Cycling Time Trial Performance May Be Impaired by Whey Protein and L-Alanine Intake During Prolonged Exercise

Abstract

Previous studies reported that adding protein (PRO) to carbohydrate (CHO) solutions enhances endurance performance. The ergogenic effect may be a function of additional protein/amino acid calories, but this has not been examined. In addition, although supplemental L-alanine (ALA) is readily oxidized during exercise, the subsequent impact on metabolism and prolonged endurance performance is unknown. The purpose of this investigation was to independently gauge the impact of whey PRO hydrolysate and ALA supplementation on performance and various physiological parameters. Eight cyclists (age: 22.3 ± 5.6 yr, weight: 70.0 ± 8.0 kg, VO2max: 59.4 ± 4.9 ml · kg(-1) · min(-1)) performed 120 min of constant-load cycling (55% of peak power) followed by a 30-km time trial (TT) under placebo (PLA), PRO, and ALA conditions. Magnitude-based qualitative inferences were applied to evaluate treatment differences and data are presented as percent difference between treatments ± 90% confidence limit. Both ALA (2.1 ± 2.7%) and PRO intake (-2.1 ± 2.2%) possibly harmed performance compared with PLA. Of interest, heart rate was possibly lower with ALA than PLA at 20- (-2.7 ± 3.4%) and 120-min (-1.7 ± 2.9%) of constant-load cycling and the serum interleukin-6 (IL-6) response to 120 min of cycling was likely attenuated with PRO compared with PLA (PLA, 6.6 ± 3.7 fold vs. PRO, 2.9 ± 1.8 fold). In addition, blood glucose levels were lower with PRO than PLA at 20- (-8.8 ± 2.3%; very likely) and 120-min (-4.9 ± 4.6%; likely) of constant-load cycling. Although ALA intake appears to lower HR and PRO ingestion dampens the IL-6 response to exercise, the ingestion of PRO (without CHO) or ALA does not enhance, and may actually impair, performance following prolonged cycling.

Nutritional interventions and the IL‐6 response to exercise

“…Plasma IL‐6 increased immediately after exercise and was lower in subjects consuming the protein and placebo compared to the glutamine beverage. A similar attenuation in circulating concentrations of muscle‐derived IL‐6 was observed in cyclists consuming a protein beverage during 2h constant‐load cycling at 55% W max followed by a 30 km time trial compared to those consuming an alanine or noncaloric placebo beverage (82). However, studies involving exercise of shorter duration failed to observe attenuation in IL‐6 (73, 83).…”

“…Interestingly, some studies have examined the effects of protein and/or individual amino acids on the musclederived IL-6 response (73,(81)(82)(83). Hiscock et al (81) provided subjects with a glutamine, protein, or maltodextrin placebo beverage during and after 2 h of cycling at 75% VO 2peak .…”

Magnitude‐based Inference is not Bayesian and is not a valid method of inference

“…In reviewing numerous MBI papers, we have noticed that authors commonly log-transform their data with little explanation given other than that they did so to "deal with the non-uniformity of errors." [38][39][40][41][42][43] This phrase is not conventional statistical language at all: a Google search reveals that it is used on www.sport sci.org and then almost exclusively in MBI papers in the sports medicine literature. In most cases, there is no indication that authors have actually examined their data distributions or checked assumptions such as normality and homogeneity of variances to warrant a log transformation.…”

Post-exercise Glucose Response Following Whey Protein Ingestion in Healthy Young People: A Randomized Pilot Study

“…They ingested their assigned beverage and waited 15 minutes before completing a time-matched Bruce Protocol Treadmill Test, such that participants ran the same time and stage as Visit 2. The second set of blood samples was collected by standard venipuncture 30 minutes post-exercise, based on previous studies demonstrating this time point was optimal for seeing changes in our variables [6,17]. Blood collected in the Lithium Heparin tubes was centrifuged at 1000G for 10 minutes at 4°C to separate the plasma, which was stored at -80°C in ~1ml aliquots until analysis.…”

“…There have also been inconclusive findings when whey protein is combined with an exercise bout. In healthy humans receiving whey protein before and during a 120 minute cycling challenge, blood glucose was reduced compared to those who consumed alanine and placebo [17]. Qin et al [33] provided participants with a whey protein carbohydrate combination drink during a long exercise session.…”