Left ventricular responses during prolonged treadmill walking with heavy load carriage

Area of Science:

• Exercise Physiology
• Cardiovascular Physiology

Background:

• Load carriage significantly impacts physiological responses during exercise.
• Understanding the effects of prolonged, heavy load carriage on cardiac function is crucial for military and occupational contexts.

Purpose of the Study:

• To investigate the influence of different load carriage levels (38 kg vs. 50 kg) on left ventricular systolic function, hemodynamics, and cardiovascular responses during 4 hours of treadmill walking.
• To determine if increased load carriage affects steady-state cardiac function over extended exercise durations.

Main Methods:

• Utilized metabolic cart and echo-Doppler to assess cardiovascular parameters in 26 aerobically trained male subjects.
• Subjects underwent two 4-hour treadmill walking sessions, each with a different load carriage (38 kg or 50 kg).
• Measured oxygen consumption (VO2), heart rate, blood pressure, rate pressure product, and aortic valve Doppler indices.

Main Results:

• Significant increases in VO2, heart rate, diastolic blood pressure, and rate pressure product were observed with the 50-kg load compared to the 38-kg load.
• No significant differences were found in systolic blood pressure, perceived exertion, or aortic valve Doppler indices between the two load conditions.
• Left ventricular systolic function, assessed via Doppler indices, remained unchanged despite increased workload.

Conclusions:

• Prolonged treadmill walking with load carriage up to 66% of body weight does not impair left ventricular systolic function in well-trained young men.
• Cardiovascular responses like heart rate and blood pressure increase with higher loads, but the heart's pumping function remains stable.
• These findings suggest a high tolerance for sustained physical exertion with heavy loads in this population.