title: Comparison of energy supplements during prolonged exercise for maintenance of cardiac function: carbohydrate only versus carbohydrate plus whey or casein hydrolysate.
abstract: Cardiac function is often suppressed following prolonged strenuous exercise and this may occur partly because of 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% peak aerobic power output 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-postexercise time effects occurred selectively. Although diastolic function measured by pulsed-wave Doppler early-to-late (E/A) transmitral blood flow velocity was suppressed in all trials from pre- to postexercise (mean change post-pre exercise: -0.53 (95% CI -0.15 to -0.91)), TDI early-to-late (e'/a') tissue velocity was significantly suppressed pre- to postexercise only with placebo, CHO-only, and CHO-whey (septal and lateral wall e'/a' average change: -0.62 (95% CI -1.12 to -0.12); -0.69 (95% CI -1.19 to -0.20); and -0.79 (95% CI -1.28 to -0.29), respectively) but not with CHO-casein (-0.40 (95% CI -0.90 to 0.09)). LV contractility was, or tended to be, significantly reduced pre- to postexercise with placebo, CHO-only, and CHO-whey (systolic blood pressure/end systolic volume change, mm Hg·mL(-1): -0.8 (95% CI -1.2 to -0.4), p = 0.0003; -0.5 (95% CI -0.9 to -0.02), p = 0.035; and -0.4 (95% CI -0.8 to 0.04), p = 0.086, respectively), but not with CHO-casein (-0.3 (95% CI -0.8 to 0.1), p = 0.22). However, ejection fraction (EF) and ventricular-arterial coupling were significantly reduced pre- to postexercise only with placebo (placebo change: EF, -4.6 (95% CI -8.4 to -0.7)%; stroke volume/end systolic volume, -0.3 (95% CI -0.6 to -0.04)). Despite no treatment-by-time interactions, pre-to-postexercise time effects observed with 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 calls for further verification.
authors.affiliation: Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa.|Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa.
authors.forename: Tanja
authors.initials: T
authors.lastname: Oosthuyse
authors.affiliation: Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa.|Exercise Laboratory, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2193, South Africa.
authors.forename: Aletta M E
authors.initials: AM
authors.lastname: Millen
mesh_terms: D000328:Adult; D001642:Bicycling; D001783:Blood Flow Velocity; D015992:Body Mass Index; D002364:Caseins / Q000008:administration & dosage*; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D019587:Dietary Supplements; D004311:Double-Blind Method; D004452:Echocardiography; D015150:Echocardiography, Doppler; D002149:Energy Intake; D015444:Exercise / Q000502:physiology*; D006352:Heart Ventricles / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D010807:Physical Endurance; D016277:Ventricular Function, Left / Q000187:drug effects; D000067816:Whey Proteins / Q000008:administration & dosage*
chemical_list: D002364:Caseins; D004040:Dietary Carbohydrates; D000067816:Whey Proteins; C475729:casein hydrolysate
keywords: carbohydrate supplements; echocardiography; endurance exercise; exercice d’endurance; fonction ventriculaire gauche; imagerie Doppler tissulaire; left ventricular function; protein supplements; suppléments de protéines; suppléments de sucre; tissue Doppler imaging; échocardiographie