Prior to the late 1980s the practice of resistance training to improve baseball performance was considered taboo for fear players would lose mobility and speed due to increased muscle volume (DeRenne, 2007). On the contrary, a significant relationship exists between increasing body mass indexes and offensive performances in Major League Baseball players following the year 1980 (Crotin et al., 2014). Of more importance to this study population, lean body mass, lower- and upper-body power, and strength are all positively associated with greater bat velocity (a major component of hitting success) in high school and collegiate baseball players (Miyaguchi and Demura, 2012; Reyes et al., 2010). Additionally, lower body strength and body composition are associated with increased sprinting and jumping abilities in collegiate athletes (Macdonald et al., 2013; Platanou and Varamenti, 2011; Wisloff et al., 2004). The use of periodized resistance training to increase strength, lean mass, and power therefore contributes to improved batting, throwing, and base running performance (Derenne et al., 2001; Szymanski et al., 2009).
Increases in force output with resistance training are a result of both neural and hypertrophic adaptations. A direct relationship exists between muscle cross sectional area and force production (Maughan et al., 1983), however the ability to increase lean mass and force production decreases with training age (Andersen and Aagaard, 2010). As such, nutritional interventions may be necessary to further augment resistance training adaptations. In particular, encouraging athletes to eat higher protein diets (Guimaraes-Ferreira et al., 2014) (1.8 - 2.2 g/kg) with more frequent protein feedings (Morton et al., 2015) (4 5 feedings/day) in combination with an adequate energy intake is most likely to have the greatest contributions towards enhancing resistance training efforts (Holway and Spriet, 2011).
While baseball competitions may be considered a "sedentary-power" sport for all but pitchers and catchers, athletes in the off- and pre-season training phase often have energy needs twice those of resting requirements due to twice-daily training sessions (Soo and Naughton, 2007). Despite increased energy needs and a recognition of increased protein requirements by NCAA Division I male athletes (Fox et al.,2011), Hinton et al. (2004) reported inadequate carbohydrate and protein intakes from a sample of 180 male NCAA Division I athletes that included baseball players. Inadequate energy and protein intake can lead to skeletal muscle atrophy, reduced strength and power performance, and increased risk of injury or illness (Rodriguez et al., 2009). Moreover, although NCAA Division I baseball players believe good nutrition will improve on field success (Pawlak et al., 2009) nutrition knowledge in NCAA Division I athletes is inadequate. Torres-McGehee reported only 9% of participants in a cohort of 185 NCAA Division I athletes scored higher than 75% on questions assessing knowledge of micro- and macronutrients, supplements and performance, weight management, and hydration (Torres-McGehee et al., 2012). Therefore, improving athlete nutritional knowledge may improve nutritional status thus leading to leaner body compositions and enhanced performance.
Despite the importance placed on nutrition by collegiate strength and conditioning coaches, a paucity of studies have evaluated the effectiveness of sport nutrition education interventions on nutritional knowledge and dietary status in NCAA Division I athletes. Abood et al. (2004) reported that 8 1-hour nutrition education sessions improved nutritional knowledge and nutritional self-efficacy but not total energy, carbohydrate, or protein intake in NCAA Division I female athletes. Because the content was delivered once a week over the course of 8 weeks, and the post-test took place following the 8th session, the authors suggested that more time may have been required to provide the athletes more time to practice the nutritional strategies and skills acquired during the intervention.
Valliant et al. (2012) investigated the effects of a nutrition education intervention in NCAA Division I female volleyball players during a 16 week offseason. The subjects met with the primary research once monthly for nutrition education. Compared to the control off=-season (offseason of the previous year), the nutrition education intervention increased total energy, carbohydrate, and protein intake, but subject intake of total energy and carbohydrate were still less than that required. Fat mass decreased and lean mass increased over the course of the intervention season, however body composition changes were not assessed during the control offseason, so whether these changes were a result of increased training demands or improved nutrition is unknown. Moreover, the relationships between improvements in nutritional status and metrics of strength and power performance have yet to be investigated. Additionally, many NCAA Division I programs do not have the resources or man power to provide one-on-one nutrition education to every athlete. Thus, the results obtained by investigating the effectiveness of brief, group based sport nutrition education interventions (SNEI) on nutritional knowledge and behavior may be of importance to coaches and athletic directors.
The purpose of this study is to investigate the effects of a brief SNEI on nutritional knowledge, nutrition status, body composition, and performance during a 12 week offseason in NCAA Division I baseball players.
Experimental approach to the problem
The present study was designed to evaluate dietary intake and nutrition knowledge during the fall baseball season, and to determine if a SNEI improves dietary intake, nutrition knowledge, body composition, and physical performance during 12 weeks of offseason training in collegiate baseball players. An independent groups design was used. Nutritional status was defined as energy and macronutrient intake, and was assessed using 3-day food records preand post-intervention. Subjects were instructed on how to keep a dietary log and were given information regarding the estimation of portion size without receiving any nutrition education. A sport nutrition specific knowledge questionnaire was administered pre- and post-intervention. Body composition was measured pre- and post intervention. Measures of physical performance were defined as 5-10-5 shuttle test, vertical jump, broad jump, and 1 RM back squat, and were measured pre- and post-intervention. All subjects took part in the same structured National Strength and Conditioning Association Certified Strength and Conditioning Specialist (NSCA-CSCS) supervised resistance training, conditioning, and offseason baseball practice.
Subjects were recruited from a Division I baseball team with approval of the athletic department and head baseball coach. Subjects were required to pass a collegiate athletic physical which screens for gastrointestinal disorders; cardiovascular conditions that may have placed them in serious risk upon exertion; spinal injuries, and limiting musculoskeletal injuries. Subjects that did not pass the athletic physical requirements were excluded from the study. Baseline subject characteristics are displayed in Table 1. All methods and procedures were approved via expedited review by the University Institutional Review Board prior to data collection. Subjects were fully informed of the scope and risks of the study prior to signing an IRB approved informed consent.
Eighteen players volunteered for the SNEI, however three missed intervention sessions and thus only the data from the players (n = 15) that completed all intervention sessions were included in the final analysis. The intervention group (NI) was matched with nonparticipating players that served as controls (C; n = 15) for body composition and performance according to the position played (infielders, outfielders, catchers, and pitchers). NI met with the principal investigator at the start of the intervention to receive 90 min of nutrition education and then in groups of 5 every 3 weeks thereafter at dinner for educational reinforcement and questions. All group comparative measures taken (body composition and performance) remained blind to the principal investigator until all data had been collected and analyzed statistically.
Procedures Dietary intake
Nutrient intake was measured at the start of the fall season (pre-intervention) and at the end of the 12 week offseason (post-intervention) via three-day food diaries that consisted of two weekdays and one weekend day to best reflect typical intakes. Total intake for the three days was then averaged and represented as pre- and post-intervention intakes. Subjects met with the investigators at pre- and post-intervention and were interviewed about food records to increase accuracy. Total energy intake, fluids, protein, carbohydrates, and fats will be analyzed using Diet Analysis Plus Version 10 (Cengage, USA).
Total energy expenditure (TEE) was estimated by adapting the Gerrior et al. (2006) method...