LEFT-VENTRICULAR RESPONSES DURING PROLONGED TREADMILL WALKING WITH HEAVY LOAD CARRIAGE

This study examined with metabolic cart and echo-Doppler the influence of different load carriage during 4 h of treadmill walking on left ve ntricular systolic function, hemodynamics, and cardiovascular response s. Twenty-six aerobically well-trained male subjects (VO2max = 65.2 +/ - 5 ml.kg-(1).min(-1)) volunteered for this study. Subjects carried a load of 38 kg during one session and a load of 50 kg during the other session. Following the 4-h exercise in each session, significant (P < 0.05) differences were noted between the 38-kg and 50-kg workloads wit h regard to VO2: 14.4 +/- 2 and 19 +/- 5 ml.kg(-1).min(-1); heart rate : 104 +/- 14 and 125 +/- 17 beats min(-1); diastolic blood pressure: 6 9 +/- 4 and 79 +/- 4 mm Hg; and rate pressure product 140.4 +/- 15 and 173.8 +/- 20 index.10(-2), respectively. No significant differences w ere noted between the workloads in regard to systolic blood pressure, perceived exertion rating, and aortic valve Doppler indices. We conclu ded that during prolonged treadmill walking in well-trained young subj ects, the additional load above 50% up to 66% of body weight did not c hange the steady state of left ventricular systolic function, hemodyna mics, and cardiovascular responses throughout the course of the 240 mi n of effort.