The International Scientific Journal of Physical Education and Sport Sciences ISJPESS September 2015 ϭ ISJPESS Volume (2) Issue (2) Sep 2015 www.isjpes.com Effects of Protein Hydrolysates on Physical Performance and Immunity in Male Soccer Players *Mohamed Nader Shalaby Suez Canal University To investigate the effects of protein hydrolysates on Physical performance and immunity in male players aged 18-21 years. Blood samples were drawn from 2 groups of athletes (10 subjects each). The first group ingested protein hydrolysates 0.4 g/k for 15 days, the second one ingested placebo for 15 days. All participants were subjected to Copper test as a field test for V02 max determination, according to standardized protocol of Burke (1996). The other parameters determined were, Leucocytes, Neutrophils, CD 45+ (lymphocytes) D14+ (monocytes), together with free testosterone, cortisol and insulin, using coulter counter, flow cytometer and Elisa techniques. Results: Protein hydrolysates revealed an increased cellular parameters WBCS, CD45+, CD14+), together with elevated free testosterone and insulin concentrations with lower cortisol. VO2 max increased following protein hydrolysates administration. In response to protein hydrolysates ingestions some immunological variables are enhanced together with higher anabolic hormones and lower cortisol concentration, this might stimulate physical performance. Key words: Protein hydrolysates, immunity, physical performance, flow cytometry. Introduction Immunological alterations in response to a number of different exercise protocols are well documented (Pedersen, 1997 and Mackinnon 1999, 2000). Published studies have investigated changes in circulating cell populations in response to one bout of acute exercise (Gabriel & Kindermann, 1997 and Bishop et al., 1999) or repeated exercise (Ronsen et al., 2001) or different exercises (Mohamed et al., 2012). It has been suggested that decreased number of lymphocytes and/or natural killer (NK) cells during the hours after strenuous exercise may increase the risk of infections (Pedersen, 1997). In well-trained athletes, the number of circulating leucocytes and monocytes at rest are usually within normal clinical limits (Mackinnon, 2000) but NK cell numbers may be elevated in some athletes (Nieman et al., 1995). Studies have shown that immunological variables change during different training periods and in response to variations in exercise intensity and duration (Gleeson et al., 1995 and Gabriel & Kindermann 1997). The clinical relevance of acute changes in immunological variables in blood samples after physical exercise has been debated (Mackinnon, 2000) because these changes may simply reflect a brief upset in homeostasis and a direct correlation to changed resistance to infections has not been made. *Department of Sports Science, Faculty of Physical Education, Suez Canal University, Egypt, Email: msh6662005@yahoo.com