Backpack carriage occurs in day-to-day tasks and has applications in school, physical training, recreational activities and sports. Using metabolic cart and echocardiograph, this study determined and examined the effects of two different load carriages on left ventricular function during 30 min. of treadmill walking in healthy adolescent male subjects. Seventeen males (13.1 ± 0.5 yrs.) walked on a treadmill at a speed of 4 km·h^-1, each carrying a load relative to his body mass at 333 gr·kg^-1 body weight during one session and without weight during the other session. Significant (p < 0.05) differences were noted between the 333 gr·kg^-1 body weight and the no weights with regard to: VO₂ 13.6 ± 1.3 and 10.5 ± 1.1 ml·kg^-1·min^-1; heart rate: 133.2 ± 7.1 and 121.4 ± 5.6 beats·min^-1; mean arterial blood pressure; 95. 4 ± 4.3 and 87.5 ± 3.8 mmHg and systolic blood pressure 147.7 ± 7.0 and 129.8 ± 7.1 mmHg respectively. No significant differences were noted between the two exercises with regard to left ventricular function variables. This study suggests that in adolescents as in adults, the vasodilatation mechanism dominates during combined dynamic and isometric exercises. Thus, the opposing force to the left ventricular ejection is reduced which in turn does not change the left ventricular global function. In addition, the vasodilatation mechanism enables oxygen supply to the contracting muscles via aerobic energy pathways.

• This study suggests that in adolescents as in adults, the vasodilatation mechanism dominates during combined dynamic and isometric exercises.

• Thus, the opposing force to the left ventricular ejection is reduced which in turn does not change the left ventricular global function.

• In addition, the vasodilatation mechanism enables oxygen supply to the contracting muscles via aerobic energy pathways.