| 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.
KEY
WORDS: Echocardiography, oxygen uptake, systolic function, steady
state, vasodilatation.
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