Physiological And Psychological Indices Of Protein-infused Beverage On Aerobic Fitness In Males

BACKGROUND: Consumption of protein-infused (PI) drinks are common among recreational and elite athletes. PURPOSE: Investigate the effects of PI drinks on aerobic fitness and perceived exertion in males. METHODS: Ten males volunteered (age: 25.54 ± 2.62 yrs, height: 171.98 ± 6.93 cm, weight: 63.9 ± 9.15 kg) in this study, which adopted a randomized crossover design with a 7-day washout period between each trial. Participants consumed 500 ml of either water, PI or carbohydrate-infused (CI) beverage on first session, followed by the two other drinks in the subsequent sessions. Participants rested an hour before running the modified Astrand protocol and terminated upon volitional exhaustion. Treadmill speed was kept at 10 km·h-1 throughout with only gradient increment at 2.5% for the first 3-minute and subsequently for every 2-minute. Heart rate (HR) and rate of perceived exertion (RPE) were obtained with a Polar HR transmitter and OMNI RPE scale respectively, at the last 10-second of each stage. Blood lactate (Bla) via finger prick was obtained immediately and at the 3rd and 5th minute upon termination. RESULTS: No significant difference was observed between three drinks in VO2max (water: 3.41 ± 0.67 ml·kg-1·min-1, CI: 3.50 ± 0.7 ml·kg-1 min-1, PI: 3.56 ± 0.66 ml·kg-1 min-1, p = 0.26) and time to exhaustion (TTE) (water: 727 ± 151.1 s, CI: 732.1 ± 154.75 s, PI: 745.6 ± 140.43 s, p = 0.50). No significant difference was observed in percentage of maximal HR (%HRmax) at end stage between three drinks (water: 93.41 ± 7.41%, CI: 95.89 ± 5.51%, PI: 93.87 ± 5.35%). Significant differences were observed in main effects of treatment (p < 0.001) and interaction between treatment and time (p = 0.00) in Bla (water; 0 min: 9.42 ± 2.58 mmol·l-1, 3 min:9.6 ± 2.32 mmol·l-1, 5 min: 10.15 ± 2.62 mmol·l-1, CI; 0 min:9.27 ± 2.42 mmol·l-1, 3 min: 8.86 ± 2.67 mmol·l-1, 5 min: 8.95 ± 2.77 mmol·l-1, PI; 0 min: 8.56 ± 2.45 mmol·l-1, 3 min: 8.17 ± 2.85 mmol·l-1, 5 min: 8.05 ± 2.73 mmol·l-1). No significant differences were observed in main effect of time (p = 0.95) in Bla. CONCLUSION: Consumption of CI, PI and water showed significant difference in Bla produced from the aerobic test over time. VO2max, TTE and %HRmax at end stage were not influenced by drinks ingested. Further studies could investigate the effects of protein drinks for sprints due to the significant reduction in Bla.