Osteoporosis is a concern for each of us as there are millions of individuals around the world suffering from this debilitating condition. As the world’s ageing population seems to increase the prevalence of osteoporosis and osteopenia also increases characterized by decreased bone mass and increased fragility risk. According to the Osteoporosis Consensus Development osteoporosis is a metabolic bone disease characterized by low bone mass and microarchitectural deterioration of bone tissue leading to enhanced bone fragility and a consequent increase in fracture risk. When the condition is not prevented it progresses until the bone is fractured (mostly includes regions of the hip, wrist and lumbar spine). Menopause brings about numerous hormonal changes in women and they can lose around 20% of bone mass in the initial 5-7 years which finally can result in osteoporosis. Its been shown that 50% of women and 25% of men over the age of 50 will suffer from fracture due to osteoporosis in their lifetime.
Bone is a living tissue that constantly breaks down and rebuilds but with the advent of diseases such as osteoporosis there is more breakdown than building up. But this is not irreversible and exercising helps in rebuilding bones and reducing the likelihood of fracture. Exercising has been recommended as an inexpensive and safe intervention technique for preserving musculoskeletal health but all types of exercises don’t have the same beneficial effect on bone mineral density (BMD). According to the World Health Organization (WHO) osteoporosis and osteopenia are defined as the lowest BMD T-score of ≤-2.5 and -2.5 to 1.0 measured at the lumbar hip or spine. Present guidelines include resistance training and weight-bearing exercises for preventing bone loss and preserving bone mass in patients with osteoporosis.
Strength training helps to maintain or rather improve BMD, promote increased levels of bone formation markers (such as type 1 collagen amino-terminal propeptide (P1NP)) and decrease levels of bone resorption markers (such as type 1 collagen C breakdown products (CTX)) in the blood. We have reports on a positive association between maximal muscle strength measured as 1-repetition maximum (1RM) and bone mass. We have strength training programs that focus on 1RM improvements to be helpful in improving BMD and bone mineral content (BMC), especially in postmenopausal women.
A study focused on 1-year and 4-year results from the Bone Estrogen Strength Training (BEST) Study was the most extensive study in United States that began in 1995 focusing mainly on how strength training combined with calcium intake impacts BMD in two groups of postmenopausal women. Anyone whether or not they were undergoing hormone replacement therapy (HRT) were allowed to participate in the study which meant a total of 266 women aged 45-65 years completed the first year of study. Sedentary (<120 minutes of exercise per week) postmenopausal women were selected and were randomly assigned to either control or exercise group and all participants took 800mg of calcium citrate supplements daily. Each of the participants’ dietary intake through the first year was assessed using 8 randomized days of dietary recall (DR) collected at baseline, 6 months and 12 months of study. While those in the control group continued with their sedentary lifestyle those in the exercise group performed weight bearing and resistance exercises 30 days per week on non-consecutive days. These exercise sessions lasted for 60-75 minutes and included weight-bearing activities for warm up, strength training and cardio weight bearing circuit of moderate impact activities at 70-80% of maximum heart rate such as stair climbing on step boxes wearing weight-bearing vests and small muscle exercises including stretching and balancing ones. All types of exercises and its duration was regularly monitored and the data entered by BEST trainers.
The participants performed strength training exercises using free weights and machines focusing on major muscle groups. 8 different exercises were performed that included seated leg press, weighted march, lat pull down, seated row, back extension, one-arm military press, squats and rotary torso machine. All the subjects completed two sets of 6-8 repetitions at 70% (twice a week) and 80% (once per week) of the one-repetition maximum.
Results were positive for those who exercised as exercise group participants witnessed improved BMD compared to the control group. In those who used HRT, the use of calcium, HRT supplements and exercising increased hip, neck and femoral BMD by 1-2% while the use of supplements with no exercise performance had a non-significant effect on BMD. In those participants who did not undergo HRT, the performance of regular exercise improved BMD by almost 1% whereas abstinence from exercising decreased their BMD to a great extent. The study clearly proves increased advantage for those women who use HRT.
Besides BMD, BEST intervention also had positive effects on soft tissue composition-inclusion of all body components except bone. DXA measurements showed that women who exercised regularly displayed whole body and regional (arms and legs) lean soft tissue (LST). Though there was no improvement in LST in those who used HRT the use of HRT did prevent loss of LST in those women who did not exercise. There was significant fat mass loss in those women who used HRT and also exercised. Nutrition intake also had a significant effect on BMD-a greater intake of calcium, iron, zinc, magnesium, phosphorus and vitamin D was significantly linked to better BMD at the end of the first year of study. At baseline, a subsample of 242 women who completed DRs having dietary iron intake levels greater than 20 mg/day was linked to greater BMD at several bone sites when the participant’s daily calcium intake was from 800-1200 mg/day only. At the end of the first year of study 228 women had complete DR data. Among the 228 women, those who took HRT and consumed lowest amount of calcium showed increase in BMD as iron intake levels increased from 7 mg/day to 32 mg/day. In those who did not take HRT there was BMD increase only in those who took highest calcium intake with no changes due to iron intake levels.
The study showed that when women lifted more weights, they experienced greatest improvements in BMD, more specifically at the hips. Bone loss is not a short-term effect but something that takes place for many years after menopause and performing exercise meanwhile can definitely curb this effect. There are many studies dealing with the effects of exercise only on short-term advantages-one that happens within 1-2 years of exercising. The BEST study focused on long-term results and found that two sets of exercise was sufficient to increase BMD and the initiate to lift weights was necessary to further improve BMD levels. To help participants continue with the BEST exercise program the duration of exercising was reduced to 45 minutes and 6 strength training exercises that excluded rotary torso machine and weighted march. Some of them were also involved in doing yoga, spinning and Pilates to break the monotony and bring in variety to their exercising schedule.
It was only 167 women who completed 4 years of participation in the BEST study. At the end of the first year all of them were encouraged to exercise on their own and also have yearly DXA assessments conducted by the study group. At the end of the second year, supervision was reduced in the facilities, in the other years trainers were there in the facility only once a month. After 4 years the participants’ exercise frequency varied from 0-94% of the various exercises mentioned above. those participants who were actively engaged in exercising maintained or improved BMD at the hip and lumbar spine (LS). Those who showed maximum exercising efficiency experienced greatest BMD improvements at all bone sites than those who exercised less often. But it was observed that greatest increase in LST and BMD occurred in the first year of the BEST study regardless of HRT use. While LST increased during first year the effect was lost for years 2-4 yet the overall gain remained well above normal ranges. It was the LS BMD that continued to improve consistently for 4 years of participation in the BEST study program.
Those women who completed 4 years of the study taking 800 mg/day of calcium supplements but who were not on HRT showed maximized improvements in BMD than those taking less calcium supplements. Those women not on HRT and following BEST exercise schedule need at least 1700mg/day (this is 500 mg more than recommended DRI values for women aged 50+) of calcium supplements to preserve BMD. This shows that calcium too apart from exercising plays a pivotal role in determining BMD in individuals.
At the end of the 4-year period it was noticed that women who attended maximum exercise sessions and lifted greatest amount of weights showed greatest gains in LS BMD compared to those women who attended minimum exercise sessions and lifted least amount of weights. At the end of 4 years training, there was a 2.5% difference in LS BMD between those women who lifted greatest amount of weight and those who lifted least. Those who lift the greatest weights reaped maximum BMD benefits. This study thus shows that physicians and health experts can use the BEST exercise program for improved bone density.
Strength Training Effect on Postmenopausal Women
We have one study reporting that power training focusing on high-speed contractions was more effective than conventional strength training for reducing bone loss while another study showed that neuromuscular performance (this makes rate of force development (RFD) capacity more important for skeletal adaptations) determined bone strength in postmenopausal women. Maximal strength training (MST) is characterized by high loads and fewer repetitions and till date there are no studies that have applied interventions combining heavy loads with high concentric acceleration as in MST promoting both 1RM and RFD improvements. The study below focused on the effect of squat exercise on MST on 1RM, RFD and bone-related parameters in patients with osteoporosis and osteopenia. 21 participants all of whom were at least 2 years postmenopausal, <75 years and having a BMD score between -1.5 and -4.0 at the lumbar spine, hip or neck were randomly assigned to either the training group (TG, n=10) or control group (CG, n=11). Participants in the training group followed a training program that comprised of MST for 12 weeks with 3 exercise sessions per week amounting to 36 sessions totally. The training sessions consisted of one exercise which used the lower extremities in a squat exercise machine-it started with a warm up including 2 sets of 8-12 repetitions at approximately 50% of the participant’s training load followed by 4 sets of 3-5 repetitions at 85-90% of 1 RM. The training load was increased by 2.5 kg if the participants could perform >5 repetitions.
Each of the participant’s vitamin D levels were measured and treadmill tests were performed to define aerobic capacity among participants. The research team was left with 16 participants with 8 of them in each group completing the study. Results showed that:
We have studies showing that performing resistance exercises (REs) 2-3 times per week for a year maintained or increased BMD at the lumbar spine and hip in postmenopausal women. Combining RE and weight-bearing aerobic exercises improves musculoskeletal outcomes including BMD, muscle mass and strength in older men as well as women. Another study with an 18-month RE and weight-bearing impact activity showed significant increase in bone strength and BMD in middle-aged men and women. A systemic review and meta-analysis on the effects of exercising on postmenopausal women suggested that exercise decreased bone mass loss.
Performing exercises to build and maintain muscle mass and strength leads to stronger bones which in turn help in minimizing risk of fractures due to osteoporosis.
Preventing Osteoporosis the Bone Estrogen Strength Training Way: https://journals.lww.com/acsm-healthfitness/Fulltext/2007/01000/Preventing_Osteoporosis_the_Bone_Estrogen_Strength.8.aspx?WT.mc_id=HPxADx20100319xMP
Maximal Strength Training in Postmenopausal Women with Osteoporosis or Osteopenia: https://journals.lww.com/nsca-jscr/Fulltext/2013/10000/Maximal_Strength_Training_in_Postmenopausal_Women.32.aspx
Effects of Resistance Exercise on Bone Health: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6279907/pdf/enm-33-435.pdf
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