prior high-intensity exercise

Area of Science:

• Exercise Physiology
• Sports Science
• Human Performance

Background:

• Understanding physiological responses to exercise is crucial for optimizing training protocols.
• The lactate minimum intensity represents a specific exercise threshold relevant to endurance performance.
• The impact of prior high-intensity exercise on subsequent sustained efforts requires further investigation.

Purpose of the Study:

• To investigate the physiological differences during constant-load exercise at lactate-minimum-intensity.
• To compare these responses with and without preceding high-intensity exercise (hyperlactatemia induction).
• To determine if physiological parameters reach a steady state under these conditions.

Main Methods:

• Eleven recreationally trained males participated in the study.
• Participants underwent a graded exercise test, a lactate minimum test, and two constant-load tests to exhaustion.
• Constant-load tests were performed at lactate-minimum-intensity, with one condition preceded by a 30-second Wingate test to induce hyperlactatemia.

Main Results:

• Significant differences (P < 0.05) were observed in pulmonary ventilation, blood lactate concentration ([La(-)]), pH, bicarbonate concentration ([HCO3]), and partial pressure of carbon dioxide during the initial minutes of the constant-load tests.
• Oxygen uptake and respiratory exchange ratio showed steady-state behavior within each test, but heart rate and rating of perceived exertion increased significantly over time in both conditions.
• While initial physiological markers differed after high-intensity exercise, variables like [La(-)], pH, and [HCO3] normalized by the end of the exercise bout, approximately 30 minutes into the effort.

Conclusions:

• Constant-load exercise at lactate-minimum-intensity, even after high-intensity exercise, does not consistently lead to a steady state for all physiological parameters.
• Prior high-intensity exercise transiently alters initial physiological responses during sustained exercise at lactate-minimum-intensity.
• Key metabolic and acid-base balance variables ([La(-)], pH, [HCO3]) demonstrate a capacity for recovery and normalization within approximately 30 minutes of sustained exercise.