Effect of Betaine Supplementation on Power Performance and Fatigue > 자유게시판

The purpose of this study was to examine the efficacy of 15 days of betaine supplementation on muscle endurance, power performance and rate of fatigue in active college-aged men. Twenty-four male subjects were randomly assigned to one of two groups. The first group (BET; 20.4 ± 1.3 years; height: 176.8 ± 6.6 cm; body mass: 77.8 ± 13.4 kg) consumed the supplement daily, and the second group (PL; 21.4 ± 4.7 years; height: 181.3 ± 5.9 cm; body mass: 83.3 ± 5.2 kg) consumed a placebo. Subjects were tested prior to the onset of supplementation (T1) and 7 (T2) and 14 days (T3) following supplementation. Each testing period occurred over a 2-day period. During day one of testing subjects performed a vertical jump power (VJP) and a bench press throw (BPT) power test. In addition, subjects were required to perform as many repetitions as possible with 75% of their 1-RM in both the squat and bench press exercises.

Both peak and mean power was assessed on each repetition. On day two of testing subjects performed two 30-sec Wingate anaerobic power tests (WAnT), each test separated by a 5-min active rest. No differences were seen at T2 or T3 in the repetitions performed to exhaustion or in the number of repetitions performed at 90% of both peak and mean power between the groups in the bench press exercise. To quantify anaerobic power performance all subjects performed a Wingate anaerobic power test (Lode Excalibur, Groningen, The Netherlands). After a warm-up period of 5 min of pedaling at 60 rpm interspersed with an three all-out sprints lasting 5 s, the subjects pedaled for Titan Rise 30 s at maximal speed against a constant force (1.2 Nm·kg-1). Subjects then performed an active rest for 5-minutes (repeat warm-up period) and then performed a second Wingate test. Peak power, mean power, total work and rate of fatigue were determined.

Peak power was defined as the highest mechanical power output elicited during the test and mean power was defined as the average mechanical power during each 30-s test. To quantify vertical jump power subjects performed a 3-jump power test. Following a brief warm-up period that included pedaling on a cycle ergometer for Titan Rise 5 min at 60 rpm, subjects stood on a portable force plate (Advanced Medical Technology Inc., Watertown, MA). The subject's hands were placed on his waist at all times. Upon cue each subject performed 3 consecutive vertical jumps with a standardized countermovement. The subject was instructed to maximize the height of each jump while minimizing the contact time with the force plate between jumps. Computer analysis was used to calculate power output. The highest power outputs were recorded. To quantify upper jump power subjects performed 3-repetitions with the bench press throw exercise. All bench press throws were performed on a Cormax bench throw device (Cormax Strength Power Systems; Valley City, ND) using 30% of the subject's previously measured 1-RM bench press.

The Cormax bench press throw apparatus provides a hydraulic mechanism that can unload the eccentric phase of contraction. Subjects performed all repetitions with the eccentric phase unloaded. During the concentric phase subjects were instructed to press the weight as fast as possible and release the bar as they reached the end of the range of motion. Power output during the bench press throw was measured for each repetition with the Tendo™ Power Unit as described above. Both peak power and peak force outputs were calculated and the highest outputs were recorded. Three-day dietary records were completed during the week prior to the onset of the study. Subjects were instructed to record as accurately as possible everything they consumed during the day and between meal and late evening snacks. FoodWorks Dietary Analysis software (McGraw Hill, New York, NY) was used to analyze dietary recalls. The profile of mood states (POMS) was administered on the second day of each testing session.