Of late, a common approach in the exercise/sport nutrition supplement industry is the development of multiingredient products with the intent of simultaneously upregulating multiple ergogenic-related physiological mechanisms in order to increase muscle mass, strength, and performance. For example, a multi-ingredient product that could potentially increase muscle strength and mass while concomitantly improving metabolic function, oxidative stress, and body composition may prove to be superior to a single-ingredient product. Many multi-ingredient products on the market contain whey protein, amino acids, carbohydrate, and creatine, and a number of these products have shown to augment physiological responses to resistance training (Candow et al., 2006; Shelmadine et al; Spillane et al., Willoughby et al., 2007). Positive out comes emanating from clinical studies involving these type of multi-ingredient products are challenging because it is difficult to determine which ingredient(s) contained within the product may be inducing the ergogenic outcome. Nevertheless, since more of these types of products are appearing on the market, more research is necessary to substantiate their alleged effectiveness and efficacy.
A multi-ingredient product available on the market with a comprehensive list of ingredients is SizeOn Maximum Performance (Gaspari Nutrition, Inc., Lakewood, NJ), which contains a variety of ingredients alleged to augment the effects of resistance training. This product has recently been shown to be preferentially effective when compared to a protein/carbohydrate/creatine comparator at improving body composition and muscle performance (Schmitz et al., 2010). This multi-ingredient product contains a blend of vitamins and minerals containing vitamin C, thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, calcium, phosphorus, magnesium, sodium, and potassium. These vitamins and minerals help maintain normal cellular function during stress-inducing situations such as exercise (Fenech and Ferguson, 2001). In addition, the product contains a blend of carbohydrates with different rates of absorption. This blend consists of the disaccharides iso-maltulose, trehalose, as well as monomeric glucose. Apparently, the alleged rationale for adding three different types of carbohydrates is to ensure proper glycogen replenishment in response to exercise due to the different rates in which each type of carbohydrate is absorbed (Lina et al., 2002; Sola-Penna and Fernandes, 1998; Jentjens and Jeukendrup, 2003). Apparently, to enhance glycogen replenishment, pterostilbene is included in the ingredient profile. Pterostilbene, an extract of blueberries, appears to enhance insulin sensitivity by enhancing hepatic enzymes associated with glucose uptake (Pari and Satheesh, 2006). In addition, the product contains a blend of hydrolyzed whey protein with free-form and branched-chain amino acids (BCAAs). Hydrolyzed whey protein and BCAAs have been shown to enhance the skeletal muscle protein synthesis in response to exercise (Borsheim et al., 2002; Manninen, 2009; Tang et al., 2007; Paddon-Jones et al., 2006). The product also contains creatine monohydrate and its salts (magnesium creatine chelate, disodium creatine phosphate). Creatine and its salts have been shown to enhance muscle mass and strength via increased protein synthesis in skeletal muscle tissue (Rawon and Volek, 2003; Sakkas et al., 2009; Selsby et al., 2004). Finally, SizeOn Maximum Performance contains a blend of electrolytes: sodium glycerophosphate, calcium glycerophosphate, potassium glycerophosphate, and the amino acids L-taurine, L-alanyl-L-glutamine, and magnesium glycyl glutamine. This blend of electrolytes and amino acids apparently act as an osmoregulator to ensure proper cellular hydration for optimal cellular function (Fumarola et al., 2005; Goodman et al., 2009).
The purpose of this study was to determine the effects of the peri-exercise nutritional supplement, SizeOn Maximum Performance, versus a conventional protein/carbohydrate/ creatine comparator supplement on indices of muscular adaptations to resistance training in young men. We hypothesized that SizeOn Maximum Performance would preferentially improve muscle strength and mass and body composition, along with increasing blood and skeletal muscle markers associated with muscle anabolism.
In a randomized, double-blind, parallel design, nonresistance-trained males participated in a 4-day/week heavy resistance training program for 6 weeks in conjunction with the peri-exercise ingestion of either a multi-ingredient SizeOn Maximum Performance or protein/carbohydrate/creatine comparator supplement. Body composition and muscle performance were assessed, along with venous blood samples and muscle biopsies being obtained, before and after the 6-week intervention.
Twenty-four apparently healthy, resistance trained [regular, consistent resistance training (i.e. thrice weekly) for at least 1 year prior to the onset of the study], males between the ages of 18-35 and a body mass index between 18.5-30 kg * [m.sup.-2] volunteered to participate in the double-blind study. Enrollment was open to men of all ethnicities. Only participants considered as low risk for cardiovascular disease and with no contraindications to exercise as outlined by the American College of Sports Medicine (ACSM) and who had not consumed any nutritional supplements (excluding multi-vitamins) 3 months prior to the study were allowed to participate. All participants provided written informed consent and were cleared for participation by passing a mandatory medical screening. All eligible subjects signed university-approved informed consent documents and approval was granted by the Institutional Review Board for the Protection of Human Subjects in Research of Baylor University. Additionally, all experimental procedures involved in the study conformed to the ethical consideration of the Helsinki Code.
Assessment of body composition and muscle performance
A testing session was performed prior to the first dose of supplement and beginning of the resistance training program (day 0) and on day 43, after 42 days of supplementation and resistance training. Body and composition and muscle performance were determined during these two testing sessions.
The determination of the one-repetition maximum (1-RM) for the angled leg press and knee extension exercises was based upon our previous procedures (Shelmadine et al; Spillane et al., Willoughby et al., 2007). As a warm-up, an estimated 50% 1-RM was utilized to complete 10 repetitions. After a 2.5 min rest period, a load of 70% of estimated 1-RM was utilized to perform five repetitions. At this point, the weight was gradually increased until a 1-RM was reached, with a 2.5 min rest period in between each successful lift. Test-retest reliability of performing these strength assessments on subjects within our laboratory has demonstrated low mean coefficients of variation and high reliability for the angled leg press (2.3%, intra-class r = 0.94) and knee extension (0.82%, intra-class r = 0.93), respectively. In order to assess muscle endurance, using the bench press and angled leg press exercises, participants performed as many repetitions as possible with 75% of their 1-RM (Spillane and Willoughby, 2012).
Total body mass (kg) was determined on a standard dual beam balance scale (Detecto, Webb City, MO). Percent body fat, fat mass, and fat-free mass, were determined using dual-energy x-ray absorptiometry (DEXA; Hologic Discovery Series W, Waltham, MA) based on our previous guidelines (Shelmadine et al., 2009; Spillane et al., 2009; Willoughby et al., 2007). Baseline hemodynamic measurements at rest were completed. Heart rate was determined by palpation of the radial artery using standard procedures. Blood pressure was assessed in the supine position after resting for 5-min using a mercurial sphygmomanometer using standard procedures.
For the 72 hours immediately prior to reporting to the lab for testing at Day 0 and 43, participants were instructed to record their dietary intake. During each of these 72-hour time periods, participants were instructed to not change their usual dietary habits. The dietary data were analyzed with the Food Processor dietary assessment software (ESHA Research, Salem, OR, USA) for determination of the average intake of total food energy and intake of the macronutrients.
Venous blood sampling and muscle biopsies
Venous blood samples and muscle biopsies were obtained during the testing sessions at Day 0 and 43. Blood was collected from the antecubital vein into a 10 ml Vacutainer tube. Blood samples were allowed to stand at room temperature for 10 minutes and then centrifuged. The serum was removed and frozen at -80[degrees]C for later analysis.
Percutaneous muscle biopsies (50-70 mg) were obtained from the middle portion of the vastus lateralis muscle of the dominant leg at the midpoint between the patella and the greater trochanter of the femur at a depth between 1 and 2 cm. For the two biopsies, attempts were made to extract tissue from approximately the same location as the initial biopsy by using the pre-biopsy scar, depth markings on the needle, and a successive incision that was made approximately 0.5 cm to the former from medial to lateral. After removal, adipose tissue was trimmed from the muscle specimens and immediately frozen in liquid nitrogen and then stored at -80[degrees]C for later analysis.
In double-blind fashion, participants were assigned a 6week (42-day) supplementation protocol consisting of the oral ingestion of either a 50 grams/day of a comparator (PCC) supplement or SizeOn Maximum Performance (SIZE) (Gaspari Nutrition, Inc., Lakewood, NJ). Both supplements contained 39 grams of maltodextrose, 7 grams of whey protein, and 4...