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Effect of 15 Days of Betaine Ingestion on Concentric and Eccentric Force Outputs During Isokinetic Exercise

Hoffman, Jay R1; Ratamess, Nicholas A2; Kang, Jie2; Gonzalez, Adam M2; Beller, Noah A2; Craig, Stuart A S3

Journal of Strength and Conditioning Research: August 2011 - Volume 25 - Issue 8 - p 2235-2241
doi: 10.1519/JSC.0b013e3182162530
Original Research
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Hoffman, JR, Ratamess, NA, Kang, J, Gonzalez, AM, Beller, NA, and Craig, SAS. Effect of 15 days of betaine ingestion on concentric and eccentric force outputs during isokinetic exercise. J Strength Cond Res 25(8): 2235-2241, 2011—The purpose of this study was to examine the efficacy of 15 days of betaine supplementation on peak concentric (CON) and eccentric (ECC) force during isokinetic exercise in active college-aged men. Eleven men volunteered for this study (21.7 ± 5.1 years; height: 178.5 ± 6.4 cm; body mass: 79.8 ± 10.3 kg). Subjects were randomly assigned to either a supplement (BET) or placebo (PL) group. Supplementation occurred for 15 days. Subjects reported to the Human Performance Laboratory on 5 occasions during this period, separated by 72 hours, for a testing and exercise session on an isokinetic chest press device. After each exercise protocol, subjects rated their fatigue and muscle soreness on a 15-cm visual analog scale. Subjects then consumed no daily BET for 4 weeks but maintained familiarity with the exercise device once per week. After the washout period, subjects resumed the BET protocol using the opposite drink and repeated the same 15-day protocol. No differences were noted in maximum CON force output between pre (335.9 ± 78.3 and 321.6 ± 63.6 N) and post (330.3 ± 74.8 and 330.2 ± 71.6 N) workouts in both BET and PL, respectively. In addition, no differences were noted in maximum ECC force output between pre (352.0 ± 90.6 and 324.4 ± 85.2 N) and post (353.2 ± 98.2 and 366.9 ± 128.5 N) workouts in BET and PL, respectively. No differences in subjective measures of soreness and fatigue were seen, but a significant reduction in Δ fatigue was observed in BET compared to PL. In conclusion, 15 days of betaine supplementation did not increase peak CON or ECC force outputs during an isokinetic chest press but did appear to reduce subjective measures of fatigue to the exercise protocol.

1Sport and Exercise Science, The University of Central Florida, Orlando, Florida; 2Department of Health and Exercise Science, The College of New Jersey, Ewing, New Jersey; and 3Danisco A/S, Tarrytown, New York

Address correspondence to Dr. Jay R. Hoffman, jrhoffma@mail.ucf.edu.

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Introduction

Betaine is a trimethyl derivative of the amino acid glycine. Its structure allows it to serve as a methyl donor to guanidinoacetate via methionine that can synthesize creatine in skeletal muscle (10). In consideration of these physiological effects, it has been hypothesized that supplementing with betaine may provide an ergogenic effect by enhancing strength and power performance from an increase in skeletal muscle creatine concentration (7). Research showed that 14 days of betaine supplementation resulted in no significant change in the number of repetitions performed in the squat or bench press exercise (13). However, significant improvements in bench press throw power, isometric bench press force, vertical jump power, and isometric squat force were seen. Using a similar dosing protocol, Hoffman et al. (11) reported that 2 weeks of betaine supplementation in active college men improved muscle endurance in the squat exercise and increased the quality of repetitions performed (e.g., number of repetitions performed at 90% of 1-repetition maximum [1RM]). These performance improvements were experienced within 7 days of supplementation. However, no changes in power performance were noted during the investigation. Although these recent studies have all shown some ergogenic potential with short-term betaine ingestion, the type of performance improvements has not been consistent between these investigations.

The synthesis of creatine is considered to be the primary benefit from the methyl donor S-adenosylmethionine (SAM) (17). Dietary ingestion of betaine serves as a source for increasing the methyl pool and subsequent methyl donation (8). However, evidence also suggests that the creatine synthesis from methyl donation may be overestimated and that phosphatidylcholine synthesis may be a greater consumer of endogenous methyl groups (19). If the synthesis of phosphatidylcholine is indeed a major factor from betaine ingestion, then the ergogenic benefits derived from betaine supplementation could be enhanced, or it may suggest that performance benefits may be the function of different physiological mechanisms resulting from methyl donation.

Phosphatidylcholine has an important role in the synthesis of the neurotransmitter acetylcholine. Neurons are unable to synthesize choline and must rely on dietary intake to ensure sufficient acetylcholine production (2). A deficiency could result in a multitude of physiological problems. Although several studies have reported that choline supplementation can enhance memory and cognition (2,4,5,9), its role in enhancing athletic performance is unclear. A recent study has demonstrated that phosphatidylcholine supplementation may contribute to improvements in reaction time, enhanced focus and alertness, and a decrease in subjective measures of fatigue after exhaustive exercise (12). Considering that betaine supplementation may serve to provide methyl groups for the formation of both creatine and phosphatidylcholine, the ergogenic benefit may be the result of a combination of these 2 mechanisms. Thus, the purpose of this study was to examine the efficacy of 15 days of betaine supplementation on concentric (CON) and eccentric (ECC) force outputs and objective ratings of fatigue and soreness in college-aged men.

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Methods

Experimental Approach to the Problem

Subjects reported to the Human Performance Laboratory (HPL) on 10 separate occasions to perform a resistance exercise protocol using a multiple-joint isokinetic dynamometer (Exerbotics, Tulsa, OK, USA). Before the onset of the study, subjects were familiarized (3 sessions) with the testing and exercise procedures of the device. After the familiarization period, subjects were randomly assigned to either the supplement (BET) or placebo (PL) group. Supplementation occurred for 15 days. During this period, subjects reported to the HPL on 5 separate occasions for a testing and training session. Each session was separated by 72 hours. Subjects then consumed no daily BET for 4 weeks but maintained their familiarity with the isokinetic testing device by once per week workouts. After the 4-week washout period, subjects resumed the BET protocol using the opposite drink and repeated the same 15-day exercise protocol. After each exercise protocol, subjects rated their fatigue and muscle soreness on a 15-cm visual analog scale (VAS). Figure 1 depicts the testing protocol.

Figure 1

Figure 1

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Subjects

Eleven men volunteered for this study (21.7 ± 5.1 years; height: 178.5 ± 6.4 cm; body mass: 79.8 ± 10.3 kg; body fat %: 11.0 ± 1.4%). After an explanation of all procedures, risks, and benefits, each subject gave his informed consent to participate in this study. The Institutional Review Board of the College approved the research protocol. Subjects were not permitted to use any additional nutritional supplementation during the course of the study. Screening for additional BET use was accomplished via a health history questionnaire completed during subject recruitment. All subjects were college students and recreationally active for at least the past 3 months including participation in a resistance training program. The study was conducted in a double-blind, crossover design format.

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Isokinetic Peak Force

Peak CON and ECC force (N) was measured using the multiple-joint isokinetic dynamometer (Exerbotics). The exercise selected for testing was the chest press. Each subject assumed a sitting position on the device, was properly fitted and stabilized, and the exercise range of motion was established and standardized for all subsequent sessions. Range of motion was established so that the dynamometer arm was aligned with the torso at one end (i.e., at the beginning of the CON phase) and to a position of ∼5-10° of full elbow extension at the opposite end (i.e., at the end of the CON phase). Duration was set at 3 seconds for each CON and ECC phase. Subjects performed 3 maximal repetitions consecutively, and the highest CON and ECC force output was recorded for analysis. For the ECC phase, each subject was instructed to resist the dynamometer arm as maximally as possible. For the CON phase, each subject was instructed to “push” as maximally as possible. Force was measured via force transducers built into the dynamometer and was displayed on the computer monitor located directly in front of the subject. The isokinetic device produced real-time force output thereby enabling the subject to visualize effort and adjust force output accordingly. Peak CON and ECC force was measured each time the subjects came to the laboratory after a general warm-up. Test-retest reliability of the dynamometer has been established in our laboratory as r = 0.99.

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Isokinetic Protocol

After peak isokinetic force testing, each subject performed an acute isokinetic resistance exercise protocol. The protocol consisted of performing 5 sets of the chest press for 6 repetitions at 80% of peak CON and ECC force, respectively, with 2-minute rest intervals in between sets. The duration of the CON and ECC phases of each repetition was set at 3 seconds. Intensity was prescribed based upon peak isokinetic force. The isokinetic device monitor displayed peak force and a line representing the force curve needed to attain 80% of peak force throughout the exercise range of motion. Subjects were instructed to provide enough force so that the real-time force output mimicked the standard line on the monitor. In the event the subjects could no longer reach the 80% marker, they were encouraged to provide maximal effort until the required numbers of repetitions were performed. Peak and mean CON and ECC force was recorded for each repetition of each set. The protocol was performed at baseline and during each of the supplemental conditions. Subjects attended 2-3 familiarization sessions before beginning the study to not only accommodate to the device but also to practice providing force sufficient to match the curves. As a training tool, each subject returned to the laboratory once per week to perform the protocol. Subjects performed all testing at the same time of the day and were requested to maintain their normal sleeping and dietary habits throughout the study.

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Questionnaires

Subjects were instructed to assess their general fatigue and body soreness after each workout using a 15-cm VAS. The VAS was assessed immediately after each workout. The subjects were asked to assess how they feel at that time with words anchored at each end of the VAS that expresses the most positive (no fatigue/soreness) and most negative (maximum fatigue/soreness) rating.

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Supplement Schedule

The subjects consumed either the BET (2.5 g of betaine mixed in 500 ml of a sport drink) or PL (sports drink only) once per day. The betaine for the supplement was extracted from sugar beet molasses. Both the BET and PL were identical in appearance and taste. Because the betaine was added to the sports drink, the seal on the lid of each sports drink for the PL group was also cracked to provide the same appearance as the supplement drink. The subjects consumed the drink every day for 2 weeks but consumed the drink 60 minutes before each training session. All drinks were consumed in the HPL, except for weekends. Subjects, after Friday's consumption were given their BET or PL for the weekend. Supplementation continued for 15 days. Both the dosing and length of ingestion were identical to those of previous studies that have shown positive ergogenic benefits of betaine supplementation (11,13). The betaine supplement was obtained from Danisco USA, Inc (New Century, KS, USA).

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Statistical Analyses

Statistical evaluation of performance changes was accomplished using a repeated-measures analysis of variance. In the event of a significant F ratio, least significant difference post hoc tests were used for pairwise comparisons. Statistical evaluation of Δ scores (fifth workout − first workout) was accomplished using paired t-tests. Significance was accepted at an alpha level of p ≤ 0.05. All data are reported as mean ± SD.

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Results

During the 15-day study, no significant differences were noted in maximum CON force output from pre (335.9 ± 78.3 and 321.6 ± 63.6 N) to post (330.3 ± 74.8 and 330.2 ± 71.6 N) workouts in both BET and PL, respectively. In addition, no significant differences were noted in maximum ECC force output from pre (352.0 ± 90.6 and 324.4 ± 85.2 N) to post (353.2 ± 98.2 and 366.9 ± 128.5 N) workouts in both BET and PL, respectively. Examination of the specific workout logs revealed no significant differences between subjects consuming the BET or PL in peak or mean CON or ECC forces during the study (see Figures 2-5, respectively). Examination of the Δ scores revealed no significant differences between the first and final workout in either group, and no differences were observed between the groups.

Figure 2

Figure 2

Figure 3

Figure 3

Figure 4

Figure 4

Figure 5

Figure 5

Examination of subjective measures of soreness and fatigue resulted in no significant differences between the groups throughout the study (see Figures 6 and 7, respectively). However, comparison of the Δ scores of fatigue revealed a significant reduction (Figure 8) in subjective measures of fatigue in BET compared to PL. No difference between the groups was observed in Δ soreness scores.

Figure 6

Figure 6

Figure 7

Figure 7

Figure 8

Figure 8

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Discussion

The results of this study indicated that 15 days of betaine ingestion did not increase isokinetic force output during CON and ECC movements in the chest press exercise. In addition, the quality of the workout (as determined by the mean peak and average force outputs per workout) was not significantly affected by the BET. Although subjective soreness ratings were not changed by betaine ingestion, supplementation did appear to reduce subjective feelings of fatigue.

The results of this study do not support the ergogenic benefits reported by previous studies (11,13). It is likely that differences related to the mode of exercise (isokinetic vs. dynamic constant resistance) or study protocol used contributed to the contrasting results. In the investigations reporting a significant ergogenic benefit from betaine ingestion, investigators employed a dynamic constant resistance exercise protocol that required subjects to lift a specific percentage of their 1RM. As a result, performance improvements were relative to the baseline strength measures performed before the supplementation protocol. In this study, peak CON and ECC force outputs were determined before each workout, and the subsequent training loads were relative to that outcome. Thus, previous studies examined workout quality relative to the initial assessment, whereas this study investigated workout quality relative to the daily change in force output. Regardless, no significant changes were noted in peak CON or ECC force outputs during the BET protocol.

There have been several mechanisms attributed to the ergogenic potential of betaine ingestion. One potential mechanism involves the role of betaine as an osmolyte. Under stressful conditions, such as from perturbing electrolytes, urea or ammonia, cells may accumulate betaine to maintain normal function (7,14). This has been demonstrated in a variety of tissues including muscle (1), where it may have an important role in maintaining skeletal muscle myosin ATPase activity (18). Betaine acts by redistributing water in cells leading to more effective biopolymer hydration and increased cytoplasmic osmolality (6). The role of betaine as an osmolyte has been suggested to be related its role in the synthesis of creatine (1). However, this is only speculative considering that muscle creatine concentrations have not been demonstrated to be increased from betaine intake in humans. Betaine supplementation has previously been shown to increase muscle creatine concentrations, albeit in chickens (18). There have been no studies known to date that have examined changes in muscle creatine concentrations in humans supplementing with betaine. The donation of methyl groups from betaine is thought to occur via a series of enzymatic reactions in the mitochondria of liver and kidney cells (6). Betaine donates a methyl group to homocysteine to form methionine. This transfer is controlled by the enzyme betaine homocysteine methyl transferase that results in betaine being converted to dimethylglycine. Methionine is converted to SAM, which acts as a methyl donor contributing to the synthesis of creatine, and a number of other proteins (5). Dietary betaine has been shown to increase serum methionine, transmethylation rate, and methionine oxidation in healthy men (16), and animals injected with betaine have shown a dose-response increase in red blood cell SAM (17). However, the relationship of betaine ingestion and muscle creatine synthesis in humans is yet to be established. It is possible that longer ingestion periods may be necessary to result in significant elevations in muscle creatine concentrations or that creatine synthesis is not the primary benefactor from the increase in the methyl pool from betaine ingestion. Recent reports have indicated that creatine synthesis from methyl donation may be overestimated and that phosphatidylcholine synthesis may be a greater consumer of the increase in endogenous methyl groups (15).

An elevation in phosphatidylcholine concentration may have potential ergogenic implications for athletic performance. Considering that choline intake is important for enhancing neurotransmitter concentration, the ability to enhance strength, power, or ability to react to external stimuli could be enhanced with greater neurotransmitter formation. However, there is only limited research conducted examining the ergogenic potential of choline. Although improvements in memory and cognition have been reported from choline ingestion (1,3,4,7), there have been only limited investigations regarding choline and athletic performance and no studies known to have examined choline ingestion and resistance exercise. A recent study showed that phosphatidylcholine intake contributed to enhanced reactive ability to both visual and auditory stimulus after exhaustive exercise (10). In addition, subjects consuming the Bet also reported significantly lower subjective measures of fatigue. This is consistent with the results reported in this study and suggests, although speculative, that betaine ingestion may have contributed to increases in phosphatidylcholine concentrations.

Previous research has suggested that betaine supplementation may enhance mood in a clinical population suffering from motor neuron disease (12). Although this provides support to the role that betaine may have in elevating phosphatidylcholine concentrations, our previous study was unable to support those findings (9). The soreness ratings seen in this investigation were similar to what we previously reported, but the lower fatigue rate does provide support for a potential ergogenic benefit. Although this may be related to increases in phosphatidylcholine concentrations, recent research has indicated that creatine ingestion may also have an important role in cognitive and psychomotor performance (13). McMorris et al. (16) have reported that creatine ingestion can improve mood states after sleep deprivation, whereas others have indicated that creatine has important neuroprotective effects (2). Regardless, the precise mechanism that underlies betaine's ergogenic role still needs to be elucidated suggesting that additional research is warranted concerning the contribution that betaine ingestion has on both creatine and phosphatidylcholine synthesis.

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Practical Applications

Two weeks of betaine supplementation in active, college men did not appear to improve isokinetic CON and ECC force outputs in the chest press exercise but did appear to lower subjective feelings of fatigue after exercise. This study was unable to support previous investigations showing the ergogenic effects of similar dosing durations of betaine. These differences are likely related to differences in mode of exercise between the studies and the lack of clarity regarding the mechanism governing the proposed ergogenic benefits.

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References

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Keywords:

supplementation; ergogenic aid; sport nutrition; sport

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