Thursday, June 25, 2015

Yes, Men Can Have Low Bone Mineral Density, Too | But Can Jump Training Really Keep up W/ Resistance Training as a Bone Builder For Rel. Young Men W/ Low BMD?

In view of the fact that there are women in the photos, it should be obvious that these are not the study subjects ;-)
Rope skipping is probably not exactly the exercise you'd be thinking of when it comes to bigger or I should say stronger bones, right? You'd think of squats, of deadlifts of farmers' walks - all the exercises where you can and have to move large amounts of weight - weight bearing exercises that is, those exercises of which studies in post-menopausal women of whom you'd expect them to have low bone mass show that they are effective bone builders (Bassey. 1995; Etherington. 1996; Dalsky. 1998).

Well, I have to admit that I was similarly surprised when I read that jumping had a similar beneficial effect on the bones as resistance training in relatively young (25-60 year-old) male subjects in a recent study from the University of Missouri (Horton. 2015).
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As a cursory glance at the abstract reveals, the "jumping training" the subjects did 3 times per week consisted of jumps with progressing intensity (e.g. jump off box more “intense” than squat jump) and complexity of the movement (e.g., single-leg jump more intense than double-leg jump).
  • Weeks 1–2 were comprised of low-intensity jumps (10 repetitions of squat jump, forward hop, split squat and lateral box push-off jumps); 
  • Weeks 3–4 also included moderate-intensity jumps (10 repetitions of 6–8 different jumps, which included bounding, lateral bounding, box jump, lateral hurdle, zig-zag jumps, or single-leg lateral hurdle and 2 randomly selected low-intensity jumps);
  • Weeks 5-6 also included high-intensity jumps like depth jumps and jumps off a box (10 repetitions of 10–12 different jumps, which included depth jumps and jumps off a box and 8–10 randomly selected low- and moderate-intensity jumps). 
  • Week 7 was a rest week after wards the cycle was repeated for 8 cycles.
Those of the participants who had been randomly assigned to the resistance training group (RT) trained only twice a week.
" The RT intervention included exercises that load the hip and spine: squats, bent-over-row, modified dead lift, military press, lunges, and calf raises. To minimize risk of injury and to account for strength adaptations as a result of strength training improvements, the RT intervention also used a progressive intensity design based on a 6-week cycle followed by a rest week; a total of 8 cycles were completed" (Hinton. 2015).
As it was the case for the JUMP group, the intensity increased gradually over a 6-week cycle based on new 1-RM tests that were made every 2nd week. In that,...
"[...] weeks 1–2 were light intensity, consisting of one warm-up set of 10 repetitions at 20% 1RM and 3 sets of 10 repetitions at 50% 1RM; weeks 3–4 were moderate intensity with one warm-up set of 10 repetitions at 20% 1RM, two sets of 10 repetitions at 60% 1RM, and one set of 6–8 repetitions at 70–75% 1RM; and weeks 5–6 were high-intensity, starting with one warm-up set of 10 repetitions at 20% 1RM, followed by 2 sets of 10 repetitions at 60% 1RM, and one set of 3–5 repetitions at 80–90% 1RM" (Hinton. 2015)" 
The participants were instructed to perform the eccentric phase of each lift in 2–3 seconds and to perform the concentric contraction "explosively."
Figure 1: Despite significantly increased activity levels in almost all subjects, there were no beneficial changes in body composition and accordingly no inter-group differences (Hinton. 2015).
Now, you should be able to see that both groups underwent at best minimal changes in body composition, which is not surprising considering the fact that the total physical activity of the 44 ± 2 year-old (25-60y) subjects who were not inactive and/or obese and didn't even know about their low bone mineral density before they volunteered for a study that included a free bone mineral density (BMD) scan.
Figure 2:1-RM strength from week 0-12; rel. change to baseline in % above the bars (Hinton. 2015).
What did improve and that even highly significantly are the preformance markers. The average subjeft in the RT group almost doubled his / her squat weight. In comparison, the "gains" the JUMP group made (8% in vertical jump height) look pretty pathetic.

The lack of impressive performance gains in the JUMP group does not negate that osteocalcin and OCX, one increases, the other decreases the bone mass improves significantly in subjects in both groups. It does however stand in line with the lack of impressive improvements in bone mass. Improvements that reached statistical significance only in the RT group.
Whole body bone mineral density in physically active (≥ 4 h/wk) men with osteopenia of the hip or spine at baseline and after 6 and 12 months of resistance training or jump training 
So what? If you can strength train, do it! It's good for bone and muscle and you need both now and as you age.

I originally wanted to write that you'd need bones and muscle "even more so as you age", but technically that's not correct. On the other hand, you'll have a much harder time maintaining and maybe even increasing the bone and muscle mass you have as you age. I am not saying it's impossible, but I am saying the difference we see between the actual effects on bone mineral density when comparing weight bearing = resistance training exercise with jumps is to large to be ignored.
References:
  • Bassey, E. J., and S. J. Ramsdale. "Weight-bearing exercise and ground reaction forces: a 12-month randomized controlled trial of effects on bone mineral density in healthy postmenopausal women." Bone 16.4 (1995): 469-476.
  • Dalsky, Gail P., et al. "Weight-bearing exercise training and lumbar bone mineral content in postmenopausal women." Annals of internal medicine 108.6 (1988): 824-828.
  • Etherington, J., et al. "The effect of weight‐bearing exercise on bone mineral density: a study of female ex‐elite athletes and the general population." Journal of Bone and Mineral Research 11.9 (1996): 1333-1338.
  • Hinton, Pamela S., Peggy Nigh, and John Thyfault. "Effectiveness of resistance training or jumping-exercise to increase bone mineral density in men with low bone mass: A 12-month randomized, clinical trial." Bone (2015).