HMB bulks muscle without strength training

HMB can boost muscle strength and quality even if you don’t do strength training. Sports scientist Jeffrey Stout, of the University of Central Florida, draws this conclusion in a human study involving nearly fifty over 65s. The results of the study have been published in Experimental Gerontology.

HMB [right in the figure below] is a metabolite of leucine [left in the figure below]. Muscle cells crank up their anabolic machinery when supplied with large amounts of leucine – and part of the anabolic effect is probably due to HMB.


Sports scientists and anti-aging researchers are studying HMB in the hope that the compound can help reduce or reverse the loss of muscle mass in the elderly.

HMB can boost muscle strength and quality even if you don’t do strength training. Sports scientist Jeffrey Stout, of the University of Central Florida, draws this conclusion in a human study involving nearly fifty over 65s. The results of the study will soon be published in Experimental Gerontology.
As humans are living longer and longer thanks to medical science, the number of elderly people who are losing so much muscle mass that they need help is also increasing. In the US, 30 percent of men and 64 percent of women over the age of 74 are no longer able to lift a weight of 4.5 kg. [Am J Public Health. 1981 Nov;71(11):1211-6.]

Stout wondered whether HMB can help maintain muscle strength in the over 65s, without them having to do weight training. He did a trial with just under 50 subjects, all over the age of 65. Their average age was in the early seventies.

Stout gave half of his subjects a placebo for 24 weeks. The other half was given 3 g HMB daily. They were given the traditional, calcium salt form of HMB [CaHMB].

In the 24 weeks that the subjects took HMB, their lean body mass increased by half a kilogram and their muscle mass by 300g. Both effects were statistically significant.


The researchers also measured the strength the subjects were able to develop when doing leg extensions [Extensor] and leg curls [Flexor] of 60 and 180 degrees. The table below shows that the HMB group became significantly stronger on a number of points.


The researchers did another experiment in which they got a comparable group of subjects to do weight training for 24 weeks. Half of this group were given a placebo, and the other half 3 g HMB per day. Both groups progressed, but the HMB group did slightly better than the placebo group.

This last experiment added more weight to the growing pile of evidence that strength training is good for the over 65s, the researchers believe. In their view all elderly people who notice they are losing muscle strength and mass should do some kind of resistance training.

“However, there are three potential limitations: 1) low adherence to high intensity resistance exercise programs, 2) discontinuation of resistance exercise will result in rapid loss of benefits, and 3) in frail elderly, resistance exercise may not be adequate to reverse loss of muscle function”, the researchers add as a cautionary note.

“Accordingly, non-exercise interventions (nutritional or pharmacological) that can improve body composition, muscle quality and functionality, are critically important”, they conclude. “The findings of the present pilot study indicate that CaHMB without resistance exercise enhances strength and muscle quality in elderly men and women, thereby supporting its potential as a nutritional intervention to prevent sarcopenia and its associated functional decline in people as they age.”

Abbot Nutrition funded the study and provided one of the researchers.

Effect of calcium ?-hydroxy-?-methylbutyrate (CaHMB) with and without resistance training in men and women 65+yrs: A randomized, double-blind pilot trial.

Stout JR, Smith-Ryan AE, Fukuda DH, Kendall KL, Moon JR, Hoffman JR, Wilson JM, Oliver JS, Mustad VA.


Institute for Exercise Physiology and Wellness Research, University of Central Florida, Orlando, FL, USA. Electronic address:



Evidence suggests CaHMB may impact muscle mass and/or strength in older adults, yet no long-term studies have compared its effectiveness in sedentary and resistance training conditions. The purpose of this study was to evaluate the effects of 24weeks of CaHMB supplementation and resistance training (3dwk-1) or CaHMB supplementation only in ?65yr old adults.


This double-blinded, placebo-controlled, trial occurred in two phases under ad libitum conditions. Phase I consisted of two non-exercise groups: (a) placebo and (b) 3g CaHMB consumed twice daily. Phase II consisted of two resistance exercise groups: (a) placebo and resistance exercise and (b) 3g CaHMB consumed twice daily and resistance exercise (RE). Strength and functionality were assessed in both phases with isokinetic leg extension and flexion at 60°·s-1 and 180°·s-1 (LE60, LF60, LE180, LF180), hand grip strength (HG) and get-up-and-go (GUG). Dual X-Ray Absorptiometry (DXA) was used to measure arm, leg, and total body lean mass (LM) as well as total fat mass (FM). Muscle Quality was measured for arm (MQHG=HG/arm LM) and Leg (MQ60=LE60/leg LM) (MQ180=LE180/leg LM).


At 24weeks of Phase I, change in LE60 (+8.8%) and MQ180 (+20.8%) for CaHMB was significantly (p<0.05) greater than that for placebo group. Additionally, only CaHMB showed significant (p<0.05) improvements in total LM (2.2%), leg LM (2.1%), and LE180 (+17.3%), though no treatment effect was observed. Phase II demonstrated that RE significantly improved total LM (4.3%), LE60 (22.8%), LE180 (21.4%), HG (9.8%), and GUG (10.2%) with no difference between treatment groups. At week 24, only CaHMB group significantly improved FM (-3.8%) and MQHG (7.3%); however there was no treatment main effect for these variables.


CaHMB improved strength and MQ without RE. Further, RE is an effective intervention for improving all measures of body composition and functionality.