Cardiovascular responses to static exercise in boys: insights from tissue Doppler imaging

Abstract

Ventricular functional changes and mechanisms of the cardiovascular responses during static exercise have not been well delineated in children. In this study, Doppler echocardiographic techniques were utilized to assess cardiovascular adaptations to bilateral isometric leg extension at 30% maximal voluntary contraction for three minutes in a group of 14 healthy boys (mean age 10.2 +/- 1.5 years). Mean heart rate rose from 77 +/- 9 to 106 +/- 11 bpm, stroke volume fell from 59 +/- 9 to 52 +/- 7 ml, and cardiac output increased from 4.58 +/- 0.58 to 5.62 +/- 0.81 l min(-1) (P < 0.05). Mean arterial pressure rose from 86 +/- 7 to 109 +/- 9 mm Hg, with no significant change in peripheral vascular resistance. By tissue Doppler imaging markers, inotropic function improved by 59%, while lusitropic function increased 38%. These findings suggest that (1) cardiovascular responses to static leg extension in boys are similar to those in adult men, and (2) isometric leg extension triggers modest increases in both systolic and diastolic function.

Cardiovascular Responses to Static Exercise: A Re-Appraisal

“…A true understanding of the cardiovascular dynamics during static exercise, then, requires an analysis of blood flow rate and its relationship to mean arterial pressure per beat, during blood flow. In a recent study of ventricular function during leg extension static exercise, we obtained information using Doppler ultrasound that provided insights into these relationships [23]. The cardiovascular responses to 30 % MVC exercise in this study were consistent with the expected scenario: average value of mean arterial pressure rose by 23 mmHg.…”

“…Instead, the cardiac adaptations to isometric exercise, reflecting reflex increases in sympathetic activity (as well as parasympathetic withdrawal), serve to maintain circulatory flow rather than to increase blood pressure. Besides tachycardia, cardiac responses to static exercise are characterized by modest increases in myocardial contractility, an effect documented by enhancements in left ventricular dP/dt [21], peak flow velocity [6], ejection fraction [17], and myocardial velocity [23]. The magnitude of this response exceeds that expected from the inotropic effect of increased heart rate itself (the Bowditch effect) [21] and is presumably triggered by reflex sympathetic stimulation during resistance exercise [19].…”

The Effect of Acute Aerobic and Resistance Exercise on Working Memory

“…Recent nonhuman animal models have observed that exerciseinduced increases in cerebral blood flow do not occur globally across all regions of the brain but instead are localized to specific regions involved with locomotion, equilibrium, and cardiorespiratory control as well as areas of the hippocampus (8). Considering that resistance exercise exerts a very different metabolic response compared with aerobic exercise, manifested by lower oxygen consumption despite higher levels of muscular exertion (16), and lower levels of systemic blood flow (29,30), it may be possible that resistance exercise affects cerebral blood flow differently compared with aerobic exercise. Given the cardiorespiratory and metabolic differences between aerobic and resistance exercise, future research should address the relationship between resistance exercise, cerebral blood flow, and cognition to provide additional insight into the relationship between cognition and exercise behavior.…”

Blood Pressure During Leg Extension in Children

“…During the static testing of leg extension, the average BP increased by 41/50 mmHg during 5SM in the present study. Rowland et al [ 27 ] found a modest rise in sBP (23 mmHg) during bilateral static leg extension at 30 % of 1RM in 3 min. Thus, a maximum isometric work immediately gave higher BP increase than isometric work at 30 % of 1RM, even when the maximum contraction was only held for 5 s as shown in the present study.…”

“…Thus, a maximum isometric work immediately gave higher BP increase than isometric work at 30 % of 1RM, even when the maximum contraction was only held for 5 s as shown in the present study. Rowland et al [ 27 ] also revealed that the bilateral isometric leg extension led to a HR increase from 77 beats per minute (bpm) to 106 bpm. Both resting HR and the HR responses to the tests were considerably higher in the present study.…”