| The effect of protein supplementation on athletic performance
and hormonal changes was examined in 21 experienced collegiate strength/power
athletes participating in a 12-week resistance training program. Subjects
were randomly assigned to either a protein supplement (PR; n = 11)
or a placebo (PL; n = 10) group. During each testing session subjects
were assessed for strength (one repetition maximum [1-RM] bench press
and squat), power (Wingate anaerobic power test) and body composition.
Resting blood samples were analyzed at weeks 0 (PRE), 6 (MID) and
12 (POST) for total testosterone, cortisol, growth hormone, and IGF-1.
No difference was seen in energy intake between PR and PL (3034 ±
209 kcal and 3130 ± 266 kcal, respectively), but a significant difference
in daily protein intake was seen between PR (2.00 g·kg body mass[BM]-1·d-1)
and PL (1.24 g·kgBM-1·d-1). A greater change
(p < 0.05) in the ∆ 1-RM squat was seen in PR (23.5 ± 13.6
kg) compared to PL (9.1 ± 11.9 kg). No other significant strength
or power differences were seen between the groups. Cortisol concentrations
were significantly lower at MID for PL and this difference was significantly
different than PR. No significant changes were noted in resting growth
hormone or IGF-1 concentrations in either group. Although protein
supplementation appeared to augment lower body strength development,
similar upper body strength, anaerobic power and lean tissue changes
do not provide clear evidence supporting the efficacy of a 12-week
protein supplementation period in experienced resistance trained athletes.
KEY
WORDS: Sport nutrition, resistance training, endocrine, testosterone.
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