The aim of this study was to investigate the effects of a four-week weight reduction period (WRP) with high protein and reduced carbohydrate intake on body composition, explosive power, speed, serum hormones and acid-base balance in male track and field jumpers and sprinters. Eight participants were assigned to a high weight reduction group (HWR; energy restriction 750 kcal / day), and seven to a low weight reduction group (LWR; energy restriction 300 kcal / day). Energy and carbohydrate intake decreased significantly (p <= 0.05) only in HWR by 740 +/- 330 kcal / day and 130 +/- 29 g / day, respectively. Furthermore, total body mass and fat mass decreased (p <= 0.05) only in HWR by 2.2 +/- 1.0 kg and 1.7 +/- 1.6 kg, respectively. Fat-free mass (FFM), serum testosterone, cortisol, and SHBG did not change significantly. Ca2+-ion and pH decreased (p <= 0.05) only in HWR (3.1 +/- 2.8 % and 0.8 +/- 0.8 %, respectively), whereas HCO3- declined (p <= 0.05) in both groups by 19.3 +/- 6.2 % in HWR and by 13.1 +/- 8.5 % in LWR. The counter-movement jump and 20-m sprint time improved consistently (p <= 0.05) only in HWR, by 2.6 +/- 2.5 cm and 0.04 +/- 0.04 s, respectively. Finally, athletes with a fat percentage 10% or over at the baseline were able to preserve FFM. In conclusion, altered acid-base balance but improved weight bearing power performance was observed without negative consequences on serum hormones and FFM after a four-week weight reduction of 0.5 kg / week achieved via reduced carbohydrate but maintained high protein intake.
Copyright (C) 2014 by the National Strength & Conditioning Association.