An increase in peak bone mass has been recommended as a prophylactic against osteoporosis1. The growth period is an opportune time to stimulate bone modeling due to the hormonal milieu associated with maturation. In support of this notion, exercise intervention studies in children appear to be more effective for bone formation compared with elderly where exercises is used as a prevention measure of bone loss2. Resistance exercise has been promoted as an effective method to stimulate bone formation2. Therefore, incorporating resistance exercise during the growth period would be beneficial in maximizing peak bone mass and has potential to attenuate bone loss associated with aging. However, the amount of resistance exercise needed during the growth period for maximal stimulation of bone accrual is not known.
The research . . .
Recently, a study was conducted to determine the minimum amount of resistance exercise that would be just as effective as higher volumes of resistance exercise for stimulating increases in bone mineral density (BMD) during the growth period in rats3.
If low volumes of resistance exercise stimulate bone formation to the same extent as high volumes of resistance exercise, this would indirectly support the existence of an exercise threshold where additional work would not further increase BMD.
Four groups were compared performed different volumes of resistance exercise per training session. The resistance exercise protocol has previously been shown to stimulate bone formation4. Animals were required to climb a vertical ladder with weights where the animal conducted 13 lifts per limb. Resistance trained animals exercised 3 days/week for 6 weeks. Intensity started at 30% of body mass and the carrying weight was elevated by 30% every week for the next 4 wks (i.e., 30%, 60%, 90%, and 120%) until beginning of week 5 where they carried 135% body mass and week 6 carried 150% of body mass. There was a control group which remained sedentary and four resistance-trained groups as follows: group 1-one ladder climb per exercise session (1LC), group 2-two ladder climbs per exercise session (2LC), group 3- three ladder climbs per exercise session (3LC), and group 4-four ladder climbs per exercise session (4LC).
It was hypothesized that a low amount of resistance exercise performed during the growth period would be just as effective as greater volumes of resistance training in stimulating elevation in BMD and bone strength3.
The results . . .
Results showed that after 6 weeks of resistance exercise, left tibia BMD was significantly greater for 2LC, 3LC, and 4LC when compared with control. Left femur BMD was significantly greater for 2LC, 3LC, and 4LC when compared with 1LC and control. There were no differences in BMD between 2LC, 3LC, and 4LC groups.
These results suggest that a low volume of resistance training is just as effective as higher amounts of resistance training for maximal stimulation of bone formation during the growth period. This was supported by the comparable increase in BMD for the 2LC, 3LC, and 4LC groups compared with control, despite the significant difference in work performed by each resistance-trained group. There were no significant differences between the 2LC, 3LC, or 4LC groups for BMD and bone strength.
A limitation of the above research study is that it was done in rats where the epiphyseal plates do not close, thus would favor a bone formation response and limit an extrapolation of the results to adult humans 3. Nevertheless, this was a very well-controlled study, and the researchers were able to ‘tease-out’ the differences in resistance training volume.
Bottom line . . .
The results of this study support the belief of an exercise threshold whereby increased in work per exercise session did not yield further elevations in bone modeling. This research also supports the use of low volume, high-intensity resistance training as recommended by Max-OT. Besides the benefits for enhancing muscle size and strength, the use of Max-OT seems to be the ideal way to train to enhance bone formation!
References:
1. Welten DC, Kemper HC, Post GB, et al. Weight-bearing activity during youth is a more important factor for peak bone mass than calcium intake. J Bone Miner Res 1994;9:1089-96.
2. Suominen H. Muscle training for bone strength. Aging Clin Exp Res 2006;18:85-93.
3. Ahles CP, Singh H, Joo W, et al. High volumes of resistance exercise are not required for greater bone mineral density during growth. Med Sci Sports Exerc 2013;45:36-42.
4. Godfrey JK, Kayser BD, Gomez GV, Bennett J, Jaque SV, Sumida KD. Interrupted resistance training and BMD in growing rats. Int J Sports Med 2009;30:579-84.
