3 In a study of young adult men aged 19–29 who consumed 3g of HMB per day in combination with 1.5 hours of weight training 3 days per week and a protein-rich diet (1.4g/kg/day), there was a significant reduction in exercise-induced rises in urinary 3-methylhistidine levels, a marker of muscle protein breakdown, during the first 2 weeks of the study compared to control.