Background: Previously we reported that acute supplementation with an amylopectin- chromium complex combined with a six-gram dose of whey protein increased rates of muscle protein synthesis. The purpose of this study was to examine if chronic supplementation with the same amylopectin-chromium complex plus a higher dose of protein could impact resistance training adaptations, recovery, and biomarkers of safety.Methods: Using a randomized, active-controlled, double-blind design, 35 recreationally active men (mean ± age, height, weight: 40.9 ± 7.6 y, 180.2 ± 6.1 cm, 95.8 ± 14.5 kg) were matched according to HOMA-IR and resistance-training experience and then randomly allocated to one of three groups: an active group consisting of 2 g amylopectin-chromium complex + 15 g whey protein isolate (V15P), an equivalent dose of whey protein isolate (15 g of whey protein, 15P), or a 30 gram dose of whey protein isolate (30P). Subjects consumed their respective supplement immediately following resistance exercise on days when training occurred and at the same time of day on non-training days. At 0, 4, and 8 weeks of training, body composition (4C via DXA, Bod Pod, Bioimpedance), whole-body protein balance (oral 15N-alanine), upper body and lower body performance (bench press, squat, jump power), and visual analog scale (VAS) scores for recovery, sleep quality, energy, willingness to train, and muscle soreness were assessed. Safety assessments included systemic hemodynamics, complete blood count, and comprehensive metabolic panels. Results: All groups gained strength, increased fat-free mass, and improved muscle size. Similarly, all groups increased squat repetitions to failure (RTF), with V15P experiencing a greater increase (+25.3 reps, p = 0.02) when compared to 15P (+12.0 reps) and 30P (+13.9 reps). After normalizing data to body mass, vertical jump power increased (p = 0.03) more for V15P (+2.1 Watts/kg) than either 15P (+0.4 Watts/kg) or 30P (+0.3 Watts/kg). Vertical jump height calculated from power output increased more in V15P (+8.7 cm, p = 0.04) than 15P (+1.6 cm) and 30P (+0.9 cm). Net protein balance was greater (p = 0.04) in V15P compared to 15W and 30W at four weeks (p < 0.05), but this difference was not observed after eight weeks (p = 0.51). No changes in VAS were identified between groups. Diastolic blood pressure decreased in V15P (p = 0.002) compared to the other groups, and outside of an interaction for creatinine and aspartate aminotransferase (which still remained well within clinical limits), all blood- based markers of safety demonstrated no differences between groups.
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