Dietary protein intake is associated with maximal and explosive strength of the leg flexors in young and older blue collar workers.

The aim of this study was to investigate the association between dietary protein (PRO) intake and maximal and rapid strength of the leg flexors in blue collar (BC) working men. Twenty-four young (age, 23.2 ± 2.1 years) and 19 older (age, 52.8 ± 5.2 years) men employed in BC occupations completed a 3-day dietary record and isometric strength testing of the leg flexors. Food logs were analyzed for total PRO (TPRO) and essential amino acid (EAA) intake. Rapid and maximal strength capacities were examined from the rate of torque development at 50 milliseconds and peak torque of the torque-time curves, respectively. Pearson correlations and partial correlations were used to examine the relationships between TPRO and EAA intake on strength variables. Peak torque was positively correlated to TPRO and EAA intake in the young (r = 0.439 and r = 0.431; P < .05) and older (r = 0.636 and r = 0.605; P < .01) men, and rate of torque development at 50 milliseconds was correlated to TPRO and EAA intake in the young (r = 0.512 and r = 0.310; P = .01) and older (r = 0.662 and r = 0.665; P < .01) men, respectively. There were no relationships (P > .05) between TPRO and strength variables when controlling for EAA intake. Total PRO intake explained 20 to 44% of the variance in rapid and maximal strength for both age groups. Essential amino acid intake was largely responsible for the positive relationship between PRO intake and strength. Across young and older BC working male populations, PRO consumption was associated with both maximal and explosive strength capacities of the leg flexors muscle group.