Elsevier

Nutrition

Volume 16, Issue 9, September 2000, Pages 734-739
Nutrition

Applied nutritional investigation
Nutritional supplementation of the leucine metabolite β-hydroxy-β-methylbutyrate (hmb) during resistance training1

https://doi.org/10.1016/S0899-9007(00)00376-2Get rights and content

Abstract

The effects of supplementation of the leucine metabolite β-hydroxy-β-methylbutyrate (HMB) were examined in a resistance training study. Thirty-nine men and 36 women between the ages of 20–40 y were randomized to either a placebo (P) supplemented or HMB supplemented (3.0 g HMB/d) group in two gender cohorts. All subjects trained three times per week for 4 wk. In the HMB group, plasma creatine phosphokinase levels tended to be suppressed compared to the placebo group following the 4 wk of resistance training (HMB:174.4 ± 26.8 to 173.5 ± 17.0 U/L; P:155.0 ± 20.8 to 195.2 ± 23.5 U/L). There were no significant differences in strength gains based on prior training status or gender with HMB supplementation. The HMB group had a greater increase in upper body strength than the placebo group (HMB:7.5 ± 0.6 kg; P:5.2 ± 0.6 kg; P = 0.008). The HMB groups increased fat-free weight by 1.4 ± 0.2 kg and decreased percent fat by 1.1% ± 0.2% while the placebo groups increased fat-free weight by 0.9 ± 0.2 kg and decreased percent fat by 0.5% ± 0.2% (fat-free weight P = 0.08, percent fat P = 0.08, HMB compared to placebo). In summary, this is the first short-term study to investigate the roles of gender and training status on the effects of HMB supplementation on strength and body composition. This study showed, regardless of gender or training status, HMB may increase upper body strength and minimize muscle damage when combined with an exercise program.

Introduction

Leucine and certain metabolites of leucine decrease stress-related nitrogen and protein losses by inhibiting protein breakdown, which is elevated in disease and trauma.1, 2, 3, 4 It has been hypothesized that the leucine metabolite, β-hydroxy-β-methylbutyrate (HMB), may be responsible for this inhibitory effect on protein breakdown.5 HMB is produced by the liver enzyme, α-ketoisocaproate (KIC) oxygenase.6, 7, 8, 9 This enzyme normally accounts for about 5% of leucine oxidation.10 Data in humans, sheep, and pigs indicate that the majority of HMB is metabolized in the body while the rest is excreted in the urine.5

A recently published paper examined the effects of HMB supplementation on body composition changes.11 In young men undergoing an intense 3-wk resistance training program, HMB increased strength and fat-free weight compared with subjects supplemented with a placebo.11 In addition, results from a second study with young men also found that HMB supplementation increased fat-free weight gains associated with a 7-wk resistance training program.11 The mechanism of the effect appears to be related to less muscle membrane damage. In human and animal trials that were supplemented with HMB during intense exercise there were lower levels of creatine phosphokinase (CK)11, 12, 13 and lactate dehydrogenase (LDH)11 and a decrease in 3-methylhistidine (3-MH) excretion.11 Together these changes suggest that HMB may prevent or slow muscle membrane damage as well as partially prevent the increase in proteolysis that is associated with intense muscular work.

Although the effects of HMB in trained young men have been previously investigated11, 14 the roles of gender and training status have not been examined. It is hypothesized that HMB will be effective for both men and women in increasing strength while increasing fat-free weight and decreasing fat weight when combined with an exercise program. Therefore, the objectives of the present study was to further examine the effects of HMB supplementation on strength and body composition changes in both men and women following a supervised resistance training program.

Section snippets

Subjects

Forty-three men and 41 women between the ages of 20 and 40 y were recruited to participate in a 4-wk resistance training program. Men and women were studied in two separate gender cohorts. Based on sample sizes from previous experience,11 subject size was limited to approximately 20 subjects per treatment group. Subjects were originally recruited to either a trained or untrained arm of the study. Although subjects were placed in a trained or untrained group, all subjects were familiar with a

Results

Of the 43 men initially recruited, 39 completed the 4 wk of training. One subject was removed initially due to an abnormal blood-screening test, and 3 other subjects had to drop due to injuries during the training program. Of the 41 women initially recruited for the study, 36 completed the 4 wk of training. One had to drop for unrelated medical reasons, 1 due to an injury that occurred outside the study, and 3 due to time constraints. Table I and Table II show subject characteristics and

Discussion

This is the first study to evaluate the effects of short-term (4 wk) supplementation of HMB in resistance training women and the effects of training status (trained or untrained) in both men and women on muscle strength and body composition. The major findings of this 4-wk study were that 1) the response from HMB does not appear to be dependent on previous training levels; and 2) both, women and men appear to respond to HMB supplementation. Our results agree well with a previous study by Nissen

Summary

These cohort studies showed that regardless of gender or training status, HMB may increase upper body strength and minimize muscle damage when combined with a 4-wk resistance training program.

Acknowledgements

The authors wish to thank Leigh Ann Cannon (ISU) and Janet Gammon (ISU) for their contribution. Results of the present study do not constitute endorsement of the product by the authors.

References (16)

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    It is also used to preserve or increase lean body mass in patients with chronic diseases associated with muscle wasting as well as in individuals ≥65 y of age [6–8]. HMB intake with muscle training has been shown to lead to a gain in lean body mass, a decrease in fat components, and suppression of proteolysis among healthy individuals [9]. Furthermore, May et al. reported that HMB used as a blended nutrient was effective in increasing fat-free mass in patients with advanced (stage IV) cancer [10].

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1

Study funded by Metabolic Technologies, Inc.

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