Effects of soy milk ingestion on anaerobic performance and physiological measures

Abstract

The purpose of this study was to investigate the effects of soy protein supplementation to improve performance and recovery during repeated running anaerobic sprint test (RAST). Ten males (age: 23.2 ± 1.23 yrs) performed two RAST with a soy milk intervention (SOY; 500 mL soy milk + 4 g stevia sweetener) and a placebo control (CON; 500 mL water + 4 g stevia sweetener) over 7 days. The RAST consisted of six 35-m sprints with a 10-sec recovery between each sprint. The total effort time (sec) was not significant between SOY (32.77 ± 1.23) and CON (33.28 ± 1.71) (P = 0.179). Fatigue index in SOY (31.64 ± 5.20) was significantly lower than CON (37.30 ± 5.70) (P = 0.023). Mean power (Watts) (Soy: 499.27 ± 62.72, Con: 486.39 ± 86.13) (P = 0.410), relative power (Watts) (Soy: 9.34 ± 1.02, Con: 9.55 ± 1.51) (P = 0.461), peak blood lactate (mmol·L-1) (Soy: 9.75 ± 1.61, Con: 10.24 ± 1.90) (P = 0.488), and peak blood glucose (mmol·L-1) (Soy: 23.94 ± 3.90, Con: 25.09 ± 4.61) (P = 0.497) between trials were not significant. Peak blood lactate (r = -0.654) and glucose (r = -0.662) concentrations were inversely associated with mean power in the SOY trial. The results indicate that the soy milk intervention in RAST significantly lowered the fatigue index and, therefore, may be used to enhance sports performance involving anaerobic activities.