|In view of the anti-strength effects observed in the study at hand: It's almost sarcastic that many of the proteins that are specifically marketed to older men and women contain soy protein.|
One of the most visible signs of aging is the loss of skeletal muscle mass and strength, which leads to decrements in physical function and may predispose to disability (Kooman. 2009). As Thomson et al. point out in their latest paper it is thus "important to develop strategies that promote maintenance of lean tissue mass, strength and physical function in older adults [...] to reduce disability into older age." (Thomson. 2015).
One of the ways to do that, i.e. to reduce disability into older age, is to combine resistant training with an increased protein intake. Both the optimal amount of protein and the optimal source are yet still debated. According, the
"aim of [Thomson et al.'s] study was to evaluate whether, when protein intake was at least 20 g at each meal, the consumption of a eucaloric high protein diet rich in dairy protein would provide greater increases in muscle strength, lean mass and physical function compared with either an isocaloric diet representative of the typical Australian dietary protein intake (i.e. ∼1.1 g/kg/d ) or an isocaloric diet high in non-dairy (i.e. soy) protein in older adults undertaking a program of resistance training" (Thomson. 2015).To this ends, 179 healthy older adults (age 61.5 ± 7.4 yrs, BMI 27.6 ± 3.6 kg/m²) performed resistance training three times per week for 12 weeks and were randomized to one of three eucaloric dietary treatments which delivered >20 g of protein at each main meal or immediately after resistance training from either...
Table 1: Average dietary intake during the 12 week study period (Thomson. 2015).
- high soy protein (HP–S, >1.2 g of protein/kg body weight/d; ∼27 g/d soy protein);
- usual protein intake (UP, <1.2 g of protein/kg body weight/d).
|Figure 1: Relative changes in muscle strength values at baseline (Week 0) and after the intervention (Week 12) for participants compliant with the study protocol (Thomson. 2015).|Figure 2: CONSORT diagram (HP-D, high dairy protein diet; HP-S, high soy protein diet; UP, usual protein diet | Thomson. 2015).
- three days per week on non consecutive days
- five exercises per formed on weight stack pin loaded machines
- leg press, chest press, knee extension, lat pull down and leg curl, as well as seated bent knee hip flexions.
- training load was progressive and started with one set of eight reps at a resistance equivalent to the participant's 8 repetition maximum (RM; maximum weight lifted for eight repetitions)
- resistance was maintained until participants could perform three sets of 12 repetitions; resistance was then increased so only eight repetitions could be performed again in the first set, and this resistance was maintained until participants could again perform three sets of 12 repetitions
- for the seated bent knee hip fl exions participants gradually increased the number of repetitions and sets throughout the training period until they could perform two sets of 20 repetitions, and this was then maintained for the remainder of the study period
- all exercise programs were performed under supervision of trainers
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- Thomson, Rebecca L., et al. "Muscle strength gains during resistance exercise training are attenuated with soy compared with dairy or usual protein intake in older adults: A randomized controlled trial." Clinical Nutrition (2015).
- Veldhorst, Margriet AB, et al. "Dose-dependent satiating effect of whey relative to casein or soy." Physiology & behavior 96.4 (2009): 675-682.