High intensity interval training alters substrate utilization and reduces oxygen consumption in the heart

Area of Science:

• Cardiovascular Physiology
• Exercise Metabolism
• Cardiac Energetics

Background:

• Exercise training improves cardiac function, but its impact on myocardial substrate metabolism and efficiency is less understood.
• High-intensity training (HIT) demonstrates more significant effects on cardiovascular function and aerobic capacity than moderate-intensity training (MIT).

Purpose of the Study:

• To investigate the metabolic and mechanoenergetic adaptations in the heart following endurance exercise of both high and moderate intensity.
• To compare the effects of high-intensity interval training (HIT) versus moderate-intensity training (MIT) on cardiac substrate utilization and efficiency.

Main Methods:

• Mice (C57BL/6J) underwent 10 weeks of treadmill running, divided into HIT and MIT groups.
• Maximal oxygen uptake, heart weight-to-body weight ratio, cardiac substrate oxidation (glucose and fatty acid), and myocardial oxygen consumption were assessed.

Main Results:

• High-intensity interval training (HIT) significantly increased maximal oxygen uptake.
• Both HIT and MIT increased heart weight-to-body weight ratio; however, only HIT altered cardiac substrate utilization, increasing glucose oxidation by 36% and decreasing fatty acid oxidation.
• HIT improved cardiac efficiency by reducing work-independent myocardial oxygen consumption and enhanced maximal mitochondrial respiratory capacity.

Conclusions:

• High-intensity training (HIT) is crucial for inducing changes in cardiac substrate utilization and energetics.
• These adaptations likely contribute to the superior improvements in aerobic capacity observed with HIT compared to MIT.