Much attention has been given to determining the influence of total protein intake and protein source on gains in lean body mass (LBM) and strength in response to resistance exercise training (RET). Acute studies indicate that whey protein, likely related to its higher leucine content, stimulates muscle protein synthesis to a greater extent than proteins such as soy and casein. Less clear is the extent to which the type of protein supplemented impacts strength and LBM in long-term studies (≥6 weeks). Therefore, a meta-analysis was conducted to compare the effect of supplementation with soy protein to animal protein supplementation on strength and LBM in response to RET. Nine studies involving 266 participants suitable for inclusion in the meta-analysis were identified. Five studies compared whey with soy protein, and four studies compared soy protein with other proteins (beef, milk, or dairy protein). Meta-analysis showed that supplementing RET with whey or soy protein resulted in significant increases in strength but found no difference between groups (bench press: χ2 = 0.02, p = .90; squat: χ2 = 0.22, p = .64). There was no significant effect of whey or soy alone (n = 5) on LBM change and no differences between groups (χ2 = 0.00, p = .96). Strength and LBM both increased significantly in the “other protein” and the soy groups (n = 9), but there were no between-group differences (bench: χ2 = 0.02, p = .88; squat: χ2 = 0.78, p = .38; and LBM: χ2 = 0.06, p = .80). The results of this meta-analysis indicate that soy protein supplementation produces similar gains in strength and LBM in response to RET as whey protein.
Mark Messina, Heidi Lynch, Jared M. Dickinson and Katharine E. Reed
Katharine E. Reed, Darren E.R. Warburton, Crystal L. Whitney and Heather A. McKay
Low physical fitness is associated with increased risk of cardiovascular disease (CVD) in adults and a higher incidence of CVD risk factors in children. Our aim was to compare the aerobic performance of Canadian children in 2004 with that of children measured 2 decades ago. We conducted a cross-sectional comparison of 2 data sets: (a) a 2004 cohort (n = 252) and (b) data from Leger’s 1981 cohort (n = 2,151). Performance was assessed using Leger’s 20 m Shuttle Run Test. First, we compared VO2max by cohort (in age and sex subgroups). Second, we used 1981 derived data, to re-create the original distribution curves, then calculated a 1981 equivalent percentile for each 2004 cohort child. We found that aerobic performance was lower at all ages in 2004 compared with 1981 (p < .01). Thus, the 50th percentile for fitness of children in 2004 was equivalent to that of children in the lowest 20% of fitness in 1981. We support the view that the performance of children on aerobic fitness tests is declining.