Abstract
Physical exercise has a favorable impact on bones, but optimum training strategies are still under discussion. In this study, we compared the effect of slow and fast resistance exercises on various osteodensitometric parameters. Fifty-three postmenopausal women were randomly assigned to a strength training (ST) or a power training group (PT). Both groups carried out a progressive resistance training, a gymnastics session, and a home training over a period of 12 mo. During the resistance training, the ST group used slow and the PT group fast movements; otherwise there were no training differences. All subjects were supplemented with Ca and vitamin D. At baseline and after 12 mo, bone mineral density (BMD) was measured at the lumbar spine, proximal femur, and distal forearm by dual-energy X-ray absorptiometry. We also measured anthropometric data and maximum static strength. Frequency and grade of pain were assessed by questionnaire. After 12 mo, significant between-group differences were observed for BMD at the lumbar spine (P < 0.05) and the total hip (P < 0.05). Whereas the PT group maintained BMD at the spine (+0.7 +/- 2.1%, not significant) and the total hip (0.0 +/- 1.7%, not significant), the ST group lost significantly at both sites (spine: -0.9 +/- 1.9%; P < 0.05; total hip: -1.2 +/- 1.5%; P < 0.01). No significant between-group differences were observed for anthropometric data, maximum strength, BMD of the forearm, or frequency and grade of pain. These findings suggest that power training is more effective than strength training in reducing bone loss in postmenopausal women.
My comments:
This was an interesting study because it directly separated out concentric speed (the lifting part) of weight lifting (as fast as possible in the power training group) vs lifting the weight over 4 seconds in the strength training group. The power group maintained BMD over a year, while the regular strength training group lost some bone mineral density. Set and repetition range was not given (which would have been nice of them to mention) but training intensity was said to be 70-90% of their 1 repetition max (1 RM) for 12 weeks, interspersed with a 4-5 week recovery period training at 50% of their 1 RM. The exercises were machine based; leg presses, leg curls, bench press, rowing, leg adduction and abduction, abdominal flexion, back extension, lat pulldown, hyperextension, leg extensions, shoulder raises and hip extensions. Given that the weight training sessions were only 6 minutes long, including a 20 minute warm up, followed by some jump training before starting the weights; the large number of machines used and the Arthur Jones’esc use of 4 seconds up and 4 seconds down, I’m going to guess they did only one, and maybe just 2 sets per exercise.
Another variable that might have affected overall outcomes is that these women were not untrained having just preceding 3 year study in which they were weight training. I’ll have to read the prior study to be sure but they likely had already gained a fair degree of bone mineral density, after which point additional gains would be more difficult. Also I think the 4 second eccentric period, in even the power training group, would lessen their overall training load. If my physical therapy patients and personal training clients take longer than half a second to lower the weights I tell them to go faster. 4 seconds down is REAL SLOW and you can’t lift as heavy a weight that slow, so overall training intensity is lessened. Known to just about every weightlifter, powerlifter, bodybuilder, or strength and conditioning coach (but apparently not every researcher) is that nobody strong trains like that. Strong people generally lower their weights (eccentric contraction) in a smooth but swift manner, and if they really know what they are doing, they lift those weights (concentric contraction) as fast as they can, the latter as done in the power training group here. So I don’t really like the power training vs strength training terms used in this study. Rather I would have called them slow vs fast strength training, for which prior research has shown that faster strength training is better for both strength and power, while slower training is lame for both, though probably not as lame as yoga;)
So all my criticisms aside, even with the slow 4 second eccentric phase the power training group was able to maintain bone mineral density in pre-trained postmenopausal women, while the slow strength training group was not. Being as this was a 2005 study, it likely helped researchers towards the more recent program performed on osteoporotic women using “Maximal Strength Training” which led to substantial increases in bone mineral density in just 12 weeks. It’s also why I am skeptical of use of yoga, particularly given the potential for injury in women with osteopenia and osteoporosis.
Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember SpineFit Yoga for you or someone you know in the future.
Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.
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