THE EFFECTS OF CARBOHYDRATE LOADING ON REPETITIVE JUMP SQUAT POWER PERFORMANCE : The Journal of Strength & Conditioning Research

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THE EFFECTS OF CARBOHYDRATE LOADING ON REPETITIVE JUMP SQUAT POWER PERFORMANCE

HATFIELD, DISA L.1; KRAEMER, WILLIAM J.1,2; VOLEK, JEFF S.1; RUBIN, MARTYN R.1; GREBIEN, BIANCA3; GÓMEZ, ANA L.1; FRENCH, DUNCAN N.1; SCHEETT, TIMOTHY P.4; RATAMESS, NICHOLAS A.5; SHARMAN, MATTHEW J.2; MCGUIGAN, MICHAEL R.2; NEWTON, ROBERT U.2; HÄKKINEN, AND KEIJO6

Author Information

1Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, Connecticut 06269; 2School of Biomedical and Sports Science, Edith Cowan University, Joondalup, Western Australia, Australia; 3Department of Movement Sciences, University of Masstricht, Masstricht, Netherlands; 4School of Human Performance and Recreation, The University of Southern Mississippi, Hattiesburg, Mississippi 39406; 5Department of Health and Exercise Science, The College of New Jersey, Ewing, New Jersey 08628; 6Department of Biology of Physical Activity, University of Jyväskylä, P.O. Box 35, 40014 University of Jyväskylä, Finland.

Address correspondence to Dr. William J. Kraemer, [email protected].

Journal of Strength and Conditioning Research 20(1):p 167-171, February 2006.
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Abstract

The beneficial role of carbohydrate (CHO) supplementation in endurance exercise is well documented. However, only few data are available on the effects of CHO loading on resistance exercise performance. Because of the repetitive use of high-threshold motor units, it was hypothesized that the power output (power-endurance) of multiple sets of jump squats would be enhanced following a high-CHO (6.5 g CHO kg body mass−1) diet compared to a moderate-CHO (4.4 g CHO kg body mass−1) diet. Eight healthy men (mean ± SD: age 26.3 ± 2.6 years; weight 73.0 ± 6.3 kg; body fat 13.4 ± 5.0%; height 178.2 ± 6.1 cm) participated in 2 randomly assigned counterbalanced supplementation periods of 4 days after having their free-living habitual diet monitored. The resistance exercise test consisted of 4 sets of 12 repetitions of maximal-effort jump squats using a Plyometric Power System unit and a load of 30% of 1 repetition maximum (1RM). A 2-minute rest period was used between sets. Immediately before and after the exercise test, a blood sample was obtained to determine the serum glucose and blood lactate concentrations. No significant difference in power performance existed between the 2 diets. As expected, there was a significant (p ≤ 0.05) decrease in power performance between the repetitions in every set. Blood lactate concentrations were significantly higher postexercise with both the high-CHO and the moderate- or lower-CHO diet, but there were no differences between conditions. The results indicated that the power output during multiple sets of maximal jump squats was not enhanced following a higher-CHO diet compared to a moderate- or lower-CHO diet. These data show that elevated carbohydrate intake is not needed to optimize a repetitive power-endurance performance when it is done as the first exercise in a workout.

© 2006 National Strength and Conditioning Association