Whole-body protein turnover (WBPTO) reflects the relationship between protein synthesis and protein breakdown. The influence of consuming a beverage containing both carbohydrate and protein on WBPTO during recovery from an endurance exercise bout is not clear.
PURPOSE: The purpose of this study was to determine WBPTO in moderately trained endurance runners following consumption of fat free chocolate milk (CMILK) after an endurance exercise bout.
METHODS: Moderately trained male runners (N=6, 21.3 ± 1.2 y, 71.3 ± 2.7 kg, BMI = 23.3 ± 0.74, body fat = 12.5 ± 1.0%, VO2peak = 54.0 ± 0.75 mL·kg-1·min-1) participated in a two week long randomized, crossover-design study during which they consumed a eucaloric diet that provided protein intake at 1.5 g·kg-1. On days 7 and 14, blood and breath samples were obtained during 3 h of recovery following a 45-min run at 65% of VO2peak after which participants consumed 16 oz. of either CMILK or a non-nitrogenous, isocaloric control beverage (CON). A primed, continuous infusion of L-[1-13C] leucine was used to assess WBPTO. Expired breath and arterialized blood were sampled for 13CO2 and plasma 13C-a-ketoisocaproate (KIC) enrichments, respectively. Leucine rate of appearance (Ra), leucine oxidation (Ox), non-oxidative leucine disposal (NOLD), an indicator of protein synthesis, and net leucine balance (LBAL) (mean ± SE; μmol/kg-1·hr-1) were determined using the reciprocal pool model.
RESULTS: During the 3-h recovery interval, Ra and NOLD was less for CMILK compared to CON (114 ± 2.5 vs. 120 ± 3.0, p<.05 and 77.6 ± 1.8 vs. 99.5 ± 2.6, p<.01, respectively). Ox was greater after CMILK than after CON (36.5 ± 2.3 vs. 20.6 ± 1.5, p<.01). LBAL after CON was less negative compared to CMILK (20.6 ± 1.5 vs. 36.5 ± 2.3, p<.01).
CONCLUSIONS: Findings suggest chocolate milk consumption during recovery from a moderate intensity run attenuates whole body protein breakdown compared to a carbohydrate beverage. The long term benefits of chocolate milk to whole body, as well as skeletal muscle, protein utilization in endurance athletes warrants further investigation.
Supported in part by Dairy Management Inc.