Abstract
Milk and/or whey protein plus resistance exercise (RT) increase strength and muscle size, and optimize body composition in adult males and females. Greek yogurt (GY) contains similar muscle-supporting nutrients as milk yet it is different in several ways including being a semi-solid food, containing bacterial cultures and having a higher protein content (mostly casein) per serving. GY has yet to be investigated in the context of a RT program. The purpose of this study was to assess the effects of GY consumption plus RT on strength, muscle thickness and body composition in lean, untrained, university-aged males. Thirty untrained, university-aged (20.6 ± 2.2 years) males were randomized to 2 groups (n = 15/group): fat-free, plain GY or a Placebo Pudding (PP; isoenergetic carbohydrate-based pudding) and underwent a combined RT/plyometric training program 3 days/week for 12 weeks. They consumed either GY (20 g protein/dose) or PP (0 g protein/dose) daily, 3 times on training days and 2 times on non-training days. After 12 weeks, both groups significantly increased strength, muscle thickness and fat-free mass (FFM) (p < 0.05). The GY group gained more total strength (GY; 98 ± 37 kg, PP; 57 ± 15 kg), more biceps brachii muscular thickness (GY; 0.46 ± 0.3 cm, PP; 0.12 ± 0.2 cm), more FFM (GY; 2.4 ± 1.5 kg, PP; 1.3 ± 1.3 kg), and reduced % body fat (GY; −1.1 ± 2.2%, PP; 0.1 ± 2.6%) than PP group (p < 0.05 expressed as absolute change). Thus, consumption of GY during a training program resulted in improved strength, muscle thickness and body composition over a carbohydrate-based placebo. Given the results of our study, the general benefits of consuming GY and its distinctiveness from milk, GY can be a plausible, post-exercise, nutrient-rich alternative for positive strength, muscle, and body composition adaptations.
Highlights
The use of protein supplements to facilitate resistance training (RT) adaptations has long been documented in human populations [1,2,3]
Post-testing was completed on all three of these subjects and their data were included in the analysis, except for the injured participant who did not complete the 1 repetition maximum (1-RM) post-testing
There were no differences at baseline for any variable between groups except for % body fat, with placebo pudding (PP) being higher than Greek yogurt (GY) (p = 0.049)
Summary
The use of protein supplements to facilitate resistance training (RT) adaptations has long been documented in human populations [1,2,3]. Casein, which constitutes 80% of dairy protein, is a more slowly absorbed protein, and is able to prolong elevated levels of plasmaAAs and enhance whole-body protein turnover [10] This unique characteristic of casein protein may act to attenuate muscle protein breakdown (MPB), further research is required to determine this. Both proteins allow for a net positive protein balance (or a less negative balance) over a prolonged period time [11] Because of this (and other important features), dairy protein, and especially milk, which has garnered the majority of research, has been shown to be an effective beverage for facilitating adaptations to RT [12, 13]. This poses the question; would other dairy products elicit the same positive adaptations to RT as milk?
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