Left ventricular systolic function during treadmill walking with load carriage in adolescents

Area of Science:

• Exercise Physiology
• Cardiovascular Physiology
• Adolescent Health

Background:

• Backpack carriage is common in daily activities and sports.
• Understanding its physiological impact on adolescents is crucial for health and performance.
• Previous research has explored load carriage effects in adults, but less is known about adolescents.

Purpose of the Study:

• To investigate the effects of backpack carriage on cardiovascular function and left ventricular function in adolescent males.
• To compare physiological responses during treadmill walking with and without a significant load (333 gr·kg(-1) body weight).

Main Methods:

• Seventeen healthy adolescent males (13.1 ± 0.5 yrs.) participated in the study.
• Subjects walked on a treadmill at 4 km·h(-1) for 30 minutes under two conditions: with a load of 333 gr·kg(-1) body weight and without load.
• Metabolic cart and echocardiography were used to measure oxygen consumption (VO2), heart rate, blood pressure, and left ventricular function.

Main Results:

• Significant increases were observed in VO2, heart rate, mean arterial blood pressure, and systolic blood pressure when carrying the load compared to no load (p < 0.05).
• No significant differences were found in left ventricular function variables between the loaded and unloaded conditions.
• These findings suggest that the vasodilatation mechanism dominates during combined dynamic and isometric exercises.

Conclusions:

• Backpack carriage at 333 gr·kg(-1) body weight increases cardiovascular workload in adolescents but does not impair left ventricular function.
• The dominant vasodilatation mechanism reduces the opposing force to left ventricular ejection, maintaining global function.
• This physiological response facilitates oxygen supply to muscles via aerobic pathways during loaded activities.