Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate-only verse carbohydrate plus whey or casein hydrolysate
Tanja Oosthuyse Applied Physiology, Nutrition, and Metabolism February 2016
Cardiac function is often suppressed following prolonged strenuous exercise and may partly occur due to an energy deficit. This study compared left ventricular (LV) function by 2-dimensional echocardiography and tissue Doppler imaging (TDI) before and after ~2.5 h of cycling (2-h steady-state 60%Wmax plus 16-km time trial) in 8 male cyclists when they ingested either: placebo, carbohydrate-only (CHO-only), carbohydrate-casein hydrolysate (CHO-casein) or carbohydrate-whey hydrolysate (CHO-whey). No treatment-by-time interactions occurred, but pre-to-post exercise time effects occurred selectively. While diastolic function measured by pulsed-wave Doppler early-to-late (E:A) transmitral blood flow velocity was suppressed in all trials from pre to post exercise (E:A, mean change post-pre exercise(95%CI): -0.53(-0.15;-0.91), TDI early-to-late (e’:a’) tissue velocity was only significantly suppressed pre to post exercise with placebo, CHO-only and CHO-whey (septal and lateral wall e’:a’ average change(95%CI): -0.62(-1.12;-0.12); -0.69(-1.19;-0.20); -0.79(-1.28;-0.29), respectively) but not with CHO-casein (-0.40(-0.90;0.09)).
Left ventricular contractility was or tended to be significantly reduced pre to post exercise with placebo, CHO-only and CHO-whey (systolic blood pressure/end systolic volume, change(95%CI) mmHg∙mL-1: -0.8(-1.2;-0.4) p=0.0003; -0.5(-0.9;-0.02) p=0.035; -0.4(-0.8;0.04) p=0.086, respectively), but not with CHO-casein (-0.3(-0.8;0.1) p=0.22). However, ejection fraction (EF) and ventricular-arterial coupling were only significantly reduced pre to post exercise with placebo (placebo change(±95%CI): EF, -4.6(-8.4;-0.7)%; stroke volume/end systolic volume, -0.3(-0.6;-0.04)). Despite no treatment-by-time interactions, pre-to-post exercise time-effects with only specific beverages may be meaningful for athletes.
Tentatively, the order of beverages with least-to-most variables displaying a time-effect indicating suppression of LV function following exercise was: CHO-casein < CHO-only and CHO-whey < placebo, and motivates further verification.